Volume 43, Issue 5 (2023)
Specially Invited Article
Review of design for combined base asphalt pavements with asphalt treated base and cement stabilized subbase
LI Xuelian, CHEN Peng, and CHA Xudong
Date posted: 11-24-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.05.001
At present, there are great differences in the material composition, structure form, damage type, disease cause, design index, and design method of asphalt pavement with asphalt-treated base and cement-stabilized base in various countries. In view of this, this paper summarized the material type and structure form selected in China and abroad and analyzed the damage type and disease cause of this kind of asphalt pavement structure. This paper discussed the differences in the design methods of combined base asphalt pavement in different countries and summarized the disease control types and design indexes in different countries. On this basis, the reasonable material, structure combination, and design indexes of combined base asphalt pavements were recommended, which provided a reference for the design and application of this kind of asphalt pavement.
Subgrade Engineering
Stability analysis of be dding slope with soft rock under changing hydraulic environment
PAN Rongjian, ZHONG Qifeng, LIU Xianlin, and LV Xilin
Date posted: 11-24-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.05.002
In order to study the influence of moisture content change and rainfall infiltration on the stability of bedding slopes with soft rock interlayer, a highway slope in Guangxi was taken as an example. The moisture content change of bedding slope and the influence law of rainfall infiltration condition on slope safety factor was analyzed by considering the change characteristics of strength parameters of soft rock interlayer with moisture content. The results show that there is a negative exponential relationship between the strength parameters of soft rock interlayer and the moisture content, and there is a critical moisture content. When the moisture content of the soft rock interlayer exceeds the critical value, the most dangerous sliding surface will change from the slope toe circle to sliding along the soft interlayer. Under the condition of rainfall infiltration, the increase in sliding force caused by rainfall in the early stage has no obvious effect on the slope safety factor. As the rainfall continues, the areas in the shallow surface of the slope affected by rainfall infiltration are more prone to instability.
Experimental study on highway subgrade of aeolian sand consolidated by strong compaction in desert shallow water lake area
HE Liping, LIU Zhijun, WANG Xuegang, and TENG Chao
Date posted: 11-24-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.05.003
As a backfill with abundant reserves and poor gradation in desert areas, aeolian sand has been successfully applied to some highway subgrades in China, but the treatment of aeolian sand is mainly focused on the superficial surface, and there are few studies on its deep or underwater treatment methods and applicability. Combined with the aeolian sand subgrade in Taitema Lake section of Urumqi–Yuli Expressway project in Xinjiang, the dynamic compaction method was used to treat the aeolian sand in deep water. The aeolian sand sediment, uplift, and excess pore water pressure during compaction were monitored, and the effects of dynamic compaction before and after reinforcement were compared. The results show that the optimum single point compaction energy is 2 500 kN·m in the aeolian sand subgrade of desert lakes with a depth of 5 m, and the optimum single point compaction number is 8–9. The distance between compaction points is 4.5 m, and the surface uplift is small during compaction. The excess pore water pressure dissipates quickly, and continuous operation can be performed when multiple points are compacted. The reinforcement effect before and after dynamic compaction of aeolian sand is obvious, and it can be used as a backfill of highway subgrades.
Research on combined prediction model of subgrade settlement based on set pair analysis theory
DING Jianjun, LUO Jinfeng, and WANG Qishun
Date posted: 11-24-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.05.004
In order to predict subgrade settlement under the influence of uncertain factors, this paper constructed a combined prediction model of subgrade settlement based on set pair analysis theory and statistical decision idea. Firstly, the single-item prediction model was selected, and the predicted value and the measured value were constructed as a set pair according to the prediction results of the single-item prediction model. Then, the normal distribution theory was used to determine the set pair relationship partition standard, and the combined weight coefficient was determined based on the connection number to realize the optimal combination of prediction information. Finally, the combined prediction model was proposed by the prediction error evaluation, and the effectiveness of the combined prediction model applied to the subgrade settlement was verified by the settlement data of a subgrade.
Pavement Engineering
Study on performance and dynamic response of composite stress absorber layer
YANG Sanqiang, LI Pengfei, LIU Lu, and CAO Zilong
Date posted: 11-24-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.05.005
In order to compare the performance difference among the composite stress absorption layer, SBS stress absorption layer, and glass grille stress absorption layer, the dynamic response law of the composite stress absorption layer was explored. In this paper, based on the composite stress absorption layer composed of glass grille + rubber-modified asphalt gravel sealing layer, the UTM-25 test system was employed to carry out inter-layer shear, inter-layer tension, low temperature bending, and four-point fatigue test. By laying test sections and sensors, strain information of the stress absorption layer under different conditions was collected. It was found that the bonding force of the composite stress absorption layer was 0.58 MPa; the internal friction angle was 12.84°; the tensile strength of the composite layer specimen was 0.48 MPa, and the maximum flexural strain was 3 936 με (−10 °C). According to the field test, the dynamic response model of vehicle speed (under standard axle load) was proposed. The test section was observed one year later, and no road disease was observed. The results show that the bonding properties, shear properties, low temperature bending properties, and fatigue properties of the composite stress absorption layer are better than those of the traditional stress absorption layer because of the locking effect of the glass grille and the bonding effect of the rubber-modified asphalt. The reinforcement effect of the glass grille makes the effect of the composite stress absorption layer more obvious in the low-speed climbing section.
Test and evaluation of bearing capacity of crushed layer of old concrete pavement
YUE Aijun, WANG Wei, LI Wangming, and TAN Jinshou
Date posted: 11-24-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.05.006
In order to accurately evaluate the bearing capacity of the structural layer of old concrete pavement with semi-rigid bases and flexible soil bases after crushing and provide accurate design parameters for the reconstruction of old cement concrete pavement, this paper adopted the bearing plate and Beckman beam to compare the equivalent resilience modulus and bending of the top surface of the structural layer of old cement concrete pavement after crushing. The results show that the average equivalent resilience modulus of the top surface of the old concrete pavement with semi-rigid bases after resonance crushing is 444.20 MPa, and that of the top surface after multi-hammer crushing is 408.15 MPa. The average equivalent resilience modulus of the top surface of the old concrete pavement with soil bases after resonance crushing is 326.71 MPa, and the representative value of deflection is 329.68 (0.01mm). The variation coefficient of deflection is 88.02%. The structural layer stiffness of the old concrete pavement with semi-rigid bases after crushing is suitable for the asphalt pavement structure with flexibility. The structural layer of the old concrete pavement with soil bases after resonance crushing is only equivalent to the heterogeneous graded gravel layer, and the asphalt layer should be added after the structure reinforcement.
