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2024 Vol. 41, No. 7
Published: 2024-07-15
Urban Rail Construction
Terminal,Station yard and Building
Information Technology
Engineering Materials
Main Line:Engineering Geology and Subgrade
Main Line:Bridge Engineering
Main Line:Tunnel Engineering
Risk Management and Research
Main Line:Railway and Track
 
       Main Line:Engineering Geology and Subgrade
1 Analysis of Uplift Bearing Capacity of Inclined Anchor Plate in Soil Slope
WANG Hongtao, XU Yongshuai, MEN Yanqing, LIU Hao, GAO Guanglong
Research purposes: A reasonable estimation of anchor plate's pulling capacity is an important guarantee to maintain the stability of anchor plate foundation. This paper focused on the inclined strip anchor plate buried in the soil slope stratum, constructed an asymmetric pulling failure mechanism of anchor plate under the limit state, and assumed that the soil failure hypothesis follows the nonlinear strength criterion and its non-correlated flow law. Based on the failure mechanism, the analytical expressions of the ultimate pulling capacity of anchor plate and the failure surface equation of soil above the anchor plate were derived by using the upper limit method and variational principle, and the influence of each parameter on the pulling capacity of anchor plate was systematically studied.
Research conclusions:（1）The analytical expressions of the ultimate uplift bearing capacity of the anchor plate and the failure surface equation of the soil above the anchor plate were derived, and the effectiveness of the analysis method was verified by comparison with the existing literature results.（2）The failure range of soil above the inclined anchor plate presents a certain asymmetric feature. As the angle of anchor plate increases, the failure range of soil gradually shifts to the downward slope. Soil failure range is positively correlated with soil dilatancy coefficient and initial cohesion, and negatively correlated with nonlinear coefficient, unit weight and surface load.（3）The embedment depth ratio of anchor plate, embedment angle, surface inclination angle, soil cohesion and dilatancy coefficient have significant effects on the uplift bearing capacity of anchor plate and the uplift failure range of soil, which should be paid attention to in engineering design to realize the optimal layout of anchor plate foundation and the effective use of bearing capacity.
2024 Vol. 41 (7): 1-10 [Abstract] ( 12 ) HTML (1 KB)  PDF  (1394 KB)  ( 0 )
11 Study on the Characteristics of Saturated Subgrade Mud Pumping under Train Load
ZHANG Jiasheng, JIA Yu, DING Yu, WANG Xuan, YAN Hongye, CHEN Xiaobin
Research purposes: The increase of heavy-haul train axle load enhances the dynamic stress at different depths of the subgrade, leading to more and more serious subgrade issues such as mud pumping. In this paper, a series of refined model tests were carried out to study the characteristics of mud pumping of saturated silty clay subgrade under the heavy-haul train load. The influence of cyclic loading amplitude and loading frequency on the axial strain, excess pore water pressure, and fine particles migration characteristics of the sample was analyzed.
Research conclusions: (1) The cyclic loading amplitude has a significant impact on the characteristics of mud pumping from silty clay subgrade. As the cyclic loading amplitude increases, axial strain and excess pore water pressure rise, intensifying mud pumping. (2) The loading frequency has a certain influence on the characteristics of subgrade mud pumping. In general, higher loading frequencies decrease the final axial strain and excess pore water pressure, reducing mud pumping quality post-test. The increased frequency can't accelerate the mud pumping severity, but can shorten the duration of mud pumping. (3) Under cyclic loading, the excess pore water pressure gradient drives the migration of fine particles in the subgrade soil, resulting in mud pumping. (4) The research results can provide a reference for the treatment of the mud pumping issues in the heavy-haul train subgrade.
2024 Vol. 41 (7): 11-17 [Abstract] ( 8 ) HTML (1 KB)  PDF  (1733 KB)  ( 0 )
       Main Line:Railway and Track
18 Rail Surface Defect Detection Based on Improved YOLOv7
CHEN Renxiang, PAN Sheng, YANG Lixia, GAO Xiaopeng, WANG Jianxi
Research purposes: Surface defects of steel rails are important hidden dangers for safe operation of railway traffic, accurate detection of surface defects on steel rails is crucial. The complex environment in which steel rails are in service may cause them to be contaminated with stains, at the same time, the shape of rail defects is often inconsistent. To address the problems of false detection due to stains and difficulty in accurate detection due to different shapes of defects in rail surface defect detection, an improved YOLOv7-based rail surface defect detection method is proposed.
