Volume 43, Issue 6 (2023)
Subgrade Engineering
Analysis of stability of trench formation and effect of ground deformation of ground⁃connected wall in rock⁃throwing reclamation area
BAO Xiaohua, PAN Jihao, CUI Hongzhi, WAN Bo, and ZHOU Zhen
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.001
By studying the construction process of ground-connected wall slurry trenches in the rock-throwing reclamation areas, this paper explored the effects of such factors as trench section width, weight of the slurry trench, parameters of the rock-throwing layer, the reinforcement zone range of the trench wall, and grouting parameters on the stability of the trench wall and the disturbance of the surrounding strata. Meanwhile, it measured the deformation modulus of the grouting reinforcement zone by experiments, and obtained the shear strength parameters from empirical formulas. The ground deformation characteristics induced by the construction of ground-connected wall in rock-throwing reclamation areas under different grouting reinforcement schemes were calculated and analyzed via the finite element method. The calculation results indicate that the maximum lateral displacement of the soil on the trench wall occurs at 1/3 to 1/2 of the trench section depth. Reinforcing the surrounding strata of the trench wall via grouting can reduce the trench wall’s lateral deformation and surface settlement. Additionally, compared to single slurry reinforcement, the joint grouting of mortar and double liquid slurry is more conducive to trench wall stability. The decreases in the deformation modulus of the rock-throwing layer and width of the trench section are beneficial for reducing the lateral deformation of the soil on the trench wall. Under too much weight of mud, the horizontal displacement of the soil on the trench wall presents an “inverted S-shaped” curve with the increasing depth, which means that lateral deformation of the soil on the trench wall will occur near the bottom of the trench section.
Analysis of effect of grouting micro⁃pile strengthening subgrade based on heterogeneous layer model
ZHOU Ke, LEI Jinsheng, LIU Jinxin, LIU Wanchun, SHI Zhiqiang, and DANG Runmeng
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.002
In view of subgrade sedimentation and other hazard control problems of road subgrade diseases, this paper considered the spatial heterogeneity of soil parameters of subgrade with diseases and analyzed the characteristics of grouting micro⁃pile strengthening subgrade. Meanwhile, based on the stochastic fractal search algorithm, it generated a random distribution profile of voidage, elastic modulus, and permeability coefficient, built a heterogeneous formation model, and simulated grouting diffusion in the subgrade. According to the calculation results of grouting diffusion, the effect of grouting micro-piles on strengthening subgrade was analyzed. The results show that due to the uneven distribution of geophysical parameters, the diffusion boundary and solidification area of the grouting slurry are irregularly distributed. Filling the soil pores around the pile with slurry, and conducting hardening and cementing to form a stone body can significantly improve the physical and mechanical properties of the soil around the piles, and increase the frictional resistance at the pile side and resistance at the pile end. Additionally, the subgrade strengthened by grouting micro-piles significantly reduces displacement and sedimentation under load, and the bearing capacity of the subgrade is significantly improved after strengthening.
Numerical simulation of slope reinforcement effect with inclined and vertical piles under overloading at slope top
CHEN Emei, LI Hongshun, YAN Zongsong, MIN Jiangang, ZHANG Lei, YANG Xufeng, and WANG Chuangye
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.003
To study the effect of reinforcing slopes with inclined piles under the action of overload at the slope top, this paper adopted Flac3D to build a numerical analysis model, with the interaction between piles and soil considered. Meanwhile, based on the strength reduction method, it explored the influence of the pile inclination and position on slope stability, and compared and analyzed the differences in horizontal displacement and bending moment changes between inclined piles and vertical piles under overload at the slope top. The results indicate that as the inclination of the "negative inclination" anti-slide pile increases, the slope's safety factor rises, while the horizontal displacement and bending moment decrease. The variation rules of horizontal displacement and bending moment of the "negative inclination" anti-slide pile with the pile depth are consistent with those of the vertical pile. The horizontal displacement decreases with the increasing depth and increases with the rising overload at the slope top, with the maximum growth rate at the pile top. The bending moment of the pile increases first and then decreases along the pile length, with the maximum bending moment occurring around 0.58L (L is pile length). In practical engineering, the anti-slide piles can be set as a "negative inclination" slope to enhance bending resistance, and the effect of setting the pile in the upper part of the slope is better.
Cofferdam deformation monitoring and soft foundation treatment for hydraulic reclamation artificial island
KUANG Yicheng, YANG Kaibo, YIN Pingbao, and WANG Jie
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.004
The artificial island of the western anchorage of Lingdingyang Bridge in Shenzhen-Zhongshan Link adopts a flexible geotextile cofferdam for temporary island construction, which is relatively rare in offshore land reclamation projects. Therefore, it is urgent to carry out on-site monitoring tests to analyze the stability of this approach. The artificial island employs waterborne cement mixing piles and geotextile to construct a cofferdam, the foundation is treated by preloading and plastic drainage plates, and the island foundation is treated with waterborne cement mixing piles for soft foundation. In the artificial island of the western anchorage, the on-site monitoring results of the sedimentation and deep horizontal displacement of the cofferdam in the foundation treatment area treated by plastic drainage plates show that after adopting the plastic drainage plates for foundation treatment, the sedimentation and sedimentation rate in this area significantly increase. The monitoring time is 265 d in total and the maximum sedimentation of the foundation during this period is 2194 mm. In the area treated by waterborne cement mixing piles where the maximum foundation sedimentation is about 195 mm, the sedimentation rate is significantly lower than that of the area treated by plastic drainage plates. The horizontal displacement of the deep cofferdam and the cumulative horizontal displacement of the original mud surface at the front end both remain stable. The cofferdam shifts outward in all directions, with maximum cumulative horizontal displacement of 330 mm. During the construction process, the artificial island of the western anchorage is basically in a stable state, indicating that the utilization of flexible geotextile cofferdams can help effectively carry out offshore artificial island filling and ensure the stability.
Numerical simulation analysis of one⁃side stacking effects for piles in karst area
MIN Jiangang, GU Honglin, DU Peng, XU Lei, WU Shunyuan, and NING Yuehu
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.005
Single-side loading of pile foundations in karst areas may cause ground subsidence, lateral displacement of piles, and even engineering accidents. Revealing the loading effect is beneficial for maintaining pile safety and guiding engineering decisions. This paper employed Abaqus to build a model for pile-soil interaction in karst areas and reveal the single-side loading effect of pile foundations in karst areas, thus providing a basis for pile foundation design and single-side loading decision-making in karst areas. The results show that under the action of single-side loading, the sedimentation and lateral displacement at the pile top increase with the rising single-side loading. Under the same single-side loading capacity, the pile top sedimentation, peak lateral displacement, and peak bending moment of the soil layer pile decrease with the growing loading distance. The lateral displacement at the pile top, peak soil pressure before and after the pile, and peak axial force of the pile decrease exponentially with the increasing loading distance. As the loading distance increases, the p-y curve becomes easier to converge. Under the loading distance of less than 4 m, the most dangerous section is at 1/4 and 1/2 of the soil depth, while under the loading distance more than 4 m, the most dangerous section is at the soil rock interface. The influence of karst caves of the pile on the pile top sedimentation, lateral displacement, internal force, soil pressure before and after the pile, and p-y curve of socketed piles is not significant.
Experimental study on drainage performance of new drainage pipe in seepage ditch structures
WANG Gang, ZOU Jingrong, LI Jiayi, and SUN Yikai
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.006
At present, geotextile-wrapped PVC drainage pipes with holes and filled with crushed stones (gravel) inside are the most commonly employed seepage ditch structure in most highway subgrade projects. This kind of structure has sound drainage effect in the early stage of utilization, but once the wrapped geotextile is damaged, this can easily cause the drainage pipe to be blocked or even the entire seepage ditch to fail. To improve the drainage life of the seepage ditch, this paper carried out a new type of seepage ditch structure test indoors for six months, and then compared the drainage performance of three types of drainage pipes, including the plastic blind ditch, hard permeable pipe, and perforated PVC pipe, under different seepage ditch filling structures. Additionally, the variation law of the seepage ditch's drainage performance of different pipe materials under different reversed filters and water pressure conditions was systematically studied. The results show that when the reversed filter is made of medium coarse sand, the drainage efficiency of several drainage pipes is slightly higher than that of using gravel as the reversed filter. Among the three types of drainage pipe, the plastic blind ditch has the optimal drainage effect in two types of seepage ditch structures, with the drainage efficiency more than twice that of perforated PVC pipes. The plastic blind ditch filled with medium coarse sand as a reversed filter in the seepage ditch structure can significantly improve the drainage efficiency of the seepage ditch.
Finite element analysis of interface between new structure and old subgrade in pile slab structure
CHEN Jun, WAN Shui, FU Lixiang, and XU Haotian
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.007
Based on the design of the pile-slab structures in highway reconstruction and expansion projects, this paper built a finite element numerical simulation model, which includes multiple parts such as pile-slab structures, cast-in-place sections, transverse slabs, old subgrade, and soil. Meanwhile, it adopted Ansys surface-surface contact to simulate the overlap between the new structure and the old subgrade. By conducting finite element simulation, this paper systematically studied the changes in contact normal stress, friction normal stress, and deformation between the contact surfaces of pile-slab structures in different working conditions for single, double, and four vehicles. The results show that under the arrangement of four vehicles, the normal stress and friction stress of the structural contact surface are both the highest, and in the working condition of 23 (constant load+distance of 6.05 m between the outermost wheel and the cantilever end of the bearing plate), the globally most unfavorable stress situation occurs. At this time, the maximum contact normal stress is 302.936 kPa and the maximum contact friction stress is 90.881 kPa. Additionally, in the working condition of 24, the maximum horizontal gaps between the side of the cast-in-place section and the old subgrade, and between the bottom of the cast-in-place section and the soil are 0.731 mm, with the maximum vertical gap of 0.043 mm. The most unfavorable situation for the horizontalgap of the transverse slab is in the working condition of 25, with a gap of 0.273 mm. The most unfavorable situation for the vertical gap of the transverse slab is in the working condition of 7, with a gap of 0.203 mm.
Analysis of stability of trench formation and effect of ground deformation of ground⁃connected wall in rock⁃throwing reclamation area
BAO Xiaohua, PAN Jihao, CUI Hongzhi, WAN Bo, and ZHOU Zhen
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.001
By studying the construction process of ground-connected wall slurry trenches in the rock-throwing reclamation areas, this paper explored the effects of such factors as trench section width, weight of the slurry trench, parameters of the rock-throwing layer, the reinforcement zone range of the trench wall, and grouting parameters on the stability of the trench wall and the disturbance of the surrounding strata. Meanwhile, it measured the deformation modulus of the grouting reinforcement zone by experiments, and obtained the shear strength parameters from empirical formulas. The ground deformation characteristics induced by the construction of ground-connected wall in rock-throwing reclamation areas under different grouting reinforcement schemes were calculated and analyzed via the finite element method. The calculation results indicate that the maximum lateral displacement of the soil on the trench wall occurs at 1/3 to 1/2 of the trench section depth. Reinforcing the surrounding strata of the trench wall via grouting can reduce the trench wall’s lateral deformation and surface settlement. Additionally, compared to single slurry reinforcement, the joint grouting of mortar and double liquid slurry is more conducive to trench wall stability. The decreases in the deformation modulus of the rock-throwing layer and width of the trench section are beneficial for reducing the lateral deformation of the soil on the trench wall. Under too much weight of mud, the horizontal displacement of the soil on the trench wall presents an “inverted S-shaped” curve with the increasing depth, which means that lateral deformation of the soil on the trench wall will occur near the bottom of the trench section.
Analysis of effect of grouting micro⁃pile strengthening subgrade based on heterogeneous layer model
ZHOU Ke, LEI Jinsheng, LIU Jinxin, LIU Wanchun, SHI Zhiqiang, and DANG Runmeng
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.002
In view of subgrade sedimentation and other hazard control problems of road subgrade diseases, this paper considered the spatial heterogeneity of soil parameters of subgrade with diseases and analyzed the characteristics of grouting micro⁃pile strengthening subgrade. Meanwhile, based on the stochastic fractal search algorithm, it generated a random distribution profile of voidage, elastic modulus, and permeability coefficient, built a heterogeneous formation model, and simulated grouting diffusion in the subgrade. According to the calculation results of grouting diffusion, the effect of grouting micro-piles on strengthening subgrade was analyzed. The results show that due to the uneven distribution of geophysical parameters, the diffusion boundary and solidification area of the grouting slurry are irregularly distributed. Filling the soil pores around the pile with slurry, and conducting hardening and cementing to form a stone body can significantly improve the physical and mechanical properties of the soil around the piles, and increase the frictional resistance at the pile side and resistance at the pile end. Additionally, the subgrade strengthened by grouting micro-piles significantly reduces displacement and sedimentation under load, and the bearing capacity of the subgrade is significantly improved after strengthening.
Numerical simulation of slope reinforcement effect with inclined and vertical piles under overloading at slope top
CHEN Emei, LI Hongshun, YAN Zongsong, MIN Jiangang, ZHANG Lei, YANG Xufeng, and WANG Chuangye
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.003
To study the effect of reinforcing slopes with inclined piles under the action of overload at the slope top, this paper adopted Flac3D to build a numerical analysis model, with the interaction between piles and soil considered. Meanwhile, based on the strength reduction method, it explored the influence of the pile inclination and position on slope stability, and compared and analyzed the differences in horizontal displacement and bending moment changes between inclined piles and vertical piles under overload at the slope top. The results indicate that as the inclination of the "negative inclination" anti-slide pile increases, the slope's safety factor rises, while the horizontal displacement and bending moment decrease. The variation rules of horizontal displacement and bending moment of the "negative inclination" anti-slide pile with the pile depth are consistent with those of the vertical pile. The horizontal displacement decreases with the increasing depth and increases with the rising overload at the slope top, with the maximum growth rate at the pile top. The bending moment of the pile increases first and then decreases along the pile length, with the maximum bending moment occurring around 0.58L (L is pile length). In practical engineering, the anti-slide piles can be set as a "negative inclination" slope to enhance bending resistance, and the effect of setting the pile in the upper part of the slope is better.
Cofferdam deformation monitoring and soft foundation treatment for hydraulic reclamation artificial island
KUANG Yicheng, YANG Kaibo, YIN Pingbao, and WANG Jie
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.004
The artificial island of the western anchorage of Lingdingyang Bridge in Shenzhen-Zhongshan Link adopts a flexible geotextile cofferdam for temporary island construction, which is relatively rare in offshore land reclamation projects. Therefore, it is urgent to carry out on-site monitoring tests to analyze the stability of this approach. The artificial island employs waterborne cement mixing piles and geotextile to construct a cofferdam, the foundation is treated by preloading and plastic drainage plates, and the island foundation is treated with waterborne cement mixing piles for soft foundation. In the artificial island of the western anchorage, the on-site monitoring results of the sedimentation and deep horizontal displacement of the cofferdam in the foundation treatment area treated by plastic drainage plates show that after adopting the plastic drainage plates for foundation treatment, the sedimentation and sedimentation rate in this area significantly increase. The monitoring time is 265 d in total and the maximum sedimentation of the foundation during this period is 2194 mm. In the area treated by waterborne cement mixing piles where the maximum foundation sedimentation is about 195 mm, the sedimentation rate is significantly lower than that of the area treated by plastic drainage plates. The horizontal displacement of the deep cofferdam and the cumulative horizontal displacement of the original mud surface at the front end both remain stable. The cofferdam shifts outward in all directions, with maximum cumulative horizontal displacement of 330 mm. During the construction process, the artificial island of the western anchorage is basically in a stable state, indicating that the utilization of flexible geotextile cofferdams can help effectively carry out offshore artificial island filling and ensure the stability.
Numerical simulation analysis of one⁃side stacking effects for piles in karst area
MIN Jiangang, GU Honglin, DU Peng, XU Lei, WU Shunyuan, and NING Yuehu
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.005
Single-side loading of pile foundations in karst areas may cause ground subsidence, lateral displacement of piles, and even engineering accidents. Revealing the loading effect is beneficial for maintaining pile safety and guiding engineering decisions. This paper employed Abaqus to build a model for pile-soil interaction in karst areas and reveal the single-side loading effect of pile foundations in karst areas, thus providing a basis for pile foundation design and single-side loading decision-making in karst areas. The results show that under the action of single-side loading, the sedimentation and lateral displacement at the pile top increase with the rising single-side loading. Under the same single-side loading capacity, the pile top sedimentation, peak lateral displacement, and peak bending moment of the soil layer pile decrease with the growing loading distance. The lateral displacement at the pile top, peak soil pressure before and after the pile, and peak axial force of the pile decrease exponentially with the increasing loading distance. As the loading distance increases, the p-y curve becomes easier to converge. Under the loading distance of less than 4 m, the most dangerous section is at 1/4 and 1/2 of the soil depth, while under the loading distance more than 4 m, the most dangerous section is at the soil rock interface. The influence of karst caves of the pile on the pile top sedimentation, lateral displacement, internal force, soil pressure before and after the pile, and p-y curve of socketed piles is not significant.
Experimental study on drainage performance of new drainage pipe in seepage ditch structures
WANG Gang, ZOU Jingrong, LI Jiayi, and SUN Yikai
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.006
At present, geotextile-wrapped PVC drainage pipes with holes and filled with crushed stones (gravel) inside are the most commonly employed seepage ditch structure in most highway subgrade projects. This kind of structure has sound drainage effect in the early stage of utilization, but once the wrapped geotextile is damaged, this can easily cause the drainage pipe to be blocked or even the entire seepage ditch to fail. To improve the drainage life of the seepage ditch, this paper carried out a new type of seepage ditch structure test indoors for six months, and then compared the drainage performance of three types of drainage pipes, including the plastic blind ditch, hard permeable pipe, and perforated PVC pipe, under different seepage ditch filling structures. Additionally, the variation law of the seepage ditch's drainage performance of different pipe materials under different reversed filters and water pressure conditions was systematically studied. The results show that when the reversed filter is made of medium coarse sand, the drainage efficiency of several drainage pipes is slightly higher than that of using gravel as the reversed filter. Among the three types of drainage pipe, the plastic blind ditch has the optimal drainage effect in two types of seepage ditch structures, with the drainage efficiency more than twice that of perforated PVC pipes. The plastic blind ditch filled with medium coarse sand as a reversed filter in the seepage ditch structure can significantly improve the drainage efficiency of the seepage ditch.
Finite element analysis of interface between new structure and old subgrade in pile slab structure
CHEN Jun, WAN Shui, FU Lixiang, and XU Haotian
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.007
Based on the design of the pile-slab structures in highway reconstruction and expansion projects, this paper built a finite element numerical simulation model, which includes multiple parts such as pile-slab structures, cast-in-place sections, transverse slabs, old subgrade, and soil. Meanwhile, it adopted Ansys surface-surface contact to simulate the overlap between the new structure and the old subgrade. By conducting finite element simulation, this paper systematically studied the changes in contact normal stress, friction normal stress, and deformation between the contact surfaces of pile-slab structures in different working conditions for single, double, and four vehicles. The results show that under the arrangement of four vehicles, the normal stress and friction stress of the structural contact surface are both the highest, and in the working condition of 23 (constant load+distance of 6.05 m between the outermost wheel and the cantilever end of the bearing plate), the globally most unfavorable stress situation occurs. At this time, the maximum contact normal stress is 302.936 kPa and the maximum contact friction stress is 90.881 kPa. Additionally, in the working condition of 24, the maximum horizontal gaps between the side of the cast-in-place section and the old subgrade, and between the bottom of the cast-in-place section and the soil are 0.731 mm, with the maximum vertical gap of 0.043 mm. The most unfavorable situation for the horizontalgap of the transverse slab is in the working condition of 25, with a gap of 0.273 mm. The most unfavorable situation for the vertical gap of the transverse slab is in the working condition of 7, with a gap of 0.203 mm.
Pavement Engineering
Non⁃contact detection technology of pavement skid resistance based on three⁃dimensional laser imaging
TANG Mingyou, HE Xianlin, LIU Zhiming, LAI Beibei, WANG Bing, and ZHAN You
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.008
To address the shortcomings of existing testing methods for anti-skid performance of asphalt pavement and friction prediction models, this paper adopted a non-contact measurement method for data collection and proposed a non-contact testing technology for anti-skid performance based on 3D laser imaging. It mainly analyzed the three-dimensional data of asphalt pavement collected by the LS-40 portable three-dimensional laser surface analyzer. Meanwhile, Fourier transform and high-low pass filters were employed to separate the macro and micro textures, and eight indicators were proposed for the separated macro and micro texture data. The indicators include mean profile depth (DMPD), height average (HA), root mean square (RRMS), skewness (Rsk), kurtosis (Rku), two points slope variance (V2pts), mean peak-to-valley height (Hz (DIN)), and averaging of the double amplitudes (Da). Finally, the indicators were combined with temperature and BPN data measured by a pendulum friction meter for model training. A total of 336 sets of data were collected, with 75% of the sample data adopted for random forest model training and 25% for testing. Finally, the R2 values of the training set and testing set reached 0.92 and 0.77 respectively. Importance analysis indicates that temperature and the traditional DMPD indicator are key factors affecting the friction prediction model, and the model's prediction accuracy is improved with both the macro and micro textures considered.
Structural stress analysis of small⁃size cement concrete slab in village
XIA Zhihao, BAI Tao, and LI Chaoyuan
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.009
To save funds for rural road construction and alleviate huge financial pressure on highway construction, this paper conducted a study on the stress of economic small-size cement concrete slab pavement structures. By carrying out finite element stress calculation and combining the fatigue equation of cement concrete, regression was conducted on the axial load conversion index, and the influence of factors such as the slab size and pavement structure on the structural stress was studied. The results reveal that the conversion factor for the single axle and single wheel in thinner pavement structures is higher than the standard value, while that for the single axle and double wheels is similar to the standard value. Compared to traditional large-size slabs, small-size slabs have reduced various stress, which is more conducive to structural stress. In highway construction, the utilization of small-size single-layer cement slab pavement structures is optimal, which is beneficial for highway construction under financial constraints.
Clean construction assessment of in⁃situ thermal recycling of asphalt pavement
GUO Xiaohong, Deng Li, and Zhou Mingxu
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.010
To facilitate decision-makers to grasp the technical level and environmental influence of different in-situ thermal recycling units during construction, this paper proposed an evaluation method for in-situ thermal recycling and clean construction of asphalt pavement based on the game theory combination weighting and matter-element extension model. Firstly, based on the construction technology level and environment, a comprehensive analysis of in-situ thermal recycling construction was conducted, with the clean construction concept proposed. Meanwhile, the literature query and field research were adopted to construct an evaluation index system for clean construction. Secondly, to ensure the scientific rationality of the evaluation process, this paper introduced game theory into the hierarchy entropy to comprehensively determine the weight, and adopted an improved matter-element extension model to calculate the cleanliness level of different in-situ thermal recycling construction technologies. Finally, a comprehensive analysis was conducted and relevant suggestions were provided. By taking the preventive maintenance project of asphalt pavement in Chaohu City (in-situ thermal recycling technology) as an example, the cleanliness level of multiple schemes was evaluated and compared. The results show that the cleanliness level of the hot air circulation heating technology construction scheme was level I, which both ensures construction quality and conforms to the green development concept.