Application and research of microwave‑assisted heating hot in‑place recycling in expressway maintenance
ZHU Haoran, ZHANG Yang, MA Hui, FU Shi, and WANG Gui
Date posted: 11-24-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.05.007
Microwave heating is a kind of heating method studied recently in China and abroad, which has the advantages of deep heating, good uniformity, and high energy utilization. In the past, microwave heating technology was mostly applied to the daily maintenance of asphalt pavement but was not applied to hot in-place recycling in asphalt pavement. Based on the principle and characteristics of microwave heating, this paper put forward the unique combined process flow of microwave-assisted heating and hot in-place recycling in China and abroad and carried out the application of microwave-assisted heating and hot in-place recycling in Lianyungang–Khorgos Expressway maintenance project. The research results show that the scheme with a microwave heater directly heating the original road surface is not suitable, and the scheme with a microwave heater for secondary heating is determined. The hot in-place recycling project practice of Lianyungang–Khorgos Expressway shows that after microwave heating, the heating temperature inside the milling material can be increased by 14 °C, which ensures the mixing and paving temperature and construction quality of the subsequent mixture.
Date posted: 11-24-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.05.008
Based on the example of using the double-layer continuous paving technology for a cement-stabilized gravel base with a large thickness of 36 cm of a highway connection line in Guangdong Province, the key problems in the construction process of double-layer continuous paving, such as road length, interlayer bonding, rolling process, and quality detection, were compared by designing and paving four sections with different technical measures. Finally, according to the test results of the construction section, the construction suggestions were put forward.
Analysis on application of pixel‑level segmentation and measurement algorithm road pavement cracks based on Crack Mask R‑CNN model
LIU Jianhua, DONG Jiaxiu, WANG Niannian, and FANG Hongyuan
Date posted: 11-24-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.05.009
In view of the existing problems in pavement crack segmentation, this paper proposed a Crack Mask R‑CNN pixel-level segmentation algorithm. Crack Mask R‑CNN is a case segmentation framework for pavement crack images, which can not only detect cracks in the image but also give a high-quality segmentation result for the specific contour of each crack. Firstly, the big data of collected road cracks was denoised and enhanced, and the data set for model training and testing was constructed. Secondly, by optimizing the proportion and size of anchor frames in the segmentation algorithm, the accuracy of the model in selecting crack candidate regions was improved, and the IoU‑guided non‑maximum suppression (NMS) algorithm was used to replace the traditional algorithm, so as to improve the segmentation accuracy of road cracks. In the aspect of model learning-based hyperparameter optimization, by training a variety of combination examples, the hyperparameter combination with the best segmentation effect was selected, and finally, the segmentation model with a segmentation accuracy of 93.45% was trained. Finally, by extracting the topological feature information of the crack region, the pixel-size information of the crack could be effectively measured.
Study on the mechanism of interlayer failure of solid encapsulated photovoltaic pavement
HE Xiaobin
Date posted: 11-24-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.05.010
In view of the interlayer stripping failure mode of solid-encapsulated photovoltaic pavement, a three-dimensional finite element model was established by finite element analysis method to carry out plate stress analysis of solid-encapsulated photovoltaic pavement under different loading conditions and different bonding sizes. The mechanism and key influencing factors of the interlayer stripping failure mode of solid-encapsulated photovoltaic pavement were studied, and suggestions for optimal design were put forward. The results show that due to the difference in interlayer bonding force and encapsulating materials, the solid-encapsulated photovoltaic pavement structure is prone to interlayer stripping damage. As the adhesive layer height is closer to the loading surface, the stratified damage of interlayer bonding failure is more likely to occur. On the premise of ensuring power generation, it is recommended to reduce the bonding layer height and bonding area and adopt rivet technology, which is conducive to improving the structure life.
Study on pavement life and cost of glass fiber modified asphalt for tension belt
BAI Wei, KONG Weikang, and MENG Yongjun
Date posted: 11-24-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.05.011
Adding fiber to asphalt mixture can improve the performance. As an alternative to wood fiber, glass fiber can be used as an additive to asphalt mixtures such as stone mastic asphalt. The effect of adding loose glass fiber on the properties of different asphalt mixtures was studied. The influence of glass fiber on the fatigue and stiffness properties of asphalt mixture was studied through the cyclic indirect tensile test by selecting glass fiber with a constant mass ratio of 0.5%, and the application of these asphalt mixtures as tension bands was further studied. The pavement service life and economic benefits were calculated. The results show that adding glass fiber with a mass ratio of 0.5% can make different asphalt mixtures have better fatigue and stiffness properties and can reduce the thickness of the asphalt layer in the pavement structure. It is proven that the performance of glass fiber-modified asphalt is better, and the pavement cost can be significantly reduced by laying tension bands with glass fiber-modified asphalt mixture.
Laboratory trabecular test of anti‑reflection crack of modified asphalt overlaying
ZHANG Zhiying, JIE Jianguang, ZHANG Bingyang, ZHU Yiwei, and ZHAO Yong
Date posted: 11-24-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.05.012
In view of the disadvantages of surface reflection cracks that are easy to occur after asphalt layer overlay on airport cement pavement, a laboratory beam three-point bending test was conducted to investigate the generation and development process of reflection cracks of modified asphalt and cement composite beams under different types of bottom cracks, and the ability of different modified asphalt mixtures to resist surface reflection cracks was evaluated. The results show that under the three-point bending loading mode, the development process of cross crack and transverse crack is similar, and the influence of vertical crack on the reflection crack is small. The NRP-modified asphalt mixture has a better ability to resist reflection cracks than the ordinary SBS-modified asphalt.
Bridge Engineering & Tunnel Engineering
Reliability analysis of RC simply supported beams strengthened by UHPC
ZHANG Jie and LIN Pengzhen
Date posted: 11-24-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.05.013
In order to study the reliability of reinforced ultra-high performance concrete (UHPC), a calculation model of the flexural capacity of the reinforced UHPC section was proposed, and the applicability of the model was verified by the existing test results. Through the calculation example of strengthening RC simply supported beams by increasing the section of UHPC, the JC check point method was finally employed to obtain the reliability before and after reinforcement, combined with the error transfer formula and the uncertainty of various factors. An in-depth analysis of the improvement effect of UHPC reinforcement on structural reliability and the improvement of reliability after reinforcement compared with ordinary concrete was conducted. The influence of reinforcement thickness and reinforcement was also considered. The results show that UHPC reinforcement can greatly improve the reliability of the structure. Compared with ordinary concrete reinforcement, the reliability performance is also significantly improved. In a certain range, the thickness of the reinforced layer has a positive correlation with the reliability index, and adding appropriate reinforcement to the UHPC layer can effectively improve the reliability index.
