Volume 42, Issue 5 (2022)
Subgrade Engineering
Failure Mode Analysis and Stability Study of High-Fill Spoil Ground of Expressway in Southwest Mountain Area
Yuan Xukai, Xu Wanzhong, Yan Tiejun, and Hu Mingxin
Date posted: 11-8-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.05.001
The engineering geological conditions in southwest mountain areas are complex, and landslide instability often occurs in the high-fill spoil ground of mountainous expressways, thus seriously hindering the expressway construction. By taking the high-fill spoil ground of an expressway in the southwest mountainous area as the research object, this paper employed data analysis and on-site survey to analyze the possible failure modes of the spoil ground. By combining the construction scheme and protective engineering design of the spoil ground, the safety of the spoil ground was qualitatively evaluated. Additionally, this paper conducted a comprehensive and systematic safety assessment of the stability, local and overall stability, and the stability of the retaining structure of the spoil ground by quantitative calculations, with the interception and drainage system verified. This can provide important analogical data and technical references for the stability assessment of high-fill spoil ground on other expressways.
Research on Static and Dynamic Mechanical Test of Large-Scale Model of Geocell-Reinforced Earth Retaining Wall
Zhang Wenhai, Hou Senlei, Wang Jiaquan, and Zhang Jun
Date posted: 11-8-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.05.002
To study the stress and deformation characteristics of geocell-reinforced earth retaining wall under static and dynamic loads, this paper designed large model tests of reinforced earth retaining walls under static and dynamic loads, and analyzed the distribution laws of parameters such as vertical earth pressure, vertical sedimentation, horizontal displacement of face plates, and dynamic acceleration of reinforced earth retaining walls. The experimental results show that the increasing number of reinforcement layers enhances the lateral confinement effect of geocells, making the internal stress of the retaining wall more sufficient and balanced. The ultimate bearing capacity is increased by 120%, and the maximum horizontal displacement of the wall surface is reduced by 14.3%. The ultimate bearing capacity of the retaining wall model under dynamic loads is 70% of the ultimate bearing capacity of the static load model, and the horizontal displacement of the wall surface at the model failure time is twice that of the static load model in the same conditions. Compared with the amplitude of dynamic loads, the dynamic load frequency has a weak effect on the vertical earth pressure of retaining walls. Therefore, it is recommended that frequency should not be considered as a key influencing factor during calculating and analyzing the earth pressure of reinforced earth retaining walls under dynamic loads.
Application of Improved Seeker Optimization Algorithm in Slope Stability Analysis
Zhou Liang and Li Gang
Date posted: 11-8-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.05.003
In response to such problems as the complex calculation of safety factors and the interrelations between optimization variables of slip surfaces in slope stability analysis, an improved seeker optimization algorithm (ISOA) was adopted to search for the critical slip surface of slopes, with the introduction of the chaotic strategy in ISOA to improve local search capability. Meanwhile, the utilization of seven benchmark functions for testing shows that ISOA has significantly improved accuracy, stability, and efficiency compared to the original seeker optimization algorithm (SOA). By further combining the ISOA algorithm with the finite element stress algebraic sum method to analyze slope stability, two ACADS test cases were analyzed. The results show that the safety factor error between the stress algebraic sum method based on ISOA and the traditional limit equilibrium method is relatively small, and the slip surface position is basically consistent. Additionally, ISOA can more efficiently and accurately search for critical slip surfaces, making it suitable for applications in complex soil slopes with non-uniform soil layers.
Research on design method of cement mixing piles under american standards
Wang Yanping, Sun Qingnan, and Chen Haoruo
Date posted: 11-8-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.05.004
At present, Chinese scholars have not conducted research on the design methods and calculation theories of cement mixing pile foundation treatment under American standards. This paper analyzed and discussed the design methods and calculation steps of deep cement mixing piles for soft soil foundation by the Federal Highway Administration of the United States, and compared the differences in cement mixing pile design between Chinese and American standards to provide technical references for American standard research and geotechnical engineering design in regions obeying American standard.
Study on Deterioration of Soil Properties on Mountain Road Slopes under Different Wet and Dry Effects
Wu Guopeng, Yu Xiangpeng, Cui Kai, and Gao Hong
Date posted: 11-8-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.05.005
The physical and mechanical properties of road slope soil in the mountainous area of the middle reaches of the Bailongjiang River are prone to deterioration under the strong dry and wet environment formed by concentrated rainfall and high surface temperature in summer, resulting in deformation and instability of road slope soil. To study the degradation process of road slope soil in such drying-wetting conditions, this paper selected the Huama landslide soil as the research object. Meanwhile, it tested the indicators such as particle grading composition, density, liquid plastic limit, shear strength, and uniaxial compressive strength of the soil under multiple times of strong drying-wetting and daily drying-wetting action. The results show that the above indicators undergo significant changes after multiple different drying-wetting cycles, and the change rate in each indicator of the sample after strong drying-wetting cycles is greater than that of daily drying-wetting cycles. Under multiple times of drying-wetting action, the sand content inside the soil decreases, the clay content increases, and the pores expand, thus increasing the uniformity of the sampled particles and the porosity, and reducing roundness.
Study on Risk Assessment Model of Operation Highway Slope Based on Unstable Index Method
Tian Qingyan, Zhang Qingqing, Yin Quanchun, and Yang Jun
Date posted: 11-8-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.05.006
Based on a large number of detection cases of operation highway slopes, this paper proposed a theoretical calculation model and assessment criteria for assessing the potential risk of highway slope failure. Meanwhile, it explored the main factors and their degree of influence on the technical conditions of highway slopes, and adopted practical projects as an example to predict and analyze the slope risk degree. The analysis results show that the unstable index method based on a large number of slope cases can better reveal the main factors affecting the risk of operation highway slopes. The key factor affecting the highway slope failure is mainly the technical conditions of the slope itself, and the weight of factors such as technical conditions of the slope protection structure, and terrain and landforms of the slope surface has relatively low weight. The utilization of mathematical statistical methods for assessing and grading the potential risk of slope failure has certain rationality, and the calculation misjudgement error of the established potential risk area of slope failure can be effectively reduced.
Numerical Simulation of Road Widening by Pile-Geogrid Combined Disposal
Chang Cheng and Xu Yongfu
Date posted: 11-8-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.05.007
This paper built a finite element model of the highway widening project on the soft soil foundation by employing Abaqus, and simulated the working conditions of the subgrade and foundation 15 years after the start of construction and completion. By comparing methods such as no reinforcement, pile foundation reinforcement, geogrid reinforcement, and combined reinforcement, the problems such as post-construction sedimentation, geogrid tensile force, and stability safety factor of subgrade were analyzed. The calculation results show that the combined action of piles and geogrids is better than the sum of the individual action of the two disposal methods. The combined reinforcement method can significantly change the stress distribution of the subgrade soil, reduce the uneven sedimentation of the subgrade, and increase the overall integrity and stability of the widened subgrade. The obtained geogrid tensile force is consistent with the actual project, indicating the rationality of the simulation.
