Volume 42, Issue 4 (2022)
Article
Study on Road Performance of High Content Phosphogypsum Cement Stabilized Red Clay
YANG Dezhong, CHEN Kaisheng, and LI Qiang
Date posted: 8-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.04.034
In response to the waste of phosphogypsum resources and engineering characteristics of red clay, by referring to the mix ratio design method of fly ash mixtures, 18 sets of mix ratio samples were set up indoors. By conducting compaction tests, seven-day unconfined compression strength tests, water-stability tests, and CBR tests, exploratory research was conducted on the road performance of high content phosphogypsum stabilized red clay. The results indicate that the optimal water content of high content phosphogypsum stabilized red clay is lower than that of plain red clay. The seven-day unconfined compression strength is 1.8-3.7 times that of plain red clay. After soaking for 24 hours, the strength loss reaches over 50%, with overall poor water stability. Water glass can enhance the water stability of phosphogypsum stabilized soil. As the content of phosphogypsum grows, the water stability coefficient also increases. The CBR value of high content phosphogypsum stabilized red clay is far greater than that of plain red clay, which can meet the requirements of the CBR value of roadbed fillers on expressways and first-class highways. By considering the strength and water stability requirements of the roadbed and starting from the perspective of reducing cement content and increasing phosphogypsum content, it is recommended to adopt 4% cement, 2% sodium silicate, and a phosphogypsum-clay ratio of 1:1.
Subgrade Engineering
Research on Reliability Design Method of Gravity Retaining Wall Based on Moment Method
JIA Liang and LUN Peiyuan
Date posted: 8-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.04.001
To study the application of the moment method in gravity retaining walls, this paper established functional functions for the anti-sliding and anti-overturning limit states of gravity retaining wall structures, and developed a reliability analysis method based on the third-order moment method for a single failure mode. The analysis results show that compared with Monte Carlo simulation method (MCS) and first-order second-order moment method (FOSM), employing the moment method for stability and reliability analysis of retaining walls can both improve calculation efficiency, ensure calculation accuracy, and obtain the first three-order statistical moments of the functional function. Then, based on the moment method, sensitivity analysis was conducted between the reliability index and design parameters of the retaining wall structures. Finally, the sub-coefficients of the anti-sliding and anti-overturning limit state equations were obtained based on the moment method. Compared with the sub-coefficients obtained by the other two methods, the third-order moment method is a fast and efficient reliability calculation method.
Study on Drawing Mechanical Properties of Conduit Soil Interface for Conduit Grouting
XU Yangshaojun, ZHOU Yong, RONG Hongliu, PAN Yanyi, and ZHONG Xianqing
Date posted: 8-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.04.002
This paper introduced the action mechanism of adopting conduit grouting reinforcement technology for slope reinforcement and protection, and analyzed the problems in calculating the anchoring force of grouting conduits by employing the traditional slope stability calculation method under the action of traditional reinforcement force. Meanwhile, the influence of such factors as the buried depth and water ash ratio of the grouting conduit on the conduit-soil bond strength was studied via the drawing test of the grouting conduit. The finite difference software FLAC3D was utilized to model the anchor body and its surrounding soil, simulate the deformation and stress distribution of the soil inside the soil during the drawing process, and derive the mechanical model of the anchor body interface based on theoretical analysis. As a result, the constitutive relation between axial drawing force and interface shear force was obtained. The results indicate that the properties of the slurry have a significant influence on the interface mechanical properties between the conduit and the original soil, as well as the anchoring depth, bearing capacity of external loads, and the stability of conduit anchoring. During the drawing process, the closer distance between soil and the anchor body leads to greater radial deformation increment of the soil, and the maximum stress exists within a certain range at the boundary between the anchor body and the soil. The error between the calculated drawing force based on the constitutive relation derived from theoretical analysis and the measured drawing force is very small, indicating that the calculation accuracy of this constitutive theory is sound.
Research on Dynamic Resilience Modulus of Typical Subgrade Soil in Inner Mongolia
ZHANG Yiluo, LI Ning, DENG Zhanwei, DONG Xuechao, and CHENG Yinglun
Date posted: 8-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.04.003
Inner Mongolia is characterized by a vast area, large east-west span, complex and variable climate environment, numerous types of road engineering landforms, and subgrade soil includes sandy soil and yellow soil, with significant differences in engineering properties. To study the dynamic resilience modulus of typical subgrade soil in Inner Mongolia, this paper selected five soil samples from different regions, and adopted the repeated loading dynamic triaxial test method under the determined stress range of the subgrade. Meanwhile, the GDS dynamic triaxial apparatus was employed to test the dynamic resilience modulus of soil samples from different regions in different stress conditions at their respective optimal water content. The dynamic resilience modulus of soil samples from different regions at different water contents was tested with the same stress conditions maintained. Finally, the dynamic resilience modulus changes of soil samples from various regions after freeze-thaw cycles were tested, and the freeze-thaw cycle reduction factor for selecting soil sample regions was recommended. The results show that the dynamic resilience modulus of subgrade soil in Inner Mongolia increases continuously with the rising confining pressure and decreases continuously with the increasing deviatoric stress at the optimal water content. Additionally, the influence of confining pressure on the dynamic resilience modulus is significantly higher than that of deviatoric stress. In constant stress conditions, the dynamic resilience modulus of subgrade soil decreases with the rising water content. The higher content of fine particles in the soil samples leads to greater influence of water content changes on its resilience modulus. The resilience modulus of subgrade soil decreases continuously with the growing freeze-thaw cycles, and it takes six to nine cycles for the resilience modulus of subgrade soil to stabilize with the rising fine particle content.
Research on Temperature Field and Temperature Stress of CRC+AC Composite Pavement in Winter
DENG Fengxiang, XU Lukai, LI Sheng, and SUN Yu
Date posted: 8-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.04.004
To study the temperature field and temperature stress of CRC+AC composite pavement, this paper adopted Fortran language to develop subprograms and expand the function of the large-scale finite element software Abaqus based on the basic principles of heat transfer. Meanwhile, the external temperature changing with time was defined, and steady-state and transient heat conduction analysis was conducted. The temperature field of the continuous reinforced concrete composite pavement structure in continuous temperature conditions was simulated by utilizing 24-hour measured temperature data on a winter day of a place. The influence of structural layer parameters on the winter temperature field and temperature stress of the continuous reinforced concrete composite pavement structure was analyzed and studied. The results show that the temperature stress difference on the top surface of the continuous reinforced concrete layer during the winter cycle is as high as 2.42 MPa, and the temperature stress difference on the top surface of the asphalt layer is as high as 0.56 MPa. The thicker asphalt layer leads to lower temperature stress of each structural layer, and the thicker continuous reinforced concrete layer brings about lower temperature stress of the continuous reinforced concrete layer. Additionally, the higher modulus of the asphalt layer and continuous reinforced concrete layer means greater temperature stress. As the temperature decreases, the difference between the maximum stress and the minimum stress increases with the temperature, but the increase magnitude decreases. The pavement is prone to temperature fatigue damage, thus causing cracks.
