Volume 42, Issue 3 (2022)
Specially Invited Article
Review on Classification and Testing Methods of Clay-Bound Water
Zhang Rui, Shen Xu ning, Yang Xiangzhan, Xiao Yupeng, Zhou Shijie, and Cheng Xianyang
Date posted: 6-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.03.001
The bound water in clay has a significant influence on the engineering properties of clay. The influence of bound water and its properties on the mechanical properties of soil mass is the focus of the research on special soil engineering problems. To further deeply study the properties of bound water in the soil and its influence on the mechanical properties of soil mass, this paper reviewed the concept, classification, properties of bound water in clay and the testing methods of bound water content. Comprehensive analysis indicates that due to factors such as the different hydration mechanisms of bound water in different clays and insufficient exploration of the classification of bound water forms, there is no unified classification and definition method for bound water yet. One of the important indicators of bound water is the bound water density. However, the bound water density is not fixed, and the method for determining its accurate value awaits further research. The current methods for determining bound water have certain limitations. By comparing various testing methods, it is believed that the bound water content measured by the isothermal adsorption method and thermal analysis method is relatively accurate. It is recommended to use multiple measurement methods in combination to determine the bound water content to obtain more precise and rigorous results.
Subgrade Engineering
Prediction Model of Purifying Rainwater Effects of Planting Soil Green Belt
Gu Guohong, Zhang Chunhui, and Guan Tongjun
Date posted: 6-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.03.002
In order to predict the purification effect of planted soil green belt on urban road runoff pollutants, a mathematical model of pollutant migration in planted soil with rainwater infiltration was established based on the principle of mass conservation by considering the infiltration of rainwater into the planted soil as a one-dimensional seepage and pollutant migration process. Combined with the working conditions of the lower boundary of the planted soil green belt, the simplified processing method of the lower boundary of the model was proposed, and then the prediction model of the planted soil green belt for purifying road runoff rainwater was given. The model was used to predict the purification effect of planted soil green belt on road runoff rainwater at different rainfall durations, and the main conclusions are as follows: ① The water purification performance of planted soil green belt predicted by the model is basically the same as the experimental results, and the model is reasonable, which provides a method for the assessment of the water purification performance of planted soil green belt; ② Increasing the thickness of the planted soil can effectively increase the purification effect of the planted soil on the pollutants in the road runoff rainwater. When the thickness of the planted soil is increased from 60 cm to 80 cm, the purification effect of planted soil on chemical oxygen demand (COD) and suspended solids (SS) increases by 62.2% and 69.4%, respectively.
Progressive Failure Mechanism Analysis of Loose Deposit Slope under Seismic Load
Qiu Yi and Shang Yu
Date posted: 6-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.03.003
A loose deposit slope is a special kind of rocky slope, whose material composition is characterized by nonlinearity, nonhomogeneity, and discontinuity, and China is a country with a high incidence of earthquakes, so the stability problem of loose deposit slope is particularly prominent. In this paper, the numerical simulation of the actual loose deposit slope MK0 + 455 of Ya’an–Kangding Expressway was carried out by using the particle flow code (PFC) to analyze its mechanical behavior and dynamic characteristics under seismic loading and reveal the progressive damage mechanism of the loose deposit slope. The results show that under seismic loading, the progressive damage of the loose deposit slope is mainly divided into the loosening and landslide of the loose deposit accumulation layer, as well as the cohesion damage and fissure development of the bedrock layer; the progressive development of the cohesion state and the fissure distribution of the loose deposit slope is related to time and space. Through the analysis of the time-range change of the void rate, strain rate, and kinetic energy, a preliminary summary of progressive damage characteristics of loose deposit slopes was provided.
Research on Advances and Engineering Application of Draining Geogrids
Xu Chao, Ma Huangxiang, and Yang Yang
Date posted: 6-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.03.004
Coarse-grained soil should be used as fill material for reinforced soil structures, but in engineering practice, sometimes people have to use fill material with high fine-grained content, which leads to problems of poor constructability, poor drainage, and excessive deformation of reinforced soil structures. In order to cope with this situation, a reinforced material with a drainage function is required, and drainage geogrid comes into being. Experimental research and engineering practice have shown that reinforced materials with a drainage function can quickly dissipate the over-pore pressure generated during the compaction construction of fine-grained soil and accelerate the consolidation of fill soil. Drainage geogrid can effectively drain and improve the structural stability of reinforced soil. The paper summarized the research results of reinforced materials with a drainage function and focused on the design method and engineering practice of reinforced soil structure of drainage geogrids. In view of the problems still faced at present, suggestions for further research on the reinforced soil structure of drainage geogrids were put forward.
Date posted: 6-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.03.005
Goaf seriously restricts the overall planning, ecological environment, and economic development of Urumqi City. In view of the characteristics of large mining thickness, shallow buried depth, and steep slope of coal seams in Urumqi, this paper adopted full filling pressure grouting reinforcement measures to treat the goaf of steep slope coal seams under the east second ring road project in Urumqi City. The research results show that the underlying goaf in the study area has the characteristics of steep inclination, common development of multi-layer goaf, and transboundary mining. The maximum residual settlement of the goaf under the road section in the study area is about 877 mm, which is still in an unstable state. The treatment scheme of full filling pressure grouting is mainly used to fill the goaf and reinforce the security coal pillar area. The length of the treatment is 300 m; the width is 234 m, and the grouting volume is about 45 174 m3. Finally, the safety test is carried out by means of a drilling test, wave velocity logging in the hole, and ground settlement observation. The grout strengthens the grouting effect to a certain extent, and the grouting quality meets the requirements.
Pavement Engineering
Study on Performance of Clogging and Permeability of Pervious Concrete Pavement in Sponge City
Zhu Runtian, Liu Shan, Zhang Xiaoming, Liu Fuqiang, Wan Zhengwu, and Zheng Mulian
Date posted: 6-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.03.006
To address the clogging issue of permeable concrete pavement in sponge cities, clogging and permeability tests were designed to investigate the influence of clogging materials on the permeability of surface layers, base layers, and their combined permeable concrete structures with different gradations and determine the sensitive particle size ranges of clogging materials for various permeable pavement structures. The results indicate that permeable concrete surface and base layers with coarse gradation exhibit superior resistance to permeability attenuation; for combined surface-base layer structures, the residual permeability coefficient primarily depends on the surface layer design, with minimal correlation to the base layer; the sensitive particle size range accounting for the highest proportion of clogging materials in surface layers, base layers, and their combinations is 0.3–0.6 mm. In graded permeable concrete design, the content of 9.5–16 mm aggregates should be appropriately increased while ensuring strength. Through the regression of the attenuation formulas of the permeability residual coefficient of different structures, the attenuation law of the permeability of the permeable pavement layer was obtained, which could guide the timing selection for vacuum adsorption or pressure purgation cleaning and maintenance of the permeable pavement structural layer, thereby ensuring its service performance.