Application of wind speed probability distribution models in calculation of basic wind speed of bridge
CHEN Hongxin, CENG Jiadong∗, and ZHANG Zhitian
Date posted: 11-24-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.05.014
By comparing the applicability of various wind speed probability distribution models in the calculation of the basic wind speed of bridges, the differences between different distribution models were analyzed, and the important influence of different distribution models on the value of extreme wind speed of highway bridges was studied. This paper also discussed how to select suitable wind speed probability models according to regional characteristics. Based on the measured wind speed data of five regions, the differences between the models were verified based on the statistical results of the maximum annual average wind speed, and the rationality and applicability of the probability distribution model for each region were discussed according to the regional distribution heat map of the current Wind-resistant Design Specification for Highway Bridges (JTG/T 3360-01-2018). The results show that the current code increases the value of the basic wind speed in the strong wind area, and the changing trend of each wind speed model decreases in different recurrence periods, which can effectively ensure the safety of the basic wind speed value of the bridge and the continuity of wind field distribution. Extreme wind speed predicted based on generalized extreme value distribution is the largest, and that based on generalized Pareto distribution is the smallest. The five probability distribution models can be roughly divided into three categories: wind speed increase type, wind speed growth type, and wind speed stabilization type, and different types of models are suitable for different wind speed variation areas.
Study on seismic isolation of concrete filled steel tubular tied arch bridge considering traveling wave effect
GAO Zhonghu, WU Zhongtie, DI Shengkui, WU Yun, and WANG Xiaoqin
Date posted: 11-24-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.05.015
By using the finite element analysis software Midas/Civil, two types of models of concreted-filled steel tube arch bridges with and without shock isolation were established. By considering the longitudinal travelling wave effect of the bridge, the different response values of the arch ribs and piers of the two models were compared under the wave velocity of 100 m/s, 500 m/s, 2 000 m/s, and longitudinal consistent seismic excitation, respectively. It is concluded that because the travelling wave effect of different wave velocities is complicated, the models both have good isolation effects for different wave velocities.
Temperature control and simulation analysis of mass cap in winter
TIAN Zhongchu, NING Chen, MA Lianfeng, ZHONG Zhong, and XU Binlin
Date posted: 11-24-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.05.016
Due to the hydration heat reaction of concrete during the construction of the mass cap in winter, the temperature inside and outside the cap is greatly different, and the water temperature of the cooling pipe is difficult to control, which is easy to produce large stress and lead to cracks. In this paper, by means of high-frequency temperature monitoring and high-density measurement point layout, finite element software was used to simulate the humidity change process of large-scale concrete construction on the mass cap. The calculated results were consistent with the measured temperature change trend, and the maximum percentage of peak temperature reduction was 1.60% when the inlet temperature was reduced by 5 °C. The maximum tensile stress near the cooling pipe increased by 4.98%, and the sensitivity of inlet temperature to the tensile stress near the cooling pipe was greater than the peak temperature. Combined with a self-circulation water tank, cotton quilt insulation, and other reasonable temperature control measures, the set control goal was achieved, and the temperature control scheme was verified to be reasonable. It is recommended that for the mass cap constructed in winter, the inlet temperature of the cooling pipe should not be lower than 5 °C, and 10–25 °C is appropriate. The mold removal time around the cap should be controlled to 4–5 days, and the thermal insulation maintenance should be carried out immediately after the mold removal to ensure the construction quality of the mass cap.
Measurement and analysis of hydration heat effect between adjacent segments of cast‑in‑place PC box girder
HONG Jinsheng, LIU Luming, PEI Bingzhi, ZHU Zuhuang, HUANG Ning, and FANG Zhi
Date posted: 11-24-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.05.017
In order to determine the effect of hydration heat of the post-cast section of cast-in-place prestressed concrete box girder on its own section and adjacent poured section during the construction process, the mechanical properties, temperature field of hydration heat, and strain field of early-age concrete N13 section of the southern span concrete box girder were measured on site against the background of Wuxue Yangtze River Bridge. The finite element models of the N13 section and its adjacent poured sections were established to analyze the development law of hydration heat temperature field and stress field between adjacent sections of the concrete box girder. The results show that under the action of hydration heat at the early age of the post-cast section, the concrete of the post-cast section cannot move freely and thus produce compressive stress due to the transverse bridge constraint effect of adjacent sections. The temperature-induced tensile stress in the inner web and roof of the adjacent poured sections at about 1.0 m away from the joint surface is relatively large, with the maximum tensile stress being 3.93 MPa and 4.54 MPa, respectively, which exceeds the tensile strength of the concrete sections at the corresponding time and may lead to the cracking of the box girder. The effective measures to prevent concrete cracking are to reduce the temperature rise of hydration heat and stretch the horizontal and vertical prestress in the adjacent sections before pouring of post-cast section.
Analysis of influencing factors of internal force of four‑column bridge pier and cover beam
CENG Xianying, WANG Yuesong, and JIANG Tianyong
Date posted: 11-24-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.05.018
In order to study the factors affecting the internal force of a four‑column bridge pier and cover beam and solve the problem of inconsistent weight load of left and right sides, Midas/Civil was used to establish a finite element model of the bar system. By comparing the internal force under different weight ratios of left and right sides, temperature, and uneven settlement, the influence of weight ratios of left and right sides, temperature, and uneven settlement on the internal force of a four‑column bridge pier and cover beam was analyzed. The results show that when the weight of the left side is unchanged, as the weight of the right side decreases, the weight ratio of the left and right sides increases. It has little influence on the internal force of the four‑column bridge pier and cover beam near the left side, and the internal force changes by about 10%. The internal force of the four‑column bridge pier and cover beam near the right side is greatly affected and changes by more than 30%. Under the overall temperature load, the internal force of the four-column bridge pier and cover beam changes symmetrically, about 10%. The non-uniform settlement will cause the cover beam to be strained at the lower part of the pier column settlement position and the upper part of the adjacent pier column without settlement position, resulting in a sharp change in the internal force of the four-column bridge pier and cover beam. When the uneven settlement is 5 mm, the positive bending moment at the center of the left side increases by 42%, while the internal force at the center of the right side is slightly affected. In practical engineering, it is necessary to pay close attention to the uneven settlement of bridge piers.