Study on Axle Load Limit of Heavy Cargo Transportation Vehicles on Cement Concrete Pavement
DUAN Tongjun, ZHENG Shuai, PEI Fucai, SHAN Jingsong, and SUN Peili
Date posted: 8-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.04.005
Heavy cargo transportation generally refers to the transportation and distribution of large equipment, which is characterized by large volume and weight, and has strict requirements for the bearing capacity of vehicles and roads for transportation. The current cement concrete pavement design does not fully consider the load characteristics of large transport vehicles with multiple lines and axles. Firstly, this paper adopted the finite element method to build cement pavement models for different levels of highways, with the axle number of vehicles for heavy cargo transportation and load changes of multiple lines and axles considered. Meanwhile, it analyzed the stress characteristics of cement pavement under the action of heavy cargo transportation loads. Then, based on the limit state method of cement pavement design, the inverse calculation was conducted on the limit load stress of highways of different levels and zoning. Furthermore, by comparing the stress response of cement pavement under the action of vehicles for heavy cargo transportation with the ultimate bearing capacity of cement pavement, the axle load limit of vehicles for heavy cargo transportation was determined. This study provides guidance for regulating the axle load of vehicles for heavy cargo transportation from the perspective of the bearing capacity of cement pavement.
Influence of Solar Reflective Coating on Temperature Characteristics of Cement Pavement and Urban Environment
YANG Fei and CHEN Jiahao
Date posted: 8-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.04.006
The too high temperature of cement concrete pavement is both an important cause of pavement diseases and an important factor exacerbating the heat island effect. To reduce the temperature and temperature gradient of high-temperature cement pavement panels in summer and alleviate the urban heat island effect, this paper prepared a reflective coating whose binder is fluorosilicon-modified acrylic acid, conducted experimental research, and measured the pavement temperature and temperature gradient before and after utilizing the coating. Meanwhile, it conducted theoretical analysis, calculated the influence of reflective coatings on the warping deformation of pavement panels, and analyzed the effect of coatings on the heat release of pavement, with the influence of coatings on urban heat island effect explored. The results show that under high-temperature weather in summer, the highest temperature of the pavement is 59℃, and the maximum positive temperature gradient is 96.1℃/m. Additionally, the reflective coating can reduce the temperature of cement concrete pavement by about 9℃, and reduce the maximum positive temperature gradient by 31.7℃/m. Before applying the reflective coating, the maximum warping stress of the pavement reaches 2.16 MPa, and after applying the reflective coating, the maximum warping stress is 1.7 MPa, a decrease of about 30%. The utilization of reflective coatings can effectively reduce the heat emitted by cement pavement to the air by about 15%, thus alleviating the heat island effect in summer to some extent.
Analysis on Design Index Effect of Long-Life Asphalt Pavement Based on Optimal Mixed Design Method
MA Shibin and HE Miao
Date posted: 8-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.04.007
This paper adopted the 311-A optimal mixed design method and employed Kenpave software to calculate the values of various design indexes under different material design parameter combinations. Meanwhile, it studied the influence of design parameters on various design indexes, and utilized statistical analysis software for regression analysis to build a polynomial regression model. Finally, by carrying out computer simulation, a comprehensive analysis shows that the combination scheme when the asphalt pavement life reaches the optimum is 4 cm (9750 MPa) wearing course SMA-13+8 cm (13000 MPa) connecting course AC-20+18 cm (7000 MPa) upper course ATB-25+17 cm (190 MPa) graded macadam course+20 cm (11500 MPa) mud-stabilized macadam subbase+(55MPa) soil foundation.
Pavement Engineering
Study on Key Design Parameters of the Constructional Safety of the Leaning Single-Tower Cable-Stayed Bridges
TONG Zhifeng, XIONG Lei, LIU Xiaoqi, and CAO Hongyou
Date posted: 8-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.04.008
Based on the Xiangxi River Bridge project in Xiakou, Xingshan County, Yichang, Hubei Province, this paper adopted Midas/Civil to build a finite element model of the entire bridge space. Meanwhile, it selected the size and angle of the supporting active jacking force during the bridge tower construction of leaning single-tower cable-stayed bridges, counterweight of the main beams, and tensile force of the cables as the structural parameters to study the bridge towers and support stress performance. The results show that as the jacking force increases, the maximum stress during the construction phase of the bridge tower and support gradually increases. As the jacking force angle increases, the maximum stress during the construction stage of bridge towers and support gradually decreases, especially when the jacking force angle is between 40° and 60°. Additionally, the support stress changes more significantly with the angle. The counterweight of the main beams has a significant influence on the supporting axial force. As the counterweight position of the main beam on the main span side gradually moves away from the bridge tower, the maximum axial force during the supporting construction stage shows a trend of first increasing and then decreasing. The tensile force of the cables has the most significant effect on the supporting axial force and the highest sensitivity. Reducing the tensile force of the cables on the side span can significantly decrease the supporting axial force.
Experimental Analysis of Dynamic Characteristics of Pile-Cap Interaction under Vertical Excitation Load
FAN Hong, CHEN Hede, GONG Weiming, DAI Guoliang, and CAO Xiaolin
Date posted: 8-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.04.009
To study the overall bearing performance of piles and caps, this paper conducted on-site vertical excitation tests on the free field, single pile, and two pile caps. By analyzing the variation laws of pile head acceleration, pile head displacement amplitude, and vertical stiffness with the frequency, the joint bearing performance of piles and caps was studied. The experimental results show that the acceleration of the free field is much greater than the acceleration amplitude of a single pile and two piles, and the acceleration amplitude of a single pile head is about twice that of two piles. Meanwhile, the displacement amplitude of the free field and single pile shows a trend of first increasing and then decreasing with the increasing frequency, and a resonance region appears, with the resonance frequency of a single pile greater than the vibration frequency of the free field. The displacement amplitude of two piles increases first and then stabilizes with the rising frequency, with no resonance zone appearing. Comparing the variation curves of displacement amplitude of the free field, a single pile, and two piles with the frequency, it can be seen that the displacement amplitude of the free field is much larger than that of a single pile and two piles, and the displacement amplitude of the two-pile cap pile foundation is the smallest.
Analysis on Influence of Longitudinal Drift for Long-Span Cable-Stayed Bridge with Single-Tower Hybrid Main Girder
TU Guangya and OUYANG Xing
Date posted: 8-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.04.010
For large-span semi-floating system single-tower hybrid girder cable-stayed bridges, the cable force of the side span is generally greater than that of the main span during construction to prevent the main tower from pre-deviating toward the side span to resist the adverse effects of vehicle loads and other variable effects after the bridge is completed. Meanwhile, after the temporary consolidation is released, the unbalanced cable force will cause longitudinal drift of the main girders. After the bridge closure, the paving of the bridge deck system and vehicle load action will also generate new unbalanced horizontal force on the main girder, causing longitudinal drift of the main girders. To study the influence of longitudinal drift on tower deviation, elevation, cable force, and stress of a single-tower hybrid girder cable-stayed bridge, this paper adopted the finite element method and BDCMS software to calculate and analyze the Jiangwan Bridge in Shaoguan, Guangdong. The calculation results show that for a semi-floating system single-tower hybrid girder cable-stayed bridge, the main girder has a certain degree of longitudinal drift in the conditions of the system conversion, paving bridge deck system, and main span arrangement of vehicle loads. Longitudinal drift has a significant influence on the tower top deviation, but a certain influence on the elevation of the main girder and cable-stayed cable force, with a relatively small effect exerted on the stress of the main girder. In longitudinal drift calculation of the main girders, the friction of bearing should be considered, otherwise it may cause distortion or excessive error in the calculation results.