Analysis of Mechanical Characteristics of Void Area of Road Deck under the Load of the Aircraft
Guo Yunfei, Guo Chengchao, and Yan Weihong
Date posted: 6-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.03.007
To study the void problem of airport cement concrete pavement slabs, a three-dimensional model of the airport pavement structure was established using finite element software. The stress distribution of the pavement slabs under the action of self-weight stress and aircraft load was calculated, and the force characteristics of different voids at different positions along the joints were studied. The calculation results show that under the action of self-weight stress, in addition to the stress concentration occurring in the middle of the void, the stress concentration phenomenon will also occur at the edge of the void, that is, the critical surface between the void area and the non-void area. Under the action of aircraft load, stress concentration occurs in the middle of the void area, and the panel with a large void area has a higher stress peak than the one with a small void area. Therefore, for the void area at the bottom of the plate, it is necessary to track and detect it in a timely manner and deal with it promptly to prevent further aggravation of the void.
Application Research on BIM Technology in Construction Simulation of Asphalt Pavement
Liu Kexin, Xu Min, Li Xu, Liu Fengyang, and Chang Ruiqi
Date posted: 6-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.03.008
In view of the poor traceability and low accuracy of the commonly used asphalt pavement construction methods at present, a research method for asphalt pavement construction simulation technology based on BIM was proposed. The basic models of the asphalt pavement construction stage were developed based on the Revit platform, including the construction vehicle model, three-dimensional geological model, etc., making the construction process visual and interactive. 3D simulation of construction animation based on Navisworks software, combined with the creation and application of features, can effectively avoid conflicts in advance. This paper expanded and deepened the application of BIM technology in the construction of asphalt pavement in road engineering, effectively promoting the development of information-based construction of asphalt pavement.
Research on Texture Feature of Rut Surface Based on 3D Laser
Lu Shurong
Date posted: 6-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.03.009
Rutting damage on the road surface seriously affects driving safety, often causes traffic accidents, and results in significant economic losses. In order to explore the texture characteristics of the rutting surface, this paper designed an experiment to simulate the formation process of rutting. It used a depth camera based on a 3D laser to collect point cloud data of rutting and non-rutting and calculated the surface texture feature parameters of rutting. It selected the mean profile depth (MPD), functional parameters, and volume parameters. After the analysis of the calculation results, the MPD values with rutting, the height Svk of the protruding valley, and the void volume Vvv of the valley were all smaller than those of the non-rutting. By using these three parameters to establish the rutting judgment prediction model of SVM, the judgment accuracy rate was 91.7%.
Research on Optimization Method of Maintenance Decision Model of Highway Asphalt Pavement
Lin Likuan
Date posted: 6-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.03.010
Through theoretical calculation, combined with big data statistical analysis, this paper found the boundary conditions for restoring the overall damage condition index of the pavement through the treatment of local pavement diseases. During the process of maintenance decision-making and maintenance demand analysis, based on this boundary condition, sections with poor current road conditions and those that can effectively restore the road condition level only through daily maintenance measures could be quickly screened out. Therefore, it effectively reduced the capital demand for the maintenance projects of the entire road network and improved the utilization efficiency of maintenance funds. In addition, the maintenance demand analysis model constructed by using two indicators, namely the cracking rate and the grouting rate, and combining three indicators, namely PCI, RQI, and PSSI, can more accurately classify the types of maintenance sections and improve the accuracy of maintenance scheme design.
Bridge Engineering & Tunnel Engineering
Research on Vibration Comfort of Steel-Concrete Composite Footbridge with Long-Span Flexible Arch
Li Dongyang, Li Dong, Guo Xinyan, He Fan, Huang Zheng, Guo Jiye, and Chi Hang
Date posted: 6-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.03.011
This paper took a pedestrian overpass with a large-span flexible arch steel-concrete composite beam as an example to introduce the verification method of pedestrian-induced vibration comfort of the overpass. A finite element model was established through Midas/Civil software to analyze the dynamic characteristics of the overpass. The time-history analysis method was adopted to investigate the dynamic responses of the overpass under four crowd load models specified in the code. The relationship between the walking frequency and the crowd density, the damping ratio, and the influence of the support setting form on the dynamic response of the structure were studied. Finally, the comfort of the pedestrian overpass was verified and comprehensively evaluated based on the comfort evaluation standards stipulated in different specifications. The research results show that the comfort of the pedestrian overpass meets the verification requirements of each specification.
Finite Element Analysis of Mechanical Performance of a Small Radius Cast-in-Place Box Girder Bridge Pier-Beam Connection Method
Wang Yiguang and Zheng Yuanxun
Date posted: 6-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.03.012
Due to the significant variation in alignment, the force of small-radius curved bridges is rather complex. Different connection methods of piers and beams can have a considerable impact on the overall force performance of small-radius curved bridges, which requires careful consideration during the design process. This paper took the two-span small-radius curved cast-in-place box girder bridge of a certain expressway ramp bridge as an example. The finite element model of the bridge was established by using Midas/Civil software, and the static performance of the bridge under the conditions of simply supported piers and beams and consolidated piers and beams was analyzed from three aspects: strength, stiffness, and stability. The results show that under the consolidation condition of piers and beams, the longitudinal and transverse displacements of the pier top and the box girder are smaller, and the stability is higher. However, the bending moment of the piers is larger. Therefore, the reinforcement ratio should also be increased accordingly in the design. Due to the relatively small stiffness of the pier body, the longitudinal and transverse displacements of the first hollow piers are relatively large. The consolidation of piers and beams has a significant influence on the stress of piers and a relatively small influence on the stress of box girders. Based on the analysis of the three aspects of comprehensive stiffness, strength, and stability, the consolidation of piers and beams is more suitable for the connection of piers and beams in small-radius cast-in-place box girder bridges.
Finite Element Analysis of Mechanical Performance of a Small Radius Cast-in-Place Box Girder Bridge Pier-Beam Connection Method
Hong Xiaojiang, Guo Ning, Qian Bo, Lan Fei, and Li Hongming
Date posted: 6-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.03.013
In order to solve the problem that the traditional GM(1,1) grey model has low prediction accuracy in the alignment control of the cantilever assembly construction bridge, this paper used the fractional operator GM(1,1) model to predict the elevation of the bridge construction segment, optimized the construction method of the model background value, and established a new fractional GM(1,1) model with three parameters. This model achieved a dual optimization of the order and background values of the traditional GM(1,1) model. In order to test the prediction accuracy, the proposed model was compared with the traditional GM(1,1) model and the fractional GM(1,1) model. The results show that the average relative error of the optimized fractional GM(1,1) is 5.9%, which is 11.6% lower than that of the traditional GM(1,1), and the prediction accuracy is further improved.
Research on Design Optimization for Integral Joint in Support Region
Wang Cheng, Ning Pinghua, Wang Ronghui, Le Xiaogang, Hu Huiyong, and Zhou Yu
Date posted: 6-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.03.014
The overall nodes at the support positions are subjected to large forces, often resulting in stress concentration and excessive local stress. To study the force characteristics of the overall nodes at the support positions and provide a basis for design optimization, this paper took the MG22 node of Guangzhou Mingzhu Bay Bridge as the research background and established an Ansys finite element model considering the support effect. The stress distribution law and structural optimization method of this node were studied. The results show that the welded end of the vertical stiffening ribs of the support is usually the stress concentration area. The local stiffness of the structure within the support range and the smoothness of the stiffness change will directly affect the stress peak of the overall node. Optimizing the distribution and coverage of the stiffening ribs in this area can make the force transmission of the plate more reasonable, thereby improving the stress condition of the overall node. After optimization, the amplitudes of the maximum equivalent stress and fatigue stress of the plate decrease to 328.7 MPa and 38.2 MPa, respectively. The stress distribution of the nodal plate and the base plate becomes more uniform. Among them, the peak value of the equivalent stress and the amplitude of the maximum fatigue stress of the nodal plate decrease from 416.6 MPa to 307.2 MPa and from 59.1 MPa to 33.5 MPa, respectively. The equivalent stress peak and the maximum fatigue stress amplitude of the base plate decrease from 396.8 MPa to 257.5 MPa and from 38.3 MPa to 25.2 MPa, respectively. The stress levels of each plate have been greatly reduced, verifying the rationality of the node structure and the effectiveness of force transmission.