Demonstration and Analysis of Deep Foundation Pit Dewatering in Water-Rich Sand and Cobble Layer under Condition of No Water Stop
Mu Qingjun and Chen Cheng
Date posted: 11-8-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.05.008
Based on a deep foundation pit project in Xiangyang, this paper conducted single well and group well pumping tests on site, comparing and analyzing the test data, theoretical calculations, and numerical simulation results to obtain the water charging laws of groundwater and surrounding lakes in the area. Meanwhile, the permeability coefficient of the strata was reviewed to provide necessary basis for subsequent adoption of reasonable water stopping measures. The results show that after 36 pumping wells operate at full power, they still fail to meet the requirement of lowering the groundwater level to 1 m below the basement, with high water supply degree of the aquifer. There is a significant difference in the precipitation rate between the observation wells near and far from the pumping wells, indicating poor permeability of the strata. In the early stage, the static reserves of the strata are mainly consumed. Based on on-site measured data, the average permeability coefficient calculated by the steady flow analysis method is 56.97 m/d, while that calculated by adopting the unsteady flow method is 64.5 m/d. For safety purposes, the comprehensive permeability coefficient is taken as 64.5 m/d to provide a basis for the construction of subsequent grid-connected walls. After determining the number and placement position of precipitation wells, increasing the power of the water pump appropriately can shorten the construction period. When the groundwater level drops to the design depth, precipitation can be carried out as needed, and the number of water pumps that are turned on can be appropriately reduced to decrease the total groundwater extraction amount and protect the geological environment.
Pavement Engineering
Evaluation and Construction Control of Balance between New and Old Pavements in Highway Reconstruction and Expansion
Xiong Chunlong, Li Weixiong, and Wang Zhaodong
Date posted: 11-8-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.05.009
Based on the reconstruction and expansion project of a certain expressway, this paper adopted the falling weight deflectometer (FWD) to detect the deflection of the reconstruction, expansion, and new and old overlap positions, thus evaluating the balance of the new and old pavement structures in the reconstruction and expansion. By combining the construction process investigation, the influencing factors of the balance of the new and old pavement structures were analyzed, with measures for controlling the balance of the new and old pavement structures in the reconstruction and expansion proposed. The results show that after adding 6 cm AC-20C, the deflection value of the overtaking lane on the old road surfaces decreases by about 50%, and the deflection value of the heavy lane on the old road surfaces decreases by about 61.5%, with the strength of the road structure significantly improved. The representative deflection value in the overlap area of the new and old pavement reaches 19.6 (0.01 mm), which is significantly higher than the deflection values in other positions of the new and old pavement structures. The balance of the new and old pavement structures is relatively low. Additionally, the balance of the new and old pavement structures in the reconstruction and expansion of expressways is related to the treatment of old pavement structure diseases and the refinement level of new and old pavement overlap construction. By conducting construction control, the balance of pavement structures can be improved by about 60%.
Detection and Evaluation of Cement Grouting Reinforcement Effect in Widening Joint of Cement Pavement
Yuan Weisuo
Date posted: 11-8-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.05.010
Based on the actual project of cement pavement reconstruction and expansion of composite pavement grouting treatment to widen the joint, three professional grouting companies were commissioned to develop three different grouting schemes for the 200 m grouting test section to grout the widening joints. Meanwhile, the reinforcement effect of the pavement was tested by employing such methods as the falling weight deflectometer (FWD), geological radar, pavement core drilling, and on-site pavement structure slotting. By comparing and analyzing the dynamic deflection and radar reflection detection results, on-site core sampling, and on-site pavement excavation conditions before and after the grouting of the test section, the effect of the three cement grouting schemes in treating widening cement pavement joints was evaluated. The results show that scheme of utilizing cement grouting for treating widening joints of cement pavement can produce certain effects in local loose and hollow areas within a certain diffusion radius, and can quickly and effectively improve the pavement bearing capacity in the short term. Additionally, pavement radars can be adopted as a detection tool to evaluate the cement grouting effect of widening joints of cement pavement.
Study on Influencing Factors of Noise Reduction Performance of Porous Asphalt Concrete Pavement
He Honglin, Zou Xiaoling, Ye Xiangqian, and Zeng Tao
Date posted: 11-8-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.05.011
A large number of indoor or outdoor tests show that porous asphalt mixtures have excellent noise reduction performance, but it is difficult for the measured data to analyze the influence of single factor changes on sound absorption performance. This paper adopted Virtual.lab finite element software to study the influence of porosity, thickness, viscosity characteristic length, and thermal effect characteristic length on the sound absorption coefficient of porous asphalt mixtures via numerical simulation, and analyzed the main influencing factors of the sound absorption coefficient of asphalt mixtures based on grey correlation theory. The results reveal that the numerical simulation model has high reliability. As the thickness, porosity, and viscous characteristic length increase, the sound absorption coefficient shows a trend of increasing, increasing, and gradually decreasing respectively. However, the thermal effect characteristic constant has little effect on the sound absorption coefficient, with the influence degree in the order of porosity>thickness>viscous characteristic length>thermal effect characteristic length. Under the premise of ensuring the road performance, it is advisable to prioritize the porosity increase to improve the sound absorption performance of asphalt mixtures.
Bridge Engineering & Tunnel Engineering
Anti-Fatigue Design of Orthotropic Steel Deck of Maputo Bridge
Yi Bei, Zhou Guibin, Ding Shaoling, and Nie Shangjie
Date posted: 11-8-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.05.012
To reduce the fatigue stress at the edge of the diaphragm opening of steel box girders, this paper built a finite element model of the steel box girders of the main bridge of Maputo Bridge to calculate the fatigue stress amplitude under wheel load at this location. Based on European standards, the cumulative damage method was employed to evaluate the fatigue performance of the structure and predict its fatigue life. Analysis shows that the original design cannot meet the fatigue life requirements after increasing heavy traffic volume. Therefore, this paper proposed two effective methods to reduce the fatigue stress amplitude at five fatigue locations. The first is to increase the thickness of the upper diaphragm, and the second is to add a small diaphragm 0.3 m away from the original diaphragm. The proposed measures for improving fatigue performance hold reference significance for the anti-fatigue design of orthotropic steel decks.
Research on Vibration Control of Continuous Multi-Span Curved Footbridge Based on TMD
Chen Jie, Ai Huilin, and Wang Shengyun
Date posted: 11-8-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.05.013
The structures of continuous multi-span curved footbridges are gentle, and the problem of human-induced vibration is prominent. Thus, it is essential to carry out vibration reduction design for it. This paper adopted Ansys finite element analysis software to study the changes in maximum acceleration response of each bridge span under different tuned mass damper (TMD) layout schemes based on the vibration response of a continuous multi-span curved footbridge under the action of different crowds, and evaluated the vibration reduction effect of TMDs. The results demonstrate that there is a difference in vibration response between uniformly and non-uniformly distributed crowds, and the most unfavorable response of both should be considered in vibration reduction design. The curve shape has an influence on the arrangement direction of TMDs under the lateral bending vibration mode, and the reasonable TMD arrangement direction should be determined for each bridge span based on the vibration mode and response situation. Meanwhile, the vibration reduction effect of multi-span TMDs is closely related to the vibration reduction rate of single-span TMDs, and the vibration reduction effect of single-span TMDs is generally better.