Anti-Cracking Treatment Technology for the Combination Section Near the Newand Old Concrete Interface of a Bridge Cable Tower
YANG Xiangyang, HUANG Tao, LI Xiong, WANG Gongxun, and SUN Hongxin
Date posted: 8-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.04.011
In response to the possible cracking of concrete caused by the pouring age difference between new and old concrete in the main tower of Yangmeizhou Bridge, this paper optimized the concrete mixing ratio by indoor experiments, and studied the effects of different fiber lengths and mixing contents on the dry shrinkage and anti-cracking performance of concrete. Meanwhile, the bonding performance of the new and old concrete interface was tested under different interface treatment methods, with the shrinkage stress of the new and old concrete interface analyzed by employing Midas Civil software. The results show that under the same mixing content of polypropylene fiber, the anti-shrinkage effect of long fiber concrete is better than that of short fiber concrete. Compared with benchmark concrete, the shrinkage rate of concrete with 0.92 kg/m3 polypropylene long fiber added is the smallest, with a reduction of 269 × 10-6 in the shrinkage rate. Adding long fibers can significantly reduce crack width, with the number of fine cracks increasing. The optimal way to treat the combination surface is to chisel the surface of the old concrete and apply an interface agent, and then pour fiber-reinforced concrete, which features higher bonding performance than other treatment methods. The numerical analysis results show that under the optimal treatment scheme, the maximum bonding tensile stress at the interface between new and old concrete decreases from 3.10 MPa to 2.45 MPa, effectively reducing the shrinkage stress at the interface between new and old concrete.
Study on Damage Prediction of Concrete Bridges Based on Acoustic Emission and Convolutional Neural Network
YUAN Ming, WANG Shuo, YAN Donghuang, LIU Yun, and HUANG Lian
Date posted: 8-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.04.012
To effectively identify the damage degree of concrete bridge structures and timely evaluate the structural state, this paper conducted damage model experiments on partially prestressed concrete cable-stayed bridges based on convolutional neural networks (CNNs). By analyzing the acoustic emission waveform signals of the test beams under different damage states, CNN was adopted to identify and predict the degree of damage to the test beams. Firstly, a CNN architecture consisting of convolutional layers, pooling layers, fully connected layers, and a SoftMax layer was constructed. Then, the test beam was loaded to the limit state for three times in stages to obtain three sets of acoustic emission waveform signals in the same loading conditions. Meanwhile, the first two sets of acoustic emission signals were input into the previously built CNN model and trained to obtain a CNN identification system. The third set of acoustic emission signals was employed by the identification system to predict the damage state of the test beam, thus verifying the effectiveness of the identification method. The results show that the damage degree of the test beam is successfully predicted based on CNN and acoustic emission technology, with the comprehensive accuracy of 96.71% for 3104 acoustic emission signals. The network architecture with two convolutional layers and two fully connected layers has the optimal prediction performance. Additionally, compared to traditional BP neural networks, the accuracy of CNN is 5%-10% higher.
Bridge Engineering & Tunnel Engineering
Research on Damage Identification Based on Single-Node Mode Shape Parameter with Additional Mass
SUN Hu, DI Shengkui, DU Zhuyao, WANG Lixian, and XIANG Changsheng
Date posted: 8-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.04.013
To solve the structural damage identification problem, this paper proposed a damage identification method with a single-node mode shape parameter βASS by adopting the additional mass method and mode shape parameters. This index method moves the additional mass as a constant force on the same cross-section beam structure, and extracts the mode shape parameters of the structure at a fixed point, with operation simplification conducted to accurately identify the damage location and different damage parameters of the same section beam structure by utilizing only the single-node mode shape parameters. The identification accuracy is high when the additional mass accounts for about 5% of the total beam mass and is close to one end of the fixed hinge support. In the proposed identification method, only single-node mode shape parameters on the beam structure are needed to determine the damage location, which has certain engineering application significance for damage detection of beam structures with the same cross-section.
Experimental Study on Aerodynamic Optimization of Flutter Performance of Super-Span Truss Girder Suspension Bridges
WANG Weiming, LIANG Aihong, LIU Xinhua, LI Chunguang, PENG Yuancheng, and HAN Yan
Date posted: 8-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.04.014
The steel truss girder suspension bridge has great advantages in mountainous canyon bridge sites due to its characteristic construction method. However, the wind field environment at the canyon bridge is complex, and the aerodynamic stability of the girder is often difficult to meet the requirements. By taking a large-span truss girder suspension bridge as the engineering project, this paper studied the flutter performance of the truss girder section by conducting wind tunnel tests, and proposed reasonable aerodynamic optimization measures. Firstly, a 1:50 segmental model wind tunnel test was carried out to test the critical flutter wind speed of the girder at various angles of attack. Under the most unfavorable angle of attack, the effects of the upper central stabilizer plate, lower central stabilizer plate, horizontal splitter plate, and railing wind penetration rate on the flutter performance of the girder were explored, with the influence of the girder section form on flutter performance investigated. Finally, based on the experimental results, the optimal aerodynamic scheme was selected to meet the requirements of wind-resistance design for the bridge when factors such as safety, economy, and aesthetics were considered.
Stability Analysis of Nonlinear Static Wind on Multi-Span Stiffened Girder Suspension Bridge
CAO Feng, ZHENG Mingjie, MA Peng, WANG Baoxi, and LI Maojun
Date posted: 8-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.04.015
By taking a four-tower three main-span (145+160+145) m stiffened girder suspension bridge as the research object, this paper analyzed its wind-resistance stability performance and instability mechanism. Firstly, FLUENT fluid calculation software was adopted to calculate the three-component coefficients of the static wind load on the cross-section of the stiffened girder. Then, finite element software was utilized to analyze the nonlinear static wind stability of the entire bridge. The results indicate that the multi-span effect of a four-tower three-span suspension bridge is significant, and this bridge has different instability characteristics from typical double-tower single-span suspension bridges. The lateral bending and torsional constraint effects of a four-tower three-span suspension bridge are significant, and the nonlinear static wind instability is mainly manifested as vertical torsional-flexural instability, which is different from the lateral flexural-torsional buckling and torsional instability of ordinary double-tower single-span suspension bridges.