Study on correlation between surface and base cracks of expressways in winter cold region
WANG Yuan, JIA Qinlong, FAN Xiaoyan, XUE Honghua, and ZHANG Wentao
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.011
To accurately control the crack diseases of semi-rigid base pavement structures in cold regions, this paper applied the theory of mathematical statistical analysis to investigate and statistically analyze the 66 km pavement crack data of two highways. Meanwhile, data analysis was adopted to study the correlation between surface cracks and base cracks, and the prevention and control effect of asphalt-stabilized cobble replacement on cracks in the original 20 m/lane pre-cut cracks and damaged base was analyzed. The results show that the pavement structure consists of a 16 cm asphalt surface layer and a 36 cm cement-stabilized cobble base layer. The proportion of reflection cracks in the surface transverse cracks is 76%, while that of longitudinal cracks that penetrate the base layer in the surface longitudinal cracks is 14%. The longitudinal crack diseases are more likely to occur along the wheel track direction on both sides of the base layer transverse cracks, and continue to propagate along the tip of the longitudinal cracks. The pavement structure consists of a 12 cm asphalt surface layer and a 20 cm cement-stabilized cobble base layer, with transverse cracks in the surface layer and longitudinal cracks in the base layer corresponding one by one. Additionally, 53% of the pre-cut cracks in the semi-rigid base layers will reflect to the surface layers, forming transverse cracks in the surface layers. Replacing damaged base layers with asphalt-stabilized cobble can prevent the propagation of crack tips in the base layers and eliminate reflection crack diseases.
Detection method and acc uracy analysis of asphalt pavement surface texture
CHEN Zhanquan
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.012
To accurately determine the surface texture information of asphalt pavement, this paper adopted the Florida texture meter (FTM) to detect the mean profile depth (DMPD) of 12 asphalt pavements. Based on the detected DMPD data, the FTM accuracy was analyzed, with the influencing factors of FTM measurement data explored. On this basis, FTM's reliability in measuring the surface texture information of asphalt pavement was further verified by comparing the data measured by FTM and the circular track meter (CTM). The results show that FTM can effectively detect the surface texture information of asphalt pavement, and DMPD can be rapidly measured by employing FTM. There is high correlation in the results obtained by FTM and CTM, and the FTM test results can serve as a reliable basis for characterizing the skid resistance performance of asphalt pavement. Additionally, the testing location, gradation type, and aggregate type have a significant influence on the surface texture of the tested road.
Non⁃contact detection technology of pavement skid resistance based on three⁃dimensional laser imaging
TANG Mingyou, HE Xianlin, LIU Zhiming, LAI Beibei, WANG Bing, and ZHAN You
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.008
To address the shortcomings of existing testing methods for anti-skid performance of asphalt pavement and friction prediction models, this paper adopted a non-contact measurement method for data collection and proposed a non-contact testing technology for anti-skid performance based on 3D laser imaging. It mainly analyzed the three-dimensional data of asphalt pavement collected by the LS-40 portable three-dimensional laser surface analyzer. Meanwhile, Fourier transform and high-low pass filters were employed to separate the macro and micro textures, and eight indicators were proposed for the separated macro and micro texture data. The indicators include mean profile depth (DMPD), height average (HA), root mean square (RRMS), skewness (Rsk), kurtosis (Rku), two points slope variance (V2pts), mean peak-to-valley height (Hz (DIN)), and averaging of the double amplitudes (Da). Finally, the indicators were combined with temperature and BPN data measured by a pendulum friction meter for model training. A total of 336 sets of data were collected, with 75% of the sample data adopted for random forest model training and 25% for testing. Finally, the R2 values of the training set and testing set reached 0.92 and 0.77 respectively. Importance analysis indicates that temperature and the traditional DMPD indicator are key factors affecting the friction prediction model, and the model's prediction accuracy is improved with both the macro and micro textures considered.
Structural stress analysis of small⁃size cement concrete slab in village
XIA Zhihao, BAI Tao, and LI Chaoyuan
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.009
To save funds for rural road construction and alleviate huge financial pressure on highway construction, this paper conducted a study on the stress of economic small-size cement concrete slab pavement structures. By carrying out finite element stress calculation and combining the fatigue equation of cement concrete, regression was conducted on the axial load conversion index, and the influence of factors such as the slab size and pavement structure on the structural stress was studied. The results reveal that the conversion factor for the single axle and single wheel in thinner pavement structures is higher than the standard value, while that for the single axle and double wheels is similar to the standard value. Compared to traditional large-size slabs, small-size slabs have reduced various stress, which is more conducive to structural stress. In highway construction, the utilization of small-size single-layer cement slab pavement structures is optimal, which is beneficial for highway construction under financial constraints.
Clean construction assessment of in⁃situ thermal recycling of asphalt pavement
GUO Xiaohong, Deng Li, and Zhou Mingxu
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.010
To facilitate decision-makers to grasp the technical level and environmental influence of different in-situ thermal recycling units during construction, this paper proposed an evaluation method for in-situ thermal recycling and clean construction of asphalt pavement based on the game theory combination weighting and matter-element extension model. Firstly, based on the construction technology level and environment, a comprehensive analysis of in-situ thermal recycling construction was conducted, with the clean construction concept proposed. Meanwhile, the literature query and field research were adopted to construct an evaluation index system for clean construction. Secondly, to ensure the scientific rationality of the evaluation process, this paper introduced game theory into the hierarchy entropy to comprehensively determine the weight, and adopted an improved matter-element extension model to calculate the cleanliness level of different in-situ thermal recycling construction technologies. Finally, a comprehensive analysis was conducted and relevant suggestions were provided. By taking the preventive maintenance project of asphalt pavement in Chaohu City (in-situ thermal recycling technology) as an example, the cleanliness level of multiple schemes was evaluated and compared. The results show that the cleanliness level of the hot air circulation heating technology construction scheme was level I, which both ensures construction quality and conforms to the green development concept.
Study on correlation between surface and base cracks of expressways in winter cold region
WANG Yuan, JIA Qinlong, FAN Xiaoyan, XUE Honghua, and ZHANG Wentao
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.011
To accurately control the crack diseases of semi-rigid base pavement structures in cold regions, this paper applied the theory of mathematical statistical analysis to investigate and statistically analyze the 66 km pavement crack data of two highways. Meanwhile, data analysis was adopted to study the correlation between surface cracks and base cracks, and the prevention and control effect of asphalt-stabilized cobble replacement on cracks in the original 20 m/lane pre-cut cracks and damaged base was analyzed. The results show that the pavement structure consists of a 16 cm asphalt surface layer and a 36 cm cement-stabilized cobble base layer. The proportion of reflection cracks in the surface transverse cracks is 76%, while that of longitudinal cracks that penetrate the base layer in the surface longitudinal cracks is 14%. The longitudinal crack diseases are more likely to occur along the wheel track direction on both sides of the base layer transverse cracks, and continue to propagate along the tip of the longitudinal cracks. The pavement structure consists of a 12 cm asphalt surface layer and a 20 cm cement-stabilized cobble base layer, with transverse cracks in the surface layer and longitudinal cracks in the base layer corresponding one by one. Additionally, 53% of the pre-cut cracks in the semi-rigid base layers will reflect to the surface layers, forming transverse cracks in the surface layers. Replacing damaged base layers with asphalt-stabilized cobble can prevent the propagation of crack tips in the base layers and eliminate reflection crack diseases.
Detection method and acc uracy analysis of asphalt pavement surface texture
CHEN Zhanquan
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.012
To accurately determine the surface texture information of asphalt pavement, this paper adopted the Florida texture meter (FTM) to detect the mean profile depth (DMPD) of 12 asphalt pavements. Based on the detected DMPD data, the FTM accuracy was analyzed, with the influencing factors of FTM measurement data explored. On this basis, FTM's reliability in measuring the surface texture information of asphalt pavement was further verified by comparing the data measured by FTM and the circular track meter (CTM). The results show that FTM can effectively detect the surface texture information of asphalt pavement, and DMPD can be rapidly measured by employing FTM. There is high correlation in the results obtained by FTM and CTM, and the FTM test results can serve as a reliable basis for characterizing the skid resistance performance of asphalt pavement. Additionally, the testing location, gradation type, and aggregate type have a significant influence on the surface texture of the tested road.
Non⁃contact detection technology of pavement skid resistance based on three⁃dimensional laser imaging
TANG Mingyou, HE Xianlin, LIU Zhiming, LAI Beibei, WANG Bing, and ZHAN You
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.008
To address the shortcomings of existing testing methods for anti-skid performance of asphalt pavement and friction prediction models, this paper adopted a non-contact measurement method for data collection and proposed a non-contact testing technology for anti-skid performance based on 3D laser imaging. It mainly analyzed the three-dimensional data of asphalt pavement collected by the LS-40 portable three-dimensional laser surface analyzer. Meanwhile, Fourier transform and high-low pass filters were employed to separate the macro and micro textures, and eight indicators were proposed for the separated macro and micro texture data. The indicators include mean profile depth (DMPD), height average (HA), root mean square (RRMS), skewness (Rsk), kurtosis (Rku), two points slope variance (V2pts), mean peak-to-valley height (Hz (DIN)), and averaging of the double amplitudes (Da). Finally, the indicators were combined with temperature and BPN data measured by a pendulum friction meter for model training. A total of 336 sets of data were collected, with 75% of the sample data adopted for random forest model training and 25% for testing. Finally, the R2 values of the training set and testing set reached 0.92 and 0.77 respectively. Importance analysis indicates that temperature and the traditional DMPD indicator are key factors affecting the friction prediction model, and the model's prediction accuracy is improved with both the macro and micro textures considered.
Structural stress analysis of small⁃size cement concrete slab in village
XIA Zhihao, BAI Tao, and LI Chaoyuan
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.009
To save funds for rural road construction and alleviate huge financial pressure on highway construction, this paper conducted a study on the stress of economic small-size cement concrete slab pavement structures. By carrying out finite element stress calculation and combining the fatigue equation of cement concrete, regression was conducted on the axial load conversion index, and the influence of factors such as the slab size and pavement structure on the structural stress was studied. The results reveal that the conversion factor for the single axle and single wheel in thinner pavement structures is higher than the standard value, while that for the single axle and double wheels is similar to the standard value. Compared to traditional large-size slabs, small-size slabs have reduced various stress, which is more conducive to structural stress. In highway construction, the utilization of small-size single-layer cement slab pavement structures is optimal, which is beneficial for highway construction under financial constraints.
Clean construction assessment of in⁃situ thermal recycling of asphalt pavement
GUO Xiaohong, Deng Li, and Zhou Mingxu
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.010
To facilitate decision-makers to grasp the technical level and environmental influence of different in-situ thermal recycling units during construction, this paper proposed an evaluation method for in-situ thermal recycling and clean construction of asphalt pavement based on the game theory combination weighting and matter-element extension model. Firstly, based on the construction technology level and environment, a comprehensive analysis of in-situ thermal recycling construction was conducted, with the clean construction concept proposed. Meanwhile, the literature query and field research were adopted to construct an evaluation index system for clean construction. Secondly, to ensure the scientific rationality of the evaluation process, this paper introduced game theory into the hierarchy entropy to comprehensively determine the weight, and adopted an improved matter-element extension model to calculate the cleanliness level of different in-situ thermal recycling construction technologies. Finally, a comprehensive analysis was conducted and relevant suggestions were provided. By taking the preventive maintenance project of asphalt pavement in Chaohu City (in-situ thermal recycling technology) as an example, the cleanliness level of multiple schemes was evaluated and compared. The results show that the cleanliness level of the hot air circulation heating technology construction scheme was level I, which both ensures construction quality and conforms to the green development concept.
Study on correlation between surface and base cracks of expressways in winter cold region
WANG Yuan, JIA Qinlong, FAN Xiaoyan, XUE Honghua, and ZHANG Wentao
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.011
To accurately control the crack diseases of semi-rigid base pavement structures in cold regions, this paper applied the theory of mathematical statistical analysis to investigate and statistically analyze the 66 km pavement crack data of two highways. Meanwhile, data analysis was adopted to study the correlation between surface cracks and base cracks, and the prevention and control effect of asphalt-stabilized cobble replacement on cracks in the original 20 m/lane pre-cut cracks and damaged base was analyzed. The results show that the pavement structure consists of a 16 cm asphalt surface layer and a 36 cm cement-stabilized cobble base layer. The proportion of reflection cracks in the surface transverse cracks is 76%, while that of longitudinal cracks that penetrate the base layer in the surface longitudinal cracks is 14%. The longitudinal crack diseases are more likely to occur along the wheel track direction on both sides of the base layer transverse cracks, and continue to propagate along the tip of the longitudinal cracks. The pavement structure consists of a 12 cm asphalt surface layer and a 20 cm cement-stabilized cobble base layer, with transverse cracks in the surface layer and longitudinal cracks in the base layer corresponding one by one. Additionally, 53% of the pre-cut cracks in the semi-rigid base layers will reflect to the surface layers, forming transverse cracks in the surface layers. Replacing damaged base layers with asphalt-stabilized cobble can prevent the propagation of crack tips in the base layers and eliminate reflection crack diseases.
Detection method and acc uracy analysis of asphalt pavement surface texture
CHEN Zhanquan
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.012
To accurately determine the surface texture information of asphalt pavement, this paper adopted the Florida texture meter (FTM) to detect the mean profile depth (DMPD) of 12 asphalt pavements. Based on the detected DMPD data, the FTM accuracy was analyzed, with the influencing factors of FTM measurement data explored. On this basis, FTM's reliability in measuring the surface texture information of asphalt pavement was further verified by comparing the data measured by FTM and the circular track meter (CTM). The results show that FTM can effectively detect the surface texture information of asphalt pavement, and DMPD can be rapidly measured by employing FTM. There is high correlation in the results obtained by FTM and CTM, and the FTM test results can serve as a reliable basis for characterizing the skid resistance performance of asphalt pavement. Additionally, the testing location, gradation type, and aggregate type have a significant influence on the surface texture of the tested road.
Bridge Engineering & Tunnel Engineering
Study on temperature gradient effect of corrugated steel web box girder considering influence of boundary conditions
LEI Yao, LI Ming, LU Naiwei, and LIU Yang
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.013
To study the stress characteristics of corrugated steel web box girders under vertical temperature gradient loads, this paper employed the civil structural nonlinear simulation software Midas FEA to build a three-dimensional finite element analysis model of corrugated steel web box girder bridges. Meanwhile, the temperature effects of corrugated steel web box girders under two constraint conditions of simply supported structures and continuous structures under vertical temperature gradient loads were compared and analyzed. The results demonstrate that under vertical temperature gradient loads, the temperature effect generated by corrugated steel web box girders is significant and cannot be ignored. The temperature effect of corrugated steel web box girders under continuous structural constraints is more significant than that of the simply supported structures under temperature gradient loads. Therefore, the influence of boundary constraint conditions on the temperature effect of corrugated steel web box girder bridges should be comprehensively considered. Additionally, the maximum temperature stress is obtained at the connection joint between the top and bottom concrete and the corrugated steel web, and the peak stress of this structure should be given special attention during the design stage.
Research on parameters of bridge moving vehicles load based on WOA⁃BP neural network
WANG Xiaohui, ZHANG Bangru, TAO Zhiren, CHI Xinyan, WAN Lixing, and PENG Jianxin
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.014
To efficiently and accurately identify the moving load parameters on bridge structures, this paper proposed a layered identification method for moving loads on bridges using BP neural networks based on the whale optimization algorithm (WOA), and built a moving load parameter identification model based on WOA-BP neural networks. By adopting this moving load identification model, step-by-step coupling identification was conducted on the action lane, speed, and load capacity of vehicles on the bridge. Additionally, by taking a prestressed simply supported box girder bridge as the research project, the applicability of the proposed method and neural network identification model was verified via dynamic response measurement data under the action of random traffic flow and the combination of video data of vehicles driving on the bridge. The results reveal that the proposed method for identifying moving load parameters features high identification accuracy, fast convergence speed, strong robustness and noise resistance, and can accurately identify bridges' moving load parameters.
Experimental study on effect of fiber length on axial tensile properties of UHPC
YUAN Ming, HAN Huaizhi, YAN Donghuang, HUANG Lian, and ZENG Xiaojun
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.015
To study the effect of steel fiber length on the axial tensile properties of UHPC, this paper selected straight circular fiber with the same diameter but different lengths and mixed it into UHPC. By conducting analysis on the mechanical properties, tensile deformation, and post-fracture strength of UHPC, the influence of fiber length on the axial tensile properties of UHPC was obtained. Meanwhile, the fracture resistance and toughening effects of fiber length were evaluated, with the reasons for the influence of fiber length on the axial tensile properties of UHPC clarified. The results show that the axial tensile properties of UHPC increase with the rising fiber length. The effect of 20 mm fiber length on the peak UHPC stress increases by 57.76% compared to 6 mm fiber length. The post-fracture strength of UHPC grows with the increasing fiber length. Under the same fracture width and fiber length of 20 mm, the UHPC stress is the highest, and the UHPC stress is the lowest under the fiber length of 6 mm. UHPC with 20 mm fiber length mixed has the maximum deformation in the strain hardening stage, while UHPC with 13 mm fiber length has the maximum deformation in the stress softening stage. The UHPC fluidity decreases with the increasing fiber length. Additionally, the effect of fiber length on the axial tensile properties of UHPC is altered by changing the contact surface size between the fiber and the matrix. Specifically, the longer fiber leads to the larger contact surface between the fiber and the matrix, bringing about stronger cohesion between the fiber and the matrix.
Research on lightweight method of BIM model for bridge engineering based on CATIA CAA
ZHANG Yunhe, ZHU Ming, and FAN Yufeng
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.016
Highway construction projects are mostly linear projects with zonal distribution, which contain multiple structures and are closely integrated with the geographical environment. During their applications in BIM, they often face the problems of massive data delivery and multi-source heterogeneous data fusion. Therefore, based on the secondary development of CATIA CAA, this paper proposed a lightweight method for the BIM model in bridge engineering, elaborated on the general lightweight concept, and then detailed the lightweight process, with a BIM model lightweight program independently developed. By taking the Heishuihe Bridge as an example, the functionality and stability of the program were tested, and the digital delivery and application of lightweight follow-up models on the BIM platform were achieved. Finally, the results indicate that this lightweight method has certain application prospects and practical significance.
Overall design of main bridge of qingshui river bridge in Baoji
WANG Zhen, NIU Yongzhe, and LI Haipeng
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.017
The main bridge of Qingshui River Bridge is a (65+5×120+65) m continuous rigid frame bridge. The main girder adopts a combination of corrugated steel webs and concrete box girders, with double-amplitude single-box single-chamber sections. The corrugated steel webs adopt 1600 type corrugated steel plates, and are connected to the top and bottom plates respectively with double PBL shear keys and ∟200 angle steel. Longitudinal prestressed steel bars are divided into internal tendons and external tendons. The lower structure adopts double thin-walled hollow piers, bearing platforms, and bored pile foundations, with a maximum pier height of 73 m and an average pier height of 71.4 m. The main bridge adopts a cantilever cast-in-place construction scheme, and the closure sequence is respectively the edge span, central span, secondary central span, and secondary side span. The closure temperature is 10℃, and the jacking force is 500 kN for the central span, 800 kN for the secondary central span, and 1200 kN for the secondary side span. Additionally, Ansys 14.0 was adopted to analyze the torsional cross slope and warping ratio of the central span section, which reveals that the arrangement of six diaphragms is more reasonable. By comparing the most unfavorable eccentric load and symmetrical load conditions, the live load eccentric load coefficient of the corrugated steel web under stress is determined to be 1.3. Additionally, Midas/Civil 2019 was employed for longitudinal static calculation during construction and bridge completion stages, shear yielding and flexure calculation of corrugated steel webs, shear strength calculation of shear force connectors of top and bottom plates, and transverse static and antiseismic calculation of the composite girder central span, root and pier top sections. The results show that all indicators of the bridge meet the requirements of the specifications.
Error analysis of relative angle at the central⁃span closure of long⁃span composite girder cable⁃stayed bridges
TU Guanya and ZHOU Chengyong
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.018
According to the theory of the non-stress state method, the elastic curve of the main girder during the central-span closure should remain continuous to ensure that the internal forces and alignment of the built cable-stayed bridge reach the target state after construction, which means the relative angle of the main girders on both sides of the closure should be zero. However, it is difficult to meet the condition of absolute zero of the relative angle in practical engineering. By taking the Chibi Changjiang River Highway Bridge as the engineering background, this paper studied the influence of relative angle error during the central-span closure of a large-span composite girder cable-stayed bridge on the final target state of the built bridge, thus determining the allowable range of relative angle error. The analysis results reveal that the relative angle error of the main girders on both sides of the closure gap during the central-span closure mainly has a significant influence on the stress of the main girders under the target state of the built bridge, with little effect exerted on tower deviation, cable force, and main girder alignment. For the Chibi Changjiang River Highway Bridge, the allowable relative angle error of the main girders on both sides of the closure can be set as ±1×10-3 rad during the central-span closure. Within this range, it can be considered that the elastic curves of the main girders on both sides of the closure are continuous.
Research on comprehensive early warning system with multi⁃indicators for long⁃span steel arch bridges
ZHANG Yuanchuan, SU Cheng, WANG Yonghui, and ZHENG Chun
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.019
To detect structural abnormalities timely and ensure the safe operation of bridges, this paper took the health monitoring system of Xinguang Bridge in Guangzhou as the engineering background, and conducted research on a comprehensive multi-indicator early warning system for large-span steel arch bridges. Meanwhile, it selected multiple warning indicators from the categories of environmental effects and structural responses, set early warning indicator thresholds based on the distribution pattern of measured data, and formulated scoring standards for early warning indicators to score each early warning indicator. The analytic hierarchy process (AHP) was employed to determine the weight of various early warning indicators, and calculate the comprehensive early warning scores for environmental effects and structural responses, thus obtaining the comprehensive early warning level for environmental effects and structural response. In addition, a comprehensive early warning matrix for the structure was constructed, and the comprehensive early warning level for the structure was determined, with the corresponding post-warning measures developed. The early warning system was utilized to conduct early warning and analysis on the state of Xinguang Bridge during a certain period. The results show that the bridge is in the level 2 early warning state, with generally sound conditions and normal operation of the structure. However, the monitoring frequency should be appropriately increased.
Experimental study on double cracks fatigue life of cable steel wire
XU Hongsheng, WANG Zhihong, and YAN Donghuang
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.020
At present, research on the residual fatigue life of corroded steel wires usually adopts the method of equivalent simulation of typical pits into prefabricated single cracks for treatment. However, in the actual corroded steel wires of bridge cables, multiple typical pits are often adjacent, and the effect of multiple pits on the residual fatigue life is not clear. Therefore, it is necessary to study the distribution of multiple pits on the residual fatigue life of steel wires. This paper analyzed and studied the influence of different axial distances and circumferential angles of double pits on the fatigue life of steel wires by transforming double pits into equivalent double prefabricated cracks. The experimental results show that under smaller axial distance between double cracks, the residual fatigue life of the steel wires is greater than that of a single crack. The residual fatigue life of steel wires decreases with the increasing axial distance of double-crack steel wires. The influence of the circumferential angle of double cracks on the fatigue life of steel wires has significant discreteness. In the case of lateral distribution, the residual fatigue life of single and double cracks is basically the same, with the residual fatigue life of steel wires being the smallest. Additionally, the residual fatigue life of double cracks is significantly improved under vertical distribution. Under distribution on the same side, a significant influence is exerted on the residual fatigue life of the steel wires, with the highest residual fatigue life. However, regardless of the crack distribution patterns, the mutual influence between the two gradually decreases with the increasing axial distance. When the distance between the double pits is large enough, the effect on the overall residual fatigue life of steel wires is basically equivalent to that of a single crack. Therefore, simulating the typical situation of multiple adjacent pits as a single crack evaluation method is conservative, and further research is needed to investigate its influence on residual fatigue life.