Research on Preventive Maintenance of Steel Truss Bridge
Hang Jing, Yang Libin, Shen Jianhua, and Peng Weibing
Date posted: 6-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.03.015
Changxing County in Huzhou City, Zhejiang Province is located in the Taihu Lake Basin. The plain rivers and ports are interwoven, with undulating and dense waterways. Over the past decade or so, a number of various types of steel truss bridges have been established. In recent years, steel truss bridges have been widely used due to their advantages such as a small number of components, light overall self-weight, and fast construction and assembly across waterways. As the service life of steel truss bridges increases, some components show varying degrees of aging and damage, resulting in the structural load-bearing capacity being unable to meet the operational safety requirements. To ensure the driving safety and smooth traffic flow of steel truss bridges under long-term cyclic loads, extend the service life of the bridges, and reduce the cost of periodic maintenance, this paper used unmanned aerial vehicle remote sensing technology to detect the structural surface diseases of a certain steel truss bridge in Changxing County. The research results show that the case bridge has typical diseases such as coating deterioration, steel corrosion, and bolt breakage and detachment. Based on the existing diseases of the steel bridge, the causes of the diseases were analyzed, and the research on preventive maintenance technology was carried out. The maintenance of anti-corrosion coating of steel components, inspection and treatment of welds, treatment of bending and damage of members, and preventive management and maintenance of auxiliary structures such as expansion joints and anti-collision guardrails were proposed.
Construction Control and Parametric Analysis of Cable-Stayed Bridge with Hybrid Composite Beam
Zhang Yuping, Xu Xianpeng, Li Xiangmei, and Yang Shengjiang
Date posted: 6-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.03.016
Based on a hybrid composite girder cable-stayed bridge, a finite element model was established to analyze the technical parameters such as the cable force, the weight of the main beam, and the cantilever length of the hanging basket crossing the auxiliary pier. The construction accuracy and construction control standard of cable force and main beam weight were discussed, and the maximum cantilever length of hanging basket crossing temporary and permanent auxiliary piers was demonstrated. The results show that the construction accuracy of the overstretched cable force of the medium-span cable-stayed cable should be controlled within 5%; the under-stretched cable force of the medium-span cable-stayed cable should be controlled within 1.5%, and the final cable force adjustment of a cable-stayed bridge should be controlled within 1%. The construction accuracy of concrete beam weight should be controlled within 3%, or in other words, the average error of concrete slab thickness should be controlled within 1 cm, and the weight of the composite beam should be controlled within 0.6%. The maximum cantilever length of the hanging basket crossing the temporary auxiliary pier can be two beam sections during construction, and the maximum cantilever length of the hanging basket crossing the permanent auxiliary pier can be four beam sections. In the process of construction control, alignment control should be the focus, with cable force control as the supplement.
Simplified Modeling and Load Test of Hybrid Girder Cable-Stayed Bridge with Single Cable Plane
Song Zegang, Deng Xudong, and Zhou Yuting
Date posted: 6-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.03.017
To accurately evaluate the load-bearing capacity and working performance of cable-stayed bridges when they are completed, the Liku Nujiang Second Bridge [(81 +175) m cable-stayed bridge with single-tower single-cable plane hybrid beam] was taken as the object, and a simplified modeling method based on the linear domain element simulation of the steel box girder was proposed; the finite element model of the bridge was established. Through static load and dynamic load tests, the measured values of parameters such as stress, deflection (or displacement), cable force, impact coefficient, and frequency of the control section of the bridge structure were obtained. After comparative analysis, the load-bearing capacity and working performance of the bridge structure were evaluated. The results show that the proposed simplified modeling method has the advantages of high modeling efficiency, low error rate, and simple post-processing, and its calculation accuracy meets the requirements of the overall analysis of the bridge. The bridge structure has a certain safety reserve in terms of strength and rigidity, as well as good dynamic performance, and its load-bearing capacity and working performance meet the design requirements.
Improved Method for Calculating Design Position of the Cable Saddle on Suspension Bridge
Deng Xiaokang and Deng Hengyao
Date posted: 6-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.03.018
Based on the analysis of the geometric and mechanical relationship between the main cable and the cable saddle of the suspension bridge, the equation was established by using the geometric compatibility conditions of the cable saddle and the main cable. The design position of the cable saddle was obtained by solving the equation using the dichotomy, avoiding the complex calculation of solving the eight-element nonlinear equation system using the Newton-Raphson method in the traditional method. The improved algorithm for the cable saddle position proposed in this paper has good accuracy and simple calculation. The entire calculation process does not require any initial values and can ensure the convergence of the solution.
Research on Influence of Bearing Sliding Plate Wear on Seismic Performance of Multi Tower Cable-Stayed Bridge
Luo Legen, Zhang Xun, and Zhang Jingyue
Date posted: 6-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.03.019
To study the influence of sliding plate wear of the bearing on the seismic performance of multi-tower cable-stayed bridge structures, the wear performance test of the sliding plate of the bearing replaced by a certain in-service bridge was carried out to study the friction coefficient of the sliding plate of the bearing at different wear stages throughout the entire service process. By taking the Huangmaohai Bridge as the engineering background, a spatial three-dimensional finite element model was established to compare the seismic responses of the bridge structure under different wear degrees of the bearing plates. The research results show that during the service process, the slide plate of the bearing undergoes four processes: normal state, depletion of silicone grease, complete wear of the exposed slide plate, and wear of the stainless steel mirror surface. Moreover, the friction coefficient gradually increases from 0.01 to 0.156. The bridge transforms into a consolidation system, and the bending moment at the bottom of the pier increases by 11.4%, affecting the seismic performance of the bridge structure.
Fatigue Performance Analysis of Welding Details of Steel Orthotropic Plate-Truss Composite Beams
Huang He and Qin Pan
Date posted: 6-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.03.020
Three structural details of a certain orthotropic plate steel truss composite beam were fabricated as specimens. Their fatigue properties were studied by combining static load tests, cyclic loading of fatigue tests, and the finite element method. The results show that the fatigue cracking position of the welded clamping plate of the bridge deck is in the middle part, and the crack starts to expand from the inside, indicating that the weld here is relatively weak. The reason is that the cross-sectional area of the middle clamping plate part is small. Under the action of cyclic load, it continuously bears a large tensile stress, thereby causing the component to crack. The weakest part of the welded structure between the U-rib and the diaphragm and the bridge deck is the weld between the U-rib and the bridge deck, which breaks first in the fatigue test. The fatigue cracks in the cross-weld structure of the bridge deck, the diaphragm, and the U-rib start from the weld toe and then expand diagonally. The main reason is that under the action of external loads, both the transverse and vertical stresses at the weld toe are relatively large. Under the combined action of forces in both directions, diagonal cracks are prone to occur. These weak parts verified by experiments should be given attention in fatigue design.