Influence Analysis of Section Design Parameters of Hollow Concrete-Filled Steel Tube Arch Bridge
LIAO Wanhui, YUE Yachao, YAN Donghuang, and XU Hongsheng
Date posted: 8-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.04.016
Based on the design optimization scheme of a super-large steel tube arch bridge and the integrated joint analysis method of modeling-trial design, this paper adopted the specification CECS254-2009 "Technical Specification of Hollow Concrete-Filled Steel Tubular Structures", and carried out a systematic influence analysis by calculating the verification coefficient of stable bearing capacity for the design parameters of the hollow ratio of hollow concrete-filled steel tubes and wall thickness of steel tube sections. The results show that when the outer diameter of the steel tube is 1360 mm, the slope of the curve of the influence of the hollow ratio on the verification coefficient of stable bearing capacity increases with the rising hollow ratio, which has a significant effect on the bearing capacity of the component. The verification coefficient of stable bearing capacity decreases linearly with the increasing wall thickness of steel tubes. Additionally, the slope does not change significantly with the rising wall thickness of steel tubes, and its influence on the bearing capacity of the component is relatively small.
Study on Effect of FBG Sensor Packaging Process on Stress Relaxation Performance of Self-Sensing Prestressed Reinforcement
QIN Heying and NING Jian
Date posted: 8-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.04.017
It is especially important to monitor the health of steel strand wires, which are the main load-bearing component of engineering structures. The emergence of groove embedding packaging technique for fiber grating sensors (FBGs) has achieved the integration of stress and monitoring of steel strands. To investigate the effect of groove embedding packaging technique on the relaxation performance of steel strands and steel wires, this paper conducted isothermal relaxation tests on round steel strands, epoxy steel strands, and galvanized steel wires. The results indicate that engraving grooves cannot significantly improve the relaxation rate of steel strands, while the process of untwisting, heavy twisting, and repeated tensioning has a significant influence on the relaxation rate of steel strands.
Research on Simulation of the Prestressed Reinforcement in Segment Model Analysis in Anchorage Zone of Cable-Stayed Bridge Tower
SUN Songsong and CHEN Ziyun
Date posted: 8-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.04.018
To obtain a better method for simulating prestressed reinforcement in the segment model analysis of the anchorage zone of towers on a cable-stayed bridge, this paper adopted Ansys to conduct segment model analysis on the anchorage zone of towers on a highway-railway cable-stayed bridge. In the model building, the entity segmentation method and constraint equation method were employed to simulate prestressed reinforcement. By comparing the stress differences in key parts of the tower body using two different methods, the reasons and patterns behind the differences were analyzed.
Analysis of Mechanical Response Pattern of Main Girder of Long-Span Cable-Stayed Bridge under Random Seismic Load Considering Spatial Effect
LEI Shuncheng, LIU Guokun, DENG Jichao, and WANG Qishun
Date posted: 8-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.04.019
To investigate the influence of spatial effect on the main girder of a large-span cable-stayed bridge under random earthquakes, this paper took a 450 m steel box girder cable-stayed bridge as the research object. Based on the virtual excitation method, an Ansys finite element model was built to study the influence of traveling wave effect, coherence effect, and local site effect on the internal force and displacement of the main girder of the cable-stayed bridge. The calculation results show that the traveling wave effect has a complex influence on the internal force and displacement of the main girder of the cable-stayed bridge, which is not only a simple linear relationship, but also significantly affected by the apparent wave velocity. In the QWW coherent model, the internal force response of the main girder is mainly related to the irrelevance degree. The greater irrelevance degree leads to relatively smaller internal force and displacement response values of the main girder. Additionally, the local site effect has a significant amplification effect on the dynamic response of the main girder. According to Qu Tiejun's semi-empirical formula, when the difference in soil layer thickness reaches 5 m, the bending moment response increases by 24%.
Application and Research of External Prestress in Strengthening of a Fish-Belly Box Girder Bridge
HU Chengze and SONG Chongyang
Date posted: 8-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.04.020
In response to the crack disease of the web plate and bottom plate of a fish-belly box girder bridge, numerical analysis and on-site investigation were adopted to study the crack shape, distribution law, and generation mechanism of the box girder, with a scheme for external prestress reinforcement proposed. Meanwhile, this paper introduced the overall layout of external prestress in the reinforcement design of the bridge, as well as the methods for setting anchoring blocks, turning blocks, and shock-reducing devices. The finite element calculation results and static load test results before and after reinforcement show that after the reinforcement, the structural strength, stiffness, and crack-resistance performance are all improved, confirming that the expected effect can be achieved by adopting external prestress active reinforcement. Relevant theoretical and experimental research can provide references for similar bridge reinforcement projects.
Experimental Study on Piezoelectric Monitoring of Grouting Density of Prestressed Pipe Bellows
YAO Mingxing, LI Cong, YAN Zhonghua, HE Yuan, CHEN Guan, and ZHAO Jie
Date posted: 8-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.04.021
To solve the problem of grouting quality detection of prestressed pipe bellows, this paper proposed a method for detecting the density of bellows based on the piezoelectric ceramic fluctuation method. Meanwhile, it experimentally designed a concrete specimen with bellows and prestressed reinforcement, and monitored and studied the grouting density by adopting the piezoelectric fluctuation method. An embedded piezoelectric driver was fixed on the prestressed reinforcement to emit signals, and three piezoelectric ceramic PZT pieces were arranged on the upper and lower surfaces of the bellows to receive signals. Four working conditions were designed for the experiment, including 0%, 50%, 90% grouting, and full grouting. Additionally, time-domain analysis and wavelet packet energy analysis methods were utilized to determine the grouting density of bellows. Based on the experiment in this paper, it can be concluded that as the experiment progresses, the grouting degree of the bellows increases, with the continuously increasing signal amplitude. This means the smaller grouting density of the bellows leads to the smaller time-domain signal amplitude and wavelet packet energy value.
Research on Block Hoisting Technology of Reinforcement Cage of Large Section Pier and Tower Segments
LONG Lidun, WANG Chaoguo, JI Zhongyan, and WANG Zhiwei
Date posted: 8-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.04.022
The construction of large section piers and towers such as cable towers and hollow thin-walled piers serves as the controlling project on highways, restricting the total project duration and affecting the total construction cost. The reinforcement installation efficiency is a key factor affecting the construction speed of large section piers and towers. This paper analyzed the problems in cost, safety, efficiency, and quality of reinforcement construction processes in several existing large section pier and tower segments, and proposed a block hoisting technology of segmented steel cages. Finally, a successful practice was carried out on the construction of the 4# main tower of Kaizhou Lake Bridge, which has achieved a balance between construction cost and efficiency, safety and quality, and holds sound economic benefits and reference significance.