Study on mechanical behavior of a new resistance ring grouting sleeve joint
MENG Lingxiao, FU Tao, SUN Zhonghua, XU Yingdong, and LU Peng
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.021
The construction technology of prefabricated bridges features environmental protection, noise reduction, construction quality improvement, and construction efficiency enhancement. The reliable connection of the main load-bearing steel bars in prefabricated components is the key to ensuring the sound performance of the prefabricated structure. Grouting sleeve connection is an important way of connecting steel bars in prefabricated structures. This paper proposed the construction of a new type of resistance ring grouting sleeve, and analyzed the working performance of the steel bar grouting sleeve connection in the working conditions of uniaxial tension and reciprocating tensile compression by conducting finite element numerical simulation. The results reveal that the mechanical performance of various components of the new resistance ring grouting sleeve in uniaxial tension conditions meets the requirements of the specifications. After 20 cycles of high-stress reciprocating tensile compression, the total residual deformation is 0.24 mm, which belongs to the Class I joint. As the cyclic loading continues, the energy consumption and rigidity of the grouting material decrease after the tenth cycle, and the grouting material forms a relatively stable and reliable path for load transmission. At this time, the maximum third principal stress of the grouting material under tensile compression tends to stabilize, and the grouting material forms a good force transmission combination with the steel bars and sleeve, with generally sound performance of steel bar sleeve components.
Construction control measures and temperature effect analysis of arch⁃type bridge tower
WANG Wenming, CHAI Shengbo, NIE Ningbo, and WEI Qian
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.022
To ensure that the alignment and internal forces of the cable-stayed arch-type bridge towers meet the design requirements and achieve safe construction of the bridge towers, this paper built a finite element model to study the variation rules of the alignment and stress during the construction of arch-type bridge towers, analyzing the influence of temperature effects on the arch-type bridge towers, with relevant control measures proposed. The results indicate that when the temperature gradient in the transverse direction of the bridge is only considered, under the same temperature gradient, the tensile stress of the outer tower limbs affected by sunlight is greater than that of the inner tower limbs, and the displacement of the tower limbs on both sides is the same and consistent with the sunlight direction. During the construction stage of the lower crossbeam and the closure stage of the bridge tower, the temperature effect on the bridge tower decreases. Additionally, the setting of the temporary lateral bracing, application of jacking force, and setting of the offsetting amount can reduce the axial displacement of tower limbs and tensile stress of tower limbs during construction, avoiding bridge tower cracking. After the jacking force application of the lateral bracing, the axial displacement of the bridge tower can be controlled within 5 mm. When two pieces of lateral bracing are set up, the removal sequence of temporary lateral bracing may not be considered. By comparing measured and theoretical data, it has been further verified that the setting of temporary lateral bracing and application of jacking force can effectively decrease the deviation of the bridge tower axis, with significant influence of the temperature gradient exerted on the alignment and stress of bridge towers.
Research on influence of pier abutment construction on existing business line
TAN Chenglong, GONG Tianhao, LIU Xin, and BAI Pengpeng
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.024
The construction safety problems of the business lines are increasingly catching people's attention. The pier abutment construction will inevitably cause changes in the groundwater level and stress field in the surrounding foundation, resulting in deformation of the surrounding soil and ultimately additional deformation near the business lines. In response to the above problems, based on a deep foundation pit project, this paper built a Plaxis 3D finite element model to explore the influence of construction steps of pier abutments on the displacement and deformation of the business lines' bridge abutments. Meanwhile, it simulated the actual working conditions, and compared and analyzed actual monitoring data. The results show that the pier abutment construction has little effect on the displacement of bridge abutments of the business lines. Under the most unfavorable combination, the displacement is 3-6 mm, and the finite element simulation results are basically consistent with the measured results. The excavation of the lowest soil layer in the foundation pit has the greatest influence on the displacement of the business lines.
Analysis of cable force error of cable installation system
XU Feng, SONG Junxi, ZHANG Feng, and GAO Lei
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.025
The cable installation method is a commonly employed method for the construction of large-span concrete-filled steel tube arch bridges. The cable is the main load-bearing component, and it is necessary to conduct calculation analysis and construction monitoring. By taking the Wumei River Grand Bridge as an example, this paper conducted research on the calculation method of cable force for cable installation systems. Meanwhile, it carried out cable force calculation analysis and on-site testing of the actual bridge of the 400 m suspension span cable of the upper supported concrete-filled steel tube arch bridge with a calculated span of 300 m to verify the cable force of a single cable and analyze the calculated and measured errors. The results show that the overall deviation between the calculated and measured cable force values is about 8%. As the calculated values are based on the maximum cable force state at the central span, the average deviation of the Huangping'an installation section is relatively small. In addition to calculation errors, the reverse friction force of the cable saddle at the tower during cable installation construction, temperature changes during installation, and slipping between cable fasteners and cables can also affect the results of cable force testing. After correction, the overall deviation between tested cable force values and calculated values is reduced. When the crane slides to the central span, the maximum cable force occurs at the rear cable anchor anchorage.
Study on load test of long link multi⁃span PC continuous wide box⁃girder bridge
MAO Dejun, WU Weibin, GUO Jun, LAN Shuwei, XU Baishun, and WANG Tao
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.026
To study the actual bearing performance of a long link multi-span PC continuous wide box-girder bridge in a certain city, this paper conducted on-site static and dynamic tests on it. The static tests mainly tested the sedimentation of bridge pivots, deflection and strain of control sections. The dynamic tests included the modal test and sports car test, mainly testing the natural frequency of vibration, damping ratio, and coefficient of impact of the bridge. The comprehensive results of static and dynamic tests show that under the normal use state, the bearing capacity of the bridge meets the load level requirements of City A, with the dynamic working performance satisfying the requirements for utilization. Further efforts should be made to strengthen the research on the lower limit values of the normal range of deflection verification coefficients and strain verification coefficients. It is suggested that the range of normal working values for the bridge damping ratio should be provided.
Analysis of factors affecting stress and displacement of continuous rigid frame bridge in plateau environment
HE Bowen, SUN Hao, and WANG Shuo
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.027
As China's construction industry experiences booming development and the demand for transportation is increasing, continuous rigid frame bridges have become the main structural system for large-span bridges due to their advantages of avoiding system transformation, reducing deck expansion joints, and providing comfortable driving. However, due to the characteristics of their rigid frame systems and the shrinkage and creep properties of concrete materials, continuous rigid frame bridges are sensitive to changes in environmental temperature and humidity, which can even severely result in engineering diseases such as cracks and large deformation in the bridge, causing decreased driving comfort and safety hazards. By taking the the Yarlung Zangbo River Bridge as the engineering background, this paper studied the influence of temperature and humidity on the stress of continuous rigid frame bridges in plateau environment by finite element calculation. The calculation results show that temperature changes in plateau environments significantly affect the stress of rigid frame bridges. Temperature gradient changes can easily cause uneven structural stress distribution, while overall temperature changes significantly affect the displacement of rigid frame bridges. Additionally, the influence of humidity in plateau environments on bridge structures is mainly reflected in the deflection displacement at the central span, and the deflection displacement of continuous rigid frame bridges increases significantly in low-humidity environments.
Mechanism analysis of temperature effects on closure length of main girder of long⁃span cable⁃stayed bridges
FU Chunyu, SHEN Luming, and YAN Peng
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.028
To accurately predict the closure length of the main beam of a large-span cable-stayed bridge under the action of temperature, this paper employed an elastic foundation beam model to propose a differential equilibrium equation for the axial deformation of the main beam. By combining structural temperature deformation and support boundary conditions, a prediction method for obtaining the closure length of the main beam was solved to reveal the variation law of the closure under the action of temperature. Meanwhile, the proposed method was validated by finite element numerical analysis results and continuous observation data of the Yanpingba Yangtze River Bridge. The results show that the closure length of the main beam varies linearly with the action of temperature, and compared to the temperature difference between the cable and the main beam, the overall closure length produced by the action of overall temperature difference of the main beam varies greatly. Additionally, the change is less affected by the rigidity of the cable support, but it will increase with the rising cross-sectional area of the main beam.
Bond slip characteristics of HB⁃FRP based on arc⁃length method
XU Xiangfeng, LI Pengfei, LI Xinxin, ZHANG Luke, and GAO Lei
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.029
The bonding performance between hybrid bonding FRP (HB-FRP) and concrete is crucial for HB-FRP reinforcement of concrete structures. This paper built a simple shear numerical model for HB-FRP, which considered both the interfacial bond slip between FRP and concrete by adopting bilinear constitutive analysis, and the interfacial bond slip at the steel fastener location by employing trilinear constitutive analysis. Meanwhile, the bond slip properties at the steel fastener location were simulated by double springs. Based on the arc-length method, the entire process of loading and unloading of the HB-FRP simple shear model was carried out to study its stress performance. Additionally, the experimental data was compared and analyzed to verify the effectiveness of the numerical model, reveal the bond slip properties of HB-FRP during unloading, and correct the existing bond slip model. Parameter analysis was conducted on the adhesive length, and based on the analysis results, the effective bonding length of HB-FRP was calculated to be around 2500 mm, which reveals a linear relationship between the number of steel fasteners and their ability to resist stripping loads within the effective bonding length range.
Bearing capacity analysis of steel⁃concrete composite girder⁃abutment joint by finite element method
SONG Chengzhi, XU Bing, HU Qiang, and WANG Xu
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.030
Jointless bridges can effectively alleviate and eliminate the durability problems of bridge expansion joints and supports, and have broad application prospects in small and medium span bridges. Due to the integral frame structures formed by the upper and lower structures, the stress distribution of the main girder-abutment joint in the steel-concrete composite integral abutment and jointless bridges is complex. This paper built a nonlinear main girder-abutment finite element model, and selected the embedded depth of the steel girder, deck thickness of concrete bridges, and transverse width of the abutment as research parameters to analyze their effects on the stress performance of the joints. Meanwhile, based on this, a stress analysis model of the joints was built, with a bearing capacity calculation formula for the joints proposed. The results show that the embedded depth of the main girder and transverse width of the abutment are key parameters influencing the bearing capacity of the joints. The bearing capacity calculation formula proposed in this paper is in sound agreement with the finite element calculation results.
Research on performance inspection and evaluation of in⁃service bridge bearings and improvement technology
ZHANG Jingyue, WANG Zhiqiang, and LIU Fukang
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.031
To study the quality disease and residual mechanical performance of bearings under the replacement of in-service bridges, this paper took the pot bearings under the replacement of a real bridge as an example to conduct appearance, mechanical perfornance, and raw material testing. Meanwhile, it determined the main causes of the disease led to by the replacement, analyzed the influence of bearing disease on the restrained concrete, and studied the performance improvement technology of in-service old bearings, with mechanical performance verification carried out. The results reveal that the main disease of pot bearings (replacement) is excessive wear of the sliding plates, which increases the friction coefficient of the bearings to 0.19 and changes the original constraint system of the bridge. Additionally, the process of employing steel hoops and new sliding plates can achieve rapid replacement of sliding plates of the bearings and shorten the interruption time of bridge traffic. Meanwhile, the rubber is in a closed environment, which can avoid the occurrence of aging rubber.
Study on design parameters of existing rigid frame bridges in guizhou province based on statistical analysis
GUO Wei, YANG Zhijun, and ZHENG Xinggui
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.032
To study the commonly employed design data of existing rigid frame bridges in Guizhou, this paper collected data from 166 bridges and analyzed the indicators such as overall overview, edge to main span ratio, box girder section data, and material content. With the revision of current standards and the emergence of new design concepts, the relevant analysis data in this paper can provide important practical references for the design of new rigid frame bridges in the future.
Study on mechanical performance of prefabricated concrete cap beam
WU Congxiao, GAO Pengyu, ZHANG Guanghai, and ZHANG Chongbin
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.033
To study the mechanical performance of cap beams of piers on prefabricated concrete bridges, this paper conducted static tests on the components of prefabricated cap beam shells poured with concrete. Meanwhile, finite element software Abaqus was adopted to numerically simulate the cap beam specimens with different structural measures of joint bars and concrete shear keys at the interface of prefabricated cap beam shells poured with concrete. Based on this, the model of prefabricated cap beams and cast-in-place cap beams was built, and pseudo-static low-cycle reset displacement analysis was carried out. The results show that the internal cast-in-place scheme of prefabricated shells is feasible for prefabricated cap beams. The integral casting and molding of bridge piers and corbels can temporarily fix the cap beams and enhance the connection performance of the joints. The prefabricated cap beam shells are poured with concrete at the interface, and the utilization of concrete shear keys and joint bars can demonstrate their sound force transmission performance. Prefabricated cap beams are equivalent to cast-in-place cap beams, and the peak bearing capacity of prefabricated cap beams is higher than that of cast-in-place cap beams, with a reduced ductility coefficient.
Forward difference iteration method for determining reasonable construction state of cable⁃stayed bridges with stacked girders
LI Jieli, XIA Yonghao, ZHANG Xiaowen, and ZHAO Changchun
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.034
To solve the problem of determining the cable force of composite girder cable-stayed bridges with stacked girders under the reasonable construction state, this paper proposed the forward difference iteration method for determining the reasonable design state of cable-stayed bridges based on the calculation principles of the forward iteration method and the difference iteration method for determining the cable force of cable-stayed bridges under the reasonable construction state. Meanwhile, a program for cable force calculation during the reasonable construction stage was written, and the automatic optimization function of cable force during the reasonable construction stage was realized. Additionally, after applying this method to a double-tower composite girder cable-stayed bridge with stacked girders, at the tenth iteration, most of the cable force deviations fell within 5%, while at the 15th iteration, most of the cable force deviations were within 3%. At the 20th iteration, the deviation of cable force for each inclined cable was within 0.5%. Compared with the forward iteration method based on the influence matrix method to determine the cable force during the construction stage, the forward difference iteration method does not require multiple extractions of complex influence matrices. Instead, it only needs to take the difference between the calculated bridge cable force and the target bridge cable force for each iteration, and then update the cable force during the construction stage for the next iteration based on the difference. This is convenient and easy to operate, and can satisfy the engineering accuracy requirements.
Discussion on pushing construction technology of multi⁃unit super long steel box girder for urban viaduct
XIAO Jun and WANG Ruoyu
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.035
In bridge engineering, pushing technology has significant advantages in crossing highways, railways, flood control embankments, and bustling urban streets. However, in actual construction, various technical difficulties may also be encountered due to structural and on-site environmental factors. This paper combined engineering practice to explore the technical difficulties in pushing construction of steel box girders for multi-unit super long urban viaducts, including instability problems during the pushing of the main girders, reasonable launching nose length, and reasonable connections between links. Finally, a systematic analysis method was developed to solve technical difficulties in engineering construction and ensure the smooth implementation of the projects.
Application of forward parametric design technology in steel arch of the No . 3 bridge in Ordos
PU Bozhou, WANG Guannan, and ZENG Yong
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.036
The No. 3 Bridge in Ordos adopts a half-through double arch bridge structure with a main span of 192 m. As this project has prominent landscape effects, abstract spatial relationships, and complex structural forms, conventional design ideas cannot meet the design requirements. The project utilizes the forward parameteric design concept and employs the "R+GH" design method to conduct three-dimensional parametric modeling of the main arch and secondary arch of the No. 3 Bridge. Meanwhile, by conducting finite element analysis, the influence of structural deformation on the derrick booms during the operation stage was evaluated, and the spatial angle of the cable conduits was corrected. The three-dimensional design results are transformed into two-dimensional drawings for output by relying on the powerful spatial design and interaction capabilities of forward parametric design. This paper elaborated on the application of forward parametric design in spatially irregular arch bridge structures, as well as the seamless connection between parametric design and structural finite element calculation, three-dimensional spatial display, two-dimensional result output, and other functions. Finally, references can be provided for the application of forward design in similar bridges.
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.037
To study the optimization of cable force on temporary piers during pushing construction of PC box girders, this paper took the continuous box girders of cross-railway pushing construction in Hunan as the research background, and built a finite element model for structural simulation analysis. Based on BP neural networks-genetic algorithm (GA), a method for optimizing cable force on temporary piers during the pushing construction of main girders was proposed. Meanwhile, by employing Matlab programming and finite element software, the optimization of cable force on temporary piers of PC pushing box girders was studied. The results show that after optimization, the maximum horizontal displacement at the top of each temporary pier is significantly reduced, with a maximum decrease of 35.0%. The maximum stress at the bottom of each pier also notably decreases and is distributed more evenly, with a maximum stress reduction of 37%. After optimization, the structural stress safety is effectively improved, which also verifies the effective application of BP neural network-GA in the optimization of cable force on temporary piers.
Analysis of frozen⁃thaw mechanical characteristics of in road culverts in plateau frozen soil region
LI Zhen and CHEN Zemeng
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.038
Based on the reconstruction project of Yangda Highway in Xizang, an important national project of the "the Belt and Road" initiative, this paper studied the frozen-thaw mechanical characteristics of culverts in plateau frozen soil regions. The mechanical models of steel corrugated pipe culverts and underwater antifreeze reinforced concrete pipe culverts in four working conditions were built by employing the Mi-das GTS NX finite element software. By setting the soil temperature change functions, this paper analyzed the internal force changes of soil layers, the internal force and displacement changes of pipe culverts and other structural layers, as well as the internal force changes of two-way HDPE high-density polyethylene geogrid before and after the frozen-thaw cycle for the pipe materials of culverts commonly utilized in the plateau regions. The results indicate that after experiencing the frozen-thaw cycle, the plastic zone of both types of pipe culverts increases, but employing underwater antifreeze reinforced concrete pipes has better coordinated deformation ability. After the frozen-thaw cycle, the main stress and shear stress change rates at the midpoint and both ends of the steel corrugated pipe culverts, as well as the displacement of different subgrade slope measurement points, are all smaller than those of the underwater antifreeze reinforced concrete pipe culverts, making them more suitable for the utilization in plateau cold regions. Additionally, laying the two-way HDPE high-density polyethylene geogrid can effectively reduce uneven deformation of pavement structural layers. Finally, the correctness of the method proposed in this paper was verified by comparing and analyzing the modeled theoretical calculated values with the detection data on the construction sites.
3D numerical analysis on interaction mechanism of two existing lines over⁃crossed by shield tunnel
ZHANG Baogang, XIE Jiachong, and HUANG Xin
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.039
To explore the collaborative deformation and interaction mechanism between two existing lines during tunnel crossing, this paper built a three-dimensional numerical model simulating the entire crossing process based on a water-conveyance tunnel crossing an existing subway section in Shenzhen. Based on actual measured data, it verified the effectiveness of the model and discussed the soil-structure interaction mechanism between two existing lines. The results show that there is a collaborative deformation effect between two existing lines, and crossing two lines is an unfavorable situation compared to crossing a single line. The influence of the upgoing line on the downgoing line after crossing is relatively little, mainly during the crossing period. The downgoing line that is crossed first has a significant effect on the upgoing line, and affects the entire process of crossing the upgoing line. Compared with crossing a single line, crossing two lines also has a significant influence on the deformation trend and surface sedimentation of existing tunnels.
Influence of foundation pit excavation on zero distance underground shield tunnel
ZHAO Peng
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.040
To understand the influence of foundation pit excavation on zero-distance underground shield tunnels, this paper built a section excavation model of interval tunnel foundation pits by employing PLAXIS 3D geotechnical finite element software based on the first zero-distance upper-span subway tunnel project in China, which is an overlapping section of a parking lot in Xiamen Metro and the main line. Meanwhile, soil excavation schemes were developed by adopting layered, zoning, strip, symmetrical and other methods to investigate the response of underground shield tunnels under three different excavation schemes. The results show that due to the consistent total excavation unloading amount, different layered and zoning excavation processes of foundation pits have little effect on the strata and underlying tunnels, with generally consistent response patterns. Under the three excavation schemes, the differences in extreme surface sedimentation behind the foundation pit wall, underground tunnels' vertical displacement and extreme bending moments are about 1%, 10%, and 3% respectively. Additionally, timely construction of the bottom plates of the foundation pits can provide the function of back pressure, which to some extent suppresses stratum displacement, tunnel deformation, and extreme internal force. On-site practice shows that the actual construction scheme is reliable, and the shield tunnel structure is safe and stable.
Application research on subway tunnel structure monitoring system based on BIM technology
LIU Jianhua, FAN Zhenyang, CHEN Zijun, LIN Jinkeng, HU Hongyi, and FU Xinsha
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.041
Real-time visual state monitoring during the construction and operation of subway tunnel projects is the key to improving the safety management of subway tunnel projects. Based on BIM technology, this paper built a subway monitoring and management system. Meanwhile, parameters such as the dip angle, stress, and displacement of the structures were monitored and controlled in real time by employing on-site monitoring equipment. Then, the monitoring data was connected with lightweight BIM models via database technology to display the mechanical response state of various structural components in the tunnels in real time, which enabled the visualization of massive monitoring data and conducted early warning on the structural safety of the tunnels by setting early warning thresholds. The system was applied to the structural monitoring of the subway tunnel in the second expressway project of the new Guangzhou Baiyun International Airport. The results show that the intelligent subway monitoring system based on BIM technology can achieve real-time visual monitoring of the safety state of the subway tunnel and timely early warning of safety hazards in the tunnel structure. Compared with traditional manual regular patrol and detection, the efficiency is greatly improved, which is of vital significance for tunnel construction and operational safety.
Construction technology of propping of loess tunnel carriage transverse passageway of highways in western Henan
ZHOU Peng, JIN Ming, GUO Jing, HUANG Tao, and LI Jiyan
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.042
The underground pit courtyard tunnel of the southward relocation project on National Trunk Way 310 was delayed by 258 m from the left line due to the influence of terrain and geology during the construction stage. The 8# transverse pedestrian passageway was changed to a transverse carriage passageway, and a working face was added to the main tunnel of the right line to ensure timely completion of the project. This paper first discussed the risks and existing problems of propping construction, and then elaborated on the construction process and support parameters of the transverse propping of the underground pit courtyard tunnels from several aspects, including strengthening the transverse carriage tunnel at the intersection, propping of the guide tunnel in the main tunnel, and construction of the three-bench construction method in the main tunnel. Furthermore, the key points of the construction process were discussed.