Experimental Study on Fatigue Performance of Steel Fiber Reinforced Concrete-Orthotropic Composite Bridge Deck
Ye Huawen, Tang Shiqing, Duan Zhichao, and Yang Zhe
Date posted: 6-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.03.021
Orthotropic steel bridge decks are prone to fatigue cracking. The adoption of steel fiber reinforced concrete (SFRC) composite bridge decks is one of the solutions. Through the wheeled rolling loading fatigue test simulating the actual wheel load on the full-scale model of the SFRC composite bridge deck, three connection methods, namely adhesive, stud, and a mixture of adhesive and stud, were respectively adopted between the concrete layer and the orthotropic steel bridge deck structure layer to study the fatigue deformation of the composite bridge deck and the failure evolution mode of each component. Then, the crack development behavior of the SFRC structural layer was analyzed through numerical simulation. The results show that SFRC can significantly reduce the fatigue stress of the welding construction details of the bridge deck, and its fatigue performance has been significantly improved. The stud connection makes the overall performance of the composite bridge deck better and is suitable as the connection method between the SFRC and the steel deck.
Key Technology of Suspender Replacement for Arch Bridge under the Requirement of Heavy Load and Tarffic Demand Protection
Yang Hao and Lu Wensheng
Date posted: 6-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.03.022
When the service life of the suspension rods of arch bridges approaches their designed service life, suspension rod replacement is often carried out. However, at present, cases of replacing the suspension rods of the arch bridge under traffic conditions in China are still relatively rare. Considering the actual operational requirements for heavy load and traffic demand protection of arch bridges, this paper discussed the optimization of the main processes during the replacement of suspension rods, proposed correction methods for key parameters such as monitoring the influence of environmental temperature and vehicle loads during the construction process, as well as an accurate measurement method for the internal forces of short suspension rods, and evaluated the construction effect of suspension rod replacement of arch bridges under the heavy load and traffic demand protection requirements. The results show that all the control indicators of the suspension rod replacement of the arch bridge under the heavy load and traffic demand protection conditions meet the design and specification requirements. The proposed technical method can provide a reference for the replacement of suspension rods in the same type of bridge.
Overall Design of Shayong Bridge on Binhai Bay Avenue in Dongguan City
Wang Peng
Date posted: 6-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.03.023
The Shayong Bridge on Binhaiwan Avenue in Dongguan City is a three-arch ribbed lower-supported tied arch bridge. Based on the combination of multiple arches, this paper extracted the element of waves and used the volume contrast of multiple arches to echo the shape of the waves. With a simple and lively posture, it showcased the dynamism and vitality of the Binhaiwan New Area in Dongguan City. This paper introduced the overall design of the Shayong Bridge and used large-scale finite element calculation software to establish a spatial model for structural calculation and analysis, mainly including static, dynamic, and stability analysis. The calculation results prove that the bridge is safe and reliable.
Analysis on the Causes of Cracks in Bottom Plate of Box-Girder in Wide Non-Cable Area of the Extradossed Cable-Stayed Bridge
Wu Yunpeng, Chen Jingwei, and Zhou Tianying
Date posted: 6-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.03.0024
Large-sized prestressed reinforced concrete box girder makes it easy to produce floor cracks due to construction temperature. In view of the floor cracks of a short tower cable-stayed wide box girder in Nanchong, Sichuan Province at the beginning of construction, a mixed element calculation model was established to simulate the stress calculation of the effects of temperature difference of hydration heat, sunshine temperature difference, overall cooling, and their combination factors on the floor of 7# section box girder. The stresses in some areas of the floor under the combined conditions of Ⅰ, Ⅳ, and Ⅴ reached 2.0, 4.0, and 4.9 MPa, respectively, which were greater than the allowable value of crack resistance and were consistent with the actual crack situation. Combined with the stress analysis, the subsequent box girder construction adopted the double mixing technology to reduce the hydration heat, extend the final setting time to 16 h, lower the concrete mold temperature, and improve “inner drop and outer protection” maintenance and other measures, so as to effectively control the floor cracks.
Study on Transverse Seismic System of Main Bridge of KekeDala Bridge in High Intensity Seismic Area
Chen Zuoyin and Chen Jia
Date posted: 6-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.03.025
In view of the excessive transverse seismic force of medium-span cable-stayed bridges, the main bridge of Cocodala Bridge was taken as the research object to study the working mechanism of different seismic damping and isolation methods and discuss the transverse seismic stress state of the bridge tower, transition pier, and auxiliary pier under the transverse damping and isolation measures of this type of cable-stayed bridge. The analysis shows that the transverse seismic forces of the bridge tower, transition pier, and auxiliary pier can be greatly reduced when seismic damping and isolation measures are adopted. At the same time, with the gradual increase of the horizontal yield stiffness of the special-shaped steel damper, the transverse seismic forces of the bridge tower, transition pier, and auxiliary pier increase gradually, and the transverse relative displacement of the main beam decreases gradually. When the main beam is laterally limited at the bridge tower, and seismic damping and isolation measures are applied in the transition pier and auxiliary pier, the transverse seismic force at the transition pier and auxiliary pier is greatly reduced, but the transverse seismic force at the bridge tower is increased. Meanwhile, with the gradual increase in the horizontal yield stiffness of the special-shaped steel damper, the transverse seismic force at the transition pier and auxiliary pier is gradually increased. The transverse seismic force at the bridge tower decreases gradually.
Stability Analysis of Tower Super-High Support of the Circular Arch Cable-Stayed Bridge
Wang Shuliang
Date posted: 6-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.03.026
Based on the research background of the construction of over 80 m tubular steel support in the bridge tower closure section of a cable-stayed bridge, the current research and application status of the support were introduced, and the necessity of the research of the ultra-high support was clarified. The finite element method calculation theory of the support stability analysis method was introduced in detail, and the finite element method was used to analyze the influence of wind load, constraint conditions, and initial defects on the stability of the tubular steel support. Based on the characteristics of the first-order buckling mode of the support, four kinds of parameter optimization schemes to improve the stability of the support were proposed and analyzed. The results show that wind load, constraints, and initial defects all affect the stability of the ultra-high support but do not affect the position of the support instability. As it gets closer to the top of the support, there is less influence of the change of constraint conditions on the stability of the support. A larger initial defect indicates a smaller critical load coefficient, but the effect of the initial defect on the critical load coefficient is limited. Among the four optimization schemes, the scheme of increasing the size of the scissor support between the unstable parts of the steel pipe column is more effective and economical than the other three schemes, and the stability of the support can be increased by about 47.8%.