Research Progresses on Fatigue Performance Test of Steel-Concrete Composite Beams
Bu Jianqing and Zhang Jiren
Date posted: 11-8-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.05.014
The application of steel-concrete composite beams in bridge structures is becoming increasingly widespread, and fatigue problems caused by the action of vehicles are increasingly prominent. To further reveal the fatigue performance and mechanism of steel-concrete composite beams, this paper first reviewed the development history of fatigue test schemes for composite beams, and analyzed the influencing factors and fatigue failure modes of fatigue performance of composite beams, with the research progress of fatigue performance tests of new composite beams summarized. Additionally, it sorted out the research progress of fatigue tests of composite beam concrete slabs, summed up the application status of finite element fatigue analysis, and put forward the current research shortcomings and further research directions.
Integrated erection method and equipment of full prefabrication medium and small span bridges
Tian Fei, Xia Hao, Wang Min, and Zheng Hehui
Date posted: 11-8-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.05.015
Based on a certain expressway's continuous beam bridge currently being constructed, this paper aimed to optimize the construction scheme of this type of bridge from the perspective of improving structural fabrication rate and installation efficiency. Firstly, the adaptability of different prefabricated substructure schemes was compared and analyzed, with a focus on analyzing the connection forms between prefabricated substructure components. Secondly, the rationality of integrated construction technology was demonstrated in combination with fabrication technology. Finally, an efficient integrated construction scheme suitable for small and medium-span full prefabricated bridges was proposed. The results show that after adopting the optimization scheme, compared with the background projects, the installation period is extended by 23%, but the equipment cost and temporary measures cost are reduced by 50%. Additionally, there is no need to set up a loading bridge along the optimization scheme, which greatly reduces the effect on the surrounding environment of the working area.
Study on Simulation Method of Stiffness of Prestressed Concrete Girder with Down-Warping Flexural Cracking during Jacking Process
Wu Haijun, Tang Haitao, Chen Tao, and Luo Chunyan
Date posted: 11-8-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.05.016
Currently, the down-warping flexure of the main girders is a common and serious bridge disease, and the commonly adopted reinforcement scheme is to first conduct jacking and then employ prestressed reinforcement and other measures. At present, the stiffness of the main girder during the jacking is usually a constant, with relatively little research on utilizing variable stiffness to simulate the jacking process of the main girders. However, objectively speaking, the actual stiffness of the main girders during the jacking varies, and the stiffness of the main girders gradually increases with the continuously closing cracks. For prestressed concrete girders, when compressive stress occurs at the lower edge of the main girder, or when the crack is completely closed, it can be approximated that the stiffness has basically restored to the stiffness value before down-warping flexure. Based on Branson's effective moment of inertia calculation formula, this paper employed Midas/Civil finite element software to propose a simple method for simulating the stiffness changes during the jacking of concrete girders. Based on the Shangri-La Bridge treatment project in Daocheng County, Sichuan Province, comparative analysis of calculated values and measured data was conducted to show that this method is simple, effective, and applicable.
Study on Evaluation Index of Asphalt Overlay Time of Concrete Beam Bridge Asphalt Pavement Structure
Chen Chupeng, Xu Xinquan, Li Hao, Luo Xueping, and Nie Guihai
Date posted: 11-8-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.05.017
To solve the problem of the lack of evaluation indicators for the overlay time of asphalt overlays on cement concrete beam bridges, this paper adopted the rebound test and Mohs hardness test to evaluate the surface hardness of concrete, with the rebound ratio λ and hardness value f proposed. Meanwhile, it analyzed the relationship between the rebound ratio λ, hardness value f, and interlayer bonding strength via drawing tests and 45° shear tests, and determined the overlay time of asphalt overlays. Based on physical projects, engineering verification was conducted on the overlay time of asphalt overlays. The results reveal that the overlay time of asphalt overlays for cement concrete beam bridges can be evaluated based on λ and f. When λ ≥ 75% or f ≥ 4, the overlay time of asphalt overlays for cement concrete beam bridges can be carried out.
Study on Influence of Concrete Cavity on Pullout and Shear Resistance of Shear Nails
Zhang Liuyu, Huang Lezhou, Su Ju, Jin Xin, and Jie Bin
Date posted: 11-8-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.05.018
By conducting finite element simulation, this paper analyzed the influence of the cavity volume and cavity location on the pullout and shear resistance of shear nails, and provided scientific basis for defining the error control range of shear nail construction. Based on the existing experimental results, a finite element analysis model was built. The final results show that the maximum pullout resistance bearing capacity of the shear nails remains basically unchanged with the increasing volume of the cavity around the head of the shear nails. When the position of a cavity with the same volume moves downward along the nail length from the nail head, the pullout resistance bearing capacity will decrease. Additionally, when the cavity position is within 1/3 of the shear nail length from the shear nail head, the decrease in pullout resistance bearing capacity is the most significant. When the position of the cavity of the same size moves from the nail head along the nail length direction to about 1/6 of the nail length, the shear resistance bearing capacity of the shear nail gradually increases, and remains stable from 1/6 to the nail tail. Therefore, the quality inspection standards for the concrete pouring process in the pouring area of shear nails should be more targeted.
Jitter Response and Control during Jacking Construction Period of Long-Linked Steel-Hybrid Combined Beam on High Pier
Song Yuejian
Date posted: 11-8-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.05.019
Based on the Linyi Huanghe River Bridge project in Shanxi, this paper conducted a study on the wind-induced jitter response and control measures of the maximum cantilever state during the jacking construction period of the steel box girders of long-link steel on high piers-concrete composite structure bridges. Meanwhile, the quasi-steady theory was adopted to consider the jitter force and aerodynamic self-excited force of the steel box girder's section and steel launching nose's section. Additionally, the harmonic synthesis method was utilized to simulate the wind speed time history of turbulent wind fields at the bridge location, with the wind-induced jitter response of the steel box girders in the maximum cantilever state calculated in the time domain. Based on the actual characteristics and construction methods of bridge structures, it was proposed to employ lower cable wind resistance measures to control the wind-induced jitter response of steel box girders in the maximum cantilever state during jacking. Additionally, the finite element analysis method was leveraged to calculate and analyze the control effect of wind resistance measures during the construction period. The results show that the maximum cantilever state of the steel box girders is 0.4507 Hz for the first-order vertical bending natural frequency of the steel launching noses, and 0.5344 Hz for the first-order lateral bending natural frequency of the steel launching noses. When the design wind speed at the height of the main girder is 39.4 m/s, the instantaneous extreme of the vertical displacement response at the cantilever end of the steel launching noses is 0.6314 m, and that of the lateral displacement response at the cantilever end of the steel launching noses is 0.1911 m. Temporary wind resistance measures with lower cables installed near the cantilever end of the steel launching noses can improve the vertical stiffness of the bridge structures and reduce the jitter displacement response at the cantilever end of steel launching noses, thereby increasing the maximum vertical natural frequency of the steel launching noses in the cantilever state of the bridge structures. As the stiffness of the lower cables rises, the vibration suppression efficiency increases nonlinearly. When the vertical displacement reduction ratio at the cantilever end reaches about 60%, the control effect becomes less prominent.