Influence Analysis of Wheel Load Model on Fatigue Damage Assessment of Steel Bridges
MA Shuai and YANG Li
Date posted: 8-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.04.023
To investigate the influence of wheel load models on fatigue damage assessment of steel bridges, this paper adopted wheel load surface testing and finite element analysis to obtain the fatigue stress spectrum of typical fatigue details under traffic loads. Based on the cumulative fatigue damage theory, the differences in fatigue damage assessment caused by wheel load models were analyzed. The results show that the wheel load surface has an irregular shape, with the lateral contact size remaining constant and longitudinal contact size approximately linearly changing from zeroload to full load. The contact size under different loads can be determined by utilizing the linear interpolation method. Meanwhile, the evaluation results of the wheel load model in BS5400 and Japanese steel bridge specifications are higher than those of actual fatigue damage, while the evaluation results of the wheel load model in EURO-CODE and Chinese steel bridge specifications are lower than those of actual fatigue damage. The evaluation results of AASHTO specifications are closer to the actual fatigue damage, with the wheel load model exerting a significant influence on the fatigue damage assessment of steel bridges. In assessing the anti-fatigue design or fatigue damage of steel bridges, the influence of the actual wheel load model should be fully considered, and the actual wheel load model should be employed or the evaluation results based on the standard wheel load model should be corrected.
Comparative Analysis of Two Axle Load Identification Algorithms Apply on OSD
AN Jiahe, ZHAO Hua, MA Pengfei, and ZHANG Bin
Date posted: 8-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.04.024
To improve the identification accuracy of the BWIM system on the orthotropic steel deck (OSD) and enhance its algorithm stability, this paper compared two different axle load calculation methods, including the parameter C algorithm and Moses algorithm. By conducting calibration tests on the actual bridge, two algorithms were adopted to identify the axle load of its vehicles. The identification results show that when the BWIM system is applied to OSD, the mean error value and standard deviation of the axle load identified by the parameter C algorithm are better than those of the traditional Moses algorithm. By utilizing the European standard COST 323 to evaluate the calibration results of the two algorithms, it is found that the accuracy level of the final evaluation results of the parameter C algorithm is relatively high, reaching C(15). Further analysis of the evaluation results reveals that the identification of the axle load of a single axle directly affects the accuracy evaluation of the BWIM system when the system is applied to OSD. Therefore, the key to improving the accuracy evaluation of the algorithm lies in enhancing the single axle identification accuracy.
Discussion on Calculation of Internal Force of Static Load Test for Bridge Precast Beam Based on Stress Equivalence
HE Zhi and LI Juanjuan
Date posted: 8-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.04.025
To calculate the target internal force of the static load test for precast beams, this paper discussed the problems such as the efficiency of static load tests, illustrated the basic principle of stress equivalence, and proposed a calculation method for determining the target internal force in the tests, with the method applied to the static load test of a precast box girder. The results show that the current regulations for load testing of highway bridges need further improvement in terms of the efficiency calculation of static load tests. Additionally, stress equivalence refers to the fact that the stress under the test load is the same as the stress under the most unfavorable stress state under a certain design load. The stress equivalence principle can be applied to the calculation of static load tests on precast beams. If there is a system transition during the subsequent construction of precast beams, the effect of the construction process on the stress of the precast beams should be considered.
Application of Corrugated Box Steel Plate Structure in Strengthening and Widening of Beam Bridge
PENG Haitao, ZOU Deqiang, TAN Hongping, and JIANG Xiaoli
Date posted: 8-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.04.026
To promote the application of new technologies and processes for corrugated box steel plate structures, this paper summarized the research results in scheme selection, engineering design, theoretical calculation, and construction technology by a successful case of reinforcement and widening of a typical highway small-span simple-supported beam bridge. Meanwhile, it proposed an integrated structure for old bridge reinforcement and widening, and adopted CBS-reinforced corrugated steel plate structures in the widening section, holding certain innovation and promotion significance. Engineering practice shows that corrugated steel plate structures have sound stress performance, low engineering cost, fast construction speed, strong adaptability, and have achieved producibility and industrialization of buildings, with broad engineering application prospects.
Problems and Counter measures of Chinese Enterprises in Tunnel Construction of Expressway in the Republic of Montenegro
LUO Liangqian
Date posted: 8-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.04.027
In the early stages of Chinese contractors entering the European construction market, differences in the construction standards, concepts, environment, and other aspects have caused many problems to contractors. This paper summarized the highway tunnel construction in the Republic of Montenegro and analyzed the problems and countermeasures encountered from three aspects of construction plans and procedures, construction technology, construction organization and management. Additionally, the problems were divided into several perspectives, including differences in standards, lack of familiarity and mastery of the construction environment, and local distrust of contractors, with targeted response suggestions proposed.
Study on Mechanical Properties of Cement Mortar with HME-V Anti-Cracking Agent
CEHN Yanhong, CHEN Ji, YANG Jianxin, DOU Jianyu, HUANG Yucheng, SHI Peixin, and TANG Qiang
Date posted: 8-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.04.028
After putting the urban underground tunnels into use, common tunnel diseases such as cracking, leakage, and even collapse caused by concrete cracks occur in the tunnels, making in-depth research on shrinkage-compensating concrete technology an important measure to solve the problem of concrete cracks in underground engineering. This paper studied the feasibility of applying the HME-V expanding admixture to shrinkage-compensating mortar technology from the perspective of mortar, and discussed the basic properties of cement mortar. Meanwhile, compressive, flexural, and consistency tests were conducted on the cement mortar specimens with different HME-V expanding admixture contents (0%, 4%, 8%, 12%, and 16%) and fly ash contents (15%, 20%, 25%) under the water ash ratio of 0.45. The experimental results show that the increasing content of a small amount of the expanding admixture and fly ash can achieve an early strength increase of up to 40%, while excessive content results in the development of small cracks caused by the decrease in cement bonding effect. When the content of the expanding admixture is 8% and the content of fly ash is 20%, the strength reaches its peak. The mortar with this content has sound workability, and the compressive strength at 28 days can exceed 55 MPa. Finally, Real Failure Process Analysis (RFPA) numerical simulation was conducted on the cement mortar specimens, and the simulation results were different from the actual experimental failure process, revealing the entire process from crack development to specimen failure.
Correlation Analysis between Surface Energy of Aged Asphalt Binder with Water Sensitivity of Mixture
LI Qidong, LI Bo, LI Ning, WEI Dingbang, and ZHOU Jianing
Date posted: 8-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.04.029
To better guide engineering practice, based on the surface energy theory and cohesion stripping model, this paper tested the surface energy parameters of asphalt and the aggregate. Meanwhile, combined with the water sensitivity evaluation index TSR of the asphalt binder, the correlation between the stripping work of the asphalt binder before and after aging and TSR was further analyzed. The results show that there is a sound correlation between the stripping work of the aged asphalt binder and the indicators reflecting the water stability of the asphalt binder. The smaller stripping work leads to better water damage resistance of the asphalt binder. The addition of anti-stripping agent TiKi can enhance the cohesion of asphalt itself and the cohesion of the asphalt aggregate system, and reduce the stripping work of the asphalt aggregate system, thus improving the water stability of the asphalt binder. The experiment also finds that surface energy parameters can be employed to optimize the aggregate in the design of the binder.