Seismic performance analysis of CFRP reinforced socke t pier
LI Qian and LV Wenshu
Date posted: 11-24-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.05.019
Compared with traditional cast-in-place concrete piers, prefabricated socket piers have the advantages of easy construction, but they are more likely to be damaged under earthquakes. In order to optimize its seismic performance, the CFRP reinforcement method was used to strengthen socket piers. Based on the existing tests, a three-dimensional finite element model was established by using Abaqus software to analyze the seismic performance indexes such as hysteretic properties and residual deformation of the socket piers under the combined action of axial compression load and low-cycle reciprocating load. The research results show that the advantages of the CFRP cloth are not obvious when the loading displacement grade is low, but when the loading displacement grade is high, the hysteretic properties and residual deformation of the specimens strengthened by CFRP cloth are greatly improved. CFRP can improve the bearing capacity and deformation capacity of the socket piers, which is conducive to the continued operation and overall repair of the piers after the earthquake.
Automatic measurement method of cable wire corro sion pit shape based on digital image processing
XU Hongsheng, WANG Lei, YAN Donghuang, and WU Jiadong
Date posted: 11-24-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.05.020
In order to solve the shortcomings of the manual method in the measurement accuracy of the pitting pit size and the measurement efficiency of the pitting pit location of the cable wire, the digital photos of the steel wire in the laboratory accelerated corrosion test were taken as the research object. Based on the digital image processing technology and the influence of the wire surface, an automatic measurement method for the location of the pitting pit shape parameters and the relative position between multiple pitting pits on the surface of the corroded wire was proposed. The results of automatic measurement and manual measurement were compared to analyze the engineering feasibility of the proposed method. The results show that compared with the manual measurement method, the automatic measurement method has the relative error of long axis length, spacing, and area of pitting pits within 10%, and the pitting pit recognition accuracy reaches 93.3%. The relative error of the long axis length decreases with the increase in the long axis length of the pitting pit. The automatic measurement method can save time up to 99.09% and greatly improve measurement efficiency. The automatic measurement method is superior to the manual measurement method in positioning accuracy and measurement efficiency and can meet the engineering needs of parameter measurement of pitting pits on corroded steel wire surfaces.
Research on load lateral distribution of steel plate composite wide bridge with less transverse connection
LI Liming, HOU Kun, and LI Jiquan
Date posted: 11-24-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.05.021
At present, the number of lateral connection arrangements in steel plate composite wide beam bridges tends to decrease. In order to study the transverse stress distribution of the bridge, especially load and compare the applicability of the calculation methods for the transverse load distribution coefficient, a 30 m simply supported steel plate composite wide beam bridge was studied. The finite element method and several Chinese and foreign calculation methods were used to calculate the transverse load distribution coefficient, and the thickness of the bridge panel and the size of the steel brace were selected as parameters for comparative analysis. The results show that the transverse load distribution coefficients of the middle beam and the side beam are close to each other. Compared with no lateral connection in the middle span, adding a lateral connection will slightly increase the side beam and reduce the transverse load distribution coefficient of the middle beam. The influence of the thickness of the bridge deck is small. The stiffness of the steel brace needs to be chosen according to the actual situation, rather than a fixed large value. The calculation method given by the rigid connected beam method and AASHTO LRFD code is more reliable.
Research on operation visualization of arch bridge based on BIM technology
TONG Guangxu, XIE Yan, SONG Hua, and CHANG Jun
Date posted: 11-24-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.05.022
The data of the current bridge structure in the process of operation and maintenance is messy and less visual. In order to improve the monitoring efficiency, ensure the safety of daily bridge operations, and solve the problems of monitoring information visualization, dynamic real-time early warning, and insufficient information sharing of operation and maintenance management in traditional bridge monitoring and management, the characteristics of BIM software was utilized, such as high visualization and applicability in the project life cycle. The health monitoring system was established by combining communication technology and a database. The health monitoring information was visualized, and the functions of real-time visual early warning based on monitoring information were realized. Finally, the practicability of this method was verified by an engineering example.
Research on transverse temperature gradient of flat steel box‑girder in mountainous area based on long term monitoring
YANG Wenfu and CHEN Xin
Date posted: 11-24-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.05.023
In order to realize the accurate description and prediction of the temperature field and temperature effect of the bridge structure, the characteristics of the transverse temperature gradient of a flat steel box girder in a mountainous area were analyzed. Firstly, based on the long-term monitoring data of the temperature field of the flat steel box girder structure of a suspension bridge in a mountainous area, the transverse temperature difference extremum was analyzed, and the asymmetric distribution characteristics of the structural temperature field were obtained by using cluster analysis. Then, the probability density model of the transverse temperature difference between the top and bottom plates of the steel box girder was established by statistical analysis, and the standard value of the transverse temperature difference between the top and bottom plates of the steel box girder was calculated by taking 50 years as the re-occurrence period. Finally, the transverse temperature differences at different positions were combined according to the most unfavorable condition, and the transverse temperature gradient mode of the top and bottom plates was obtained. The results show that the transverse temperature difference of the steel box is less affected by seasonal variation. Affected by the mountain landform, the structural temperature field has obvious asymmetric distribution characteristics. The probability statistical model of the transverse temperature difference between the top and bottom plates of the steel box girder is in good agreement with the double Gaussian model. Since the top plate is directly radiated by the sun, its transverse temperature difference is significantly larger than that of the bottom plate. The maximum absolute values of the standard transverse temperature difference between the top and bottom plates of the steel box girder are 37.68 °C and 13.37 °C, respectively. The top plate of the flat steel box girder in a mountainous area has three kinds of transverse temperature gradient modes: M-shape, W-shape, and oblique N-shape. The bottom plate has three kinds of transverse temperature gradient modes: V-shape, inverted V-shape, and straight line. The transverse temperature gradient modes of the top and bottom plates have obvious asymmetry.