Study on shock resistance of high performance concrete for bridge expansion joints
Ding Chuzhi, Gao Xiaohua, Li Gang, and Chi Peng
Date posted: 11-8-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.05.020
This paper introduced a kind of high-performance concrete employed for bridge expansion joints and characterized by key components of multiple microfibers and polymers. Experimental studies show that compared with ordinary concrete, steel fiber-reinforced concrete, and polypropylene fiber-reinforced concrete commonly adopted in bridge expansion joints, the shock resistance performance of high-performance concrete for bridge expansion joints has significantly improved, which holds certain application significance for solving or delaying early damage of expansion joint concrete and reducing maintenance costs.
Bridge Damage Identification Based on Time-Wavelet Energy Spectrum under Moving Load
Yang Wenfu
Date posted: 11-8-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.05.021
To ensure the safe operation of bridge structures, this paper proposed a reference-free damage identification method for bridges. Meanwhile, the finite element method was adopted to solve the structural dynamic response of simply supported beams under different weights of moving loads. The time-wavelet energy spectrum of the structural acceleration response difference under different weights of moving loads was employed as the damage identification index for damage identification, with the effects of multiple damages, damage degrees, moving load speed, and noise on the identification results considered. The results show that under the action of moving loads of different weights, the peak position of the time-wavelet energy spectrum based on the structural acceleration response difference can help identify the damage to the main beam. The identification results of the actual bridge are in sound agreement with the static and dynamic load test results. The kurtosis of the time-wavelet energy spectrum increases with the rising damage degree, and employing the kurtosis of the time-wavelet energy spectrum as an evaluation index can effectively evaluate the degree of damage to the main beam. The damage index based on the time-wavelet energy spectrum is less affected by the location and damage number, and has strong noise robustness. Therefore, even in a strong noise environment with a signal-to-noise ratio of 5 dB, damage can still be effectively identified.
Influence of Steel Fiber Content on UHPC Axial Tensile Performance
Zhou Teng, Pei Bingzhi, Huang Zhengyu, Pei Dajun, Xu Rui, and Fang Zhi
Date posted: 11-8-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.05.022
To clarify the effect of steel fiber content on axial tensile performance of ultra-high performance concrete (UHPC) materials, this paper conducted axial tensile full process tests on 16 UHPC specimens from four groups with steel fiber volume content ranging from 0% to 3%. As a result, the stress strain curves of UHPC under different fiber contents were obtained. Additionally, the effect of steel fiber content on the tensile strength, deformation performance, energy consumption ability, and ductility of UHPC was analyzed. The experimental results show that UHPC axial tensile specimens without steel fiber exhibit obvious brittle failure characteristics of single joint cracking. When the fiber content increases to more than 2%, obvious ductility failure characteristics of multiple joint cracking is shown. The uploading curve and other UHPC axial tensile stress strain curves show approximate linear variation between the initial loading, matrix cracking, and characteristic points such as the peak point, limit point, and unloading point. When the limit point is reloaded after unloading, the path of the monotonic loading curve is still basically returned to. As the steel fiber content increases, the initial crack stress and strain of UHPC materials slightly rise, with the significantly improved peak stress, peak strain, limit strain, residual strain, energy consumption ability, and ductility. The elastic moduli under tension and compression are similar, and the plastic energy consumption ability of the materials is mainly provided by the plastic deformation of the fibers in the matrix.
Date posted: 11-8-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.05.023
The continuous rigid frame box girders have complex shapes. If not properly maintained at an early stage, they are prone to cracking. By taking the actual occurrence of diagonal cracks in the web of a cast-in-place box girder in a certain project as an example, this paper measured the mechanical, thermal, and deformation performance of concrete. Based on the concrete maturity theory, three-dimensional simulation analysis technology was adopted to study the causes of cracks. The results indicate that the main cause of concrete cracking is low ambient temperature. After demoulding, the concrete temperature rapidly drops to ambient temperature, leading to the formation of large tensile stress inside the concrete. The reason for cracking along the position of the corrugated pipe is that the concrete section at that location decreases, making it prone to stress concentration. Possible cracking prevention measures include maintaining ventilation as much as possible before demoulding, controlling the highest concrete temperature, and applying covers and steam maintenance technique after demoulding to avoid direct exposure of concrete to cold air and prolong the cooling time of concrete. After adopting the optimized maintenance measures by simulation calculations, the measured temperature history and stress history show consistent trends with the calculated results, and the solid structure doesn't crack again.
Influence of Small-Box Girder Bridge Parameters on Customized Transportation Vehicle Load-Effect and Rapid Evaluation
Duan Weidang, Deng Zecheng, Shang Guanyu, and Chen Pengtao
Date posted: 11-8-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.05.024
Based on massive customized transportation data from three provinces and bridge information from nine expressways, this paper selected four typical loading models of vehicles for customized transportation, and built finite element models of small-box girder bridges with different structural forms to support the evaluation of vehicles for customized transportation. By comparing the load effect of the designed vehicle, it analyzed and summarized the response characteristics of small-box girder bridges under four typical loading models. The results show that the load effect ratio is positively correlated with the single span and negatively correlated with the single span number. However, when the span number of a small-box girder bridge exceeds 3, the load effect ratio remains stable. The correlation level between the number of main beam pieces, the spacing between main beams, and the load effect ratio is low. The small-box girder bridge with the minimum main beam pieces and maximum spacing between main beams controls the passage evaluation results of the vehicles for customized transportation. Based on the response characteristics and the load effect comparison method, a selection principle for controlled small-box girder bridges and a rapid evaluation method of route levels for the passage safety of vehicles for customized transportation were proposed and applied to practical projects.
Finite Element Analysis of Transverse Stress of Precast Box Girder
Yang Wei, Shen Yanxia, and Liu Zhongyuan
Date posted: 11-8-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.05.025
At present, segmental precast erection technology is gradually being widely popularized and applied in urban viaducts in China. As the box girder width increases, the cantilever of concrete box girder bridges becomes longer, and wide box girders are often arranged with transverse prestressed tendons, which makes the spatial performance more complex and the transverse effect of box girders increasingly obvious. Meanwhile, studying the transverse stress distribution and performance of wide box girder structures can help solve key technical problems in the analysis and design of concrete wide box girder bridges. By taking a large-cantilever continuous beam bridge with equal cross-sections in a city under construction using segmental precast erection technology as the research object, this paper built a box girder-plate element model by adopting Midas/Civil, and employed Ansys finite element software to build a three-dimensional solid finite element model of the segmental box girder. Additionally, two calculation methods were utilized to calculate the transverse stress distribution law and stress distribution of the box girders under the action of various loads. All calculation results can meet the specification requirements, with the effective load distribution width of different spans and variable cross-section flange plates studied. The results can provide some references for the design and calculation of transverse stress in similar projects.