Study on disturbance characteristics of ground in full⁃section tunnel under advance grouting
HUANG Yueting, WANG Chonghua, WANG Hui, and WANG Qingman
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.043
The advance grouting method has a wide range of applications in tunnel construction, and its effect is influenced by factors such as hydrogeological conditions and construction techniques. Improper grouting can cause local uplifts in the strata, which can have adverse effects on the safe operation of the tunnels. Based on a construction case of a subway tunnel in Shenzhen, this paper adopted the discrete element method to explore the disturbance mechanism of advance grouting of the entire tunnel section on the geological strata. Due to the fact that advance grouting of the entire tunnel section belongs to a fluidsolid coupling problem, this paper employed a pipeline-domain model to simulate the grouting process. Specifically, pipelines were utilized to connect various fluid domains, while the fluid domains were for storing information such as the fluid pressure and flow rate. The calculation results show that during the grouting process, the slurry will produce infiltration and fracturing effects in the strata. Under the combined action of the two, the stratum disturbance can be roughly divided into four stages, including the infiltration filling, rapid uplift, uniform uplift, and slow uplift. The fracturing effect can cause a rapid stratum uplift, which occurs when the grouting pressure is greater than the minimum principal stress of the strata. Therefore, the key to preventing the stratum uplift is to make the grouting pressure less than the minimum principal stress of the strata, which is consistent with the phenomenon observed during the construction.
Comparative study and implementation of seismic retrofitting measures for multi⁃span simply supported bridges in strong earthquake areas
CHENG Xianjie and HU Hao
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.044
Based on an example of a three-span simply supported girder bridge project in a strong earthquake area in the Americas, seismic response analysis was conducted to compare and analyze the seismic response of different retrofitting methods, such as replacement of ordinary plate rubber bearings, continuous decks, addition of cable restrainers between spans, and replacement of seismic isolation bearings. Meanwhile, the analysis considered the influence of soil constraints at the back of the platform and girder collisions on seismic response. The results show that ordinary plate bearings can reduce the ductility coefficient of bridge piers and achieve seismic isolation effect, but a high risk of girder collision can easily result in the occurrence of lowering of girders. The continuous decks and cable restrainers at the pier top can effectively limit the relative displacement between girders, but special attention should be paid to the bearing capacity verification and support failure of the cable restrainers. Lead core bearings can effectively improve the seismic resistance of bridges, meet the ductility requirements of bridge piers, and reduce the girder collision risk. This paper proposed a specific implementation scheme of strengthening the original bridge by employing seismic isolation bearings and continuous decks, and replacing the continuous decks and seismic isolation bearings.
Comparative study on strut stability calculation of long⁃span highway truss suspension bridge based on chinese and european specificat ions
DUAN Baoshan, DUAN Li, LI Yuansong, and ZHANG Chunhua
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.045
This paper introduced the design methods for the stability of struts in Chinese and European specifications for steel structure bridges, and compared and analyzed the differences and similarities between the section classification, overall stability curve, and local stability curve in relevant Chinese and European specifications. By taking H-shaped steel components as an example, it calculated the strut stability and compared the results with finite element calculations. The results show that in terms of section classification, JTG D64-2015 is divided into five categories (S1, S2, S3, S4, and S5), while EC3 is divided into four categories (1, 2, 3, 4), with the corresponding relationship of mechanical performance being 1-a, 2-b, 3,4-c, and 5-d. Additionally, for the overall stability curve, when the slenderness ratio λn is no more than 1.5, the coefficient of stability corresponding to the c/d curve in JTG D64-2015 is 2%-5% lower than that of EC3. When λn is more than 1.5, the coefficients of stability corresponding to the Chinese and European specifications are basically the same. In terms of local stability, JTG D64-2015 only utilizes effective cross-sectional area calculation for the web plate, while EC3 has different calculation formulas for the flange and web plate. The comparative analysis of Chinese and European specifications and finite element calculation results shows that both the specifications underestimate the ultimate bearing capacity of struts, with the results obtained by Chinese and European specifications being 3%-13% and 1%-12% lower respectively in most cases. Relatively speaking, JTG D64-2015 in Chinese specifications is more conservative in terms of stable design.
Study on temperature gradient effect of corrugated steel web box girder considering influence of boundary conditions
LEI Yao, LI Ming, LU Naiwei, and LIU Yang
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.013
To study the stress characteristics of corrugated steel web box girders under vertical temperature gradient loads, this paper employed the civil structural nonlinear simulation software Midas FEA to build a three-dimensional finite element analysis model of corrugated steel web box girder bridges. Meanwhile, the temperature effects of corrugated steel web box girders under two constraint conditions of simply supported structures and continuous structures under vertical temperature gradient loads were compared and analyzed. The results demonstrate that under vertical temperature gradient loads, the temperature effect generated by corrugated steel web box girders is significant and cannot be ignored. The temperature effect of corrugated steel web box girders under continuous structural constraints is more significant than that of the simply supported structures under temperature gradient loads. Therefore, the influence of boundary constraint conditions on the temperature effect of corrugated steel web box girder bridges should be comprehensively considered. Additionally, the maximum temperature stress is obtained at the connection joint between the top and bottom concrete and the corrugated steel web, and the peak stress of this structure should be given special attention during the design stage.
Research on parameters of bridge moving vehicles load based on WOA⁃BP neural network
WANG Xiaohui, ZHANG Bangru, TAO Zhiren, CHI Xinyan, WAN Lixing, and PENG Jianxin
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.014
To efficiently and accurately identify the moving load parameters on bridge structures, this paper proposed a layered identification method for moving loads on bridges using BP neural networks based on the whale optimization algorithm (WOA), and built a moving load parameter identification model based on WOA-BP neural networks. By adopting this moving load identification model, step-by-step coupling identification was conducted on the action lane, speed, and load capacity of vehicles on the bridge. Additionally, by taking a prestressed simply supported box girder bridge as the research project, the applicability of the proposed method and neural network identification model was verified via dynamic response measurement data under the action of random traffic flow and the combination of video data of vehicles driving on the bridge. The results reveal that the proposed method for identifying moving load parameters features high identification accuracy, fast convergence speed, strong robustness and noise resistance, and can accurately identify bridges' moving load parameters.
Experimental study on effect of fiber length on axial tensile properties of UHPC
YUAN Ming, HAN Huaizhi, YAN Donghuang, HUANG Lian, and ZENG Xiaojun
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.015
To study the effect of steel fiber length on the axial tensile properties of UHPC, this paper selected straight circular fiber with the same diameter but different lengths and mixed it into UHPC. By conducting analysis on the mechanical properties, tensile deformation, and post-fracture strength of UHPC, the influence of fiber length on the axial tensile properties of UHPC was obtained. Meanwhile, the fracture resistance and toughening effects of fiber length were evaluated, with the reasons for the influence of fiber length on the axial tensile properties of UHPC clarified. The results show that the axial tensile properties of UHPC increase with the rising fiber length. The effect of 20 mm fiber length on the peak UHPC stress increases by 57.76% compared to 6 mm fiber length. The post-fracture strength of UHPC grows with the increasing fiber length. Under the same fracture width and fiber length of 20 mm, the UHPC stress is the highest, and the UHPC stress is the lowest under the fiber length of 6 mm. UHPC with 20 mm fiber length mixed has the maximum deformation in the strain hardening stage, while UHPC with 13 mm fiber length has the maximum deformation in the stress softening stage. The UHPC fluidity decreases with the increasing fiber length. Additionally, the effect of fiber length on the axial tensile properties of UHPC is altered by changing the contact surface size between the fiber and the matrix. Specifically, the longer fiber leads to the larger contact surface between the fiber and the matrix, bringing about stronger cohesion between the fiber and the matrix.
Research on lightweight method of BIM model for bridge engineering based on CATIA CAA
ZHANG Yunhe, ZHU Ming, and FAN Yufeng
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.016
Highway construction projects are mostly linear projects with zonal distribution, which contain multiple structures and are closely integrated with the geographical environment. During their applications in BIM, they often face the problems of massive data delivery and multi-source heterogeneous data fusion. Therefore, based on the secondary development of CATIA CAA, this paper proposed a lightweight method for the BIM model in bridge engineering, elaborated on the general lightweight concept, and then detailed the lightweight process, with a BIM model lightweight program independently developed. By taking the Heishuihe Bridge as an example, the functionality and stability of the program were tested, and the digital delivery and application of lightweight follow-up models on the BIM platform were achieved. Finally, the results indicate that this lightweight method has certain application prospects and practical significance.
Overall design of main bridge of qingshui river bridge in Baoji
WANG Zhen, NIU Yongzhe, and LI Haipeng
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.017
The main bridge of Qingshui River Bridge is a (65+5×120+65) m continuous rigid frame bridge. The main girder adopts a combination of corrugated steel webs and concrete box girders, with double-amplitude single-box single-chamber sections. The corrugated steel webs adopt 1600 type corrugated steel plates, and are connected to the top and bottom plates respectively with double PBL shear keys and ∟200 angle steel. Longitudinal prestressed steel bars are divided into internal tendons and external tendons. The lower structure adopts double thin-walled hollow piers, bearing platforms, and bored pile foundations, with a maximum pier height of 73 m and an average pier height of 71.4 m. The main bridge adopts a cantilever cast-in-place construction scheme, and the closure sequence is respectively the edge span, central span, secondary central span, and secondary side span. The closure temperature is 10℃, and the jacking force is 500 kN for the central span, 800 kN for the secondary central span, and 1200 kN for the secondary side span. Additionally, Ansys 14.0 was adopted to analyze the torsional cross slope and warping ratio of the central span section, which reveals that the arrangement of six diaphragms is more reasonable. By comparing the most unfavorable eccentric load and symmetrical load conditions, the live load eccentric load coefficient of the corrugated steel web under stress is determined to be 1.3. Additionally, Midas/Civil 2019 was employed for longitudinal static calculation during construction and bridge completion stages, shear yielding and flexure calculation of corrugated steel webs, shear strength calculation of shear force connectors of top and bottom plates, and transverse static and antiseismic calculation of the composite girder central span, root and pier top sections. The results show that all indicators of the bridge meet the requirements of the specifications.
Error analysis of relative angle at the central⁃span closure of long⁃span composite girder cable⁃stayed bridges
TU Guanya and ZHOU Chengyong
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.018
According to the theory of the non-stress state method, the elastic curve of the main girder during the central-span closure should remain continuous to ensure that the internal forces and alignment of the built cable-stayed bridge reach the target state after construction, which means the relative angle of the main girders on both sides of the closure should be zero. However, it is difficult to meet the condition of absolute zero of the relative angle in practical engineering. By taking the Chibi Changjiang River Highway Bridge as the engineering background, this paper studied the influence of relative angle error during the central-span closure of a large-span composite girder cable-stayed bridge on the final target state of the built bridge, thus determining the allowable range of relative angle error. The analysis results reveal that the relative angle error of the main girders on both sides of the closure gap during the central-span closure mainly has a significant influence on the stress of the main girders under the target state of the built bridge, with little effect exerted on tower deviation, cable force, and main girder alignment. For the Chibi Changjiang River Highway Bridge, the allowable relative angle error of the main girders on both sides of the closure can be set as ±1×10-3 rad during the central-span closure. Within this range, it can be considered that the elastic curves of the main girders on both sides of the closure are continuous.
Research on comprehensive early warning system with multi⁃indicators for long⁃span steel arch bridges
ZHANG Yuanchuan, SU Cheng, WANG Yonghui, and ZHENG Chun
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.019
To detect structural abnormalities timely and ensure the safe operation of bridges, this paper took the health monitoring system of Xinguang Bridge in Guangzhou as the engineering background, and conducted research on a comprehensive multi-indicator early warning system for large-span steel arch bridges. Meanwhile, it selected multiple warning indicators from the categories of environmental effects and structural responses, set early warning indicator thresholds based on the distribution pattern of measured data, and formulated scoring standards for early warning indicators to score each early warning indicator. The analytic hierarchy process (AHP) was employed to determine the weight of various early warning indicators, and calculate the comprehensive early warning scores for environmental effects and structural responses, thus obtaining the comprehensive early warning level for environmental effects and structural response. In addition, a comprehensive early warning matrix for the structure was constructed, and the comprehensive early warning level for the structure was determined, with the corresponding post-warning measures developed. The early warning system was utilized to conduct early warning and analysis on the state of Xinguang Bridge during a certain period. The results show that the bridge is in the level 2 early warning state, with generally sound conditions and normal operation of the structure. However, the monitoring frequency should be appropriately increased.
Experimental study on double cracks fatigue life of cable steel wire
XU Hongsheng, WANG Zhihong, and YAN Donghuang
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.020
At present, research on the residual fatigue life of corroded steel wires usually adopts the method of equivalent simulation of typical pits into prefabricated single cracks for treatment. However, in the actual corroded steel wires of bridge cables, multiple typical pits are often adjacent, and the effect of multiple pits on the residual fatigue life is not clear. Therefore, it is necessary to study the distribution of multiple pits on the residual fatigue life of steel wires. This paper analyzed and studied the influence of different axial distances and circumferential angles of double pits on the fatigue life of steel wires by transforming double pits into equivalent double prefabricated cracks. The experimental results show that under smaller axial distance between double cracks, the residual fatigue life of the steel wires is greater than that of a single crack. The residual fatigue life of steel wires decreases with the increasing axial distance of double-crack steel wires. The influence of the circumferential angle of double cracks on the fatigue life of steel wires has significant discreteness. In the case of lateral distribution, the residual fatigue life of single and double cracks is basically the same, with the residual fatigue life of steel wires being the smallest. Additionally, the residual fatigue life of double cracks is significantly improved under vertical distribution. Under distribution on the same side, a significant influence is exerted on the residual fatigue life of the steel wires, with the highest residual fatigue life. However, regardless of the crack distribution patterns, the mutual influence between the two gradually decreases with the increasing axial distance. When the distance between the double pits is large enough, the effect on the overall residual fatigue life of steel wires is basically equivalent to that of a single crack. Therefore, simulating the typical situation of multiple adjacent pits as a single crack evaluation method is conservative, and further research is needed to investigate its influence on residual fatigue life.
Study on mechanical behavior of a new resistance ring grouting sleeve joint
MENG Lingxiao, FU Tao, SUN Zhonghua, XU Yingdong, and LU Peng
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.021
The construction technology of prefabricated bridges features environmental protection, noise reduction, construction quality improvement, and construction efficiency enhancement. The reliable connection of the main load-bearing steel bars in prefabricated components is the key to ensuring the sound performance of the prefabricated structure. Grouting sleeve connection is an important way of connecting steel bars in prefabricated structures. This paper proposed the construction of a new type of resistance ring grouting sleeve, and analyzed the working performance of the steel bar grouting sleeve connection in the working conditions of uniaxial tension and reciprocating tensile compression by conducting finite element numerical simulation. The results reveal that the mechanical performance of various components of the new resistance ring grouting sleeve in uniaxial tension conditions meets the requirements of the specifications. After 20 cycles of high-stress reciprocating tensile compression, the total residual deformation is 0.24 mm, which belongs to the Class I joint. As the cyclic loading continues, the energy consumption and rigidity of the grouting material decrease after the tenth cycle, and the grouting material forms a relatively stable and reliable path for load transmission. At this time, the maximum third principal stress of the grouting material under tensile compression tends to stabilize, and the grouting material forms a good force transmission combination with the steel bars and sleeve, with generally sound performance of steel bar sleeve components.
Construction control measures and temperature effect analysis of arch⁃type bridge tower
WANG Wenming, CHAI Shengbo, NIE Ningbo, and WEI Qian
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.022
To ensure that the alignment and internal forces of the cable-stayed arch-type bridge towers meet the design requirements and achieve safe construction of the bridge towers, this paper built a finite element model to study the variation rules of the alignment and stress during the construction of arch-type bridge towers, analyzing the influence of temperature effects on the arch-type bridge towers, with relevant control measures proposed. The results indicate that when the temperature gradient in the transverse direction of the bridge is only considered, under the same temperature gradient, the tensile stress of the outer tower limbs affected by sunlight is greater than that of the inner tower limbs, and the displacement of the tower limbs on both sides is the same and consistent with the sunlight direction. During the construction stage of the lower crossbeam and the closure stage of the bridge tower, the temperature effect on the bridge tower decreases. Additionally, the setting of the temporary lateral bracing, application of jacking force, and setting of the offsetting amount can reduce the axial displacement of tower limbs and tensile stress of tower limbs during construction, avoiding bridge tower cracking. After the jacking force application of the lateral bracing, the axial displacement of the bridge tower can be controlled within 5 mm. When two pieces of lateral bracing are set up, the removal sequence of temporary lateral bracing may not be considered. By comparing measured and theoretical data, it has been further verified that the setting of temporary lateral bracing and application of jacking force can effectively decrease the deviation of the bridge tower axis, with significant influence of the temperature gradient exerted on the alignment and stress of bridge towers.
Research on influence of pier abutment construction on existing business line
TAN Chenglong, GONG Tianhao, LIU Xin, and BAI Pengpeng
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.024
The construction safety problems of the business lines are increasingly catching people's attention. The pier abutment construction will inevitably cause changes in the groundwater level and stress field in the surrounding foundation, resulting in deformation of the surrounding soil and ultimately additional deformation near the business lines. In response to the above problems, based on a deep foundation pit project, this paper built a Plaxis 3D finite element model to explore the influence of construction steps of pier abutments on the displacement and deformation of the business lines' bridge abutments. Meanwhile, it simulated the actual working conditions, and compared and analyzed actual monitoring data. The results show that the pier abutment construction has little effect on the displacement of bridge abutments of the business lines. Under the most unfavorable combination, the displacement is 3-6 mm, and the finite element simulation results are basically consistent with the measured results. The excavation of the lowest soil layer in the foundation pit has the greatest influence on the displacement of the business lines.
Analysis of cable force error of cable installation system
XU Feng, SONG Junxi, ZHANG Feng, and GAO Lei
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.025
The cable installation method is a commonly employed method for the construction of large-span concrete-filled steel tube arch bridges. The cable is the main load-bearing component, and it is necessary to conduct calculation analysis and construction monitoring. By taking the Wumei River Grand Bridge as an example, this paper conducted research on the calculation method of cable force for cable installation systems. Meanwhile, it carried out cable force calculation analysis and on-site testing of the actual bridge of the 400 m suspension span cable of the upper supported concrete-filled steel tube arch bridge with a calculated span of 300 m to verify the cable force of a single cable and analyze the calculated and measured errors. The results show that the overall deviation between the calculated and measured cable force values is about 8%. As the calculated values are based on the maximum cable force state at the central span, the average deviation of the Huangping'an installation section is relatively small. In addition to calculation errors, the reverse friction force of the cable saddle at the tower during cable installation construction, temperature changes during installation, and slipping between cable fasteners and cables can also affect the results of cable force testing. After correction, the overall deviation between tested cable force values and calculated values is reduced. When the crane slides to the central span, the maximum cable force occurs at the rear cable anchor anchorage.
Study on load test of long link multi⁃span PC continuous wide box⁃girder bridge
MAO Dejun, WU Weibin, GUO Jun, LAN Shuwei, XU Baishun, and WANG Tao
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.026
To study the actual bearing performance of a long link multi-span PC continuous wide box-girder bridge in a certain city, this paper conducted on-site static and dynamic tests on it. The static tests mainly tested the sedimentation of bridge pivots, deflection and strain of control sections. The dynamic tests included the modal test and sports car test, mainly testing the natural frequency of vibration, damping ratio, and coefficient of impact of the bridge. The comprehensive results of static and dynamic tests show that under the normal use state, the bearing capacity of the bridge meets the load level requirements of City A, with the dynamic working performance satisfying the requirements for utilization. Further efforts should be made to strengthen the research on the lower limit values of the normal range of deflection verification coefficients and strain verification coefficients. It is suggested that the range of normal working values for the bridge damping ratio should be provided.
Analysis of factors affecting stress and displacement of continuous rigid frame bridge in plateau environment
HE Bowen, SUN Hao, and WANG Shuo
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.027
As China's construction industry experiences booming development and the demand for transportation is increasing, continuous rigid frame bridges have become the main structural system for large-span bridges due to their advantages of avoiding system transformation, reducing deck expansion joints, and providing comfortable driving. However, due to the characteristics of their rigid frame systems and the shrinkage and creep properties of concrete materials, continuous rigid frame bridges are sensitive to changes in environmental temperature and humidity, which can even severely result in engineering diseases such as cracks and large deformation in the bridge, causing decreased driving comfort and safety hazards. By taking the the Yarlung Zangbo River Bridge as the engineering background, this paper studied the influence of temperature and humidity on the stress of continuous rigid frame bridges in plateau environment by finite element calculation. The calculation results show that temperature changes in plateau environments significantly affect the stress of rigid frame bridges. Temperature gradient changes can easily cause uneven structural stress distribution, while overall temperature changes significantly affect the displacement of rigid frame bridges. Additionally, the influence of humidity in plateau environments on bridge structures is mainly reflected in the deflection displacement at the central span, and the deflection displacement of continuous rigid frame bridges increases significantly in low-humidity environments.
Mechanism analysis of temperature effects on closure length of main girder of long⁃span cable⁃stayed bridges
FU Chunyu, SHEN Luming, and YAN Peng
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.028
To accurately predict the closure length of the main beam of a large-span cable-stayed bridge under the action of temperature, this paper employed an elastic foundation beam model to propose a differential equilibrium equation for the axial deformation of the main beam. By combining structural temperature deformation and support boundary conditions, a prediction method for obtaining the closure length of the main beam was solved to reveal the variation law of the closure under the action of temperature. Meanwhile, the proposed method was validated by finite element numerical analysis results and continuous observation data of the Yanpingba Yangtze River Bridge. The results show that the closure length of the main beam varies linearly with the action of temperature, and compared to the temperature difference between the cable and the main beam, the overall closure length produced by the action of overall temperature difference of the main beam varies greatly. Additionally, the change is less affected by the rigidity of the cable support, but it will increase with the rising cross-sectional area of the main beam.
Bond slip characteristics of HB⁃FRP based on arc⁃length method
XU Xiangfeng, LI Pengfei, LI Xinxin, ZHANG Luke, and GAO Lei
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.029
The bonding performance between hybrid bonding FRP (HB-FRP) and concrete is crucial for HB-FRP reinforcement of concrete structures. This paper built a simple shear numerical model for HB-FRP, which considered both the interfacial bond slip between FRP and concrete by adopting bilinear constitutive analysis, and the interfacial bond slip at the steel fastener location by employing trilinear constitutive analysis. Meanwhile, the bond slip properties at the steel fastener location were simulated by double springs. Based on the arc-length method, the entire process of loading and unloading of the HB-FRP simple shear model was carried out to study its stress performance. Additionally, the experimental data was compared and analyzed to verify the effectiveness of the numerical model, reveal the bond slip properties of HB-FRP during unloading, and correct the existing bond slip model. Parameter analysis was conducted on the adhesive length, and based on the analysis results, the effective bonding length of HB-FRP was calculated to be around 2500 mm, which reveals a linear relationship between the number of steel fasteners and their ability to resist stripping loads within the effective bonding length range.
Bearing capacity analysis of steel⁃concrete composite girder⁃abutment joint by finite element method
SONG Chengzhi, XU Bing, HU Qiang, and WANG Xu
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.030
Jointless bridges can effectively alleviate and eliminate the durability problems of bridge expansion joints and supports, and have broad application prospects in small and medium span bridges. Due to the integral frame structures formed by the upper and lower structures, the stress distribution of the main girder-abutment joint in the steel-concrete composite integral abutment and jointless bridges is complex. This paper built a nonlinear main girder-abutment finite element model, and selected the embedded depth of the steel girder, deck thickness of concrete bridges, and transverse width of the abutment as research parameters to analyze their effects on the stress performance of the joints. Meanwhile, based on this, a stress analysis model of the joints was built, with a bearing capacity calculation formula for the joints proposed. The results show that the embedded depth of the main girder and transverse width of the abutment are key parameters influencing the bearing capacity of the joints. The bearing capacity calculation formula proposed in this paper is in sound agreement with the finite element calculation results.