Analysis of Monitoring Data for Super Large Underwater Steel Open Caisson Construction
Wang Zichao, Yang Qie, Chen Jianrong, and Sun Nanchang
Date posted: 6-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.03.027
The round-ended stepped caisson adopted by Pier 5 # of the Changtai Yangtze River Bridge is the world’s largest-sized underwater steel caisson. This paper monitored and analyzed the entire construction process of caisson 5 # through on-site monitoring data and relevant theoretical methods. Meanwhile, it studied the lateral distribution of lateral friction resistance, the influence of earth pressure on the outer edge foot tread surface on end resistance, and the stress distribution at the bottom of the partition wall. The research results show that a good posture of the caisson can be guaranteed through timely dynamic adjustment. After the pouring of the first section of concrete in the caisson is completed, the stress magnitude and distribution of the bottom plate of the outer partition wall have been determined. However, the stress of the inner partition wall will increase significantly in the early stage of construction and remain stable in the middle and later stages. During the middle and later construction of the caisson, the end resistance at the foot tread surface of the outer edge accounts for 35%–55% of the total end resistance of the outer edge and 25%–40% of the total resistance at the end of the caisson, which has a significant impact on the settlement of the caisson. When the sinking of the caisson is initiated, the earth pressure at the foot surface of the outer edge will change significantly. Moreover, in the initial sinking stage of the caisson, the static frictional resistance is approximately 1.1 times the dynamic frictional resistance. In the final sinking stage of the caisson, the static frictional resistance is approximately 1.6 times the dynamic frictional resistance. The lateral wall earth pressure is between the active total pressure and the passive total pressure. Meanwhile, the lateral wall earth pressure first increases, then stabilizes, and then decreases, but the decreasing trend is not obvious. The lateral distribution of the lateral wall frictional resistance varies greatly and should be calculated in segments.
Stress Analysis of Steel Bellows Culvert with High Fill and Large Aperture in Collapsible Loess Region
Jie Weijiang, Liang Kai, Hu Bin, and He Qiang
Date posted: 6-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.03.028
Relying on the experimental project, the force characteristics during the construction process of steel bellow culverts with high-fill subgrade and large aperture in collapsible loess region were tested, and the variation laws of the inner wall strain and the radial earth pressure on the outer wall of the pipe at different angles were obtained. The following conclusions were drawn through the research: Alternating tensile and compressive strain changes occur at the crest, trough, and wave side in the early stage of filling, and the stress at each angle is redistributed. The growth is rapid in the middle stage of filling and slows down in the later stage. The maximum strain values at the crest, trough, and wave side all occur at 45° of the upper or lower semi-circle, and the strain values at the same angle of the crest and trough are opposite, which is complementary. The variation law of axial strain is similar to that of tangential strain but slightly smaller overall, indicating that the steel bellow culverts are mainly subjected to tangential force and supplemented by axial force. The radial earth pressure on the outer wall of the pipe increases with the increase in the fill height, and it increases rapidly in the early stage. In the later stage, the soil arching effect tends to level off.
Research on Key Construction Technology of Adjacent Double-Arch Tunnel to Existing Tunnel under Thick Filling Platform
Mo Kun, Dai Jiabao, Luo Lijuan, Dang Nan, Ma Jiakuan, and Zhu Junhui
Date posted: 6-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.03.029
Based on the shallow-buried underground excavation project of the double-arch tunnel at the entrance and exit line of Yanming Lake Parking Lot of Xi’an Metro Line 5, and in accordance with the thick fill soil layer of the site and the engineering conditions of the existing sections near the site, this paper proposed several key construction techniques for small-section double-arch metro tunnels in loess areas. The feasibility of the construction of the middle guide tunnel + upper and lower step method was verified by means of numerical analysis. Meanwhile, different forms of advanced support methods were adopted according to the geological conditions of different construction sections, and the proportion of the excavation section of the middle guide tunnel was appropriately increased, effectively reducing the mutual influence of the construction of the left and right tunnels. In addition, the project adopted a self-designed asymmetric lining trolley for the secondary lining construction, which solved the problem of secondary lining bias and formwork shifting. In the feedback of on-site monitoring data, the maximum values of surface settlement, the subsidence of the arch top of the newly built tunnel, and the convergence of the arch waist of the existing tunnel were 14.1 mm, 8.2 mm, and 3.9 mm, respectively, all of which were less than the construction control values, verifying the rationality and safety of the key construction techniques expounded in this paper.
Pavement Structure and Materials
Effect of Limestone Powder on Strength of Cement Mortar and its Mechanism
Lv Xiaowu, Zhao Yongwei, and Yan Yongliang
Date posted: 6-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.03.030
This paper studied the influence of the dosage and fineness of limestone powder on the compressive strength of mortar. Based on the heat of hydration test and the boundary nucleation and growth model, the hydration kinetics parameters of the cement paste were calculated. The pore structure of the mortar was analyzed through a capillary water absorption test and mercury pressure test, revealing the mechanism of limestone powder on the compressive strength of mortar. The results show that with the increase in the dosage of limestone powder, the compressive strength of the mortar gradually decreases. When the dosage increases to 30%, the compressive strength of the mortar at the ages of 7, 28, and 56 days decreases by more than 20%. With the increase in the fineness of limestone powder, the compressive strength of mortar gradually increases. When the fineness of limestone powder increases from 1.084 μm2/μm3 to 2.168 μm2/μm3, the strengths of mortar at the ages of 7, 28, and 56 days increase by 6.1%, 4.2%, and 4.8%, respectively. Limestone powder reduces the hydration heat release rate, hydration heat, nucleation rate KN, and growth rate KG of hydration products of the cement slurry, thereby reducing the hydration degree of the slurry, increasing the capillary water absorption, void ratio, and maximum pore diameter of the mortar, and ultimately leading to the reduction of the compressive strength of the mortar.
Low Temperature Performance of Modified Asphalt Mixtures with Warm Mix Rubber Powder
Zhang Fei, Wang Lan, and Xing Yongming
Date posted: 6-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.03.031
To study the influence of the mesh size of rubber powder in warm-mixed asphalt mixture and the warm-mixed agent on the low-temperature performance of rubber powder-modified asphalt mixture, the bending and bending creep tests of rubber powder-modified asphalt mixture with different mesh sizes before and after warm mixing were carried out. The results show that the low-temperature performance of the modified asphalt mixture with rubber powder is improved after warm mixing, and the low-temperature performance of the 60-mesh modified asphalt mixture with rubber powder is always better than that of the corresponding mixed mesh modified asphalt mixture with rubber powder. The combined bending failure energy density and temperature strain energy density can predict the cracking temperature of asphalt mixtures. The test results show that the low-temperature performance of the modified asphalt mixture with rubber powder has improved after warm mixing, and the low-temperature performance of the 60-mesh modified asphalt mixture with rubber powder after warm mixing is the best.
Study on Influence of Aggregate Density Difference and Compaction Temperature on Mixing Proportions of Asphalt Mixture
Huang Bo, Li Chaoyuan, Hao Zhi, and Bai Tao
Date posted: 6-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.03.032
To clarify the influence of aggregate density differences and forming temperature on the mix ratio of asphalt mixtures, this paper first demonstrated the reasons for the change in volume gradation when weighing coarse and fine aggregates with large density differences. Through laboratory tests, it was confirmed that the differences in aggregate density and forming temperature had an impact on the optimal oil-to-stone ratio of asphalt mixtures. Then, Marshall specimens were formed by mass gradation and volume gradation, respectively, and their volume indicators were calculated. Meanwhile, the influence of compaction temperature on the volume indicators of Marshall specimens was analyzed. Finally, the road performance of the mixtures before and after density correction was studied. The results show that both the aggregate density differences and the molding temperature will affect the optimal oil-to-stone ratio of the mixtures. Increasing the compaction temperature will increase the density of asphalt mixtures and saturation of asphalt, reduce the void ratio and mineral void ratio, and lower the optimal oil-to-stone ratio of asphalt mixtures. Density correction of AC-13 asphalt mixture can reduce the optimal oil-to-stone ratio by 0.2%. Within the rolling temperature range of 150–180 °C, for every 10 °C increase, the optimal oil-to-stone ratio decreases by nearly 0.1%. When coarse and fine aggregates with significant density differences are used, whether density correction is carried out has a relatively obvious impact on the road performance of asphalt mixtures.