Research conclusions: (1)The problem of false detection of stains was overcome by constructing the dataset with images of rails containing stains as negative samples, with the use of label differences to enable the network to learn features that distinguish between defects and stains. (2)YOLOv7 was improved by deformable convolution with an embedded channel attention mechanism. That was, the deformable convolution replaced the fixed convolution by adding a bias to the convolution sampling points to enhance the network's ability to adapt to the geometric deformation of defects. At the same time, the channel attention mechanism was embedded in the network, and its feature of weighting different channel features made the network focus on the defect features, thus enhancing the defect feature extraction ability. (3) The effectiveness and feasibility of the proposed method was demonstrated by loading the rail surface defect dataset onto the constructed improved YOLOv7 network for end-to-end rail surface defect detection. (4) The research can provide a new method for intelligent detection of rail surface defects.
2024 Vol. 41 (7): 18-24 [Abstract] ( 5 ) HTML (0 KB)  PDF  (2232 KB)  ( 0 )
25 Transient Process of High Voltage Transmission Line Break and Shock on Railway Intersection
SUN Jixing, YANG Jiasheng, WANG Xin, HU Kaixuan, ZHAO Pengfei, MU Qing, CONG Xiancheng
Research purposes: The power lines crossing the railway will break and fall under the action of wind load and ice cover, which will threaten the safety of railway operation. Aiming at this problem, the paper established a flexible wire structure breaking model, obtained the impact transient process of the power line breaking route across the railway, and obtained the law of the influence of the hook point height and cross angle on the impact force and impact stress of the line breaking.
Research conclusions: (1) The impact force of breaking wire increases with the increase of the hanging point. For 35 kV power wire, when the height of the hanging point is 120 m, the impact force amplitude is close to 20 kN. (2) With the increase of the intersection between the power line and the railway line, the collision force is reduced by nearly 50% when the intersection angle is increased from 15° to 90°. (3) Combined with the research method of the paper, the impact force between the 110 kV power line break and the protection structure of the Beijing-Zhangjiakou Railway is 13 kN, and the impact force of the 35 kV power line break and fall is 8.4 kN, and the beam layout of the protection structure is designed based on the data. At the same time, the above results can provide data support for the strength design of power line protection shed hole.
2024 Vol. 41 (7): 25-33 [Abstract] ( 4 ) HTML (0 KB)  PDF  (1838 KB)  ( 0 )
       Main Line:Bridge Engineering
34 Influence of the Marshalling and Operation of Heavy Haul Train on Dynamic Response of Double-track Bridge
XIAO Ye, LUO Xiaoyong, FAN Yakun, LUO Yiyong
Research purposes: In order to study the influence of marshalling and operation of heavy haul train on dynamic response of double-track bridge, selecting a 32 m prestressed concrete double-track simply-supported T-beam on the Shuozhou-Huanghua railway line as the research object, the coupling finite element model of heavy haul train-track-bridge was established, and the accuracy of the finite element model was verified through field tests. The dynamic response of heavy haul trains passing through double-track bridges was studied, and the influence of different marshalling modes and single-track and double-track operation of heavy haul trains on the dynamic response of double-track bridges were analyzed.
Research conclusions:（1）The calculated results are in good agreement with the measured values, indicating the high reliability of the coupled finite element model of heavy haul train-track-bridge. （2）The loaded train marshalling has the greatest impact on the displacement response and dynamic strain of the bridge, and the smallest impact on the acceleration.The acceleration response of empty train marshalling to the bridge is the largest. The mixed marshalling of empty and loaded train takes the second place, and the mixed marshalling of empty vehicles in front of empty vehicles in the rear has a greater impact on the displacement response of empty vehicles, which may cause the derailment of empty vehicles.（3）The dynamic response of the bridge under double-track operation of loaded and empty vehicles increases with the increase of vehicle speed, which is similar to the loaded vehicles. The peak value of vertical dynamic response of the bridge under the double-track split operation is slightly larger than that under the single-track operation, while the peak value of transverse dynamic response of the bridge is smaller than that the single-track operation. （4）When the distance difference between the loaded vehicle and the empty entering the bridge is an integral multiple of the length of the vehicle body, the peak dynamic response of the bridge is basically the same as that when the loaded vehicle and the empty vehicle enter the bridge at the same time. When the distance difference into the bridge is an integral multiple of half the length of the vehicle body, the peak dynamic response of the bridge decreases.（5）The research results can have a reference for the design of new heavy haul railway double-track bridge.