Research on performance inspection and evaluation of in⁃service bridge bearings and improvement technology
ZHANG Jingyue, WANG Zhiqiang, and LIU Fukang
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.031
To study the quality disease and residual mechanical performance of bearings under the replacement of in-service bridges, this paper took the pot bearings under the replacement of a real bridge as an example to conduct appearance, mechanical perfornance, and raw material testing. Meanwhile, it determined the main causes of the disease led to by the replacement, analyzed the influence of bearing disease on the restrained concrete, and studied the performance improvement technology of in-service old bearings, with mechanical performance verification carried out. The results reveal that the main disease of pot bearings (replacement) is excessive wear of the sliding plates, which increases the friction coefficient of the bearings to 0.19 and changes the original constraint system of the bridge. Additionally, the process of employing steel hoops and new sliding plates can achieve rapid replacement of sliding plates of the bearings and shorten the interruption time of bridge traffic. Meanwhile, the rubber is in a closed environment, which can avoid the occurrence of aging rubber.
Study on design parameters of existing rigid frame bridges in guizhou province based on statistical analysis
GUO Wei, YANG Zhijun, and ZHENG Xinggui
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.032
To study the commonly employed design data of existing rigid frame bridges in Guizhou, this paper collected data from 166 bridges and analyzed the indicators such as overall overview, edge to main span ratio, box girder section data, and material content. With the revision of current standards and the emergence of new design concepts, the relevant analysis data in this paper can provide important practical references for the design of new rigid frame bridges in the future.
Study on mechanical performance of prefabricated concrete cap beam
WU Congxiao, GAO Pengyu, ZHANG Guanghai, and ZHANG Chongbin
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.033
To study the mechanical performance of cap beams of piers on prefabricated concrete bridges, this paper conducted static tests on the components of prefabricated cap beam shells poured with concrete. Meanwhile, finite element software Abaqus was adopted to numerically simulate the cap beam specimens with different structural measures of joint bars and concrete shear keys at the interface of prefabricated cap beam shells poured with concrete. Based on this, the model of prefabricated cap beams and cast-in-place cap beams was built, and pseudo-static low-cycle reset displacement analysis was carried out. The results show that the internal cast-in-place scheme of prefabricated shells is feasible for prefabricated cap beams. The integral casting and molding of bridge piers and corbels can temporarily fix the cap beams and enhance the connection performance of the joints. The prefabricated cap beam shells are poured with concrete at the interface, and the utilization of concrete shear keys and joint bars can demonstrate their sound force transmission performance. Prefabricated cap beams are equivalent to cast-in-place cap beams, and the peak bearing capacity of prefabricated cap beams is higher than that of cast-in-place cap beams, with a reduced ductility coefficient.
Forward difference iteration method for determining reasonable construction state of cable⁃stayed bridges with stacked girders
LI Jieli, XIA Yonghao, ZHANG Xiaowen, and ZHAO Changchun
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.034
To solve the problem of determining the cable force of composite girder cable-stayed bridges with stacked girders under the reasonable construction state, this paper proposed the forward difference iteration method for determining the reasonable design state of cable-stayed bridges based on the calculation principles of the forward iteration method and the difference iteration method for determining the cable force of cable-stayed bridges under the reasonable construction state. Meanwhile, a program for cable force calculation during the reasonable construction stage was written, and the automatic optimization function of cable force during the reasonable construction stage was realized. Additionally, after applying this method to a double-tower composite girder cable-stayed bridge with stacked girders, at the tenth iteration, most of the cable force deviations fell within 5%, while at the 15th iteration, most of the cable force deviations were within 3%. At the 20th iteration, the deviation of cable force for each inclined cable was within 0.5%. Compared with the forward iteration method based on the influence matrix method to determine the cable force during the construction stage, the forward difference iteration method does not require multiple extractions of complex influence matrices. Instead, it only needs to take the difference between the calculated bridge cable force and the target bridge cable force for each iteration, and then update the cable force during the construction stage for the next iteration based on the difference. This is convenient and easy to operate, and can satisfy the engineering accuracy requirements.
Discussion on pushing construction technology of multi⁃unit super long steel box girder for urban viaduct
XIAO Jun and WANG Ruoyu
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.035
In bridge engineering, pushing technology has significant advantages in crossing highways, railways, flood control embankments, and bustling urban streets. However, in actual construction, various technical difficulties may also be encountered due to structural and on-site environmental factors. This paper combined engineering practice to explore the technical difficulties in pushing construction of steel box girders for multi-unit super long urban viaducts, including instability problems during the pushing of the main girders, reasonable launching nose length, and reasonable connections between links. Finally, a systematic analysis method was developed to solve technical difficulties in engineering construction and ensure the smooth implementation of the projects.
Application of forward parametric design technology in steel arch of the No . 3 bridge in Ordos
PU Bozhou, WANG Guannan, and ZENG Yong
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.036
The No. 3 Bridge in Ordos adopts a half-through double arch bridge structure with a main span of 192 m. As this project has prominent landscape effects, abstract spatial relationships, and complex structural forms, conventional design ideas cannot meet the design requirements. The project utilizes the forward parameteric design concept and employs the "R+GH" design method to conduct three-dimensional parametric modeling of the main arch and secondary arch of the No. 3 Bridge. Meanwhile, by conducting finite element analysis, the influence of structural deformation on the derrick booms during the operation stage was evaluated, and the spatial angle of the cable conduits was corrected. The three-dimensional design results are transformed into two-dimensional drawings for output by relying on the powerful spatial design and interaction capabilities of forward parametric design. This paper elaborated on the application of forward parametric design in spatially irregular arch bridge structures, as well as the seamless connection between parametric design and structural finite element calculation, three-dimensional spatial display, two-dimensional result output, and other functions. Finally, references can be provided for the application of forward design in similar bridges.
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.037
To study the optimization of cable force on temporary piers during pushing construction of PC box girders, this paper took the continuous box girders of cross-railway pushing construction in Hunan as the research background, and built a finite element model for structural simulation analysis. Based on BP neural networks-genetic algorithm (GA), a method for optimizing cable force on temporary piers during the pushing construction of main girders was proposed. Meanwhile, by employing Matlab programming and finite element software, the optimization of cable force on temporary piers of PC pushing box girders was studied. The results show that after optimization, the maximum horizontal displacement at the top of each temporary pier is significantly reduced, with a maximum decrease of 35.0%. The maximum stress at the bottom of each pier also notably decreases and is distributed more evenly, with a maximum stress reduction of 37%. After optimization, the structural stress safety is effectively improved, which also verifies the effective application of BP neural network-GA in the optimization of cable force on temporary piers.
Analysis of frozen⁃thaw mechanical characteristics of in road culverts in plateau frozen soil region
LI Zhen and CHEN Zemeng
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.038
Based on the reconstruction project of Yangda Highway in Xizang, an important national project of the "the Belt and Road" initiative, this paper studied the frozen-thaw mechanical characteristics of culverts in plateau frozen soil regions. The mechanical models of steel corrugated pipe culverts and underwater antifreeze reinforced concrete pipe culverts in four working conditions were built by employing the Mi-das GTS NX finite element software. By setting the soil temperature change functions, this paper analyzed the internal force changes of soil layers, the internal force and displacement changes of pipe culverts and other structural layers, as well as the internal force changes of two-way HDPE high-density polyethylene geogrid before and after the frozen-thaw cycle for the pipe materials of culverts commonly utilized in the plateau regions. The results indicate that after experiencing the frozen-thaw cycle, the plastic zone of both types of pipe culverts increases, but employing underwater antifreeze reinforced concrete pipes has better coordinated deformation ability. After the frozen-thaw cycle, the main stress and shear stress change rates at the midpoint and both ends of the steel corrugated pipe culverts, as well as the displacement of different subgrade slope measurement points, are all smaller than those of the underwater antifreeze reinforced concrete pipe culverts, making them more suitable for the utilization in plateau cold regions. Additionally, laying the two-way HDPE high-density polyethylene geogrid can effectively reduce uneven deformation of pavement structural layers. Finally, the correctness of the method proposed in this paper was verified by comparing and analyzing the modeled theoretical calculated values with the detection data on the construction sites.
3D numerical analysis on interaction mechanism of two existing lines over⁃crossed by shield tunnel
ZHANG Baogang, XIE Jiachong, and HUANG Xin
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.039
To explore the collaborative deformation and interaction mechanism between two existing lines during tunnel crossing, this paper built a three-dimensional numerical model simulating the entire crossing process based on a water-conveyance tunnel crossing an existing subway section in Shenzhen. Based on actual measured data, it verified the effectiveness of the model and discussed the soil-structure interaction mechanism between two existing lines. The results show that there is a collaborative deformation effect between two existing lines, and crossing two lines is an unfavorable situation compared to crossing a single line. The influence of the upgoing line on the downgoing line after crossing is relatively little, mainly during the crossing period. The downgoing line that is crossed first has a significant effect on the upgoing line, and affects the entire process of crossing the upgoing line. Compared with crossing a single line, crossing two lines also has a significant influence on the deformation trend and surface sedimentation of existing tunnels.
Influence of foundation pit excavation on zero distance underground shield tunnel
ZHAO Peng
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.040
To understand the influence of foundation pit excavation on zero-distance underground shield tunnels, this paper built a section excavation model of interval tunnel foundation pits by employing PLAXIS 3D geotechnical finite element software based on the first zero-distance upper-span subway tunnel project in China, which is an overlapping section of a parking lot in Xiamen Metro and the main line. Meanwhile, soil excavation schemes were developed by adopting layered, zoning, strip, symmetrical and other methods to investigate the response of underground shield tunnels under three different excavation schemes. The results show that due to the consistent total excavation unloading amount, different layered and zoning excavation processes of foundation pits have little effect on the strata and underlying tunnels, with generally consistent response patterns. Under the three excavation schemes, the differences in extreme surface sedimentation behind the foundation pit wall, underground tunnels' vertical displacement and extreme bending moments are about 1%, 10%, and 3% respectively. Additionally, timely construction of the bottom plates of the foundation pits can provide the function of back pressure, which to some extent suppresses stratum displacement, tunnel deformation, and extreme internal force. On-site practice shows that the actual construction scheme is reliable, and the shield tunnel structure is safe and stable.
Application research on subway tunnel structure monitoring system based on BIM technology
LIU Jianhua, FAN Zhenyang, CHEN Zijun, LIN Jinkeng, HU Hongyi, and FU Xinsha
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.041
Real-time visual state monitoring during the construction and operation of subway tunnel projects is the key to improving the safety management of subway tunnel projects. Based on BIM technology, this paper built a subway monitoring and management system. Meanwhile, parameters such as the dip angle, stress, and displacement of the structures were monitored and controlled in real time by employing on-site monitoring equipment. Then, the monitoring data was connected with lightweight BIM models via database technology to display the mechanical response state of various structural components in the tunnels in real time, which enabled the visualization of massive monitoring data and conducted early warning on the structural safety of the tunnels by setting early warning thresholds. The system was applied to the structural monitoring of the subway tunnel in the second expressway project of the new Guangzhou Baiyun International Airport. The results show that the intelligent subway monitoring system based on BIM technology can achieve real-time visual monitoring of the safety state of the subway tunnel and timely early warning of safety hazards in the tunnel structure. Compared with traditional manual regular patrol and detection, the efficiency is greatly improved, which is of vital significance for tunnel construction and operational safety.
Construction technology of propping of loess tunnel carriage transverse passageway of highways in western Henan
ZHOU Peng, JIN Ming, GUO Jing, HUANG Tao, and LI Jiyan
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.042
The underground pit courtyard tunnel of the southward relocation project on National Trunk Way 310 was delayed by 258 m from the left line due to the influence of terrain and geology during the construction stage. The 8# transverse pedestrian passageway was changed to a transverse carriage passageway, and a working face was added to the main tunnel of the right line to ensure timely completion of the project. This paper first discussed the risks and existing problems of propping construction, and then elaborated on the construction process and support parameters of the transverse propping of the underground pit courtyard tunnels from several aspects, including strengthening the transverse carriage tunnel at the intersection, propping of the guide tunnel in the main tunnel, and construction of the three-bench construction method in the main tunnel. Furthermore, the key points of the construction process were discussed.
Study on disturbance characteristics of ground in full⁃section tunnel under advance grouting
HUANG Yueting, WANG Chonghua, WANG Hui, and WANG Qingman
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.043
The advance grouting method has a wide range of applications in tunnel construction, and its effect is influenced by factors such as hydrogeological conditions and construction techniques. Improper grouting can cause local uplifts in the strata, which can have adverse effects on the safe operation of the tunnels. Based on a construction case of a subway tunnel in Shenzhen, this paper adopted the discrete element method to explore the disturbance mechanism of advance grouting of the entire tunnel section on the geological strata. Due to the fact that advance grouting of the entire tunnel section belongs to a fluidsolid coupling problem, this paper employed a pipeline-domain model to simulate the grouting process. Specifically, pipelines were utilized to connect various fluid domains, while the fluid domains were for storing information such as the fluid pressure and flow rate. The calculation results show that during the grouting process, the slurry will produce infiltration and fracturing effects in the strata. Under the combined action of the two, the stratum disturbance can be roughly divided into four stages, including the infiltration filling, rapid uplift, uniform uplift, and slow uplift. The fracturing effect can cause a rapid stratum uplift, which occurs when the grouting pressure is greater than the minimum principal stress of the strata. Therefore, the key to preventing the stratum uplift is to make the grouting pressure less than the minimum principal stress of the strata, which is consistent with the phenomenon observed during the construction.
Comparative study and implementation of seismic retrofitting measures for multi⁃span simply supported bridges in strong earthquake areas
CHENG Xianjie and HU Hao
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.044
Based on an example of a three-span simply supported girder bridge project in a strong earthquake area in the Americas, seismic response analysis was conducted to compare and analyze the seismic response of different retrofitting methods, such as replacement of ordinary plate rubber bearings, continuous decks, addition of cable restrainers between spans, and replacement of seismic isolation bearings. Meanwhile, the analysis considered the influence of soil constraints at the back of the platform and girder collisions on seismic response. The results show that ordinary plate bearings can reduce the ductility coefficient of bridge piers and achieve seismic isolation effect, but a high risk of girder collision can easily result in the occurrence of lowering of girders. The continuous decks and cable restrainers at the pier top can effectively limit the relative displacement between girders, but special attention should be paid to the bearing capacity verification and support failure of the cable restrainers. Lead core bearings can effectively improve the seismic resistance of bridges, meet the ductility requirements of bridge piers, and reduce the girder collision risk. This paper proposed a specific implementation scheme of strengthening the original bridge by employing seismic isolation bearings and continuous decks, and replacing the continuous decks and seismic isolation bearings.
Comparative study on strut stability calculation of long⁃span highway truss suspension bridge based on chinese and european specificat ions
DUAN Baoshan, DUAN Li, LI Yuansong, and ZHANG Chunhua
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.045
This paper introduced the design methods for the stability of struts in Chinese and European specifications for steel structure bridges, and compared and analyzed the differences and similarities between the section classification, overall stability curve, and local stability curve in relevant Chinese and European specifications. By taking H-shaped steel components as an example, it calculated the strut stability and compared the results with finite element calculations. The results show that in terms of section classification, JTG D64-2015 is divided into five categories (S1, S2, S3, S4, and S5), while EC3 is divided into four categories (1, 2, 3, 4), with the corresponding relationship of mechanical performance being 1-a, 2-b, 3,4-c, and 5-d. Additionally, for the overall stability curve, when the slenderness ratio λn is no more than 1.5, the coefficient of stability corresponding to the c/d curve in JTG D64-2015 is 2%-5% lower than that of EC3. When λn is more than 1.5, the coefficients of stability corresponding to the Chinese and European specifications are basically the same. In terms of local stability, JTG D64-2015 only utilizes effective cross-sectional area calculation for the web plate, while EC3 has different calculation formulas for the flange and web plate. The comparative analysis of Chinese and European specifications and finite element calculation results shows that both the specifications underestimate the ultimate bearing capacity of struts, with the results obtained by Chinese and European specifications being 3%-13% and 1%-12% lower respectively in most cases. Relatively speaking, JTG D64-2015 in Chinese specifications is more conservative in terms of stable design.
Study on temperature gradient effect of corrugated steel web box girder considering influence of boundary conditions
LEI Yao, LI Ming, LU Naiwei, and LIU Yang
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.013
To study the stress characteristics of corrugated steel web box girders under vertical temperature gradient loads, this paper employed the civil structural nonlinear simulation software Midas FEA to build a three-dimensional finite element analysis model of corrugated steel web box girder bridges. Meanwhile, the temperature effects of corrugated steel web box girders under two constraint conditions of simply supported structures and continuous structures under vertical temperature gradient loads were compared and analyzed. The results demonstrate that under vertical temperature gradient loads, the temperature effect generated by corrugated steel web box girders is significant and cannot be ignored. The temperature effect of corrugated steel web box girders under continuous structural constraints is more significant than that of the simply supported structures under temperature gradient loads. Therefore, the influence of boundary constraint conditions on the temperature effect of corrugated steel web box girder bridges should be comprehensively considered. Additionally, the maximum temperature stress is obtained at the connection joint between the top and bottom concrete and the corrugated steel web, and the peak stress of this structure should be given special attention during the design stage.
Research on parameters of bridge moving vehicles load based on WOA⁃BP neural network
WANG Xiaohui, ZHANG Bangru, TAO Zhiren, CHI Xinyan, WAN Lixing, and PENG Jianxin
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.014
To efficiently and accurately identify the moving load parameters on bridge structures, this paper proposed a layered identification method for moving loads on bridges using BP neural networks based on the whale optimization algorithm (WOA), and built a moving load parameter identification model based on WOA-BP neural networks. By adopting this moving load identification model, step-by-step coupling identification was conducted on the action lane, speed, and load capacity of vehicles on the bridge. Additionally, by taking a prestressed simply supported box girder bridge as the research project, the applicability of the proposed method and neural network identification model was verified via dynamic response measurement data under the action of random traffic flow and the combination of video data of vehicles driving on the bridge. The results reveal that the proposed method for identifying moving load parameters features high identification accuracy, fast convergence speed, strong robustness and noise resistance, and can accurately identify bridges' moving load parameters.
Experimental study on effect of fiber length on axial tensile properties of UHPC
YUAN Ming, HAN Huaizhi, YAN Donghuang, HUANG Lian, and ZENG Xiaojun
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.015
To study the effect of steel fiber length on the axial tensile properties of UHPC, this paper selected straight circular fiber with the same diameter but different lengths and mixed it into UHPC. By conducting analysis on the mechanical properties, tensile deformation, and post-fracture strength of UHPC, the influence of fiber length on the axial tensile properties of UHPC was obtained. Meanwhile, the fracture resistance and toughening effects of fiber length were evaluated, with the reasons for the influence of fiber length on the axial tensile properties of UHPC clarified. The results show that the axial tensile properties of UHPC increase with the rising fiber length. The effect of 20 mm fiber length on the peak UHPC stress increases by 57.76% compared to 6 mm fiber length. The post-fracture strength of UHPC grows with the increasing fiber length. Under the same fracture width and fiber length of 20 mm, the UHPC stress is the highest, and the UHPC stress is the lowest under the fiber length of 6 mm. UHPC with 20 mm fiber length mixed has the maximum deformation in the strain hardening stage, while UHPC with 13 mm fiber length has the maximum deformation in the stress softening stage. The UHPC fluidity decreases with the increasing fiber length. Additionally, the effect of fiber length on the axial tensile properties of UHPC is altered by changing the contact surface size between the fiber and the matrix. Specifically, the longer fiber leads to the larger contact surface between the fiber and the matrix, bringing about stronger cohesion between the fiber and the matrix.
Research on lightweight method of BIM model for bridge engineering based on CATIA CAA
ZHANG Yunhe, ZHU Ming, and FAN Yufeng
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.016
Highway construction projects are mostly linear projects with zonal distribution, which contain multiple structures and are closely integrated with the geographical environment. During their applications in BIM, they often face the problems of massive data delivery and multi-source heterogeneous data fusion. Therefore, based on the secondary development of CATIA CAA, this paper proposed a lightweight method for the BIM model in bridge engineering, elaborated on the general lightweight concept, and then detailed the lightweight process, with a BIM model lightweight program independently developed. By taking the Heishuihe Bridge as an example, the functionality and stability of the program were tested, and the digital delivery and application of lightweight follow-up models on the BIM platform were achieved. Finally, the results indicate that this lightweight method has certain application prospects and practical significance.
Overall design of main bridge of qingshui river bridge in Baoji
WANG Zhen, NIU Yongzhe, and LI Haipeng
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.017
The main bridge of Qingshui River Bridge is a (65+5×120+65) m continuous rigid frame bridge. The main girder adopts a combination of corrugated steel webs and concrete box girders, with double-amplitude single-box single-chamber sections. The corrugated steel webs adopt 1600 type corrugated steel plates, and are connected to the top and bottom plates respectively with double PBL shear keys and ∟200 angle steel. Longitudinal prestressed steel bars are divided into internal tendons and external tendons. The lower structure adopts double thin-walled hollow piers, bearing platforms, and bored pile foundations, with a maximum pier height of 73 m and an average pier height of 71.4 m. The main bridge adopts a cantilever cast-in-place construction scheme, and the closure sequence is respectively the edge span, central span, secondary central span, and secondary side span. The closure temperature is 10℃, and the jacking force is 500 kN for the central span, 800 kN for the secondary central span, and 1200 kN for the secondary side span. Additionally, Ansys 14.0 was adopted to analyze the torsional cross slope and warping ratio of the central span section, which reveals that the arrangement of six diaphragms is more reasonable. By comparing the most unfavorable eccentric load and symmetrical load conditions, the live load eccentric load coefficient of the corrugated steel web under stress is determined to be 1.3. Additionally, Midas/Civil 2019 was employed for longitudinal static calculation during construction and bridge completion stages, shear yielding and flexure calculation of corrugated steel webs, shear strength calculation of shear force connectors of top and bottom plates, and transverse static and antiseismic calculation of the composite girder central span, root and pier top sections. The results show that all indicators of the bridge meet the requirements of the specifications.
Error analysis of relative angle at the central⁃span closure of long⁃span composite girder cable⁃stayed bridges
TU Guanya and ZHOU Chengyong
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.018
According to the theory of the non-stress state method, the elastic curve of the main girder during the central-span closure should remain continuous to ensure that the internal forces and alignment of the built cable-stayed bridge reach the target state after construction, which means the relative angle of the main girders on both sides of the closure should be zero. However, it is difficult to meet the condition of absolute zero of the relative angle in practical engineering. By taking the Chibi Changjiang River Highway Bridge as the engineering background, this paper studied the influence of relative angle error during the central-span closure of a large-span composite girder cable-stayed bridge on the final target state of the built bridge, thus determining the allowable range of relative angle error. The analysis results reveal that the relative angle error of the main girders on both sides of the closure gap during the central-span closure mainly has a significant influence on the stress of the main girders under the target state of the built bridge, with little effect exerted on tower deviation, cable force, and main girder alignment. For the Chibi Changjiang River Highway Bridge, the allowable relative angle error of the main girders on both sides of the closure can be set as ±1×10-3 rad during the central-span closure. Within this range, it can be considered that the elastic curves of the main girders on both sides of the closure are continuous.