Effect of a Vegetable Oil-Based Regenerant on Performance of Aged Asphalt
Chang Runtian, Wang Wei, Fan Changcuan, and Pei Qiang
Date posted: 6-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.03.033
In this paper, a hot regenerant ZZ-1 for asphalt pavement was formulated by compounding waste vegetable oil as the main raw material with aromatic oil and a small amount of additives. The laboratory conducted a comparative test on the Fourier transform infrared spectra, thermal stability, and regeneration effect on short-term aged asphalt between the self-made regenerant and the other two commercially purchased regenerants. The results show that the indicators such as the flash point, mass loss before and after aging, and viscosity ratio of the self-made regenerant all meet the specification requirements, and the regeneration effect is better than the other two commercially purchased regenerants. In addition, the regenerant ZZ-1 with a dosage of 5%–6% can better restore the performance of aged asphalt.
Study on Performance of High Performance Magnesium Phosphate Cement Repair Materials
Liu Tao and Li Chunwei
Date posted: 6-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.03.034
In recent years, the sound development of China’s high-speed railways is stable. The high-performance concrete applied will inevitably have many damage problems in the future service process. The search for the application of new high-performance repair materials in high-speed railways has become increasingly important. This paper conducted research on the adhesion, strength, and durability of high-performance magnesium phosphate cement repair materials, and the relevant conclusions are as follows: ① The optimal alkali-acid ratio of high-performance magnesium phosphate cement repair materials is 4:1; ② The optimal dosage of composite retarder for high-performance magnesium phosphate cement repair material is 8%. The comprehensive macro and micro conclusions show that under the action of the optimal acid-base ratio and the optimal composite retarder, the crystal phase arrangement of the microscopic morphology tends to be dense, and its adhesion, strength, and durability are the best.
Study on Fatigue Prediction Model of Asphalt Mixture with High RAP Content
Sun Liangyu, Wang Meng, Zhang Xilun, Tian Pengtao, Ma Qingwei, and Guo Ping
Date posted: 6-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.03.035
The application of pavement thermal recycling technology can reduce energy consumption, thereby improving resource utilization efficiency and bringing positive impacts to society and the economy. In order to study the influencing factors and laws of the fatigue life of recycled asphalt mixtures, this paper fitted the failure life characteristics of fatigue and the relationship between fatigue life and stress ratio of asphalt mixtures with high RAP content under different stress ratios, RAP dosages, temperatures, and loading frequencies respectively. The results show that when the RAP content, stress ratio, and test temperature increase, the fatigue life of the recycled asphalt mixture decreases. The fatigue life and stress ratio are approximately in a logarithmic relationship. By taking the RAP content, stress ratio, loading frequency, and test temperature as fatigue parameters, a fatigue prediction model of the mixture was established.
Research on New High Strength Asphalt and Mixture Road Performance and Engineering Demonstration Application
Chen Qilong, Tan Feng, Jin Weihua, and Tang Shuangmei
Date posted: 6-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.03.036
A new type of high-strength asphalt was prepared by adding high-strength modifiers and self-developed anti-rutting agents to 70# Esso heavy-duty matrix asphalt. The SHRP test and the road performance of the mixture were studied. The results show that after adding high-strength modifiers and self-developed anti-rutting agents, the anti-rutting factor and Brookfield viscosity of the new high-strength asphalt binder have been significantly improved compared with SBS modified asphalt and 70# Esso heavy-duty matrix asphalt. The PG grade of the high-strength asphalt has been raised from PG 64-22 of 70# Esso heavy-duty matrix asphalt to PG82-22, an increase of four grades. In terms of road performance, compared with SBS modified asphalt mixture, the stability of the new high-strength asphalt mixture has increased by nearly 13%; the freeze-thaw splitting ratio has increased by 2.5%, and the dynamic stability has been significantly improved. Combined with the actual engineering application, random inspections are conducted on the mixture of the demonstration section. The gradation of the mixture, the water seepage coefficient, and other indicators of the demonstration section all meet the design requirements. For high-frequency and heavy-load sections in the hot and humid regions of the south, the new type of high-strength asphalt with excellent high-temperature resistance and water damage resistance has a broader application prospect.
Experimental Study on Performance of Composite Modified Marking Material with Nitrile Rubber
Yang Sanqiang, Li Pengfei, Sun Shuang, Yan Hongxia, and Peng Xingzhi
Date posted: 6-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.03.037
Road marking coating is one of the essential materials to realize the modernization of highway traffic. Based on the scientific research project of “research on environmentally friendly hot melt marking material mixed with powder nitrile rubber”, combined with laboratory tests and grey relational theory, nitrile rubber was used as a toughening and cracking agent, and castor oil was used as a plasticizer. By adjusting the proportion of other raw materials, the influence of each component on the fluidity and compressive strength of the material was analyzed. The results show that the fluidity of the material decreases with the increase in the contents of film-forming substance A, castor oil, and PE wax and increases with the increase in nitrile rubber. The compressive strength decreases with the increase in the content of film-forming substance A, quartz sand, nitrile rubber, PE wax, and castor oil, and the weight of PE wax on the compressive strength is the largest (17.3%). Adding 1% of nitrile rubber can significantly improve the crack resistance of the coating, and the test obtains the best formula as follows: film-forming material A of 13%, heavy calcium of 27%, quartz sand of 28%, PE wax of 2%, castor oil of 2%, nitrile rubber of 1%, pigment of 6%, and reflective material E of 21%. The research results can provide technical support for improving the crack resistance of hot melt marking coatings and promoting the modernization of China’s traffic roads.
Research on effect of "activation" process on the performance of buton rock asphalt-modified asphalt based on atomic force microscope
Li Yafei, Fang Xiaokun, and Gui Qitao
Date posted: 6-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.03.038
In the process of modifying asphalt with Budun rock asphalt, in order to improve the utilization rate of Budun rock asphalt and enhance the performance of modified asphalt, this paper proposed the “activation” treatment of Budun rock asphalt, that is, the process of grinding and heating rock asphalt to make natural asphalt precipitate. Laboratory tests have found that compared with the modified asphalt without the “activation” treatment, the rock asphalt-modified asphalt after “activation” has a decreased penetration, an increased softening point, and improved ductility at 5 °C and kinematic viscosity at 135 °C. Moreover, the trend becomes more and more obvious with the increase in the dosage. When the content of Budun rock asphalt after “activation” is over 30%, the performance of the modified asphalt can reach the level of polymer modified asphalt. In order to further clarify the influence of the “activation” process on the performance of rock asphalt-modified asphalt at the microscopic level, atomic force microscopy is used for microscopic performance tests. The results show that the DMT modulus of rock asphalt-modified asphalt after “activation” is approximately 2.5 times that of the matrix asphalt, indicating that the viscosity of rock asphalt-modified asphalt after “activation” has significantly increased, and the modification effect is remarkable.