Effect of Different Storage Conditions on Rheological Properties of SBS Modified Asphalt
SONG Jiangchun, FU Shi, YU Hao, and ZHAN He
Date posted: 8-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.04.030
The effect of different storage conditions on the high and low-temperature rheological and fatigue properties of SBS modified asphalt was analyzed by conducting conventional asphalt performance tests, Brookfield rotational viscosity tests, and DSR tests. Meanwhile, the allowable storage times in different storage conditions were obtained by the attenuation law of asphalt rheological properties, and the key indicators that can reflect the performance attenuation of SBS modified asphalt were selected based on the sensitivity changes of various indicators with storage time. The results show that the high and low-temperature performance and fatigue performance of SBS modified asphalt have undergone varying degrees of attenuation after multiple times of storage. The degree of attenuation of asphalt stored at "170℃-room temperature" is greater than that stored at "150-130℃". It is recommended to adopt the storage condition of "150~130℃" for SBS modified asphalt, which allows for three storage times and only one storage time for "170 ℃-room temperature". By comparing the sensitivity changes of various performance indicators, it is recommended that the 60℃ zero shear viscosity should be the main evaluation index for the high-temperature performance of SBS modified asphalt.
Study on Mechanical Properties of Interfacial Interaction between Brick Slag Soil and Geogrid
YUAN Xikui, YANG Haotian, and LI Yurun
Date posted: 8-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.04.031
This paper analyzed the mechanical properties of the interfacial interaction between the brick slag soil and geogrid in the natural state and in the state of considering the infiltration of rainwater or groundwater via the direct shear test and drawing test methods, and compared them with the mechanical properties of unreinforced brick slag soil. The results show that adding geogrids to brick slag soil can improve the strength indicators of brick slag soil (internal friction angle and cohesion), with an increase in the internal friction angle of 2°-3°. Additionally, the effect of reinforcement on the cohesion of brick slag soil is greater than that on the internal friction angle. The cohesion of natural brick slag soil increases by 1.35 times in direct shear tests and 1.32 times in drawing tests compared to unreinforced soil. When the infiltration effect is being considered, the cohesion of reinforced brick slag soil increases by 1.65 times in direct shear tests compared to unreinforced soil, and increases by 1.54 times in drawing tests compared to unreinforced soil. For brick slag soil in the same conditions, the strength indicators of drawing tests should be greater than those of the direct shear tests, with the strength indicators of infiltrated brick slag soil lower than those of natural brick slag soil. By comparing and analyzing the shear stress and deformation relationship curves, it can be concluded that the direct shear test is suitable for situations where the relative displacement between the brick slag soil and the geogrid is small, while the drawing test is suitable for situations where the relative displacement between the brick slag soil and the geogrid is large.
Analysis on Fatigue Performance of Asphalt Mixture Based on Weibull Distribution
JIANG Zhaowei and LIANG Naixing
Date posted: 8-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.04.032
In response to the randomness and discreteness of small-sample fatigue test results, a three-parameter Weibull distribution was introduced to analyze the indirect tensile fatigue test data of AC-20 asphalt mixture. The results show that under small sample tests, the three-parameter Weibull distribution function can clearly reflect the life probability distribution of asphalt concrete materials, and the introduction of the minimum fatigue life parameter N0 can effectively avoid unreasonable estimation of the early fatigue failure probability of the test. The stress fatigue equation in different working conditions shows that as the temperature increases, the fatigue resistance of the asphalt mixture decreases exponentially, with the decreasing sensitivity of fatigue performance to stress. Excessive alternating stress on asphalt pavement at low temperatures will accelerate fatigue failure. Additionally, as the temperature increases, the k value that characterizes the fatigue resistance of the mixture will not be controlled by the assurance rate. The k value can effectively describe and distinguish the fatigue performance of asphalt mixtures at low temperatures. During estimating the fatigue life of asphalt mixtures, it is advisable to select an assurance rate based on design requirements to ensure safe conclusions and improve material performance utilization.
Experimental Study on Shear Strength of Silty Clayunder Dry-Wet Cycles
LV Guangdong
Date posted: 8-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.04.033
To investigate the effects of the dry-wet cycles, degree of compaction, saturation, and confining pressure on the strength of silty clay, this paper conducted UU tests to determine the stress-strain curves of prepared samples under the influence of several factors. The cohesion c and internal friction angle φ of the prepared samples were measured, with the deterioration rules explored. The experimental results show that with the increasing times of dry-wet cycles, the stress-strain curve of the soil changes from the strain hardening mode to the strain softening mode, and the softening rate increases after two dry-wet cycles. Meanwhile, the cohesion and internal friction angle of soil increase with the rising degree of compaction, with the former showing a greater improvement and the latter showing a limited increase. The cohesion of soil decreases with the increasing saturation, and the internal friction angle of soil presents a trend of first increasing and then decreasing with the rising saturation. Additionally, the cohesion and internal friction angle of soil deteriorate to varying degrees with the increasing dry-wet cycles, with more deterioration of the former than that of the latter. The factors that have a strong influence on cohesion are in the order of times of dry-wet cycles>saturation>degree of compaction. The only factor that has a strong effect on the internal friction angle is the times of dry-wet cycles, while the influence of other factors is not huge.
Correlation Study between Pore Structure and Frost Resistance of Basalt Fiber Reinforced Concrete Based on Grey Correlation Theory
BIAN Xuhui, SHEN Aiqin, LIAN Cheng, WU Hua, and LI Yue
Date posted: 8-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.04.035
To investigate the microscopic pore structure improvement mechanism of the addition of basalt fiber on the frost resistance of concrete, this paper prepared six kinds of basalt fiber reinforced concrete with different fiber lengths and contents, and conducted frost resistance and mercury intrusion tests on them. The results show that basalt fiber can improve the surface and internal damage of concrete caused by the freeze-thaw cycles. The quality loss rate and flexural tensile strength loss rate of concrete with 12 mm and 0.06% basalt fiber added are reduced by 73.9% and 26.4% respectively compared to the benchmark concrete. Basalt can significantly optimize the internal pore structure of concrete, reducing its average pore size and harmful pore ratio. Meanwhile, based on the grey correlation theory, this paper determined the pore structure parameter with the highest grey correlation degree with flexural tensile strength and relative elastic modulus, namely the ratio of multiple harmful pores. Finally, multivariate nonlinear regression analysis was adopted to build mathematical models for the flexural tensile strength-pore parameters and relative elastic modulus-pore parameters of basalt fiber reinforced concrete.
Experimental Study on Mechanical Properties of Cotton Fiber Asphalt Concrete
WANG Hongmei, GAO Taotao, and WANG Liying
Date posted: 8-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.04.036
To improve the mechanical properties of asphalt concrete, this paper studied the influence of cotton fiber on the mechanical properties of asphalt concrete. By taking 140# soft asphalt as an example, it respectively prepared cotton fiber asphalt concrete and plain asphalt concrete with the content of 1%, 4%, and 7%. Based on this, rutting tests, compression tests, flexural tests, and freeze-thaw tests were conducted to analyze the changes in stability, compressional strength, flexural-tensile strength, and tensile strength of cotton fiber asphalt concrete. The results show that adding a certain amount of cotton fiber (0%-4%) can significantly improve the mechanical properties of asphalt concrete. When the cotton fiber content exceeds 4%, the mechanical properties of asphalt concrete will decrease. Therefore, the optimal content of cotton fiber in asphalt concrete is 4%.