Influence of Friction Pendulum Bearing Damage on Seismic Performance of Long-Span Continuous Girder Bridge
Zhang Jingyue, Wang Zhiqiang, and Liu Fukang
Date posted: 11-8-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.05.026
To investigate the effect of wear of wear plates of friction pendulum bearings on the seismic performance of long-span continuous girder bridges, this paper conducted a rapid sliding performance test of friction pendulum bearings to study the wear degree of modified polytetrafluoroethylene wear plates in the rapid performance test. Meanwhile, by taking the 6 × 110 m long-span continuous girder bridge as the engineering background, a spatial three-dimensional finite element model was built to compare and analyze the seismic response of the bridge structure under different wear degrees of friction pendulum bearings. The results indicate that the modified polytetrafluoroethylene wear plates inside the friction pendulum bearings suffer severe wear during the rapid performance test, with the friction coefficient first increasing to 0.09 and then decreasing to 0.016. The sliding displacement of the bearing reaches its maximum and collides rigidly with the limit block. Additionally, the wear of wear plates leads to an increase in internal forces in key sections of the bridge, causing plastic deformation at the bottom of the pier and affecting the seismic performance of the bridge structure.
Discussion on Highway Tunnel Civil Structure Technical Condition Assessment of Weir Method
Quan Xun, Xu Qiang, and Li Hongzhe
Date posted: 11-8-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.05.027
The technical system for assessing the technical condition of the weir method of tunnels cannot match the current specifications. To comprehensively assess the structural technical condition of the weir method of highway tunnels, this paper built a multi-level assessment system consisting of sections, parts, subitems, and components by adopting the structural analysis concept. Meanwhile, the analytic hierarchy process (AHP) was employed to determine the weights of the subitems for each section of the tunnel structure, and develop a method for assessing the technical condition of the civil structure of highway tunnels via the weir method. The technical condition assessment of the Yangcheng West Lake Tunnel in Suzhou shows that the technical condition score of this tunnel is basically consistent with the current standards. Additionally, the assessment results are more comprehensive, which can provide references for the technical condition assessment of civil structures of highway tunnels with similar weir methods.
Pavement Structure and Materials
Study on Performance of Desulfurized Rubber Modified Asphalt with Different Original Asphalt
Li Xiaojuan, Xu Xijuan, and Wang Qingqing
Date posted: 11-8-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.05.028
To study the effect of desulfurized rubber asphalt modifiers on asphalt performance and verify the adaptability, this paper adopted a twin-screw method to prepare desulfurized rubber asphalt modifiers for modifying asphalt A, B, and C. Meanwhile, the changes in the three major indicators, segregation degree, elastic recovery, and viscosity of different modified asphalt were analyzed, with the mixing content optimized to analyze the high-temperature rheological properties of different modified asphalt. The results show that under the reasonable mixing content, desulfurized rubber asphalt modifiers can improve the high and low-temperature performance of asphalt, and equip asphalt with sound elastic recovery performance. Additionally, desulfurized rubber modified asphalt features improved storage stability, reduced viscosity, and sound working performance. The desulfurized rubber asphalt modifier exerts a good effect on the modification of asphalt A, and the optimal mixing content of modifiers is the highest at 20%. The desulfurized rubber asphalt modifier increases the complex modulus of asphalt G∗ and the rutting factor G∗/sinδ, reduces the phase angle δ, and improves the high-temperature deformation resistance of asphalt. It has sound adaptability to the original asphalt.
Research Properties of Skeleton-Density Large Graded Macadam Based on Gyratory and Vibration Compaction
Tan Bo and Yang Tao
Date posted: 11-8-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.05.029
To study the road performance of large graded macadam such as compressive and deformation performance, this paper adopted the step-by-step filling method and i method to form compact aggregate-skeleton density gradation, and the gyratory and vibration compaction method was combined to compact and form the large graded macadam mixture. Meanwhile, CBR and compressive modulus of resilience tests were conducted on the formed specimens, and then their test data was compared and analyzed with the macadam specimens of conventional particle size. The results show that the specimens formed by designing coarse aggregates using the step-by-step filling method and fine aggregates using the i method with large macadam mixture can achieve higher compaction density. In reasonable gradation conditions, the mechanical and skeleton properties of large graded macadam specimens are superior to those of graded macadam specimens with conventional particle size. Specifically, the California bearing ratio (RCBR) of large graded macadam specimens can reach 324%, and the compressive modulus of resilience can reach 358.1 MPa. The specimens formed by gyratory and vibration compaction have better compaction density and mechanical properties than those formed by other forming methods.
Effect of Polymer Composite Modified Asphalt Types on Performance of GA10 Cast Asphalt Mixture
Liu Pan, Sheng Xingyue, Hao Zengheng, Li Kai, Li Lu, and Quan Hongbin
Date posted: 11-8-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.05.030
The cast asphalt mixture is the most widely applied pavement material for large-span steel bridge decks in China, and its asphalt binder mainly employs polymer composite modified asphalt. This paper selected four types of polymer composite modified asphalt to study the flowability, high-temperature performance, low-temperature performance, and fatigue performance of their mixture GA10, and at the same time compared them with lake asphalt composite modified asphalt and its mixture GA10. The results show that the low-temperature performance and fatigue performance of polymer composite modified asphalt GA10 are significantly better than those of lake asphalt composite modified asphalt GA10. The road performance of the cast asphalt mixture is closely related to the performance of the asphalt binder. Polymer composite modified asphalt with the high high-temperature viscosity and softening point has better high-temperature stability in its mixture GA10, while polymer composite modified asphalt with the high low-temperature ductility and elastic recovery rate has better low-temperature cracking resistance and fatigue performance in its mixture GA10. According to the physical engineering requirements, suitable polymer composite modified asphalt should be selected.
Effect of Aggregate Chemical Composition on Adhesion Quality of Asphalt-Aggregate System
Yi Zhao, Li Bo, Zhang Jianjun, Li Yu, and Zhou Jianing
Date posted: 11-8-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.05.031
To investigate the influence of aggregate chemical composition on the adhesion quality of the asphalt aggregate system, this paper designed a new sampling method by improving the micrometer, and selected three different types of aggregates with different lithologies to prepare asphalt aggregate samples, with drawing tests conducted in dry and immersed conditions. Meanwhile, it obtained the maximum load and work of fracture at the sample failure time by experiments, and calculated the delamination area of the failure interface by utilizing ImageJ software. Based on the one-factor analysis of variance, the correlation between rock chemical composition and water sensitivity was studied. The results indicate that the new sampling method can effectively control the asphalt film thickness in the drawing sample and promote adhesion failure at the interface between the aggregate and asphalt. For aggregates of different lithologies, mafic rocks have better resistance to water damage than felsic rocks. Analysis of rock chemical composition reveals that oxides such as Al2O3, Fe2O3, MnO, and MgO in the asphalt aggregate system can suppress water damage, while SiO2 can promote water damage.