Study on Rheological Properties and Modification Mechanism of Crumb Rubber/Natural Asphalt Composite Modified Asphalt
Ye Changjian, Lu Shaoyi, Huang Qiushan, Li Heng, and Ye Qunshan
Date posted: 6-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.03.039
To improve the performance of asphalt pavement, this paper prepared waste rubber powder/lake asphalt composite modified asphalt and waste rubber powder/rock asphalt composite modified asphalt, respectively, the high-temperature and low-temperature rheological properties of the composite modified asphalt were studied by dynamic shear rheometer and bending beam rheology test, and the modification mechanism of the composite modified asphalt was analyzed in combination with the infrared spectroscopy test method. The research results show that compared with matrix asphalt, the complex modulus of the two composite modified asphalts, namely rubber powder/lake asphalt and rubber powder/rock asphalt at 62 °C has increased by 423.0% and 562.6%, respectively. Meanwhile, waste rubber powder can reduce or even eliminate the adverse effects of natural asphalt on low-temperature performance. By taking the composite modified asphalt of rubber powder/lake asphalt as an example, under the test conditions of −12, −18, and −24 °C, the creep stiffness is reduced by 35%, 43%, and 36%, respectively compared with the matrix asphalt. Among the two types of composite modified asphalts, waste rubber powder and natural asphalt mainly play a physical filling role.
Analysis on the Influence of Different Factors on the High Temperature Performance of Composite Rubber Asphalt
Ma Qingwei, Guo Zhongyin, Li Wenbo, Guo Ping, and Wang Guanghui
Date posted: 6-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.03.040
SBS modifiers can effectively improve the high-temperature performance of rubber asphalt and its mixtures. By taking the softening point and viscosity as the indicators characterizing the high-temperature performance of asphalt, various processes were designed to prepare composite rubber asphalt (CR/SBS). Finally, the optimal preparation process of composite rubber asphalt was selected based on the high-temperature performance. On this basis, the contents of CR and SBS and the mesh size of rubber powder of composite rubber asphalt were determined through orthogonal experiments. The influence of the number of heating times on the performance of composite rubber asphalt was explored. The results show that the optimal preparation process of composite rubber asphalt is as follows: the rubber powder and SBS are added to the asphalt simultaneously and stirred until a uniform solution is formed. The solution is then sheared at 180 °C for 30 minutes, then stirred for another 30 minutes, and finally swell in an oven for 30 minutes. The optimal material composition of CR/SBS is 17% rubber powder, 2% SBS, and 40-mesh rubber powder. After multiple heating, the high-temperature performance of the three types of asphalt all decline to a certain extent, but the decline is not obvious. The softening point difference of CR/SBS is greater than 10 °C, and the stability is poor. The stability of the other two types of asphalt is relatively good. Through microscopic observation, after multiple heats, the SBS modifier and adhesive powder in CR/SBS change from an aggregated state to a dispersed state and accumulate at the bottom.
Experimental Study on Bearing Ratio of Steel Slag Clay Based on Orthogonal Design
Guo Ou, Zhang Hongri, Lan Tianzhu, and Li Xiaoming
Date posted: 6-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.03.041
To study the load-bearing ratio characteristics of steel slag clay, the steel slag from the aged converter of a certain steel plant in Fangchenggang and the clay from a certain first-class highway construction site were used as raw materials, and the engineering characteristics of steel slag and clay were considered comprehensively. By taking the relative incorporation amount of steel slag, aging time, and particle size of steel slag as factors, the orthogonal CBR test was conducted. Research shows that the most significant factor influencing the CBR value of clay mixed with steel slag from an aged converter is the relative addition amount of steel slag, followed by the particle size of steel slag, and then the aging time of steel slag. The influence of water immersion under different factors on the CBR value of clay mixed with steel slag from the aged converter is studied. The relative addition ratio of steel slag has a significant impact on the ratio of CBR values before and after water immersion of steel slag clay. However, the aging time of steel slag and the maximum particle size of steel slag have a relatively small influence on it.
Research on Aging Resistance of Nano TiO2/MMT Composite Modified Asphalt
Liu Yi and Zou Guihua
Date posted: 6-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.03.042
Asphalt is prone to aging during use, resulting in the reduced service life of asphalt pavement. To address this problem, nano-titanium dioxide (TiO2) and montmorillonite (MMT) were adopted to modify the anti-aging performance of asphalt. The relationship between the dosage of the modifier and the performance of the modified asphalt was analyzed by Matlab software, thereby determining the optimal dosage of the modifier. The influence of the modifier on the anti-aging performance of the modified asphalt was analyzed by using the high-temperature dynamic shear rheometer (DSR) and low-temperature bending beam rheology (BBR) tests. Finally, scanning electron microscope (SEM) and gel permeation chromatography (GPC) tests revealed the interaction and modification mechanism of the modifiers. The results show that the optimal dosages of nano-TiO2 and MMT modifiers are 2% and 4%, respectively. The synergistic effect of nano-TiO2 and MMT can significantly improve the anti-aging performance of asphalt. Through microscopic experimental analysis, it can be known that nano-TiO2 promotes the adsorption and fusion of MMT in asphalt due to its nano-effect. At the same time, because nano-TiO2 is dispersed in the intercalation structure of MMT, it is difficult for it to agglomerate. The more uniform dispersion makes its modification effect better. The better anti-aging performance of nano-TiO2/MMT composite modified asphalt is also verified by analyzing the molecular weight.
Effect of Nano-Metakaolin on Durability Performance of Concrete
Peng Chong
Date posted: 6-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.03.043
By incorporating nano-metakaolin under different substitution amounts into concrete, the effects on the mechanical strength, fracture characteristics, carbonation performance, fatigue performance, and other durability properties of concrete after corrosion were studied, and the following conclusions were obtained: Nano-metakaolin can significantly enhance the resistance of concrete to acid rain corrosion, reduce the rate and loss rate of mechanical strength loss, as well as the loss rate of fracture toughness and fracture energy. After 80 corrosion cycles, the loss rate of compressive strength of the modified concrete is reduced by approximately 15% compared to the reference group. The loss rate of flexural tensile strength can be reduced by more than 10%, and both the loss rate of fracture toughness and the loss rate of fracture energy are reduced by more than 30% compared with the reference group. Meanwhile, nano-metakaolin can enhance the carbonation resistance of concrete. Within the 28-day age, nano-metakaolin can significantly reduce the carbonation depth of concrete and increase the carbonation grade of concrete by one level. All six dosages of nano-metakaolin can reduce the carbonation depth of concrete by more than 20% at the 28-day age. The addition of nano-metakaolin can also significantly improve the fatigue life of concrete. Under stress levels of 0.5, 0.65, and 0.8, nano-metakaolin with dosages of 7% and 8% can increase the fatigue life of concrete by more than one time.