2024 Vol. 41 (7): 34-40 [Abstract] ( 5 ) HTML (0 KB)  PDF  (2688 KB)  ( 1 )
41 Effect of Ballastless Track on Seismic Response of Simply-supported Girder Bridges under Different Terrain
ZHANG Yongliang, LIU Pei, WANG Chunyang, LIU Miao
Research purposes: In order to study the influence of CRTSⅡ slab ballastless track system on the seismic response for the multi-span simply supported girder bridge, integrated track and bridge model and single pier model were established respectively for the 32 m simply supported girder bridge. The influence of track longitudinal constraint effect on seismic response of piers under three typical terrain conditions is studied by response spectrum method.
Research conclusions:(1) When crossing flat terrain, under the influence of track system and end spikes, internal forces at the bottom of pier in the integrated track model show a parabolic distribution with small magnitude at boundary span and large magnitude at middle span. Compared with the single pier model, the piers in the middle span region are located in the seismic response amplification zone. (2) When crossing the V-shaped terrain, internal forces at the bottom of each pier in this area present the U-shaped distribution characteristics of significantly increasing internal forces at the bottom of critical pier and significantly decreasing internal forces at the bottom of middle-span tall pier. (3) When crossing the Λ-shaped terrain, internal forces at the bottom of piers in the region show the Λ-shaped distribution characteristic, with the middle span low pier as the center, and internal forces at the bottom of its piers increase significantly while those at the bottom of adjacent piers decrease significantly. Therefore, the middle span low pier should be paid more attention in the seismic design. (4) The research conclusions could be applied to the seismic design of high-speed railway simply supported girder bridge with similar to typical terrain conditions.
2024 Vol. 41 (7): 41-46 [Abstract] ( 4 ) HTML (0 KB)  PDF  (1021 KB)  ( 0 )
       Main Line:Tunnel Engineering
47 Stress Response Analysis of Orthotropic Steel Bridge Deck under Moving Load
TIAN Liang, XING Shouhang, FAN Lilong, ZHAO Xuemin, ZHANG Chengzhi, SI Zhiyuan
Research purposes: The orthotropic decks are increasingly used in steel bridges, but these structures are prone to fatigue cracking under cyclic vehicle loads. It is necessary to accurately evaluate the stress response of the bridge deck under moving load, which is the basis for the subsequent fatigue analysis. A multi-scale FE model of continuous three span orthotropic bridge deck is established, which combines the solid element with the shell element. Fortran language is used to compile the sub-program Dload to apply moving load, and the dynamic stress response process of bridge deck is comprehensively analyzed under different loading conditions. Therefore, the stress condition of typical structural details is clarified, which provides a scientific basis for the fatigue performance evaluation and improvement of orthotropic bridge decks.
Research conclusions:(1) The most unfavorable loading position of steel bridge deck is when the loading center line is close to the U-rib-to-deck connection weld or just above the U-rib opening. (2) For U-rib-to-deck weld joints, the stress response state can be well reflected by single wheel loading analysis, while for U-rib-floor beam weld joints and arc opening of floor beam, the stress effect caused by double wheel loading cannot be ignored. (3) Under different loading conditions, the arc opening area is always in a high stress state, which is the most unfavorable stress bearing part of the steel bridge deck and easy to cause fatigue damage. (4) The research results can be used to evaluate the stress state of steel bridge deck structures under vehicle moving loads.
2024 Vol. 41 (7): 47-55 [Abstract] ( 5 ) HTML (0 KB)  PDF  (3264 KB)  ( 0 )
56 Reason for Cracks of Double-arch Tunnel without Middle Drift and Analysis of Mechanical Characteristic
YUAN Song, WANG Feng, PAN Yingdong, ZHANG Sheng, HUANG Fan, LI Hang
Research purposes: To reveal the reason for invert lining cracking in double-arch tunnels adopting the construction technology without middle drift, this paper first obtained the force patterns of the first tunnel by field monitoring. Based on the mechanism characteristics, this study put forward a load-structure calculation model for the first tunnel considering the excavation of the second tunnel. The results of numerical simulations combined with field monitoring were utilized to analyze the causes of the invert lining cracking. Finally, the safety of the secondary lining was evaluated and the corresponding control measures were suggested.