Influence of Foamed Asphalt on Road Performance of Hot Mix Asphalt Mixture
Li Bao, Li Ning, Chen Chen, and Liu Yuxin
Date posted: 11-8-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.05.032
The utilization of foamed asphalt without lowering the production temperature of asphalt mixtures has become a new construction technique of foamed asphalt technology, but there is a lack of research on the influence of foamed asphalt on the performance of hot mix asphalt mixtures. By taking the on-site drilled core samples and indoor formed specimens as the research objects, this paper studied the influence of foamed asphalt on the high and low-temperature performance of hot mix asphalt mixtures via the dynamic creep test and SCB bending test. Finally, the construction effect of foamed hot mix asphalt mixtures was evaluated by paving the test sections. The results show that foamed asphalt can improve the high-temperature stability and low-temperature cracking resistance of traditional hot mix asphalt mixtures, and the asphalt mixture specimen formed by indoor Marshall cannot completely simulate the pavement situation of on-site asphalt mixtures. Under the same construction technique, foamed hot mix asphalt mixtures can achieve great compactness compared to ordinary ones.
Nonlinear Models of Crumb Rubber and SBS Composite Modified Asphalt
Ji Xuewen, Xu Zhiyang, Shi Pengcheng, and Shen Junan
Date posted: 11-8-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.05.033
One purpose of modified asphalt is to improve its high-temperature resistance to ruttings. This paper investigated the main influencing factors and the nonlinear prediction model of the anti-rutting performance index anti-rutting factor of crumb powder and SBS double modified asphalt. Meanwhile, a dynamic shear rheometer was adopted to test the anti-rutting factor G∗/sinδ of double modified asphalt prepared with two types of asphalt and different SBS and crumb rubber mixing contents at four different temperatures (70℃, 76℃, 82℃, and 88 ℃), with a nonlinear model for the anti-rutting factor built. The results show that the modifier mixing content factor of composite modified asphalt is exponentially related to the modifier mixing content, and the temperature factor of the rheometer test is also exponentially related to temperature.
Study on Long Term Performance of Different Types of Warm Mix Asphalt Mixture
Li Quyuan, Liang Naixing, Yang Zhuolin, and Zeng Cheng
Date posted: 11-8-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.05.034
To study the long-term performance of warm mix asphalt mixtures, this paper added three warm mix agents with different cooling mechanisms, including the organic viscosity reducer Sasobit, synthetic zeolite Aspha-min, and surfactant DWMA-1, to realize the warm mixing of mixtures. Meanwhile, the oven heating method was employed to simulate the long-term aging of mixtures. The high and low-temperature performance and water stability of mixtures before and after aging were compared, and the anti-aging properties of warm mix asphalt mixtures were analyzed, with the fatigue cracking resistance of warm mix asphalt mixtures studied via the splitting fatigue test and semi-cylindrical crack propagation test. The results show that Sasobit and Aspha-min improve the high-temperature performance of the mixture, but both degrade the low-temperature performance and water stability of the mixture to varying degrees. DWMA-1 improves the low-temperature performance and water stability of the mixture. The performance of Sasobit and DWMA-1 warm mix asphalt mixtures declines slightly after long-term aging and has sound anti-aging properties. Additionally, Sasobit improves the fatigue life of the mixture, with the specimens exhibiting brittle failure characteristics. Aspha-min and DWMA-1 have little effect on the fatigue performance of the mixture, and the specimens exhibit plastic failure characteristics. The durability indicators of warm mix asphalt mixtures are better than those of hot mix asphalt mixtures.
Study on Method of Material Classification System Based on South African Standard
Zhao Bin, Gu Yang, Zang Zhishu, Yuan Renfeng, and Bian Xiaolong
Date posted: 11-8-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.05.035
Reasonably and effectively determining the material grade is an important part of the design of the old road pavement structures in old road repair projects. Based on fuzzy logic and certainty theory, a novel South African pavement material classification system method was provided by adopting Design Equivalent Material Class (DEMAC). Starting from the discrimination principle, this paper elaborated on parameters such as the certainty factor, coefficient for sample size correction, relative certainty C(E), and relative confidence, and summarized and extracted the design process of a material classification system method based on South African standards. Case analysis shows that if experimental conditions permit, it is recommended to appropriately increase testing indicators to improve the certainty degree in determining DEMAC levels.
Study on Properties of Organic Montmorillonite Modified Bio-Asphalt under Different Aging Modes
Feng Xuemao, Bai Xianping, Wei Hui, Dai Yinhan, and Yang Xinyan
Date posted: 11-8-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.05.036
To improve the road performance of bio-modified asphalt, this paper mixed 3% organic montmorillonite with bio-modified asphalt, and prepared organic montmorillonite bio-modified asphalt by adopting the high-speed shear method. Meanwhile, by carrying out three aging tests of RTFOT, PAV and UV and combining DSR, MSCR, BBR and Brinell viscosity tests, the high and low-temperature stability and anti-aging properties of organic montmorillonite bio-modified asphalt were comprehensively analyzed from the perspective of rheology. The experimental results show that bio-asphalt has sound compatibility with base asphalt. The high and low-temperature performance of bio-modified asphalt is basically similar to that of base asphalt, but its anti-thermal aging and UV properties are poor. The mixing of organic montmorillonite with special intercalation structures can significantly improve the rutting factor, creep recovery rate, and Brinell viscosity of the bio-modified asphalt, reduce its unrecoverable creep compliance, and significantly improve its anti-rutting and aging properties.
Study on Mechanical Properties of Lime Soil Modified by Different Fibers
Qian Jian, Zhou Lin, Yang Jiandong, Zhang Weiqing, and Jiang Ping
Date posted: 11-8-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.05.037
By conducting unconfined compression strength tests, the influence of polypropylene fiber, glass fiber, basalt fiber, and carbon fiber on the mechanical properties of lime soil was studied to determine the fiber with the best modification effect on lime soil (lime mixing content of 6%, fiber content of 0, 0.5%, 0.75%, and 1% respectively). Research shows that all the four types of fiber can improve the modulus-strength ratio of lime soil. Specifically, polypropylene fiber can significantly reduce the brittleness index and improve the toughness index of lime soil, while the other three types of fiber have the opposite effect. Additionally, except for polypropylene fiber, the other three types of fiber do not significantly improve the various properties of lime soil, which is mainly because polypropylene fiber has sound dispersibility in soil, while the other three types of fiber have poor dispersibility and are prone to clumping, greatly affecting the interfacial friction and spatial confinement effect between fiber and soil particles.