Experimental Study on Durability of Polypropylene Fiber to Sea Sand Concrete
CUI Haijun
Date posted: 8-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.04.037
To achieve the green and energy-saving goals of concrete, by taking the sea sand content and polypropylene fiber content as two variables, this paper analyzed the effects of the two variables on the durability properties of concrete, such as chloride penetration resistance, permeation resistance, and carbonation resistance. The results show that under a constant fiber content, as the sea sand content increases, the electric flux, water seepage height, and carbonation depth of concrete gradually rise, and the increase rate gradually grows with the rising sea sand content. Meanwhile, when the sea sand content is constant, with the increasing fiber content, the electric flux, water seepage height, and carbonation depth of concrete gradually decrease, and the reduction rate gradually decreases with the growing fiber content. Under the sea sand content of 50%, 1% polypropylene fiber should be added to the concrete to compensate for the adverse effects of sea sand on the concrete. However, when the sea sand content is 100%, more polypropylene fiber is needed to compensate for the adverse effects of sea sand on the concrete. Therefore, given both the economic and environmental aspects, it is recommended to select a material with sea sand content of 50% and fiber content of 1% to prepare environmentally friendly concrete.
Study on Road Performance of Fiber Cement Stabilized Construction Waste
QI Shanzhong and FU Chunmei
Date posted: 8-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.04.038
To study the application of construction waste in road subgrade, this paper conducted a large number of indoor tests to investigate the mechanical properties of cement-modified construction waste, and analyze the changes in mechanical and shrinkage properties of cement-stabilized construction waste after adding polypropylene fibers. The results show that adding a certain amount of polypropylene fiber to cement-stabilized construction waste significantly improves the unconfined compression strength and splitting strength, and notably enhances the anti-shrinkage ability, meeting the road performance requirements. Additionally, there is an optimal value for the added content of polypropylene fiber.
Study on Effect of Gradation on Performance of MS3 Micro-Surfacing
HUANG Weirong, LI Huailong, WANG Cheng, and HUANG Feng
Date posted: 8-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.04.039
To study the median gradation performance of MS3 micro-surfacing, this paper designed four different gradations with 7 mm screen opening pass rates. By conducting the study on the working performance, road performance, and long-term performance of MS3 micro-surfacing, the influence of 7 mm screen opening pass rates on the long-term performance of micro-surfacing was analyzed. The results show that increasing the pass rate of the 7 mm screen opening can improve the mixing time of the micro-surfacing mixture, but will slow down its formation rate. While improving its wear resistance and skid resistance, this will reduce its rutting resistance.
Measuring Method for Binder Film Residues on Black Rock in Mixtures with High Amounts of Reclaimed Asphalt
LIU Jiayao, HAO Peiwen, ZHOU Xinyi, and JIANG Wentao
Date posted: 8-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.04.040
To determine the binder film thickness on the aggregate surface in high amounts of reclaimed asphalt mixture (RAP), this paper mixed RAP aggregate, new aggregate, and new binders, and conducted analysis by adopting electron microscope and photograph analysis techniques. Environmental scanning electron microscope (ESEM) and X-ray spectrometer analyses show that the RAP binder is not completely mixed with the new binder, but wrapped around the RAP aggregate, forming a layered structure. This structure consists of an inner layer of the RAP binder that is not mixed with new asphalt, called "black rock". The RAP binder film thickness is a function of mixing temperature, local aggregate curvature, and aggregate size. The higher mixing temperature leads to the thinner RAP binder layer. Statistical analysis of RAP binder film thickness at the microscale reveals that the binder film thickness depends on the local curvature of the aggregate, with thinner films at positive curvatures and thicker films at negative curvatures.
Study on Performances of Foamed Lightweight Dirt Road Materials in Coal-Burning Slag
JIANG Shanguo, HAN Jiaqi, CEHN Zhongping, and YU Kuangdi
Date posted: 8-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.04.041
The furnace bottom slag of a coal-fired power plant in Zaozhuang, Shandong was grinded and mixed with Portland cement and limestone powder to prepare composite powder. Meanwhile, carbonate was adopted as the excitation agent, and the slag-based foamed lightweight dirt road material was prepared by the physical foaming method. This paper mainly focused on studying the influence of wet density of slag lightweight dirt on the mechanical properties, working performance, defoaming rate, and porosity. The test results show that the unconfined compression strength of coal-fired slag-based lightweight dirt decreases significantly with the reducing wet density, the flow expansion decreases linearly with the increasing foam rate, and the defoaming rate of lightweight dirt changes little in the density range of 650-750 kg/m3. Given various performance indicators, when lightweight dirt with wet density of 650 kg/m3 was prepared by employing the slag ratio of 50%, cement content of 40%, limestone powder of 10%, and 4% excitation agent, it can better meet the working performance of cast-in-place lightweight dirt, with the relatively low defoaming rate. The 3-day strength of the sample can reach 0.79 MPa, and the 28-day strength can reach 1.63 MPa.
Sensitive Factors of Emulsified Asphalt Performance Based on Orthogonal Test
XU Yongli, SUN Sida, and ZHAO Qirui
Date posted: 8-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.04.042
This paper determined the optimal parameters of the shear emulsion mixer by conducting indoor pretests. The orthogonal experimental method was adopted to analyze the effects of asphalt heating temperature, emulsifier content, and soap pH value on the emulsification effect, with multiple statistical analysis conducted. By employing the range and standardization coefficient as evaluation indicators for the influencing factors, multivariate linear regression was utilized to analyze the experimental data to determine the most sensitive factors affecting the performance of emulsified asphalt in each stage of preparation, and to determine the optimal preparation scheme for emulsified asphalt. The emulsified asphalt performance test was conducted on the asphalt, and the test results show that all indicators meet the specification requirements.
Study on Effect of Graphene by Mechanical Peeling Method on Properties of Asphalt
LI Ke, HUANG Weirong, and REN Haisheng
Date posted: 8-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.04.043
To investigate the effect of the content of mechanical peeling graphene on the properties of original asphalt, this paper prepared modified asphalt with different graphene contents by employing mechanical peeling graphene as a modifier. Meanwhile, it studied the conventional physical and rheological properties of graphene-modified asphalt by conducting three major index tests and dynamic shear rheological tests. The experimental results show that compared to original asphalt, graphene-modified asphalt has low penetration, high softening point, and low ductility. Additionally, graphene significantly improves the high-temperature performance of asphalt, while the low-temperature performance is slightly reduced. Under the graphene content of 0.35%, there is a relatively balanced state between graphene and asphalt, and the modified asphalt material has strong resistance to high-temperature rutting deformation.