Study on Technology of Toughening and Toughening of Epoxy Resin Asphalt Mixture with Polyester Fiber
Gu Xiaoyan, Gao Jianfei, and Li Huixiang
Date posted: 6-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.03.044
In order to solve the problem that the deformation of epoxy asphalt concrete with steel bridge deck is inconsistent with that of the bridge deck, which leads to the early crack of epoxy asphalt concrete, the improvement effect of polyester fiber on the flexibility and toughness of epoxy asphalt concrete was evaluated by adding polyester fiber to epoxy asphalt concrete via using low temperature bending test and fatigue test method. The results show that polyester fiber exists in the asphalt by adsorption with the light components of asphalt, reinforcement inside the three-dimensional network, limiting, etc. At the same time, it cooperates with the craze matter generated by the asphalt to lock the forward expansion of the tip of the craze matter and the increase in the width of the craze matter. When the polyester fiber is added at the optimal content of 0.3%, Epoxy asphalt concrete has the optimal low temperature deformation capacity and fatigue resistance, and the flexibility and toughness of the mixture are optimal at this time.
Study on Solid Content Measurement of Liquid Accelerator Based on Refractometer Method
Feng YueE and Wei Yongfeng
Date posted: 6-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.03.045
In order to solve the problems of long time and poor accuracy in the determination of the solid content of accelerant, this paper proposed to use refractometer concentration testing technology to quickly determine the solid content of liquid accelerant. In addition, in order to study the accuracy of the determination method, accelerator samples with standard solid content, different solid contents, and different types were tested by the drying and weighing method and refractometer method, respectively. The results show that: ① for accelerator of the same standard, the discreteness of the test results by refractometer method is smaller, and the data is more stable. There is a better correlation with standard solid content; ② For the liquid accelerator with different solid contents, the correlation between the test results of the refractometer and standard solid content is better than that of the drying and weighing method, which can more accurately reflect the real solid content of liquid accelerator; ③ For the liquid accelerant with different solid contents, the test results of drying and weighing method and refractometer method have good linear correlation; ④ The refractometer method has good adaptability to the determination of solid content of different types/types of the accelerator, and the relative deviation between the modified results and the drying and weighing method is less than 0.8%.
Traffic Engineering and Management
Research on a New Type of Prefabricated Bridge Human-Vehicle Isolation Anti-Collision Guardrail
Zhou Jingyu, Tang Junyi, and Huang Jingyun
Date posted: 6-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.03.046
In recent years, out-of-control motor vehicles often climb the sidewalk steps, break the fence, and fall off the bridge, which has brought a series of heavy losses to people’s lives and property safety. Therefore, it is urgent to take feasible measures to improve the protective performance of bridge collision guardrails, so as to effectively control the risk of such accidents and reduce their consequences. On the basis of summarizing the application characteristics and shortcomings of existing anti-collision measures for bridges, this paper proposed a new type of prefabricated anti-collision guardrail for bridges to achieve separation of pedestrians and vehicles. The guardrail is mainly composed of the main body and the anchor seat. The vertical resistance steel plate and the horizontal resistance steel plate were respectively set up before the anchor seat and the bottom plate and connected with bolts. According to the characteristics and force of the guardrails, the concept analysis of the force transmission path was carried out first. Then, the standard collision load was selected according to the relevant design specifications, and the refined finite element method was used to compare the new type of guardrail with the traditional guardrail, and the detailed mechanical behavior of the whole and each component was considered comprehensively. On this basis, according to the standard collision load, the failure load and failure mode of the above two types of guardrails in the limit state were further analyzed. The results show that the new guardrail proposed in this paper meets the requirements of the code, and compared with the traditional guardrail, its anti-collision performance is obviously improved.
Discussion on Design Idea of Superhighway Cross-Section Composite Interchange
Zhang Jin and Pan Dan
Date posted: 6-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.03.047
Combined with the example of the Baoxia Hub interworking project design of Yunxi–Baoxia Section of Shiyan via Zhenping–Wuxi Expressway in the mountainous hilly area of western Hubei, this paper introduced the main forms of composite interworking design under the condition of the dislocated intersection of mountainous expressways, discussed the applicable conditions and characteristics of each scheme, and analyzed the advantages and disadvantages of each scheme. The results show that by choosing a reasonable composite interworking form, the normal traffic flow of the intersecting expressway is guaranteed, and the straight heading capacity of the main line under the condition of a dislocated intersection is guaranteed. In addition, the safe and efficient mutual conversion of the traffic flow between the expressways is achieved.
Research on Modern Roundabout Applications in China
Zhang Yuan, Liu Hongqi, and Chao Sui
Date posted: 6-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.03.048
The modern roundabout is different from the traditional roundabout or traffic ring. Because of its excellent performance in traffic safety, modern roundabouts have been widely used in Europe and the United States. In China, the modern roundabout is still in the stage of concept discussion, lacking practical application and applicability verification. Based on this, this paper built the first modern roundabout in China according to the concept of a modern roundabout and related technical requirements. According to the field observation data, the applicability of the modern roundabout island was evaluated from the perspectives of vehicle speed, loop behavior, truck buffer zone use, and non-motor vehicle adaptability, and the project was improved based on the evaluation results. The research results can provide a reference for the popularization and application of modern roundabouts in China.
Research on Crash Test Conditions and Standards of Isolation Guardrail
Li Chuangmin, Wang Kai, Gan Xinzhong, and Liu Qunyan
Date posted: 6-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.03.049
Due to the temporary nature of maintenance operations, the traditional permanent guardrail can not play a role. Therefore, the isolation guardrail is widely used in highway maintenance operations. However, China has not provided safety evaluation criteria for isolation guardrails, leading to a stagnation in research on them. Based on the analysis of the practical application of the isolation guardrail in China’s road maintenance operation, this paper referred to the Manual for Assessing Safety Hardware (MASH) given by the American Association of State Highway and Transportation Officials (AASHTO). Starting from factors such as the vehicle type used in the crash test, the total mass of the vehicle, the collision speed, the collision angle, and the length of the test and combining the frequent characteristics of traffic accidents and the safety index of the vehicle passengers, the safety evaluation specification of the isolation guardrails under the crash condition was proposed.
Research on Development of German Road Engineering Standards and Application Management
Fu Yu and Zhang Mouyue
Date posted: 6-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.03.050
The Federal Ministry of Transport leads the formulation and application of highway engineering standards and relies on the Federal Highway Research Institute (BASt), Highway Society (FGSV), and other research institutions to develop and improve highway engineering design standards and specifications. This paper focused on the status and role of the federal government of Germany and other bodies in the standard management system and expounded the main content, application, and characteristics of the most important highway standards in Germany, so as to provide reference experience for China to promote the understanding and management application of highway standards.
Review on Updated "Design Manual for Roads and Bridges" in the United Kingdom
Zhou Zijun
Date posted: 6-18-2022
DOI: https://doi.org/10.14048/j.issn.1671-2579.2022.03.051
In order to timely understand and master the latest developments of the newly published Design Manual for Roads and Bridges in the UK and provide an international reference for Chinese designers, consultants, managers, and practitioners of road engineering standardization in the industry involved in international projects, this paper adopted the literature research method and comparative analysis method. According to the main links of China’s highway standard system/revision, this paper systematically summarized the reasons, objectives, main changes, and highlights of the redesign of the Design Manual for Roads and Bridges in the UK, among which, it is worth referring to the practices of authorities for British highway standards to strengthen the digital application of standards, strengthen the implementation of standards, and integrate the concept of sustainable development into the design standard system to promote the management and application of standards.