Influence of Asphalt Grade on Performance of Waste Concrete Coarse Aggregate (RCA) Hot Recycled Asphalt Mixture
Wang Feifei and Jiang Fenghua
Date posted: 11-8-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.05.038
To study the effect of the asphalt grade on the basic properties of waste concrete coarse aggregate (RCA) hot recycled asphalt mixtures, this paper first prepared the RCA hot recycled asphalt mixture (Type A and Type B) with coarse aggregate, ordinary aggregate, and different grades of asphalt (60/70 asphalt or 80/100 asphalt) in a certain proportion, and then conducted volume characteristic tests and basic property tests on different mixture samples. The experimental results show that the optimal asphalt mixing content, asphalt filling void ratio (VVFB), rutting resistance, and water damage resistance of Type B mixture (80/100) are higher or better than those of Type A mixture (60/70), while the relative density, Marshall stability, modulus of resilience, and skid resistance properties are lower or worse than those of Type A mixture. Meanwhile, the addition of RCA will increase or enlarge the optimal asphalt mixing content and porosity of the mixture, while reducing the proportion, asphalt filling porosity, mineral aggregate porosity, Marshall stability, and modulus of resilience of the mixture. Compared with ordinary mixtures (without RCA), RCA hot recycled mixtures have poor resistance to rutting and water damage, but better skid resistance. For Type A and Type B mixtures, it is recommended that the maximum RCA mixing content that meets heavy traffic requirements should be 25%. When the RCA content in the hot recycled mixture is higher than 25%, it can be applied to road surfaces with lower performance requirements, such as roads with low to medium traffic volume.
Study on Properties of Alkali Activated Slag / Fly Ash Composite Concrete
Guo Zhijian and Li Wenkai
Date posted: 11-8-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.05.039
To improve the durability of concrete structures, alkali activated materials are introduced in the concrete mix design. Alkali activated material is a new type of cementitious material that is low-carbon and environmentally friendly and can effectively alleviate CO2 emissions during the production of ordinary Portland cement, with its physical, mechanical, and long-term durability properties to be verified. This paper selected alkali activated slag/fly ash composite concrete for research, and conducted tests on slump, water absorption, compressive strength, and resistance to chloride ion penetration of concrete with different slag contents, Na2O contents, water ash ratios, and sand ratios. The results show that with the increasing slag content, the fluidity and water absorption of concrete gradually decrease, while the compressive strength and resistance to chloride ion penetration gradually increase. As the Na2O content increases, the concrete fluidity first decreases and then increases, and the compressive strength and resistance to chloride ion penetration gradually rise, with the gradually decreasing water absorption rate. As the water ash ratio increases, the fluidity and water absorption of concrete gradually grow, while the compressive strength and resistance to chloride ion penetration gradually decrease. As the sand content increases, the fluidity and compressive strength of concrete first increase and then decrease, the water absorption rate gradually increases, and the resistance to chloride ion penetration is not significantly different. The mixing of alkali activated materials can improve the durability of concrete structures.
Evaluation and Analysis of Dry Wet SBS Modified Asphalt Technology Based on LCA
Li Shihua, Bai Yuduo, and Tang Guoqi
Date posted: 11-8-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.05.040
To provide suggestions for the development of asphalt modification technology, this paper developed a calculation model for energy consumption and emissions during high-temperature storage of asphalt by the heat balance relationship. Referring to the life cycle assessment (LCA) method, it compared the energy consumption and pollutant emissions of dry and wet modification processes in the production, transportation, and storage of modified asphalt. The results show that adopting a dry method can save energy consumption of 2.34 × 1010 MJ per year and reduce pollutant emissions by 1.28 million tons per year. Compared with the wet modification process, dry modification features significant environmental advantages, high promotion value and broad application prospects.
Research on Decay Law of Permeability Coefficient of Permeable Asphalt Mixture
Yu Baoyang, Liu Yupeng, Liu Meiou, and Chen Xidong
Date posted: 11-8-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.05.041
Permeable asphalt pavement is characterized by large voids, and has significant advantages in improving road drainage and ensuring driving safety in rainy days. However, due to its high void content, dust blockage, and vehicle load, it is prone to the void decay, thus degrading the drainage function. To study the decay law of the permeability coefficient of permeable asphalt mixtures in particle blockage and compaction conditions, this paper built a permeability coefficient decay model for permeable asphalt pavement based on fluid dynamics theory to predict the variation law of the permeability coefficient of permeable asphalt pavement under the effects of void blockage and driving over time. The results indicate that the decay rate of the permeability coefficient of permeable asphalt mixtures is exponentially related to the quality of void blockage and the number of compaction cycles. In practical utilization, the decay rate of the permeability coefficient of permeable asphalt pavement is directly related to the initial void content, utilization time, accumulation rate of dust particles, filtration coefficient, and compaction times.
Experimental Study on Working and Mechanical Properties for Pervious Concrete
Li Wei and Wang Zhaolun
Date posted: 11-8-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.05.042
To investigate the influence of key parameters such as the void content and water ash ratio on the performance of pervious concrete, this paper employed compressive strength, flexural strength, and flowability tests to analyze the effect of changes in the void content, water ash ratio, water-reducing agent, and curing age on the working and mechanical properties of pervious concrete. The experimental results show that the flowability index can evaluate the working properties of pervious concrete. With the rising content of the water-reducing agent, the flowability index increases, while the amount of the water-reducing agent utilized to achieve the same flowability also relatively decreases with the increasing water ash ratio. It is recommended to control the flowability at 240-250 mm. Meanwhile, as the water ash ratio increases, the compressive strength and flexural strength present a decreasing trend. With the rising void content, the compressive strength and flexural strength also significantly decrease, and the influence of void content changes on compressive strength and flexural strength is much higher than that of changes in the water ash ratio. With the increasing curing age, the compressive strength and flexural strength values show a significant increasing trend. With the increasing flowability, both compressive strength and flexural strength present an increasing trend, with the significantly growing flexural strength value.
Study on Effect of Coir Fiber Reinforcement on Improving Engineering Properties of Subgrade Expansive Soil
Li Songfeng and Chen Junfeng
Date posted: 11-8-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.05.043
As a natural material for rock and soil mass reinforcement, coir fiber has advantages such as easy degradation, low cost, and environmental friendliness compared to artificial chemical reinforcement materials. This paper studied the improvement effect of coir fiber reinforcement on the engineering properties of subgrade expansive soil by conducting the immersion swelling test, CBR test, and large-scale direct shear test, with the influence of different types of coir fiber, reinforcement positions, and reinforcement layers considered. The results indicate that under all reinforcement schemes, the expansive force ratio and expansive rate ratio are both less than 1, which indicates that coir fiber reinforcement can reduce expansion, with lime coir fiber having the most significant effect. After adopting coir fiber reinforcement, the California bearing ratio (RCBR) of the expansive soil meets the requirements of the upper embankment, and RCBR of the expansive soil reinforced with lime coir fiber satisfies the requirements of the lower roadbed. Additionally, coir fiber reinforcement significantly improves the shear strength of expansive soil, but the effect of coir fiber types on shear strength is not significant.