Research on comprehensive early warning system with multi⁃indicators for long⁃span steel arch bridges
ZHANG Yuanchuan, SU Cheng, WANG Yonghui, and ZHENG Chun
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.019
To detect structural abnormalities timely and ensure the safe operation of bridges, this paper took the health monitoring system of Xinguang Bridge in Guangzhou as the engineering background, and conducted research on a comprehensive multi-indicator early warning system for large-span steel arch bridges. Meanwhile, it selected multiple warning indicators from the categories of environmental effects and structural responses, set early warning indicator thresholds based on the distribution pattern of measured data, and formulated scoring standards for early warning indicators to score each early warning indicator. The analytic hierarchy process (AHP) was employed to determine the weight of various early warning indicators, and calculate the comprehensive early warning scores for environmental effects and structural responses, thus obtaining the comprehensive early warning level for environmental effects and structural response. In addition, a comprehensive early warning matrix for the structure was constructed, and the comprehensive early warning level for the structure was determined, with the corresponding post-warning measures developed. The early warning system was utilized to conduct early warning and analysis on the state of Xinguang Bridge during a certain period. The results show that the bridge is in the level 2 early warning state, with generally sound conditions and normal operation of the structure. However, the monitoring frequency should be appropriately increased.
Experimental study on double cracks fatigue life of cable steel wire
XU Hongsheng, WANG Zhihong, and YAN Donghuang
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.020
At present, research on the residual fatigue life of corroded steel wires usually adopts the method of equivalent simulation of typical pits into prefabricated single cracks for treatment. However, in the actual corroded steel wires of bridge cables, multiple typical pits are often adjacent, and the effect of multiple pits on the residual fatigue life is not clear. Therefore, it is necessary to study the distribution of multiple pits on the residual fatigue life of steel wires. This paper analyzed and studied the influence of different axial distances and circumferential angles of double pits on the fatigue life of steel wires by transforming double pits into equivalent double prefabricated cracks. The experimental results show that under smaller axial distance between double cracks, the residual fatigue life of the steel wires is greater than that of a single crack. The residual fatigue life of steel wires decreases with the increasing axial distance of double-crack steel wires. The influence of the circumferential angle of double cracks on the fatigue life of steel wires has significant discreteness. In the case of lateral distribution, the residual fatigue life of single and double cracks is basically the same, with the residual fatigue life of steel wires being the smallest. Additionally, the residual fatigue life of double cracks is significantly improved under vertical distribution. Under distribution on the same side, a significant influence is exerted on the residual fatigue life of the steel wires, with the highest residual fatigue life. However, regardless of the crack distribution patterns, the mutual influence between the two gradually decreases with the increasing axial distance. When the distance between the double pits is large enough, the effect on the overall residual fatigue life of steel wires is basically equivalent to that of a single crack. Therefore, simulating the typical situation of multiple adjacent pits as a single crack evaluation method is conservative, and further research is needed to investigate its influence on residual fatigue life.
Study on mechanical behavior of a new resistance ring grouting sleeve joint
MENG Lingxiao, FU Tao, SUN Zhonghua, XU Yingdong, and LU Peng
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.021
The construction technology of prefabricated bridges features environmental protection, noise reduction, construction quality improvement, and construction efficiency enhancement. The reliable connection of the main load-bearing steel bars in prefabricated components is the key to ensuring the sound performance of the prefabricated structure. Grouting sleeve connection is an important way of connecting steel bars in prefabricated structures. This paper proposed the construction of a new type of resistance ring grouting sleeve, and analyzed the working performance of the steel bar grouting sleeve connection in the working conditions of uniaxial tension and reciprocating tensile compression by conducting finite element numerical simulation. The results reveal that the mechanical performance of various components of the new resistance ring grouting sleeve in uniaxial tension conditions meets the requirements of the specifications. After 20 cycles of high-stress reciprocating tensile compression, the total residual deformation is 0.24 mm, which belongs to the Class I joint. As the cyclic loading continues, the energy consumption and rigidity of the grouting material decrease after the tenth cycle, and the grouting material forms a relatively stable and reliable path for load transmission. At this time, the maximum third principal stress of the grouting material under tensile compression tends to stabilize, and the grouting material forms a good force transmission combination with the steel bars and sleeve, with generally sound performance of steel bar sleeve components.
Construction control measures and temperature effect analysis of arch⁃type bridge tower
WANG Wenming, CHAI Shengbo, NIE Ningbo, and WEI Qian
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.022
To ensure that the alignment and internal forces of the cable-stayed arch-type bridge towers meet the design requirements and achieve safe construction of the bridge towers, this paper built a finite element model to study the variation rules of the alignment and stress during the construction of arch-type bridge towers, analyzing the influence of temperature effects on the arch-type bridge towers, with relevant control measures proposed. The results indicate that when the temperature gradient in the transverse direction of the bridge is only considered, under the same temperature gradient, the tensile stress of the outer tower limbs affected by sunlight is greater than that of the inner tower limbs, and the displacement of the tower limbs on both sides is the same and consistent with the sunlight direction. During the construction stage of the lower crossbeam and the closure stage of the bridge tower, the temperature effect on the bridge tower decreases. Additionally, the setting of the temporary lateral bracing, application of jacking force, and setting of the offsetting amount can reduce the axial displacement of tower limbs and tensile stress of tower limbs during construction, avoiding bridge tower cracking. After the jacking force application of the lateral bracing, the axial displacement of the bridge tower can be controlled within 5 mm. When two pieces of lateral bracing are set up, the removal sequence of temporary lateral bracing may not be considered. By comparing measured and theoretical data, it has been further verified that the setting of temporary lateral bracing and application of jacking force can effectively decrease the deviation of the bridge tower axis, with significant influence of the temperature gradient exerted on the alignment and stress of bridge towers.
Research on influence of pier abutment construction on existing business line
TAN Chenglong, GONG Tianhao, LIU Xin, and BAI Pengpeng
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.024
The construction safety problems of the business lines are increasingly catching people's attention. The pier abutment construction will inevitably cause changes in the groundwater level and stress field in the surrounding foundation, resulting in deformation of the surrounding soil and ultimately additional deformation near the business lines. In response to the above problems, based on a deep foundation pit project, this paper built a Plaxis 3D finite element model to explore the influence of construction steps of pier abutments on the displacement and deformation of the business lines' bridge abutments. Meanwhile, it simulated the actual working conditions, and compared and analyzed actual monitoring data. The results show that the pier abutment construction has little effect on the displacement of bridge abutments of the business lines. Under the most unfavorable combination, the displacement is 3-6 mm, and the finite element simulation results are basically consistent with the measured results. The excavation of the lowest soil layer in the foundation pit has the greatest influence on the displacement of the business lines.
Analysis of cable force error of cable installation system
XU Feng, SONG Junxi, ZHANG Feng, and GAO Lei
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.025
The cable installation method is a commonly employed method for the construction of large-span concrete-filled steel tube arch bridges. The cable is the main load-bearing component, and it is necessary to conduct calculation analysis and construction monitoring. By taking the Wumei River Grand Bridge as an example, this paper conducted research on the calculation method of cable force for cable installation systems. Meanwhile, it carried out cable force calculation analysis and on-site testing of the actual bridge of the 400 m suspension span cable of the upper supported concrete-filled steel tube arch bridge with a calculated span of 300 m to verify the cable force of a single cable and analyze the calculated and measured errors. The results show that the overall deviation between the calculated and measured cable force values is about 8%. As the calculated values are based on the maximum cable force state at the central span, the average deviation of the Huangping'an installation section is relatively small. In addition to calculation errors, the reverse friction force of the cable saddle at the tower during cable installation construction, temperature changes during installation, and slipping between cable fasteners and cables can also affect the results of cable force testing. After correction, the overall deviation between tested cable force values and calculated values is reduced. When the crane slides to the central span, the maximum cable force occurs at the rear cable anchor anchorage.
Study on load test of long link multi⁃span PC continuous wide box⁃girder bridge
MAO Dejun, WU Weibin, GUO Jun, LAN Shuwei, XU Baishun, and WANG Tao
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.026
To study the actual bearing performance of a long link multi-span PC continuous wide box-girder bridge in a certain city, this paper conducted on-site static and dynamic tests on it. The static tests mainly tested the sedimentation of bridge pivots, deflection and strain of control sections. The dynamic tests included the modal test and sports car test, mainly testing the natural frequency of vibration, damping ratio, and coefficient of impact of the bridge. The comprehensive results of static and dynamic tests show that under the normal use state, the bearing capacity of the bridge meets the load level requirements of City A, with the dynamic working performance satisfying the requirements for utilization. Further efforts should be made to strengthen the research on the lower limit values of the normal range of deflection verification coefficients and strain verification coefficients. It is suggested that the range of normal working values for the bridge damping ratio should be provided.
Analysis of factors affecting stress and displacement of continuous rigid frame bridge in plateau environment
HE Bowen, SUN Hao, and WANG Shuo
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.027
As China's construction industry experiences booming development and the demand for transportation is increasing, continuous rigid frame bridges have become the main structural system for large-span bridges due to their advantages of avoiding system transformation, reducing deck expansion joints, and providing comfortable driving. However, due to the characteristics of their rigid frame systems and the shrinkage and creep properties of concrete materials, continuous rigid frame bridges are sensitive to changes in environmental temperature and humidity, which can even severely result in engineering diseases such as cracks and large deformation in the bridge, causing decreased driving comfort and safety hazards. By taking the the Yarlung Zangbo River Bridge as the engineering background, this paper studied the influence of temperature and humidity on the stress of continuous rigid frame bridges in plateau environment by finite element calculation. The calculation results show that temperature changes in plateau environments significantly affect the stress of rigid frame bridges. Temperature gradient changes can easily cause uneven structural stress distribution, while overall temperature changes significantly affect the displacement of rigid frame bridges. Additionally, the influence of humidity in plateau environments on bridge structures is mainly reflected in the deflection displacement at the central span, and the deflection displacement of continuous rigid frame bridges increases significantly in low-humidity environments.
Mechanism analysis of temperature effects on closure length of main girder of long⁃span cable⁃stayed bridges
FU Chunyu, SHEN Luming, and YAN Peng
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.028
To accurately predict the closure length of the main beam of a large-span cable-stayed bridge under the action of temperature, this paper employed an elastic foundation beam model to propose a differential equilibrium equation for the axial deformation of the main beam. By combining structural temperature deformation and support boundary conditions, a prediction method for obtaining the closure length of the main beam was solved to reveal the variation law of the closure under the action of temperature. Meanwhile, the proposed method was validated by finite element numerical analysis results and continuous observation data of the Yanpingba Yangtze River Bridge. The results show that the closure length of the main beam varies linearly with the action of temperature, and compared to the temperature difference between the cable and the main beam, the overall closure length produced by the action of overall temperature difference of the main beam varies greatly. Additionally, the change is less affected by the rigidity of the cable support, but it will increase with the rising cross-sectional area of the main beam.
Bond slip characteristics of HB⁃FRP based on arc⁃length method
XU Xiangfeng, LI Pengfei, LI Xinxin, ZHANG Luke, and GAO Lei
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.029
The bonding performance between hybrid bonding FRP (HB-FRP) and concrete is crucial for HB-FRP reinforcement of concrete structures. This paper built a simple shear numerical model for HB-FRP, which considered both the interfacial bond slip between FRP and concrete by adopting bilinear constitutive analysis, and the interfacial bond slip at the steel fastener location by employing trilinear constitutive analysis. Meanwhile, the bond slip properties at the steel fastener location were simulated by double springs. Based on the arc-length method, the entire process of loading and unloading of the HB-FRP simple shear model was carried out to study its stress performance. Additionally, the experimental data was compared and analyzed to verify the effectiveness of the numerical model, reveal the bond slip properties of HB-FRP during unloading, and correct the existing bond slip model. Parameter analysis was conducted on the adhesive length, and based on the analysis results, the effective bonding length of HB-FRP was calculated to be around 2500 mm, which reveals a linear relationship between the number of steel fasteners and their ability to resist stripping loads within the effective bonding length range.
Bearing capacity analysis of steel⁃concrete composite girder⁃abutment joint by finite element method
SONG Chengzhi, XU Bing, HU Qiang, and WANG Xu
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.030
Jointless bridges can effectively alleviate and eliminate the durability problems of bridge expansion joints and supports, and have broad application prospects in small and medium span bridges. Due to the integral frame structures formed by the upper and lower structures, the stress distribution of the main girder-abutment joint in the steel-concrete composite integral abutment and jointless bridges is complex. This paper built a nonlinear main girder-abutment finite element model, and selected the embedded depth of the steel girder, deck thickness of concrete bridges, and transverse width of the abutment as research parameters to analyze their effects on the stress performance of the joints. Meanwhile, based on this, a stress analysis model of the joints was built, with a bearing capacity calculation formula for the joints proposed. The results show that the embedded depth of the main girder and transverse width of the abutment are key parameters influencing the bearing capacity of the joints. The bearing capacity calculation formula proposed in this paper is in sound agreement with the finite element calculation results.
Research on performance inspection and evaluation of in⁃service bridge bearings and improvement technology
ZHANG Jingyue, WANG Zhiqiang, and LIU Fukang
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.031
To study the quality disease and residual mechanical performance of bearings under the replacement of in-service bridges, this paper took the pot bearings under the replacement of a real bridge as an example to conduct appearance, mechanical perfornance, and raw material testing. Meanwhile, it determined the main causes of the disease led to by the replacement, analyzed the influence of bearing disease on the restrained concrete, and studied the performance improvement technology of in-service old bearings, with mechanical performance verification carried out. The results reveal that the main disease of pot bearings (replacement) is excessive wear of the sliding plates, which increases the friction coefficient of the bearings to 0.19 and changes the original constraint system of the bridge. Additionally, the process of employing steel hoops and new sliding plates can achieve rapid replacement of sliding plates of the bearings and shorten the interruption time of bridge traffic. Meanwhile, the rubber is in a closed environment, which can avoid the occurrence of aging rubber.
Study on design parameters of existing rigid frame bridges in guizhou province based on statistical analysis
GUO Wei, YANG Zhijun, and ZHENG Xinggui
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.032
To study the commonly employed design data of existing rigid frame bridges in Guizhou, this paper collected data from 166 bridges and analyzed the indicators such as overall overview, edge to main span ratio, box girder section data, and material content. With the revision of current standards and the emergence of new design concepts, the relevant analysis data in this paper can provide important practical references for the design of new rigid frame bridges in the future.
Study on mechanical performance of prefabricated concrete cap beam
WU Congxiao, GAO Pengyu, ZHANG Guanghai, and ZHANG Chongbin
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.033
To study the mechanical performance of cap beams of piers on prefabricated concrete bridges, this paper conducted static tests on the components of prefabricated cap beam shells poured with concrete. Meanwhile, finite element software Abaqus was adopted to numerically simulate the cap beam specimens with different structural measures of joint bars and concrete shear keys at the interface of prefabricated cap beam shells poured with concrete. Based on this, the model of prefabricated cap beams and cast-in-place cap beams was built, and pseudo-static low-cycle reset displacement analysis was carried out. The results show that the internal cast-in-place scheme of prefabricated shells is feasible for prefabricated cap beams. The integral casting and molding of bridge piers and corbels can temporarily fix the cap beams and enhance the connection performance of the joints. The prefabricated cap beam shells are poured with concrete at the interface, and the utilization of concrete shear keys and joint bars can demonstrate their sound force transmission performance. Prefabricated cap beams are equivalent to cast-in-place cap beams, and the peak bearing capacity of prefabricated cap beams is higher than that of cast-in-place cap beams, with a reduced ductility coefficient.
Forward difference iteration method for determining reasonable construction state of cable⁃stayed bridges with stacked girders
LI Jieli, XIA Yonghao, ZHANG Xiaowen, and ZHAO Changchun
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.034
To solve the problem of determining the cable force of composite girder cable-stayed bridges with stacked girders under the reasonable construction state, this paper proposed the forward difference iteration method for determining the reasonable design state of cable-stayed bridges based on the calculation principles of the forward iteration method and the difference iteration method for determining the cable force of cable-stayed bridges under the reasonable construction state. Meanwhile, a program for cable force calculation during the reasonable construction stage was written, and the automatic optimization function of cable force during the reasonable construction stage was realized. Additionally, after applying this method to a double-tower composite girder cable-stayed bridge with stacked girders, at the tenth iteration, most of the cable force deviations fell within 5%, while at the 15th iteration, most of the cable force deviations were within 3%. At the 20th iteration, the deviation of cable force for each inclined cable was within 0.5%. Compared with the forward iteration method based on the influence matrix method to determine the cable force during the construction stage, the forward difference iteration method does not require multiple extractions of complex influence matrices. Instead, it only needs to take the difference between the calculated bridge cable force and the target bridge cable force for each iteration, and then update the cable force during the construction stage for the next iteration based on the difference. This is convenient and easy to operate, and can satisfy the engineering accuracy requirements.
Discussion on pushing construction technology of multi⁃unit super long steel box girder for urban viaduct
XIAO Jun and WANG Ruoyu
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.035
In bridge engineering, pushing technology has significant advantages in crossing highways, railways, flood control embankments, and bustling urban streets. However, in actual construction, various technical difficulties may also be encountered due to structural and on-site environmental factors. This paper combined engineering practice to explore the technical difficulties in pushing construction of steel box girders for multi-unit super long urban viaducts, including instability problems during the pushing of the main girders, reasonable launching nose length, and reasonable connections between links. Finally, a systematic analysis method was developed to solve technical difficulties in engineering construction and ensure the smooth implementation of the projects.
Application of forward parametric design technology in steel arch of the No . 3 bridge in Ordos
PU Bozhou, WANG Guannan, and ZENG Yong
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.036
The No. 3 Bridge in Ordos adopts a half-through double arch bridge structure with a main span of 192 m. As this project has prominent landscape effects, abstract spatial relationships, and complex structural forms, conventional design ideas cannot meet the design requirements. The project utilizes the forward parameteric design concept and employs the "R+GH" design method to conduct three-dimensional parametric modeling of the main arch and secondary arch of the No. 3 Bridge. Meanwhile, by conducting finite element analysis, the influence of structural deformation on the derrick booms during the operation stage was evaluated, and the spatial angle of the cable conduits was corrected. The three-dimensional design results are transformed into two-dimensional drawings for output by relying on the powerful spatial design and interaction capabilities of forward parametric design. This paper elaborated on the application of forward parametric design in spatially irregular arch bridge structures, as well as the seamless connection between parametric design and structural finite element calculation, three-dimensional spatial display, two-dimensional result output, and other functions. Finally, references can be provided for the application of forward design in similar bridges.
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.037
To study the optimization of cable force on temporary piers during pushing construction of PC box girders, this paper took the continuous box girders of cross-railway pushing construction in Hunan as the research background, and built a finite element model for structural simulation analysis. Based on BP neural networks-genetic algorithm (GA), a method for optimizing cable force on temporary piers during the pushing construction of main girders was proposed. Meanwhile, by employing Matlab programming and finite element software, the optimization of cable force on temporary piers of PC pushing box girders was studied. The results show that after optimization, the maximum horizontal displacement at the top of each temporary pier is significantly reduced, with a maximum decrease of 35.0%. The maximum stress at the bottom of each pier also notably decreases and is distributed more evenly, with a maximum stress reduction of 37%. After optimization, the structural stress safety is effectively improved, which also verifies the effective application of BP neural network-GA in the optimization of cable force on temporary piers.
Analysis of frozen⁃thaw mechanical characteristics of in road culverts in plateau frozen soil region
LI Zhen and CHEN Zemeng
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.038
Based on the reconstruction project of Yangda Highway in Xizang, an important national project of the "the Belt and Road" initiative, this paper studied the frozen-thaw mechanical characteristics of culverts in plateau frozen soil regions. The mechanical models of steel corrugated pipe culverts and underwater antifreeze reinforced concrete pipe culverts in four working conditions were built by employing the Mi-das GTS NX finite element software. By setting the soil temperature change functions, this paper analyzed the internal force changes of soil layers, the internal force and displacement changes of pipe culverts and other structural layers, as well as the internal force changes of two-way HDPE high-density polyethylene geogrid before and after the frozen-thaw cycle for the pipe materials of culverts commonly utilized in the plateau regions. The results indicate that after experiencing the frozen-thaw cycle, the plastic zone of both types of pipe culverts increases, but employing underwater antifreeze reinforced concrete pipes has better coordinated deformation ability. After the frozen-thaw cycle, the main stress and shear stress change rates at the midpoint and both ends of the steel corrugated pipe culverts, as well as the displacement of different subgrade slope measurement points, are all smaller than those of the underwater antifreeze reinforced concrete pipe culverts, making them more suitable for the utilization in plateau cold regions. Additionally, laying the two-way HDPE high-density polyethylene geogrid can effectively reduce uneven deformation of pavement structural layers. Finally, the correctness of the method proposed in this paper was verified by comparing and analyzing the modeled theoretical calculated values with the detection data on the construction sites.
3D numerical analysis on interaction mechanism of two existing lines over⁃crossed by shield tunnel
ZHANG Baogang, XIE Jiachong, and HUANG Xin
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.039
To explore the collaborative deformation and interaction mechanism between two existing lines during tunnel crossing, this paper built a three-dimensional numerical model simulating the entire crossing process based on a water-conveyance tunnel crossing an existing subway section in Shenzhen. Based on actual measured data, it verified the effectiveness of the model and discussed the soil-structure interaction mechanism between two existing lines. The results show that there is a collaborative deformation effect between two existing lines, and crossing two lines is an unfavorable situation compared to crossing a single line. The influence of the upgoing line on the downgoing line after crossing is relatively little, mainly during the crossing period. The downgoing line that is crossed first has a significant effect on the upgoing line, and affects the entire process of crossing the upgoing line. Compared with crossing a single line, crossing two lines also has a significant influence on the deformation trend and surface sedimentation of existing tunnels.
Influence of foundation pit excavation on zero distance underground shield tunnel
ZHAO Peng
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.040
To understand the influence of foundation pit excavation on zero-distance underground shield tunnels, this paper built a section excavation model of interval tunnel foundation pits by employing PLAXIS 3D geotechnical finite element software based on the first zero-distance upper-span subway tunnel project in China, which is an overlapping section of a parking lot in Xiamen Metro and the main line. Meanwhile, soil excavation schemes were developed by adopting layered, zoning, strip, symmetrical and other methods to investigate the response of underground shield tunnels under three different excavation schemes. The results show that due to the consistent total excavation unloading amount, different layered and zoning excavation processes of foundation pits have little effect on the strata and underlying tunnels, with generally consistent response patterns. Under the three excavation schemes, the differences in extreme surface sedimentation behind the foundation pit wall, underground tunnels' vertical displacement and extreme bending moments are about 1%, 10%, and 3% respectively. Additionally, timely construction of the bottom plates of the foundation pits can provide the function of back pressure, which to some extent suppresses stratum displacement, tunnel deformation, and extreme internal force. On-site practice shows that the actual construction scheme is reliable, and the shield tunnel structure is safe and stable.