Research of digital delivery method for conventional bridge design information based on BIM+GIS technology
DAN Chen, ZHU Ming, and XIAO Chunhong
Date posted: 11-24-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.05.024
Conventional bridge design and construction methods have been relatively mature, but the design results are mainly presented in the form of paper documents, and the digital application of design information in the stage of bridge construction and later operation and maintenance is difficult. Based on the existing standard system, this paper conducted a systematic study on the conventional bridge structure entity decomposition, BIM model information, classification and coding, and rules by components and terms, respectively, established the digital delivery standards for conventional bridge design information, and used Revit software to develop the rapid modeling software for conventional bridges. Combined with the digital delivery standards described in the paper, the relationship of key design information such as geometry information, attribute information, project quantity, and list item number with components and terms was studied, and the digital and structured storage of design information under the premise of meeting the needs of engineering construction was achieved. At the same time, the GIS platform was used to realize the integration of various types of design data, and the data flow channel of the construction management platform was opened up in the form of a network service based on the B/S framework. The research shows that the transfer of design results based on the digital delivery method described in this paper can meet the existing technical specifications, effectively ensure the accuracy and integrity of the transferred design information, realize the digital delivery of design results, adapt to the needs of multi-user parallel work in highway engineering construction, and significantly improve the efficiency of construction management.
Analysis of error propagation in construction control of main beams of large‑span composite beam cable‑stayed bridges
YANG Rugang, CHEN Bo, and HAN Bing
Date posted: 11-24-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.05.025
At present, there are few studies on the construction error sensitivity of superimposed beams, the cause of error prediction, the change of error, and error propagation pathways. To improve this situation, this paper selected the asymmetric steel-concrete superimposed beam cable-stayed bridge, namely Yibin Nanxi Yangtze River Bridge as the support project and used the finite element analysis software to simulate the whole process of the bridge considering geometric nonlinear construction. On the premise that the sensitivity parameters in the construction process cannot be completely accurate, the influencing factors and formation mechanism of the main beam installation error were analyzed, and the alignment and stress change of the main beam with the construction stage were studied. The propagation law of the main beam installation error was revealed, which provided a theoretical basis for the determination of the allowable error and the optimal adjustment strategy of the error.
Study on mechanical behavior of epoxy asphalt pavements on thicker steel bridge decks under static load
CENG Guodong, HUANG Hongming, and XU Wei
Date posted: 11-24-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.05.026
In order to improve the durability of steel bridge deck pavement, this paper evaluated the mechanical response law of epoxy asphalt pavement with thicker steel bridge deck based on the static load test of solid steel bridge deck pavement and analyzed the transverse strain distribution, critical load, overload effect, axial and transverse strain difference, and the strain condition of epoxy asphalt pavement structure. It identified the mechanical behavior law of epoxy asphalt pavement. The results show that the bridge deck structure is basically in an elastic state under axle load; the surface strain of the bridge deck increases obviously with the increase in axle load, and the effect of wheel load on the steel bridge deck exists within the radius of 1 m. The upper edge of the axial stiffener web of the bridge deck is in the most unfavorable tension state, and fatigue cracking is easy to occur under the repeated action of wheel load. The transverse strain on the lower surface of the steel bridge deck is obviously higher than the axial strain. Epoxy asphalt pavement is mainly characterized by elastic characteristics.
Overall design of single span super wide tied arch bridge with three ribs and five cables
LIU Jie and WEI Lixin
Date posted: 11-24-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.05.027
Shayong Bridge on Dongguan Binhai Avenue is a special-shaped steel box tie arch bridge with a single span of 120 m and five cable planes. The standard section width of the bridge is 80 m. A new type of spatial special-shaped arch bridge with an ultra-wide deck for urban roads was proposed to meet the landscape and structural stress requirements. The main beam adopted the full-width crossbar beam system, and the arch rib adopted the inverted trapezoidal steel box structure with varying height and width. The rise span ratio of the middle arch rib was 1/3.05, with the design vector height f = 38.00 m. The side arch rib was inclined, the rise span ratio was 1/4.936; the vertical projection design vector height f = 23.5m, and the arch height between the middle arch and the side arch was a golden ratio. In order to reduce the dead weight of the bridge deck, optimize the size of the main beam and arch rib, and solve the fatigue and durability of the orthotropic steel bridge deck, the lightweight composite bridge deck with steel–STC ultra-high toughness concrete was used. This kind of bridge has the advantages of a novel structure, beautiful appearance, reasonable force, low engineering cost, and good structural durability. It provided a new way of thinking for the design of urban ultra-wide landscape bridges.
Analysis and application of steel‑concrete composite girder bridge design method based on american specification
YANG Kai, LIU Wanyue, and ZHOU Xiaowu
Date posted: 11-24-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.05.028
Based on the actual project of the reconstruction and expansion of the Jakarta–Chikampe Expressway in Indonesia, this paper introduced the design method, loading mode, and bearing capacity calculation of the composite beams related to the American code and analyzed the design theory based on the provisions of the code. It also summarized the division of section types, so as to provide references for bridge designers to apply and understand the American AASHTO code.
Effect of bolt force loss on fatigue performance of welded cable clamp
SONG Jian, XUE Songling, LI Hui, and LI Hongsheng
Date posted: 11-24-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.05.029
When the cable clamp is used, the bolt force will be relaxed, which will cause the stress amplitude on the cable clamp member to change. For welded cable clamps, the fatigue properties at the weld will change. In this paper, the effect of bolt force relaxation on the weld fatigue life was studied by taking the relaxation of bolt force of welded cable clamps of Xintian Yangtze River Bridge in Wanzhou District during operation as an example. Firstly, the geometric shape and structural characteristics of welded cable clamps were analyzed, and the numerical model of welded cable clamps with bolts was established. Secondly, the stress distribution of welded cable clamps under constant load and fatigue load was analyzed, and the mechanical characteristics of welded cable clamps were studied. Then, different bolt forces were applied to the welded cable clamps to study the change of stress amplitude under bolt force loss. Finally, the effect of bolt force relaxation on the fatigue life of welded cable clamps was analyzed by using the experimental data suitable for the study model. The results show that although the bolt force loss reduces the weld stress of welded cable clamps, it increases the stress amplitude of the weld, which leads to a decrease in the weld fatigue life of welded cable clamps. A larger stress amplitude means a more obvious phenomenon.
Study on selection of plane layout schemes of rock bolts on tunnel face
YANG Lihong, CHEN Danghui, and ZHENG Chao
Date posted: 11-24-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.05.030
In order to select the optimal plane layout scheme for advance anchor bolts in the tunnel face, based on Chinese and foreign engineering examples, the components of the plane layout scheme for advance anchor bolts in the tunnel face were summarized as shape and alignment. On this basis, four different plane layout schemes based on rectangular and circular shapes were summarized. Based on the Muzhailing Tunnel of Weiyuan–Wudu Expressway, the difference in supporting effect of different plane layout schemes for advance anchor bolts in the tunnel face was studied by numerical simulation under the conditions of different anchor bolt layout density, anchor bolt layout length, surrounding rock grade, and tunnel depth. The research results show that the different plane layout schemes for advance anchor bolts in tunnel face will have a certain influence on its supporting effect. Usually, the plane layout scheme based on a circular shape can increase the supporting effect by 2%–6% compared with the plane layout scheme based on a rectangular shape.