Study on Self-Healing Performance of UV- Curable Polyurethane Modified Asphalt and its Mixture
Jia Junhong and Liu Dachang
Date posted: 11-8-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.05.044
In response to the challenges faced by self-healing pavement structures such as microcapsules and steel fiber-heated pavement in terms of healing times, energy consumption, and heating time, this paper employed polyurethane with self-healing properties under UV light as a modifier to prepare UV-curable polyurethane modified asphalt (UV-PU asphalt). Meanwhile, the self-healing properties of the asphalt binder, asphalt mortar, and asphalt mixture were studied by conducting dynamic shear rheology, low-temperature beam bending, and four-point bending fatigue tests. The results show that UV-PU asphalt does not exhibit special self-healing properties during indoor tests, but after a certain period of sunlight exposure, its asphalt mortar and asphalt mixture show better self-healing properties than other asphalt mortar and mixture.
Traffic Engineering and Management
Study on Evaluation of Investment Benefit of Preventive Maintenance Based on IFS-TOPSIS
Guo Wangda, Zhang Jinxi, Zhang Yangguang, Wang Xing, and Niu Yanan
Date posted: 11-8-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.05.045
The investment benefit evaluation of preventive maintenance is of great significance for improving road maintenance management, optimizing the maintenance decision-making mechanism, and ensuring the economic benefit of highway maintenance. To explore the grading evaluation of the investment benefit of preventive maintenance, this paper selected a set of evaluation indicators based on the evaluation indicators of technical conditions of the road surface before and after conducting maintenance intervention and investment. Meanwhile, by comprehensively considering the influence of combination weighting of subjective and objective factors, a preventive maintenance investment benefit evaluation model based on intuition fuzzy set (IFS) and TOPSIS theory was proposed, with the differences in investment benefit under different maintenance opportunities analyzed. Additionally, this paper took nine road sections treated with thin-layer overlay as the evaluation objects. The results show that the evaluation method based on IFS-TOPSIS theory accurately determines the investment benefit level of preventive maintenance by the relative closeness degree, and verifies the feasibility of the evaluation model via comparing the cost-effectiveness ratio evaluation results. Determining the optimal timing for preventive maintenance is the key to ensuring economic benefit.
Research on HA-Level Beam-Column Steel Barrier Structure Based on Steel Bridge Flange Plate
Yu Bin, Wang Xin, Chi Hongkun, Yang Fuyu, Liu Siyuan, and Ma Qing
Date posted: 11-8-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.05.046
The Qipanzhou Changjiang River Highway Bridge is a super-large steel box girder suspension bridge. In accordance with standard specifications, it is necessary to install HA-level beam-column steel barriers that are reliable in safety protection performance and suitable for the bridge type to better protect the safety of operating vehicles and main structures of the bridge. By adopting theoretical analysis and computer simulation methods, this paper combined practical engineering conditions to conduct design and optimization research on the upper structure and foundation structure of HA-level beam-column steel barriers, obtaining the optimal barrier structure scheme. Additionally, it simulated the steel box girder bridge flange plate and barrier samples in a 1:1 ratio at the test site, and conducted full-scale impact tests with the most unfavorable vehicle model, with the effectiveness of the barrier structure scheme on the steel box girder bridge flange plate evaluated. The results indicate that the beam-column steel barrier structure based on the steel box girder bridge flange plate is safe and reliable, achieving HA-level protection capability. During the impact, there is no adverse influence on the steel box girder flange plate, meeting the requirements for the utilization of the main structure of the bridge. The results can improve the safety protection of Qipanzhou Changjiang River Highway Bridge, and provide design references and technical support for similar projects.
Study on Safe Distance between Tunnel Group and Interconnecting Section of Mountain Expressway
Shang Ting, Wu Peng, and Sheng Qijin
Date posted: 11-8-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.05.047
To study the minimum safe distance required for tunnel group and interconnecting sections when exit warning signs are set inside tunnels on mountainous expressways with small distances between tunnel group and interconnecting exits, this paper first built a safety distance calculation model based on factors such as the driver's eye movement characteristics, lane changing behavior, and road service level. Secondly, it designed real vehicle experiments to collect eye movement data of drivers in different tunnel environments, and adopted cluster analysis to calculate the relationship between tunnel length and light adaptation distance. Additionally, based on the lane changing characteristics of vehicles, the lane changing distance of vehicles at different road service levels was calculated. Finally, the minimum safe distance between tunnel groups of different tunnel types and service levels was calculated based on the model. The results show that at the same service level, the longer tunnel length means greater required minimum safety distance. However, when the tunnel length exceeds 3000 m, the minimum required safety distance tends to be a constant value. Under the same tunnel type, the higher road service level leads to smaller required minimum safety distance.
Research on Reconstruction and Extension Scheme for Guangling System Interchange
Cao Wentao and Hu Hao
Date posted: 11-8-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.05.048
The Guangling System in Taizhou, Jiangsu is a complex multi-limb hub for transportation transfer between the G2 Beijing-Shanghai Expressway, G40 Shanghai-Shaanxi Expressway, and G1515 Yancheng-Jingjiang Expressway. Based on the Guangling System, this paper conducted analysis of the current situation and long-term adaptability of the system, formulated principles for reconstruction and extension, and proposed multiple reconstruction and extension schemes. Meanwhile, it carried out comprehensive comparison and research from the aspects of service functions, technical indicators, economic benefits, and construction guarantee to determine the suitable recommended scheme.
Application Study of Ramp Metering Technology on Freeway in America
Gao Qinghai
Date posted: 11-8-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.05.049
Ramp metering technology is a main method of conducting traffic control management and alleviating traffic congestion. Compared with expanding highway mileage, ramp metering technology is characterized by the low cost, short cycle, fast effect, and strong sustainability, finding widespread application in engineering practice in European and American countries. Starting from the basic principles and technical difficulties of ramp metering technology, this paper elaborated in detail on the application distribution, benefit statistics, and applicable conditions of ramp metering technology in the United States. The statistical results show that the application of ramp metering technology reduces the average travel time by 38.7%, increases the average operating speed by 38.25%, and reduces the average accident rate by 30.1%. Meanwhile, based on the road management characteristics in China, the difficulties in applying ramp metering technology were analyzed, which were mainly reflected in the localization of model parameters, geometric conditions, pilot applications, and other aspects. Finally, according to the characteristics and principles of ramp metering technology, the implementation process of ramp metering technology was proposed to provide technical references for the control of freeways and urban expressways in China.
Introduction to Design of the U-Turn in Costa Rica Highway Project
Peng Xiaoguang, Xiang Jian, and Gan Xuejun
Date posted: 11-8-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.05.050
The U-turn in roads has been widely employed in the United States, Europe, and Central America. Based on the Highway 32 reconstruction and expansion project in Costa Rica, this paper analyzed and researched the U-turns based on Central American standards to introduce the U-turn design method. Meanwhile, it emphasized the application scope, selection characteristics, and design methods of the Central American region's U-turn design. The U-turns serving as a fine design method for solving left turn conflicts feature strong applicability, simple structure, and low cost. This paper can provide both guidance for similar designs based on European and American standards, and references for relevant designs in China.