Application research on subway tunnel structure monitoring system based on BIM technology
LIU Jianhua, FAN Zhenyang, CHEN Zijun, LIN Jinkeng, HU Hongyi, and FU Xinsha
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.041
Real-time visual state monitoring during the construction and operation of subway tunnel projects is the key to improving the safety management of subway tunnel projects. Based on BIM technology, this paper built a subway monitoring and management system. Meanwhile, parameters such as the dip angle, stress, and displacement of the structures were monitored and controlled in real time by employing on-site monitoring equipment. Then, the monitoring data was connected with lightweight BIM models via database technology to display the mechanical response state of various structural components in the tunnels in real time, which enabled the visualization of massive monitoring data and conducted early warning on the structural safety of the tunnels by setting early warning thresholds. The system was applied to the structural monitoring of the subway tunnel in the second expressway project of the new Guangzhou Baiyun International Airport. The results show that the intelligent subway monitoring system based on BIM technology can achieve real-time visual monitoring of the safety state of the subway tunnel and timely early warning of safety hazards in the tunnel structure. Compared with traditional manual regular patrol and detection, the efficiency is greatly improved, which is of vital significance for tunnel construction and operational safety.
Construction technology of propping of loess tunnel carriage transverse passageway of highways in western Henan
ZHOU Peng, JIN Ming, GUO Jing, HUANG Tao, and LI Jiyan
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.042
The underground pit courtyard tunnel of the southward relocation project on National Trunk Way 310 was delayed by 258 m from the left line due to the influence of terrain and geology during the construction stage. The 8# transverse pedestrian passageway was changed to a transverse carriage passageway, and a working face was added to the main tunnel of the right line to ensure timely completion of the project. This paper first discussed the risks and existing problems of propping construction, and then elaborated on the construction process and support parameters of the transverse propping of the underground pit courtyard tunnels from several aspects, including strengthening the transverse carriage tunnel at the intersection, propping of the guide tunnel in the main tunnel, and construction of the three-bench construction method in the main tunnel. Furthermore, the key points of the construction process were discussed.
Study on disturbance characteristics of ground in full⁃section tunnel under advance grouting
HUANG Yueting, WANG Chonghua, WANG Hui, and WANG Qingman
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.043
The advance grouting method has a wide range of applications in tunnel construction, and its effect is influenced by factors such as hydrogeological conditions and construction techniques. Improper grouting can cause local uplifts in the strata, which can have adverse effects on the safe operation of the tunnels. Based on a construction case of a subway tunnel in Shenzhen, this paper adopted the discrete element method to explore the disturbance mechanism of advance grouting of the entire tunnel section on the geological strata. Due to the fact that advance grouting of the entire tunnel section belongs to a fluidsolid coupling problem, this paper employed a pipeline-domain model to simulate the grouting process. Specifically, pipelines were utilized to connect various fluid domains, while the fluid domains were for storing information such as the fluid pressure and flow rate. The calculation results show that during the grouting process, the slurry will produce infiltration and fracturing effects in the strata. Under the combined action of the two, the stratum disturbance can be roughly divided into four stages, including the infiltration filling, rapid uplift, uniform uplift, and slow uplift. The fracturing effect can cause a rapid stratum uplift, which occurs when the grouting pressure is greater than the minimum principal stress of the strata. Therefore, the key to preventing the stratum uplift is to make the grouting pressure less than the minimum principal stress of the strata, which is consistent with the phenomenon observed during the construction.
Comparative study and implementation of seismic retrofitting measures for multi⁃span simply supported bridges in strong earthquake areas
CHENG Xianjie and HU Hao
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.044
Based on an example of a three-span simply supported girder bridge project in a strong earthquake area in the Americas, seismic response analysis was conducted to compare and analyze the seismic response of different retrofitting methods, such as replacement of ordinary plate rubber bearings, continuous decks, addition of cable restrainers between spans, and replacement of seismic isolation bearings. Meanwhile, the analysis considered the influence of soil constraints at the back of the platform and girder collisions on seismic response. The results show that ordinary plate bearings can reduce the ductility coefficient of bridge piers and achieve seismic isolation effect, but a high risk of girder collision can easily result in the occurrence of lowering of girders. The continuous decks and cable restrainers at the pier top can effectively limit the relative displacement between girders, but special attention should be paid to the bearing capacity verification and support failure of the cable restrainers. Lead core bearings can effectively improve the seismic resistance of bridges, meet the ductility requirements of bridge piers, and reduce the girder collision risk. This paper proposed a specific implementation scheme of strengthening the original bridge by employing seismic isolation bearings and continuous decks, and replacing the continuous decks and seismic isolation bearings.
Comparative study on strut stability calculation of long⁃span highway truss suspension bridge based on chinese and european specificat ions
DUAN Baoshan, DUAN Li, LI Yuansong, and ZHANG Chunhua
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.045
This paper introduced the design methods for the stability of struts in Chinese and European specifications for steel structure bridges, and compared and analyzed the differences and similarities between the section classification, overall stability curve, and local stability curve in relevant Chinese and European specifications. By taking H-shaped steel components as an example, it calculated the strut stability and compared the results with finite element calculations. The results show that in terms of section classification, JTG D64-2015 is divided into five categories (S1, S2, S3, S4, and S5), while EC3 is divided into four categories (1, 2, 3, 4), with the corresponding relationship of mechanical performance being 1-a, 2-b, 3,4-c, and 5-d. Additionally, for the overall stability curve, when the slenderness ratio λn is no more than 1.5, the coefficient of stability corresponding to the c/d curve in JTG D64-2015 is 2%-5% lower than that of EC3. When λn is more than 1.5, the coefficients of stability corresponding to the Chinese and European specifications are basically the same. In terms of local stability, JTG D64-2015 only utilizes effective cross-sectional area calculation for the web plate, while EC3 has different calculation formulas for the flange and web plate. The comparative analysis of Chinese and European specifications and finite element calculation results shows that both the specifications underestimate the ultimate bearing capacity of struts, with the results obtained by Chinese and European specifications being 3%-13% and 1%-12% lower respectively in most cases. Relatively speaking, JTG D64-2015 in Chinese specifications is more conservative in terms of stable design.
Pavement Structure and Materials
Numerical study on effect of heterogenicity on micro⁃cracking behavior of cement⁃stabilized macadam material
DONG Qiao, YUAN Jiawei, ZHAO Xiaokang, and CHEN Xueqin
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.046
To investigate the effect of heterogeneity of cement mortar on the micro-cracking behavior of cement-stabilized macadam (CSM) material, this paper built a circular aggregate micro-fracture model based on the finite element method (FEM). Meanwhile, the micro-cracking behavior of the material was simulated by embedding a zero-thickness cohesive element with a bilinear cohesive zone model, and the material random field with Weibull distribution was introduced to characterize the heterogeneity characteristics of the mortar matrix and interface transition zone (ITZ). Based on virtual semicircular bending (SCB) tests, this paper simulated the micro-cracking process and analyzed the influence of material homogeneity on the micro-cracking behavior of CSM. The results reveal that the built heterogeneous micro-fracture model can achieve accurate simulation of micro-fractures. The generation of macroscopic cracks in CSM material undergoes the process of micro-crack initiation and rapid penetration, and interface and pore defects are the weak areas for micro-crack propagation. The crack resistance of CSM material decreases with the increasing non-uniformity of the random field. It is recommended that effective measures should be taken to improve the mixing uniformity of cement mortar in the actual construction process to enhance the crack resistance of CSM material.
Study on preparation and properties of new temperature regeneration agent
WANG Guan, SHI Nan, FAN Wenmiao, YIN Liyang, WANG Xinyang, and ZHAO Pinhui
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.047
In the production and application of temperature regeneration asphalt mixtures, temperature regeneration agents are crucial for the performance of asphalt mixtures. Based on the functions of raw materials such as temperature mixing agents, regeneration agents and penetrants, this paper determined the appropriate mixing content by studying the influence of aged asphalt's performance. Then, a new type of temperature regeneration agent was developed by compounding, and its regeneration effect and mixture performance were evaluated. The results show that the regeneration agent can restore the performance of aged asphalt, and the mixing content of 8% is closest to the original asphalt. Meanwhile, the effect of temperature mixing agents on the performance of asphalt is relatively small, with the cooling effect mainly achieved by interface lubrication. As the mixing content increases, the contact angle of asphalt decreases. Based on the comprehensive conventional performance, the mixing content of temperature mixing agents is determined to be 0.4%. Compared with ordinary regeneration agents, the temperature regeneration agents with 0.5% of the penetrant have better penetration performance, which can penetrate into the interior of aged asphalt faster and improve the performance of aged asphalt. When the mixing content of the new temperature regeneration agent is 8%, the regeneration rate of various properties of aged asphalt is 63.5%-101.2%, and the comprehensive regeneration rate is 90.1%, indicating sound regeneration effect. Compared to thermal regeneration asphalt mixture, the new temperature regeneration agent can effectively reduce the mixing and compaction temperature of asphalt mixtures by 22℃, and the high-temperature performance of thermal regeneration asphalt mixtures is slightly reduced. Additionally, the low-temperature performance is improved, and the water stability changes are small, with all indicators meeting the specification requirements.
Research on zero shear viscosity of resin and elastomer high⁃viscosity modified asphalt
TAO Jiaqing, YU Xiaotao, CHAI Chongchong, WANG Haipeng, and YAN Chuanqi
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.048
To better evaluate the high-temperature performance of two types of high-viscosity asphalt including thermoplastic elastomers and thermoplastic resins, this paper conducted routine tests such as the penetration, softening point, low-temperature ductility, and visco-temperature curve testing on high-viscosity asphalt with different mixing contents (3%, 5%, 8%), as well as zero shear viscosity (ηZSV) rheological test analysis. Meanwhile, TEM was adopted for mechanism analysis on the two types of high-viscosity asphalt. Specifically, the influence of different experimental frequencies and fitting models on the fitting effect of ηZSV was studied. Finally, the modification effect of high-viscosity modified asphalt was evaluated by employing the results of the ηZSV test. The results show that the frequency range of 0.01-100 Hz is the most suitable for ηZSV testing. When matrix asphalt and elastic high-viscosity asphalt were tested, simplified models can be utilized to replace standard models, while for resin high-viscosity asphalt, it is recommended that the Cross standard model should be employed for fitting. The two types of high-viscosity modified asphalt have sound correlation with the ηZSV, softening point, and ductility, but have poor correlation with penetration.
Research on strength and water stability of titanium gypsum solidified by red mud and slag
LIN Xuefeng, CHEN Aijun, JIA Zhirong, YU Bin, LEI Zhen, LI Chaoyu, and LIU Heng
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.049
High water content of titanium gypsum results in diffiicult dehydration and comprehensive utilization. To achieve the large-scale application of solid waste of titanium gypsum in road subgrade, this paper employed red mud and slag as the curing agents. Meanwhile, it designed a three-factor four-level test with the gypsum-slag ratio of 4:6, 5:5, 6:4, and 7:3, red mud-slag ratio of 1:4, 1:3, 1:2, and 1:1, and mixing contents 0, 2%, 4%, and 6% of sodium silicate. The unconfined compression strength of solidified titanium gypsum at 7 and 28 days was determined, and its coefficient of softness was calculated. The microstructure of the specimens was analyzed by adopting scanning electron microscopy, energy spectrometer, and X-ray diffraction. The results show that the strength of solidified titanium gypsum is high under the gypsum-slag ratio of 4:6, red mud-slag ratio of 1:4, and sodium silicate content of 6%, with the compressive strength at 7 and 28 days reaching 7.2 MPa and 25.1 MPa respectively. The gypsum-slag ratio has the greatest influence on the strength of solidified titanium gypsum, while the red mud-slag ratio and sodium silicate exert a smaller effect. As the gypsum-slag ratio and red mud-slag ratio decrease, the strength of solidified titanium gypsum increases. When the gypsum-slag ratio is no more than 6:4, the compressive strength at 7 and 28 days exceeds 4.7 MPa and 18.2 MPa respectively, with the coefficient of softness greater than 0.95. The main reaction products of solidified titanium gypsum are ettringite crystal and hydrated calcium silicate gel, which are spatially interconnected to form a grid structure and connected with the titanium gypsum matrix to ensure the strength and water stability of solidified titanium gypsum. Generally, when the gypsum-slag ratio is not less than 6:4, the solidified titanium gypsum has sound water stability and its strength can meet the requirements of cement-stabilized subgrade for highway grade II and below.
Study on effect of self⁃healing microcapsules on asphalt and mixture performa nce
LI Zhao and MA Leixia
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.050
This paper evaluated the influence of microcapsules on the basic properties, rheological performance, and healing performance of asphalt by conducting basic asphalt index tests, temperature scans, frequency scans, linear amplitude scans, and fatigue-healing-fatigue tests. Meanwhile, the influence of microcapsules on the road performance of asphalt mixtures was evaluated by rutting tests, low-temperature bending tests on small beams, and freeze-thaw splitting tests. The results reveal that when the mixing content of microcapsules in asphalt is less than 4%, the addition of microcapsules will not significantly affect the main technical indicators and high-temperature rutting resistance of asphalt. The addition of microcapsules at medium temperatures increases the viscosity ratio of asphalt rubber cement, and microcapsules can enhance the fatigue resistance of asphalt rubber cement to a certain extent. Additionally, the healing degree index of microcapsule asphalt rubber cement increases linearly, indicating that the addition of microcapsules can enhance the fatigue healing performance of asphalt to some extent. The healing index degree of microcapsule asphalt varies with the extending healing time. With the increasing mixing content of microcapsules, the high-temperature stability of the microcapsule asphalt mixture gradually decreases, with improved low-temperature deformation ability and slightly enhanced water stability. The mixing content of microcapsules within the range of 0.4% can meet the road performance requirements.
Numerical study on effect of heterogenicity on micro⁃cracking behavior of cement⁃stabilized macadam material
DONG Qiao, YUAN Jiawei, ZHAO Xiaokang, and CHEN Xueqin
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.046
To investigate the effect of heterogeneity of cement mortar on the micro-cracking behavior of cement-stabilized macadam (CSM) material, this paper built a circular aggregate micro-fracture model based on the finite element method (FEM). Meanwhile, the micro-cracking behavior of the material was simulated by embedding a zero-thickness cohesive element with a bilinear cohesive zone model, and the material random field with Weibull distribution was introduced to characterize the heterogeneity characteristics of the mortar matrix and interface transition zone (ITZ). Based on virtual semicircular bending (SCB) tests, this paper simulated the micro-cracking process and analyzed the influence of material homogeneity on the micro-cracking behavior of CSM. The results reveal that the built heterogeneous micro-fracture model can achieve accurate simulation of micro-fractures. The generation of macroscopic cracks in CSM material undergoes the process of micro-crack initiation and rapid penetration, and interface and pore defects are the weak areas for micro-crack propagation. The crack resistance of CSM material decreases with the increasing non-uniformity of the random field. It is recommended that effective measures should be taken to improve the mixing uniformity of cement mortar in the actual construction process to enhance the crack resistance of CSM material.
Study on preparation and properties of new temperature regeneration agent
WANG Guan, SHI Nan, FAN Wenmiao, YIN Liyang, WANG Xinyang, and ZHAO Pinhui
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.047
In the production and application of temperature regeneration asphalt mixtures, temperature regeneration agents are crucial for the performance of asphalt mixtures. Based on the functions of raw materials such as temperature mixing agents, regeneration agents and penetrants, this paper determined the appropriate mixing content by studying the influence of aged asphalt's performance. Then, a new type of temperature regeneration agent was developed by compounding, and its regeneration effect and mixture performance were evaluated. The results show that the regeneration agent can restore the performance of aged asphalt, and the mixing content of 8% is closest to the original asphalt. Meanwhile, the effect of temperature mixing agents on the performance of asphalt is relatively small, with the cooling effect mainly achieved by interface lubrication. As the mixing content increases, the contact angle of asphalt decreases. Based on the comprehensive conventional performance, the mixing content of temperature mixing agents is determined to be 0.4%. Compared with ordinary regeneration agents, the temperature regeneration agents with 0.5% of the penetrant have better penetration performance, which can penetrate into the interior of aged asphalt faster and improve the performance of aged asphalt. When the mixing content of the new temperature regeneration agent is 8%, the regeneration rate of various properties of aged asphalt is 63.5%-101.2%, and the comprehensive regeneration rate is 90.1%, indicating sound regeneration effect. Compared to thermal regeneration asphalt mixture, the new temperature regeneration agent can effectively reduce the mixing and compaction temperature of asphalt mixtures by 22℃, and the high-temperature performance of thermal regeneration asphalt mixtures is slightly reduced. Additionally, the low-temperature performance is improved, and the water stability changes are small, with all indicators meeting the specification requirements.
Research on zero shear viscosity of resin and elastomer high⁃viscosity modified asphalt
TAO Jiaqing, YU Xiaotao, CHAI Chongchong, WANG Haipeng, and YAN Chuanqi
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.048
To better evaluate the high-temperature performance of two types of high-viscosity asphalt including thermoplastic elastomers and thermoplastic resins, this paper conducted routine tests such as the penetration, softening point, low-temperature ductility, and visco-temperature curve testing on high-viscosity asphalt with different mixing contents (3%, 5%, 8%), as well as zero shear viscosity (ηZSV) rheological test analysis. Meanwhile, TEM was adopted for mechanism analysis on the two types of high-viscosity asphalt. Specifically, the influence of different experimental frequencies and fitting models on the fitting effect of ηZSV was studied. Finally, the modification effect of high-viscosity modified asphalt was evaluated by employing the results of the ηZSV test. The results show that the frequency range of 0.01-100 Hz is the most suitable for ηZSV testing. When matrix asphalt and elastic high-viscosity asphalt were tested, simplified models can be utilized to replace standard models, while for resin high-viscosity asphalt, it is recommended that the Cross standard model should be employed for fitting. The two types of high-viscosity modified asphalt have sound correlation with the ηZSV, softening point, and ductility, but have poor correlation with penetration.
Research on strength and water stability of titanium gypsum solidified by red mud and slag
LIN Xuefeng, CHEN Aijun, JIA Zhirong, YU Bin, LEI Zhen, LI Chaoyu, and LIU Heng
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.049
High water content of titanium gypsum results in diffiicult dehydration and comprehensive utilization. To achieve the large-scale application of solid waste of titanium gypsum in road subgrade, this paper employed red mud and slag as the curing agents. Meanwhile, it designed a three-factor four-level test with the gypsum-slag ratio of 4:6, 5:5, 6:4, and 7:3, red mud-slag ratio of 1:4, 1:3, 1:2, and 1:1, and mixing contents 0, 2%, 4%, and 6% of sodium silicate. The unconfined compression strength of solidified titanium gypsum at 7 and 28 days was determined, and its coefficient of softness was calculated. The microstructure of the specimens was analyzed by adopting scanning electron microscopy, energy spectrometer, and X-ray diffraction. The results show that the strength of solidified titanium gypsum is high under the gypsum-slag ratio of 4:6, red mud-slag ratio of 1:4, and sodium silicate content of 6%, with the compressive strength at 7 and 28 days reaching 7.2 MPa and 25.1 MPa respectively. The gypsum-slag ratio has the greatest influence on the strength of solidified titanium gypsum, while the red mud-slag ratio and sodium silicate exert a smaller effect. As the gypsum-slag ratio and red mud-slag ratio decrease, the strength of solidified titanium gypsum increases. When the gypsum-slag ratio is no more than 6:4, the compressive strength at 7 and 28 days exceeds 4.7 MPa and 18.2 MPa respectively, with the coefficient of softness greater than 0.95. The main reaction products of solidified titanium gypsum are ettringite crystal and hydrated calcium silicate gel, which are spatially interconnected to form a grid structure and connected with the titanium gypsum matrix to ensure the strength and water stability of solidified titanium gypsum. Generally, when the gypsum-slag ratio is not less than 6:4, the solidified titanium gypsum has sound water stability and its strength can meet the requirements of cement-stabilized subgrade for highway grade II and below.
Study on effect of self⁃healing microcapsules on asphalt and mixture performa nce
LI Zhao and MA Leixia
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.050
This paper evaluated the influence of microcapsules on the basic properties, rheological performance, and healing performance of asphalt by conducting basic asphalt index tests, temperature scans, frequency scans, linear amplitude scans, and fatigue-healing-fatigue tests. Meanwhile, the influence of microcapsules on the road performance of asphalt mixtures was evaluated by rutting tests, low-temperature bending tests on small beams, and freeze-thaw splitting tests. The results reveal that when the mixing content of microcapsules in asphalt is less than 4%, the addition of microcapsules will not significantly affect the main technical indicators and high-temperature rutting resistance of asphalt. The addition of microcapsules at medium temperatures increases the viscosity ratio of asphalt rubber cement, and microcapsules can enhance the fatigue resistance of asphalt rubber cement to a certain extent. Additionally, the healing degree index of microcapsule asphalt rubber cement increases linearly, indicating that the addition of microcapsules can enhance the fatigue healing performance of asphalt to some extent. The healing index degree of microcapsule asphalt varies with the extending healing time. With the increasing mixing content of microcapsules, the high-temperature stability of the microcapsule asphalt mixture gradually decreases, with improved low-temperature deformation ability and slightly enhanced water stability. The mixing content of microcapsules within the range of 0.4% can meet the road performance requirements.
Numerical study on effect of heterogenicity on micro⁃cracking behavior of cement⁃stabilized macadam material
DONG Qiao, YUAN Jiawei, ZHAO Xiaokang, and CHEN Xueqin
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.046
To investigate the effect of heterogeneity of cement mortar on the micro-cracking behavior of cement-stabilized macadam (CSM) material, this paper built a circular aggregate micro-fracture model based on the finite element method (FEM). Meanwhile, the micro-cracking behavior of the material was simulated by embedding a zero-thickness cohesive element with a bilinear cohesive zone model, and the material random field with Weibull distribution was introduced to characterize the heterogeneity characteristics of the mortar matrix and interface transition zone (ITZ). Based on virtual semicircular bending (SCB) tests, this paper simulated the micro-cracking process and analyzed the influence of material homogeneity on the micro-cracking behavior of CSM. The results reveal that the built heterogeneous micro-fracture model can achieve accurate simulation of micro-fractures. The generation of macroscopic cracks in CSM material undergoes the process of micro-crack initiation and rapid penetration, and interface and pore defects are the weak areas for micro-crack propagation. The crack resistance of CSM material decreases with the increasing non-uniformity of the random field. It is recommended that effective measures should be taken to improve the mixing uniformity of cement mortar in the actual construction process to enhance the crack resistance of CSM material.