Case study on substitutability of national standard and european standard for I‑beams in initial tunnel support structure
LIN Bo, XIE Wenbo, XU Xiuliang, and LIU Lei
Date posted: 11-24-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.05.031
Looking for alternative steel under different standard systems to ensure the orderly progress of engineering projects is an engineering problem that needs to be faced in the field of overseas civil engineering construction. In order to evaluate the substitutability of the European standard IPE 200 I-beam and the national standard I20a I-beam in the initial support structure of the tunnel, a mechanical model of the initial support structure of the tunnel was first established, and the model parameters were calibrated using the measured test data, so as to obtain the analytical solution of the internal forces of the initial support structure corresponding to the two types of I-beams. Furthermore, the substitutability of the two types of I-beams in the initial support structure of the tunnel was compared by taking the bending moment, axial force, and shear stress as evaluation indexes. The results show that the internal force distribution of the initial support structure does not change after the exchange of the two types of I-beams, but an acceptable multiple relation is generated in numerical value. When replacing the national standard I20a I-beam with the European standard IPE200 I-beam, it is necessary to ensure the construction quality of the arch top and arch foot, and some strengthening measures can be assisted if necessary.
Pavement Structure and Materials
Research on low‑temperature performance of warm‑mixed rubber powder modified asphalt mortar under freeze‑thaw effect
FENG Lei, YANG Xin, and CHANG Junpeng
Date posted: 11-24-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.05.032
In order to study the low temperature performance of hot-mixed rubber powder-modified asphalt mortar (CR‑HMA) and SDYK type of warm-mixed rubber powder-modified asphalt mortar with surfactant (CR‑WMA‑S) under freeze-thaw cycle, trabecular three-point bending test was carried out under different salt environment (mass fraction of 0 and 8%) and freeze-thaw cycle times (0, 5, 10, 15, 20, and 25) to explore the improvement effect of salt freeze-thaw cycle on the low temperature performance of warm-mixed rubber powder modified asphalt mortar. The effect of the salt freeze-thaw cycle on the cracking characteristics of warm-mixed rubber powder-modified asphalt mortar was also analyzed. The results show that after the freeze-thaw cycle of the warm-mixed rubber powder-modified asphalt mortar, the change rule of the low temperature index is as follows. The flexural strength, maximum flexural-tensile strain, and bending strain energy density decrease significantly, and the bending stiffness modulus increases; the salt erosion on the crack resistance of asphalt mortar is more serious in salt environments. The fracture toughness of the two types of asphalt mortars decreases with the increase in the number of freeze-thaw cycles, but the SDYK type warm mixing agent has a better effect on the low temperature performance of the asphalt mortars after the salt freeze-thaw cycle.
Analysis of influencing factors on cracking resistance of soil‑cemen
CHEN Ke, LIANG Shuang, ZHAO Zhenguo, and ZHANG Haitao
Date posted: 11-24-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.05.033
In order to study the cracking resistance of cement soil, the mixing and molding methods of the mixture samples were compared. In this paper, vibration stirring and traditional stirring were adopted, and static pressure molding and roller molding were adopted. The dry shrinkage test and temperature shrinkage test of cement soil samples with different mixing methods and molding methods were carried out to study the influencing factors of cracking resistance. The comprehensive test results show that the dry shrinkage coefficient and temperature shrinkage coefficient of cement soil by vibration stirring are smaller than those by traditional stirring, indicating that the cement in cement soil by vibration stirring can be more evenly distributed in the soil particles, and the cement bonding effect can be better played to form a whole among the soil particles. The cracking resistance can be improved. Under different molding methods, the dry shrinkage (temperature shrinkage) coefficient of the samples by roller molding is smaller than that by static pressure molding, and roller molding has a greater effect on improving the cracking resistance of cement soil. The roller molding method used in the test is close to the actual roller rolling method in engineering.
Study on evaluation and affecting factors on anti‑efflorescene performance of asphalt mixture in deck pavement of cement concrete bridge
LI Ningbo, HAO Peiwen, WANG Yujin, and HU Xiaojin
Date posted: 11-24-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.05.034
This paper analyzed the causes of different efflorescence phenomena and determined that the pressure difference was the main driving force of efflorescence. A self-designed critical pressure difference test was conducted to analyze the anti-efflorescence performance of asphalt mixture under different compaction methods and gradation types, and it was proposed that “critical pressure difference”, “time to start pumping at 2 kPa”, and “pumping amount at 2 kPa for 3 min” could effectively evaluate the anti-efflorescence performance of asphalt mixture. The results show that the anti-efflorescence performance of the asphalt mixture is ranked as follows: rotary compaction forming, Marshall compaction forming, and wheel grinding forming. In the gradation design, the anti-efflorescence performance of SMA is better than that of AC, and a larger aggregate size indicates better anti-efflorescence performance.
Performance of microalgae oil modified asphalt and mixture
WU Jingjiang, CHU Fuke, YIN Weiyong, ZHANG Yong, and SHI Haixia
Date posted: 11-24-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.05.035
In order to alleviate the shortage of petroleum asphalt and explore the applicability of microalgae oil in the field of modified asphalt, the composition of microalgae oil, as well as the conventional properties and rheological properties of modified asphalt at high and low temperatures were studied by four-component analysis, three index tests, high temperature shear rheology tests, and low temperature bending creep tests. The performance of microalgae oil-modified asphalt mixture was studied by Marshall test, high temperature rutting, and low temperature bending test. The results show that the microalgae oil is similar to the gel asphalt structure with more hard components. With the increase in microalgae oil content, the softening point of modified asphalt gradually increases, and the ductility and penetration degree gradually decrease. When the content of microalgal oil is 30%, the softening point of modified asphalt is above 60 °C; the high temperature performance is PG 70 before and after aging, and the dynamic stability of the mixture is above 5 000 times/mm; the bending strain at low temperature is higher than 2 500 με, indicating great comprehensive performance. In order to ensure good high and low temperature performance, the content of microalgae oil in microalgae oil-modified asphalt should be 20%–30%.