Study on Aging Characteristics of Bio-Asphalt Modified by Rubber Powder
ZHOU Chao
Date posted: 8-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.04.044
To evaluate the effect of thermal oxidative aging on the performance of rubber powder-modified bio-asphalt, this paper adopted rheological evaluation indicators to analyze the high-temperature deformation resistance of bio-asphalt and rubber powder-modified bio-asphalt. Based on the rheological evaluation indicators, an aging kinetic model of rubber powder-modified bio-asphalt was built at different aging temperatures and times. The results show that the anti-aging ability of rubber powder-modified bio-asphalt is significantly better than that of bio-asphalt, and the larger rubber particles lead to stronger anti-aging ability. As the aging time is extended, the high-temperature deformation resistance of rubber powder-modified bio-asphalt increases non-monotonically. On this basis, aging kinetic equations were established based on three rheological indicators, including the rut factor, relative difference in the strain recovery rate, and relative difference in unrecoverable creep compliance. The aging kinetic model built by rut factor fitting shows the best correlation between the calculated values and experimental measurement values, which can reflect the actual aging process of rubber powder-modified bio-asphalt and quickly evaluate its viscoelastic properties.
Study on Improving Speed Limit Scheme of Expressway
TIAN Hua, FENG Jian, and SHEN Guanghui
Date posted: 8-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.04.045
This paper took a certain expressway as an example to calculate and demonstrate the key indicators for improving speed limits. By calculating the indicators of highway horizontal and vertical planes, lateral force coefficients, stopping sight distance, interchange service areas, and roadside safety net zones, and comparing them with the driving characteristics of vehicles after increasing the speed limit, key control indicators and engineering improvement measures for improving the speed limit of expressways were proposed. Finally, sound references are provided for considering both traffic safety and operational efficiency in expressway construction, and meeting the requirements of highway users.
Pavement Structure and Materials
Analysis of Traffic Characteristics for Expressway on Section with Emergency Lane Running
LIU Qiang, DING Fan, ZHANG Zhixiang, and YANG Yang
Date posted: 8-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.04.046
The emergency lanes on expressways can be employed for vehicle passage during emergencies, and there is no precedent in China to open them for utilization in response to high traffic flow demands. To meet the demand for improving the high traffic capacity of Shanghai-Nanjing Expressway, this paper carried out emergency lane opening test design and on-site testing for the 2019 May Day holiday. Based on the theoretical analysis method and traffic flow monitoring data, traffic running parameters were analyzed in emergency lane opening conditions, with the influence of emergency lane opening on cross-sectional traffic capacity summarized and evaluated. The results indicate that the opening of emergency lanes has a significant effect on traffic flow in other lanes. Due to factors such as laws and regulations, and driving behavior, the free flow speed and traffic capacity of emergency lanes have not reached the single-lane design level. In experimental conditions, opening emergency lanes can increase the cross-sectional traffic capacity by about 10%.
New Design Method of Ramp Toll Plaza in Horizontal Curve Section
LIU Limin and WANG Haifang
Date posted: 8-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.04.047
When the ramp toll plaza is set up on a horizontal curve section of the road, the current highway regulations stipulate that the design baseline of the toll plaza should adopt a chord line determined by the toll plaza length. However, this design method has many problems. This paper proposed a new solution for the situation of low operating speed before and after setting up toll stations by conducting analysis and research. At both ends of the toll plaza, according to the design speed of 20 km/h, a circular curve of no less than 20 m was added to connect the horizontal curve and the straight line of the toll plaza. Compared with the methods required by regulations, the new method simplifies design, facilitates construction, and arranges the transition area of the toll plaza reasonably. Additionally, it ensures the smooth connection between the transition section pavement and the subgrade edge, achieving a beautiful road appearance and smooth driving trajectory.
Research on Key Technology of Fixed Inclination Sensor Applied in Deep Horizontal Displacement Measurement
XU Yufeng, LI Yiming, and KE Yu
Date posted: 8-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.04.048
In response to the insufficient theoretical basis for accuracy measurement in the layout scheme of measuring points in the existing fixed inclination sensor method for measuring deep horizontal displacement of foundation pits, this paper introduced an analysis method for the segmentation error and measurement angle error of inclination sensor measurement deformation, and obtained the measurement point layout laws of the fixed inclination sensors that meet certain measurement accuracy. Comparative experiments in the laboratory show that the error between the deep horizontal displacement measured by the fixed inclination sensor installed by adopting the described method in this paper and the actual displacement can meet the requirements of engineering measurement accuracy. The error analysis method and the arrangement of measuring points can provide theoretical basis for the measurement of deep horizontal displacement of foundation pits by employing fixed inclination sensors.
Bidding Decision of Overseas Highway Engineering Based on Dempster-Shafer Evidence Theory
YANG Wenan and CHEN Long
Date posted: 8-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.04.049
Overseas highway projects feature the large scale, wide scope, and long construction period, thus significantly increasing the complexity of project bidding evaluation and making it difficult to make simple bidding decisions. This paper built a set of 28 influencing factors for bidding decisions in three major categories, including the owners and related management parties, construction projects themselves, and bidding enterprises themselves, by conducting literature analysis. The influencing factors were screened for the proposed bidding project, with an evaluation index system constructed. Then, a decision model was built by adopting analytic hierarchy process (AHP) and D-S evidence theory to integrate expert evaluation data. As a result, while determining the overall risk level of the project, this helped further obtain the key influencing factors of the integrated project, with the decision of whether to bid or not made. Additionally, the application decision model was employed to evaluate the 2.2 highway project in the Philippines, and the result show that it is medium risk and eligible for bidding. The top three key influencing factors are the expected profit of the project, the company's ability to claim compensation, and the supply of materials and equipment required for the project. The model can handle different evaluation opinions and provide references for bidding decisions, bid document offer, and risk prevention.
Literature Analysis of Research and Application of Snowmelt Agent at Home and Abroad in Recent Ten Years
YANG Fengzhi, LI Gen, CAO Yuhai, LI Yiwei, HUANG Zhanbin, and HAN Yongping
Date posted: 8-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.04.050
To understand the research and application development trends of snowmelt agents at home and abroad, and provide references for researchers and decision-makers in the field of snowmelt agent research, based on the Web of Science full-text database and CNKI database, this paper adopted the bibliometric analysis method to analyze the annual publication number, published journals, research directions, research institutions, and highly cited papers of relevant literature in the field of snowmelt agents at home and abroad from 2010 to 2019. The results show that the overall number of publications in this field has been on the rise both domestically and internationally, with Germany and the United States having significant international influence in this field. Among the top ten Chinese academic journals and institutions, institutions such as Chang'an University have significant influence in the field of snowmelt agents. The number of publications in the field of snowmelt agents in China and internationally is basically the same, but there has been a downward trend in China in the past five years. Although the number of publications is not low, there is a lack of high-level papers, research institutions and funding support with international high influence, indicating that there is still a significant gap between China's development and research in the field of snowmelt agents and the international advanced level. Based on this, this paper proposed countermeasures and suggestions for the research and application of snowmelt agents in China.