Research conclusions: (1) Before the excavation of the second tunnel, the secondary lining of the first tunnel is in a symmetrical stress state and the safety factor of each section is greater than 2.4. After the excavation of the second tunnel, the first tunnel is under an unsymmetrical stress state, and the safety factor of the right side of invert is only 1.25. The inner surface of the right side of invert is exactly where the maximum tensile stress is located, which is consistent with the actual position of observed cracking. (2) The cracks of invert lining in the first tunnel is caused by uneven settlement and unsymmetrical pressure due to the excavation of the second tunnel. (3) Enhancing the support resistance factor could improve the safety of the lining structure, but the safety factor has little change when the support resistance factor is higher than a certain value. (4) The research results can provide guidance for the design and construction of similar double-arch tunnels.
2024 Vol. 41 (7): 56-62 [Abstract] ( 4 ) HTML (0 KB)  PDF  (2504 KB)  ( 0 )
63 Research on the Calculation Method for Deformation Pressure of TBM Tunnel in Squeezing Ground
LI Zhijun, WANG Mingnian, WANG Zhilong, YU Li, JIANG Zhiyi, ZHANG Xiao, SHANGGUAN Yuwen
Research purposes: At present, research on double shield TBM is mainly focused on equipment selection and construction technology under squeezing geological conditions both domestically and internationally. However, there is relatively little research on the design of pipe segment structures. In order to make up for the lack of research in this area, based on the temporal and spatial effects of TBM tunnel construction, the focus was on the calculation method of deformation pressure of double shield TBM tunnel segments in squeezing ground.
Research conclusions: (1) By using a genetic creep model, the temporal effects of surrounding rock deformation were simulated and integrated into the longitudinal deformation curve of the tunnel, thus forming a method for calculating the longitudinal deformation curve of the tunnel that takes into account the temporal and spatial effects. In addition, the advanced deformation in the first stage was also considered and a formula for the characteristic curve of surrounding rock was constructed based on the equivalent excavation diameter. (2) Using the elastic theory of thick walled cylinders, a stiffness calculation formula for pipe segment gravel composite support was derived, and an expression for calculating the critical elastic modulus was established. (3) Based on the principle of convergence constraint analysis, the formulas for the combined support force and displacement were derived, further forming a calculation method for the deformation pressure of pipe segments. Finally, the accuracy of the deformation pressure calculation method was verified through practical engineering cases. (4) The research result can be applied to the design of TBM tunnel segment structure in squeezing ground.
2024 Vol. 41 (7): 63-68 [Abstract] ( 9 ) HTML (0 KB)  PDF  (541 KB)  ( 0 )
       Terminal,Station yard and Building
69 Seismic Performance of Prefabricated Platform Canopy with Mortise-tenon Connection
CHANG Yuzheng, KUANG Jiuyi
Research purposes: In order to improve the construction speed, reduce the cost, and promote the development and application of assembly technology in the construction of railway facilities, a prefabricated platform canopy structure system based on " mortise and tenon " joints was proposed, and the seismic performance of the assembled " Y " -shaped single-column platform canopy structure connected by " mortise and tenon " was studied. A single-layer single-span two-bay roof panel assembled platform canopy specimen was designed and fabricated. The failure mode, hysteretic characteristics, bearing capacity, ductility and energy dissipation capacity were analyzed by low-cycle repeated loading test, and the finite element software ABAQUS was used to analyze the parameters of the specimen.
Research conclusions:(1) The hysteresis curve of the specimen exhibits pinching effect with shear slip characteristics. (2)The ultimate story drift ratio is 1/17, and the displacement ductility coefficient exceeds 4.5, indicating good deformation ability and ductility. (3)Plastic hinges appear sequentially at the end of the flat beam and the footing of the prefabricated column, the damage mode shows a "beam hinge" mechanism.(4) The parameters analysis indicates as the longitudinal rebar ratio increased,the seismic performance including the initial stiffness, ultimate bearing capacity, and ductility was increased. As the linear stiffness ratio of the flat beam and column increased, the initial structural stiffness and ultimate bearing capacity increased, but the ductility of the structure decreased, the same applied to the height of the plate.(5) The research results can provide the basis for the application and engineering design of the assembled platform canopy in the construction of railway facilities.