Study on meso‑distribution uniformity of coarse aggregate based on image processing
LIN Bohuang, SHI Liwan, LIAO Weijie, and XIAO Xin
Date posted: 11-24-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.05.036
The uniformity of asphalt mixture has an important influence on its physical and mechanical properties and is an important component and research object of the asphalt mixture genome. In order to provide a reference for the fine design of asphalt mixture, this paper, based on digital image technology, analyzed the uniform characteristics of the coarse aggregate distribution of Marshall specimen under different compaction conditions for three groups of different gradation levels and then evaluated the relationship between the quantitative index of coarse aggregate distribution uniformity and the macroscopic mechanical properties of asphalt mixture. The results show that the coarse aggregate distribution of Marshall specimens has the characteristics of slightly less at both ends and more in the middle, and the maximum amount of coarse aggregate appears at 1/3–2/3 of the height of the specimen. The increase in compaction times helps to increase the distribution uniformity of the asphalt mixture. The coarse gradation has an important effect on the distribution uniformity of coarse aggregates. The coarse gradation has better uniformity. For aggregates with different particle sizes, smaller particle size indicates better distribution uniformity. The standard difference can be used as a quantitative evaluation index of distribution uniformity of coarse aggregate. With the decrease in standard deviation, the asphalt mixture has better and better rutting resistance.
Research on durability of C 40 sandstone gravel concrete in cold areas
YUE Zhicai, CHEN Yang, WANG Qilong, HUANG Weirong, SUN Zhiyuan, and XU Wei
Date posted: 11-24-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.05.037
In order to utilize local materials and save project costs, sandstone gravel from Datong County of Qinghai Province was used as coarse concrete aggregate to prepare C40 bridge structural concrete in cold areas, and the durability of sandstone gravel concrete was studied. The results show that the sandstone gravel C40 concrete and basalt gravel C40 concrete are very dense, and the impermeability grade is higher than P30, which can meet the requirements of anti-impermeability of engineering projects. The electric flux of sandstone gravel concrete is less than 1 200 C, which can meet the requirement of a 100-year design life of the concrete structure. The 28 d carbonization depth of sandstone gravel concrete is not obvious, and it has good carbonization resistance. The evaluation grade of sulfate erosion resistance of sandstone gravel concrete is greater than KS120. It also meets the requirements of freezing resistance of concrete in a Class II environment. The sandstone gravel can be used to prepare C40 concrete for structures in cold areas.
Development and performance evaluation of cement concrete pavement joint fillers
LONG Liqin, ZHANG Dongzhang, and WANG Jinyong
Date posted: 11-24-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.05.038
Poor road performance of joint filler is one of the main reasons for the damage to cement concrete pavement. In this paper, a new type of joint filler was developed. The bonding property, shear resistance, and durability of the joint filler were compared through tests, and the performance of the joint filler was verified in solid engineering. The results show that the joint filler has good performance and has no obvious damage in the actual project within five years, so it has high engineering practical value.
Date posted: 11-24-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.05.039
In the current process, the mixing and compaction temperature required for the production of waste rubber powder-modified asphalt (CRMA) is relatively high, which is often improved by adding a warm mixing agent. In order to investigate the influence of the addition of a warm mixing agent on the rutting and fatigue properties of CRMA, two kinds of wax-based warm mixing agents (pine wax and polypropylene wax) were added into CRMA, and the rotary viscosity (RV), dynamic shear rheometer (DSR), multiple stress creep recovery (MSCR), and linear amplitude scanning (LAS) tests were carried out, so as to evaluate the influence of warm mixing agent on rutting and fatigue properties of CRMA. The results show that the viscosity of CRMA can be decreased significantly by adding two kinds of wax-based warm mixing agents. Due to the lower non-recoverable creep compliance (Jnr3.2) and higher strain recovery rate (R), CRMA with 2% polypropylene wax has better rutting resistance than that with 4% and 6% polypropylene wax. LAS test results show that CRMA with 6% pine wax has the longest fatigue life, especially at low strain levels.
Performance evaluation of water‑based polymer SRX graded broken stone
ZHANG Ping, ZHANG Hongjiang, and DENG Rongsheng
Date posted: 11-24-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.05.040
In order to investigate whether water-based polymer solution road soilfix (SRX) graded gravel can be used in the base, this paper studied the optimal SRX dosage, mechanical properties, water stability, temperature shrinkage performance, and high temperature stability of water-based polymer SRX graded gravel through laboratory molding test. The results show that the optimal SRX dosage of water-based polymer SRX graded gravel should be 0.5%. For every 0.25% increase in SRX dosage, RCBR (California bearing ratio) and compressive strength increase by at least 6.6% and 9.8%, respectively. Water-based polymer SRX graded gravel belongs to flexible base material. The elasticity modulus and dynamic stability increase with the increase in SRX dosage. It is suggested that the dynamic modulus value of 0.5%SRX should be 600–650 MPa when the SRX polymer base is designed and calculated for pavement structure. In the range of −20–20 °C, the temperature shrinkage coefficient decreases first and then increases with the increase in temperature. The temperature shrinkage coefficient reaches the minimum in the range of −10–0 °C. With the increase in freeze-thaw cycles and soaking time, the maximum reduction of RCBR is not more than 4.8%. The results show that the water-based polymer SRX graded gravel has higher resilience modulus, mechanical strength, and dynamic stability, as well as better water stability and smaller temperature shrinkage coefficient, which indicates that the water-based polymer SRX graded gravel can be popularized and used in grassroots.
Influence of humidity on performance of asphalt mixture
MAO Hongwei and CHEN Zhonghua
Date posted: 11-24-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.05.041
In order to study the influence of humidity on the performance of asphalt mixture, vacuum drying oven and constant temperature and humidity box were used to carry out humidity curing on AC-20C asphalt mixture specimen. A uniaxial penetration test, triaxial test, low temperature bending test, and uniaxial compression dynamic modulus test were carried out to obtain the high and low temperature performance of the selected asphalt mixture and the dynamic modulus and phase angle under different temperatures and frequencies. The main curve of the dynamic modulus was drawn. Through the analysis of the test results, the following conclusions are obtained: Humidity has a great influence on the high temperature performance of asphalt mixture. With the increase in humidity, the cohesiveness of the asphalt mixture decreases, and its high temperature stability mainly depends on the interlocking action of aggregate. The conversion of gaseous water to a solid state in the asphalt mixture due to the decrease in temperature will destroy the asphalt–aggregate interface characteristics of the asphalt mixture, resulting in a rapid decline in the low temperature performance of the asphalt mixture. Humidity also has a great influence on the viscoelastic properties of asphalt mixture at room temperature. Specifically, with the increase in humidity, the phase angle is more sensitive to temperature change, and the main curve of dynamic modulus of asphalt mixture gradually decreases in the low frequency range, which damages the ability of the asphalt mixture to resist permanent deformation in this region.