Study on preparation and properties of new temperature regeneration agent
WANG Guan, SHI Nan, FAN Wenmiao, YIN Liyang, WANG Xinyang, and ZHAO Pinhui
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.047
In the production and application of temperature regeneration asphalt mixtures, temperature regeneration agents are crucial for the performance of asphalt mixtures. Based on the functions of raw materials such as temperature mixing agents, regeneration agents and penetrants, this paper determined the appropriate mixing content by studying the influence of aged asphalt's performance. Then, a new type of temperature regeneration agent was developed by compounding, and its regeneration effect and mixture performance were evaluated. The results show that the regeneration agent can restore the performance of aged asphalt, and the mixing content of 8% is closest to the original asphalt. Meanwhile, the effect of temperature mixing agents on the performance of asphalt is relatively small, with the cooling effect mainly achieved by interface lubrication. As the mixing content increases, the contact angle of asphalt decreases. Based on the comprehensive conventional performance, the mixing content of temperature mixing agents is determined to be 0.4%. Compared with ordinary regeneration agents, the temperature regeneration agents with 0.5% of the penetrant have better penetration performance, which can penetrate into the interior of aged asphalt faster and improve the performance of aged asphalt. When the mixing content of the new temperature regeneration agent is 8%, the regeneration rate of various properties of aged asphalt is 63.5%-101.2%, and the comprehensive regeneration rate is 90.1%, indicating sound regeneration effect. Compared to thermal regeneration asphalt mixture, the new temperature regeneration agent can effectively reduce the mixing and compaction temperature of asphalt mixtures by 22℃, and the high-temperature performance of thermal regeneration asphalt mixtures is slightly reduced. Additionally, the low-temperature performance is improved, and the water stability changes are small, with all indicators meeting the specification requirements.
Research on zero shear viscosity of resin and elastomer high⁃viscosity modified asphalt
TAO Jiaqing, YU Xiaotao, CHAI Chongchong, WANG Haipeng, and YAN Chuanqi
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.048
To better evaluate the high-temperature performance of two types of high-viscosity asphalt including thermoplastic elastomers and thermoplastic resins, this paper conducted routine tests such as the penetration, softening point, low-temperature ductility, and visco-temperature curve testing on high-viscosity asphalt with different mixing contents (3%, 5%, 8%), as well as zero shear viscosity (ηZSV) rheological test analysis. Meanwhile, TEM was adopted for mechanism analysis on the two types of high-viscosity asphalt. Specifically, the influence of different experimental frequencies and fitting models on the fitting effect of ηZSV was studied. Finally, the modification effect of high-viscosity modified asphalt was evaluated by employing the results of the ηZSV test. The results show that the frequency range of 0.01-100 Hz is the most suitable for ηZSV testing. When matrix asphalt and elastic high-viscosity asphalt were tested, simplified models can be utilized to replace standard models, while for resin high-viscosity asphalt, it is recommended that the Cross standard model should be employed for fitting. The two types of high-viscosity modified asphalt have sound correlation with the ηZSV, softening point, and ductility, but have poor correlation with penetration.
Research on strength and water stability of titanium gypsum solidified by red mud and slag
LIN Xuefeng, CHEN Aijun, JIA Zhirong, YU Bin, LEI Zhen, LI Chaoyu, and LIU Heng
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.049
High water content of titanium gypsum results in diffiicult dehydration and comprehensive utilization. To achieve the large-scale application of solid waste of titanium gypsum in road subgrade, this paper employed red mud and slag as the curing agents. Meanwhile, it designed a three-factor four-level test with the gypsum-slag ratio of 4:6, 5:5, 6:4, and 7:3, red mud-slag ratio of 1:4, 1:3, 1:2, and 1:1, and mixing contents 0, 2%, 4%, and 6% of sodium silicate. The unconfined compression strength of solidified titanium gypsum at 7 and 28 days was determined, and its coefficient of softness was calculated. The microstructure of the specimens was analyzed by adopting scanning electron microscopy, energy spectrometer, and X-ray diffraction. The results show that the strength of solidified titanium gypsum is high under the gypsum-slag ratio of 4:6, red mud-slag ratio of 1:4, and sodium silicate content of 6%, with the compressive strength at 7 and 28 days reaching 7.2 MPa and 25.1 MPa respectively. The gypsum-slag ratio has the greatest influence on the strength of solidified titanium gypsum, while the red mud-slag ratio and sodium silicate exert a smaller effect. As the gypsum-slag ratio and red mud-slag ratio decrease, the strength of solidified titanium gypsum increases. When the gypsum-slag ratio is no more than 6:4, the compressive strength at 7 and 28 days exceeds 4.7 MPa and 18.2 MPa respectively, with the coefficient of softness greater than 0.95. The main reaction products of solidified titanium gypsum are ettringite crystal and hydrated calcium silicate gel, which are spatially interconnected to form a grid structure and connected with the titanium gypsum matrix to ensure the strength and water stability of solidified titanium gypsum. Generally, when the gypsum-slag ratio is not less than 6:4, the solidified titanium gypsum has sound water stability and its strength can meet the requirements of cement-stabilized subgrade for highway grade II and below.
Study on effect of self⁃healing microcapsules on asphalt and mixture performa nce
LI Zhao and MA Leixia
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.050
This paper evaluated the influence of microcapsules on the basic properties, rheological performance, and healing performance of asphalt by conducting basic asphalt index tests, temperature scans, frequency scans, linear amplitude scans, and fatigue-healing-fatigue tests. Meanwhile, the influence of microcapsules on the road performance of asphalt mixtures was evaluated by rutting tests, low-temperature bending tests on small beams, and freeze-thaw splitting tests. The results reveal that when the mixing content of microcapsules in asphalt is less than 4%, the addition of microcapsules will not significantly affect the main technical indicators and high-temperature rutting resistance of asphalt. The addition of microcapsules at medium temperatures increases the viscosity ratio of asphalt rubber cement, and microcapsules can enhance the fatigue resistance of asphalt rubber cement to a certain extent. Additionally, the healing degree index of microcapsule asphalt rubber cement increases linearly, indicating that the addition of microcapsules can enhance the fatigue healing performance of asphalt to some extent. The healing index degree of microcapsule asphalt varies with the extending healing time. With the increasing mixing content of microcapsules, the high-temperature stability of the microcapsule asphalt mixture gradually decreases, with improved low-temperature deformation ability and slightly enhanced water stability. The mixing content of microcapsules within the range of 0.4% can meet the road performance requirements.
Traffic Engineering and Management
Research progress es on guide sign system of highways
LI Meiling, CHEN Yanan, RAN Jin, ZHANG Junhua, MA Xiaogang, and ZHU Xiangmin
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.051
Guide signs are important traffic management measures to ensure fast and safe passage on highways. With the gradual construction of China's highway network, the transportation mode has shifted from the early single line travel to network travel with the interchange between multiple highways. However, the content form and combination layout of traditional guide signs are difficult to match the real environment, which is not beneficial for drivers to recognize information quickly and safely. This paper systematically summarized the current status, research hotspots, existing problems, optimization measures, utility evaluation methods, and future development trends of standard specifications for highway guide sign systems at home and abroad from the four aspects, including the layout design, information content, position setting, and utility evaluation of guide signs. The review shows that from the perspectives such as ergonomics, psychology, physiology, and cognitive science, it is possible to analyze the influence of the selection and arrangement of information elements in guide sign layouts on the legibility of drivers. The research on the information content threshold of guide signs and information release process of guide systems should comply with the information processing characteristics of drivers. Meanwhile, the technologies including the adoption of diversified data collection and aggregation, driving simulation and human factor testing, multi-dimensional data mining modeling, and immersive mechanism analysis were employed to study different scenarios for guide sign setting, thus providing theoretical support for scientific and reasonable guide sign setting. By adopting the methods such as descriptive statistical analysis, multi-objective weighting, and comprehensive quantitative evaluation, a comprehensive evaluation of the setting effect of the guide sign systems can be achieved.
Study on traffic behavior and optimization for tunnel exit shaped connection sections ：Taking Guanzhou tunnel exit in Guangzhou university town as an example
LAI Haidong, ZANG Xiaodong, ZHOU Shaobo, LIU Yuanqian, and LUO Qiang
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.052
To reduce the influence of the irregular connection sections at the tunnel exits on traffic safety and improve the safety management of tunnel exits, this paper deeply analyzed the traffic flow characteristics of each characteristic section in the connection sections based on the measured data of the irregular connection sections at the exit of Guanzhou Tunnel in Guangzhou Higher Education Mega Center. Meanwhile, it explored the shortcomings in traffic design and management, and proposed specific traffic improvement schemes, with safety evaluation methods provided. A simulation model was built by employing the VISSIM traffic simulation platform, and after model calibration and accuracy verification, the driving status before and after the improvement of the tunnel connection sections was simulated. Additionally, by conducting in-depth analysis of simulation data, the average potential accident risk value and speed difference of each vehicle on the road section were utilized to evaluate road section safety. Based on this, delay and queuing length indicators were leveraged to carry out efficiency evaluation on special road sections, which was then adopted to comprehensively evaluate the optimization effect of the improvement scheme. The evaluation results indicate that there is significant room for improvement in the traffic operation scheme of the connection sections at the exit of Guanzhou Tunnel. The improvement scheme proposed in this paper can improve the driving safety and traffic operation efficiency of the connection sections at tunnel exits, and provide theoretical support for the improvement of traffic safety management in irregular connection sections of the tunnel exits.
Analysis of interchange setting under condition of mountain eolluvial deposit
TIAN Yinan
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.053
This paper combined the diseases such as slope instability occurring during the implementation of the complex joint project Shihui Interchange along the route from Shizhu, Chongqing to Qianjiang Expressway. Based on this, it explored the ideas and methods for selecting interchange schemes under mountain eolluvial deposits. The interchange's location has complex terrain and geological conditions, with many extreme weather events such as rainstorm. During studying the interchange schemes, the stability calculation should be carried out by fully combining the objective conditions and the cause of diseases. Additionally, the current terrain should be employed as more as possible to avoid protruding bad geological ranges, with the route to be flexibly extended. The interchange alignment indicators need to be controlled in combination with the actual conditions of bridges, subgrade protection and other projects. The indicators such as functionality, safety, economy, and applicability need to be considered to determine the final design scheme.
Study on interchange complex under complicated environments
PENG Yong, YANG Wei, and ZHANG Tao
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.054
The terrain and geological environment in mountainous areas are complex, and facilities such as interchange service areas have high requirements for the sites, which makes it very difficult to develop schemes in complex terrain and geological conditions. This paper took the Jinkouhe Interchange Complex of the Emeishan-Hanyuan Expressway as an example to analyze the site selection rationality of the complex from the perspectives of bridge and tunnel distribution and terrain conditions. Meanwhile, by combining the study of the main line location, the complex's layout was improved by shortening tunnels and increasing the length of the open lines. Based on the terrain, traffic organization, and implementation difficulty, the comprehensive scheme comparison and selection was studied to determine the recommended scheme. From the aspects of vehicle driving, driving recognition, and ramp layout improvement for functional services, this paper facilitated the integration of the complexes in interchange service areas to adapt to both the complex terrain and geological environment of mountainous highways and the characteristics of the high bridge-tunnel ratio, and meet the functional needs of connecting local areas and serving for transportation.
Study on the compilation standard of design quantities for highway engineering construction projects
XIAO Meifeng, WANG Yanping, and YI Wanzhong
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.055
During design quantity compilation for existing highway construction projects, there are problems such as inconsistent and non-standard forms of design quantity expression and statistical standards, and lack of connections between design quantities and valuation quantities of the estimate, budget, and bill of quantities. Additionally, there is a mismatch between the fineness of design quantity tables and precision degree of project management, and also misalignment between the compilation level of design quantity tables and the development of highway construction informationization. To this end, this paper sorted out the basic situation of the compilation and management of design quantities, and informationization applications conducted by various parties involved in highway construction in China. Meanwhile, it studied the link between design quantity compilation standards for highway construction projects and other standards, compilation content of design quantities to be standardized, main table forms, and quality requirements. Finally, a standard system of design quantities with a reasonable structure, clear hierarchy, unified classification, and standard content and form was constructed, thus laying a solid foundation for informationization applications to achieve in-depth application of modern information technology in highway engineering.
Research progress es on guide sign system of highways
LI Meiling, CHEN Yanan, RAN Jin, ZHANG Junhua, MA Xiaogang, and ZHU Xiangmin
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.051
Guide signs are important traffic management measures to ensure fast and safe passage on highways. With the gradual construction of China's highway network, the transportation mode has shifted from the early single line travel to network travel with the interchange between multiple highways. However, the content form and combination layout of traditional guide signs are difficult to match the real environment, which is not beneficial for drivers to recognize information quickly and safely. This paper systematically summarized the current status, research hotspots, existing problems, optimization measures, utility evaluation methods, and future development trends of standard specifications for highway guide sign systems at home and abroad from the four aspects, including the layout design, information content, position setting, and utility evaluation of guide signs. The review shows that from the perspectives such as ergonomics, psychology, physiology, and cognitive science, it is possible to analyze the influence of the selection and arrangement of information elements in guide sign layouts on the legibility of drivers. The research on the information content threshold of guide signs and information release process of guide systems should comply with the information processing characteristics of drivers. Meanwhile, the technologies including the adoption of diversified data collection and aggregation, driving simulation and human factor testing, multi-dimensional data mining modeling, and immersive mechanism analysis were employed to study different scenarios for guide sign setting, thus providing theoretical support for scientific and reasonable guide sign setting. By adopting the methods such as descriptive statistical analysis, multi-objective weighting, and comprehensive quantitative evaluation, a comprehensive evaluation of the setting effect of the guide sign systems can be achieved.
Study on traffic behavior and optimization for tunnel exit shaped connection sections ：Taking Guanzhou tunnel exit in Guangzhou university town as an example
LAI Haidong, ZANG Xiaodong, ZHOU Shaobo, LIU Yuanqian, and LUO Qiang
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.052
To reduce the influence of the irregular connection sections at the tunnel exits on traffic safety and improve the safety management of tunnel exits, this paper deeply analyzed the traffic flow characteristics of each characteristic section in the connection sections based on the measured data of the irregular connection sections at the exit of Guanzhou Tunnel in Guangzhou Higher Education Mega Center. Meanwhile, it explored the shortcomings in traffic design and management, and proposed specific traffic improvement schemes, with safety evaluation methods provided. A simulation model was built by employing the VISSIM traffic simulation platform, and after model calibration and accuracy verification, the driving status before and after the improvement of the tunnel connection sections was simulated. Additionally, by conducting in-depth analysis of simulation data, the average potential accident risk value and speed difference of each vehicle on the road section were utilized to evaluate road section safety. Based on this, delay and queuing length indicators were leveraged to carry out efficiency evaluation on special road sections, which was then adopted to comprehensively evaluate the optimization effect of the improvement scheme. The evaluation results indicate that there is significant room for improvement in the traffic operation scheme of the connection sections at the exit of Guanzhou Tunnel. The improvement scheme proposed in this paper can improve the driving safety and traffic operation efficiency of the connection sections at tunnel exits, and provide theoretical support for the improvement of traffic safety management in irregular connection sections of the tunnel exits.
Analysis of interchange setting under condition of mountain eolluvial deposit
TIAN Yinan
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.053
This paper combined the diseases such as slope instability occurring during the implementation of the complex joint project Shihui Interchange along the route from Shizhu, Chongqing to Qianjiang Expressway. Based on this, it explored the ideas and methods for selecting interchange schemes under mountain eolluvial deposits. The interchange's location has complex terrain and geological conditions, with many extreme weather events such as rainstorm. During studying the interchange schemes, the stability calculation should be carried out by fully combining the objective conditions and the cause of diseases. Additionally, the current terrain should be employed as more as possible to avoid protruding bad geological ranges, with the route to be flexibly extended. The interchange alignment indicators need to be controlled in combination with the actual conditions of bridges, subgrade protection and other projects. The indicators such as functionality, safety, economy, and applicability need to be considered to determine the final design scheme.
Study on interchange complex under complicated environments
PENG Yong, YANG Wei, and ZHANG Tao
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.054
The terrain and geological environment in mountainous areas are complex, and facilities such as interchange service areas have high requirements for the sites, which makes it very difficult to develop schemes in complex terrain and geological conditions. This paper took the Jinkouhe Interchange Complex of the Emeishan-Hanyuan Expressway as an example to analyze the site selection rationality of the complex from the perspectives of bridge and tunnel distribution and terrain conditions. Meanwhile, by combining the study of the main line location, the complex's layout was improved by shortening tunnels and increasing the length of the open lines. Based on the terrain, traffic organization, and implementation difficulty, the comprehensive scheme comparison and selection was studied to determine the recommended scheme. From the aspects of vehicle driving, driving recognition, and ramp layout improvement for functional services, this paper facilitated the integration of the complexes in interchange service areas to adapt to both the complex terrain and geological environment of mountainous highways and the characteristics of the high bridge-tunnel ratio, and meet the functional needs of connecting local areas and serving for transportation.
Study on the compilation standard of design quantities for highway engineering construction projects
XIAO Meifeng, WANG Yanping, and YI Wanzhong
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.055
During design quantity compilation for existing highway construction projects, there are problems such as inconsistent and non-standard forms of design quantity expression and statistical standards, and lack of connections between design quantities and valuation quantities of the estimate, budget, and bill of quantities. Additionally, there is a mismatch between the fineness of design quantity tables and precision degree of project management, and also misalignment between the compilation level of design quantity tables and the development of highway construction informationization. To this end, this paper sorted out the basic situation of the compilation and management of design quantities, and informationization applications conducted by various parties involved in highway construction in China. Meanwhile, it studied the link between design quantity compilation standards for highway construction projects and other standards, compilation content of design quantities to be standardized, main table forms, and quality requirements. Finally, a standard system of design quantities with a reasonable structure, clear hierarchy, unified classification, and standard content and form was constructed, thus laying a solid foundation for informationization applications to achieve in-depth application of modern information technology in highway engineering.
Research progress es on guide sign system of highways
LI Meiling, CHEN Yanan, RAN Jin, ZHANG Junhua, MA Xiaogang, and ZHU Xiangmin
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.051
Guide signs are important traffic management measures to ensure fast and safe passage on highways. With the gradual construction of China's highway network, the transportation mode has shifted from the early single line travel to network travel with the interchange between multiple highways. However, the content form and combination layout of traditional guide signs are difficult to match the real environment, which is not beneficial for drivers to recognize information quickly and safely. This paper systematically summarized the current status, research hotspots, existing problems, optimization measures, utility evaluation methods, and future development trends of standard specifications for highway guide sign systems at home and abroad from the four aspects, including the layout design, information content, position setting, and utility evaluation of guide signs. The review shows that from the perspectives such as ergonomics, psychology, physiology, and cognitive science, it is possible to analyze the influence of the selection and arrangement of information elements in guide sign layouts on the legibility of drivers. The research on the information content threshold of guide signs and information release process of guide systems should comply with the information processing characteristics of drivers. Meanwhile, the technologies including the adoption of diversified data collection and aggregation, driving simulation and human factor testing, multi-dimensional data mining modeling, and immersive mechanism analysis were employed to study different scenarios for guide sign setting, thus providing theoretical support for scientific and reasonable guide sign setting. By adopting the methods such as descriptive statistical analysis, multi-objective weighting, and comprehensive quantitative evaluation, a comprehensive evaluation of the setting effect of the guide sign systems can be achieved.
Study on traffic behavior and optimization for tunnel exit shaped connection sections ：Taking Guanzhou tunnel exit in Guangzhou university town as an example
LAI Haidong, ZANG Xiaodong, ZHOU Shaobo, LIU Yuanqian, and LUO Qiang
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.052
To reduce the influence of the irregular connection sections at the tunnel exits on traffic safety and improve the safety management of tunnel exits, this paper deeply analyzed the traffic flow characteristics of each characteristic section in the connection sections based on the measured data of the irregular connection sections at the exit of Guanzhou Tunnel in Guangzhou Higher Education Mega Center. Meanwhile, it explored the shortcomings in traffic design and management, and proposed specific traffic improvement schemes, with safety evaluation methods provided. A simulation model was built by employing the VISSIM traffic simulation platform, and after model calibration and accuracy verification, the driving status before and after the improvement of the tunnel connection sections was simulated. Additionally, by conducting in-depth analysis of simulation data, the average potential accident risk value and speed difference of each vehicle on the road section were utilized to evaluate road section safety. Based on this, delay and queuing length indicators were leveraged to carry out efficiency evaluation on special road sections, which was then adopted to comprehensively evaluate the optimization effect of the improvement scheme. The evaluation results indicate that there is significant room for improvement in the traffic operation scheme of the connection sections at the exit of Guanzhou Tunnel. The improvement scheme proposed in this paper can improve the driving safety and traffic operation efficiency of the connection sections at tunnel exits, and provide theoretical support for the improvement of traffic safety management in irregular connection sections of the tunnel exits.
Analysis of interchange setting under condition of mountain eolluvial deposit
TIAN Yinan
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.053
This paper combined the diseases such as slope instability occurring during the implementation of the complex joint project Shihui Interchange along the route from Shizhu, Chongqing to Qianjiang Expressway. Based on this, it explored the ideas and methods for selecting interchange schemes under mountain eolluvial deposits. The interchange's location has complex terrain and geological conditions, with many extreme weather events such as rainstorm. During studying the interchange schemes, the stability calculation should be carried out by fully combining the objective conditions and the cause of diseases. Additionally, the current terrain should be employed as more as possible to avoid protruding bad geological ranges, with the route to be flexibly extended. The interchange alignment indicators need to be controlled in combination with the actual conditions of bridges, subgrade protection and other projects. The indicators such as functionality, safety, economy, and applicability need to be considered to determine the final design scheme.
Study on interchange complex under complicated environments
PENG Yong, YANG Wei, and ZHANG Tao
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.054
The terrain and geological environment in mountainous areas are complex, and facilities such as interchange service areas have high requirements for the sites, which makes it very difficult to develop schemes in complex terrain and geological conditions. This paper took the Jinkouhe Interchange Complex of the Emeishan-Hanyuan Expressway as an example to analyze the site selection rationality of the complex from the perspectives of bridge and tunnel distribution and terrain conditions. Meanwhile, by combining the study of the main line location, the complex's layout was improved by shortening tunnels and increasing the length of the open lines. Based on the terrain, traffic organization, and implementation difficulty, the comprehensive scheme comparison and selection was studied to determine the recommended scheme. From the aspects of vehicle driving, driving recognition, and ramp layout improvement for functional services, this paper facilitated the integration of the complexes in interchange service areas to adapt to both the complex terrain and geological environment of mountainous highways and the characteristics of the high bridge-tunnel ratio, and meet the functional needs of connecting local areas and serving for transportation.
Study on the compilation standard of design quantities for highway engineering construction projects
XIAO Meifeng, WANG Yanping, and YI Wanzhong
Date posted: 1-18-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.06.055
During design quantity compilation for existing highway construction projects, there are problems such as inconsistent and non-standard forms of design quantity expression and statistical standards, and lack of connections between design quantities and valuation quantities of the estimate, budget, and bill of quantities. Additionally, there is a mismatch between the fineness of design quantity tables and precision degree of project management, and also misalignment between the compilation level of design quantity tables and the development of highway construction informationization. To this end, this paper sorted out the basic situation of the compilation and management of design quantities, and informationization applications conducted by various parties involved in highway construction in China. Meanwhile, it studied the link between design quantity compilation standards for highway construction projects and other standards, compilation content of design quantities to be standardized, main table forms, and quality requirements. Finally, a standard system of design quantities with a reasonable structure, clear hierarchy, unified classification, and standard content and form was constructed, thus laying a solid foundation for informationization applications to achieve in-depth application of modern information technology in highway engineering.