Study on dependence of dynamic mechanical properties of asphalt mixture on surrounding compressive
SHI Zhongzhou, LUAN Huafeng, and DONG Hongyun
Date posted: 11-24-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.05.042
In order to study the confining stress dependence of dynamic mechanical properties of asphalt mixtures, triaxial dynamic modulus tests were carried out on AC-20 (AH‑30#) and AC-25 (AH‑30#) asphalt mixtures at different test temperatures, different scanning frequencies, and different confining pressure levels. Firstly, the effects of confining stress on the dynamic mechanical properties of asphalt mixtures at different temperatures and frequencies were analyzed. Secondly, based on the time–temperature equivalent principle, Boltzmann and Gussamp function models were used to draw the principal curves of dynamic modulus and phase angle of asphalt mixtures with a reference frequency of 10 Hz, respectively. The results show that the confining pressure has little effect on the dynamic mechanical properties of the two asphalt mixtures at different scanning frequencies when the test temperature is lower than 20 °C. When the temperature is 55 °C, and the scanning frequency is 0.1 Hz, the maximum dynamic modulus ratio of AC-20 (AH‑30#) and AC-25 (AH‑30#) asphalt mixtures is 3.50 and 2.49, respectively. When the test temperature is 50 °C, and the scanning frequency is 0.1 Hz, the minimum phase angle ratio is 0.59 and 0.65, respectively. At high temperatures, a larger confining pressure level means a larger dynamic modulus ratio and a smaller phase angle ratio. The dynamic mechanical properties of the two asphalt mixtures have a significant confining stress dependence. The dynamic modulus of asphalt mixtures and the principal curve as a whole have the same change trend, but in the high temperature region, the confining pressure level increases; the dynamic modulus increases, and the phase angle decreases. The confining pressure stress plays a hardening effect on the asphalt mixture, and there are significant differences in the principal curve. In this case, the asphalt mixture should be regarded as a nonlinear viscoelastic material. It is suggested to introduce confining pressure into the dynamic modulus test of asphalt mixtures and explore a new triaxial dynamic modulus test method to replace the existing uniaxial compression dynamic modulus test for asphalt mixtures.
Study on rheological properties of asphalt modified by different types of anti‑stripping agents and rubber
HUANG Shihong
Date posted: 11-24-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.05.043
In order to study the effects of different types of anti-stripping agents on asphalt, this paper used two different anti-stripping agents (amines and silanes) to modify rubber powder-modified asphalt (AR). The rheological properties of the rubber powder-modified asphalt by anti-stripping agents of amines and silanes were evaluated by rut factor, recovery rate, non-recovery creep compliance, stiffness modulus, and creep rate. The results show that the fatigue factor of AR can be increased by the two different anti-stripping agents, and the fatigue performance of AR can be reduced. At the same time, the high temperature PG grade of AR is improved by anti-stripping agents of silanes, while the low temperature PG grade of AR is not affected by the two anti-stripping agents. In addition, the recovery rate of AR is improved by anti-stripping agents of silanes, and the non-recoverable creep compliance is decreased, while the addition of anti-stripping agents of amines has the opposite effect. It is also observed that anti-stripping agents of amines and silanes have a slight effect on the low temperature cracking resistance. In summary, the types of anti-stripping agents have a significant impact on the rheological properties of AR and should be fully considered before the use of specific anti-stripping agents.
Traffic Engineering and Management
Research on optimization and utilization of low impact development technology of sponge city in coastal area
JIANG Zaolong, ZHANG Weibo, ZHANG Zhijun, JIN Bo, and FENG Xiaozhe
Date posted: 11-24-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.05.044
In view of the characteristics of large rainfall intensity, short duration, and tidal backwater effect in coastal areas of southern China, this paper studied the combination and layout scale of low impact development (LID) facilities suitable for sponge cities in coastal areas. By establishing the storm water management model (SWMM) of the research area, four LID facility combinations were designed to simulate and analyze the runoff control effect of different LID combinations and the pipe network load under the action of tides, and the LID combination with the best comprehensive effect was determined. A multi-objective optimization model was established with cost and total runoff control rate as optimization objectives, and the NSGA‑Ⅱ algorithm was used to optimize the layout scale of LID facilities. The results show that Combination 1 has the best performance in reducing the total runoff and relieving the pressure of the pipe network under the action of the tide. When the rainfall return period is two and five years, Combination 1 is slightly inferior to other combinations in terms of reducing the peak flow and delaying the peak time, but it is better under the rainfall return period of 10 years. Through the multi-objective optimization method, the LID layout scheme after scale optimization is obtained, which saves 29.06% of the construction cost compared with the original scheme on the premise of meeting the control objectives. Through research and analysis, an LID design scheme suitable for coastal areas with lower costs is obtained.
Crash study of new type of guardrail with wave girders in central median of sam class
WANG Zhiyong, GAN Shubing, and WANG Sheng
Date posted: 11-24-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.05.045
According to the demand of road traffic in China, this paper designed a new type of guardrail in the central median suitable for highways. In order to verify the protective effect of the guardrail, the finite element simulation method was used to verify the collision of the standard section of the guardrail after the three-dimensional model design. Through the collision simulation analysis of the new guardrail, it can be seen that the anti-collision grade of the designed guardrail reaches the SAm level. At the same time, the new guardrail is compared with the traditional guardrail, and it is found that the new guardrail is more applicable for highways.
Research on route scheme of highway in difficult and dangerous mountainous area based on construction and rescue factors
YANG Changfeng and YU Shuyu
Date posted: 11-24-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.05.046
In the high-intensity dangerous mountainous areas of western China, the terrain is complex, and geological disasters are developing. Highway routes need to avoid major geological disasters and choose favorable terrain layout. Meanwhile, highway construction also faces difficulties in the approach of construction and emergency rescue during operation. In the design of the route scheme for Tongtou Gorge section of Leying–Baoxing Expressway in Sichuan Province, two Yonglin combined cableway bridges across the canyon were cleverly set up, making the laying of the route on the opposite bank of the existing road possible. It transformed one ultra-long tunnel into three long tunnels. Meanwhile, problems such as ventilation and emergency rescue during the construction approach and operation period were solved, and comprehensive disaster resistance was improved. It saved project investment and could provide a reference for similar projects in mountainous areas.