2024 Vol. 41 (7): 69-74 [Abstract] ( 5 ) HTML (0 KB)  PDF  (1150 KB)  ( 0 )
75 Analysis of Wind Pressure on the Surface of the Elevated Station Building when the High-speed Train Passes through the Station
CAI Chenzhi, AI Yuyan, ZHOU Zhihui, HE Xuhui, ZOU Yunfeng, ZHANG Yong, ZHOU De
Research purposes: Due to the lighter and more flexible development in the long-span elevated high-speed railway station, it shows more sensitive to the wind pressure changes of the station structure surface generated by aerodynamic force of high-speed trains. In order to explore the wind pressure characteristics of the floor surface when the high-speed trains pass through the long-span elevated station structure, the Fluent dynamic grid and CFD numerical simulation technology was used to analyze the wind pressure characteristics of long-span elevated station's floor surface with the high-speed train running at 350 km per hour in the form of single and double tracks. Both the time-history characteristics and spatial distribution characteristics of the wind pressure on the floor surface were studied.
Research conclusions: (1)The superimposed effect of the train wind on the floor surface has a significant effect on the wind pressure amplitude of the floor surface when the double-track train runs in mid-span intersection compared with the single-track high-speed train. (2)Compared with the single-track running condition, the positive and negative wind pressure extreme values of the head wave at each measuring point in the mid-span area increased to a greater extent, and the minimum increases of the positive and negative wind pressure extreme values of the measuring point were 62.30% and 64.36%. (3)The research results can provide a reference for further optimization of wind resistance design of long-span station structures.
2024 Vol. 41 (7): 75-81 [Abstract] ( 5 ) HTML (0 KB)  PDF  (1051 KB)  ( 0 )
       Information Technology
82 Intelligent Tamping Technology for Railway Ballasted Track Based on Inertial Navigation Data
XU Hong, WEN Zhu
Research purposes: With the continuous development of railway construction, the speed of China's ballasted railways is also constantly increasing. Currently, ballasted railways with a speed of 200 km/h and above have accounted for a considerable proportion in railway construction. Correspondingly, in the Construction Quality Acceptance Standards for High Speed Railway Track Engineering (TB 10754-2010) released in 2010, the process of track precision adjustment and sorting was added based on the characteristics of high-speed ballasted railways. This process was adopted in the subsequent 2018 version. At present, due to different interpretations of technical specifications by various construction units, their practices in track precision adjustment and sorting operations vary greatly, and the results also differ greatly. The intelligent compaction technology for railway ballasted tracks based on inertial navigation data aims to use the CPⅢ track control network as a basis, and use the inertial vehicle measurement system for measurement and data analysis, providing timely and effective data support for the precise adjustment operation of large machinery maintenance equipment. By upgrading and renovating the GVA control system of the 08-32 tamping truck, it is possible to import track measurement data in bulk, avoiding errors and misoperations when manually entering data, and improving the quality and efficiency of precision tuning operations. Through the application of the advanced technologies mentioned above, a complete set of precision adjustment process methods suitable for high-speed railway ballasted tracks has been summarized, enabling the newly built ballasted tracks to quickly achieve high smoothness and stability, ensuring construction quality, reducing the number of on-site precision adjustment operations and disturbance to fasteners, improving construction efficiency, and ensuring construction safety.
Research conclusions: (1) Based on the inertial navigation vehicle measurement system and the independently upgraded 08-32 compaction vehicle, a complete set of technology for precise adjustment and sorting of ballasted tracks has been developed, which has high precision, advanced technology, safety and reliability, and significant work efficiency.(2) The application of inertial navigation vehicle measurement system for measuring and data analysis of ballast track precision adjustment construction has high measurement efficiency and accuracy, which can provide timely and effective data support for the precision adjustment operation of large machinery maintenance equipment.(3) The upgraded and renovated 08-32 tamping truck with GVA control system has improved the level of automation, increased operational efficiency, expanded the scope of adaptation, and achieved high operational accuracy.(4) This technology can be widely applied to the precise adjustment of railway ballasted tracks with a speed of 200 km/h or above, achieving rapid compliance of the geometric dimensions of ballasted tracks.
2024 Vol. 41 (7): 82-86 [Abstract] ( 5 ) HTML (0 KB)  PDF  (1529 KB)  ( 0 )
87 The Operating Principle and Equilibrium Optimization Algorithm of a New Type of Green Digital Intelligent Passenger Station
SHI Tianyun, SHEN Haiyan, LU Yulong, YANG Guoyuan, LI Jun, LI Chao, YANG Lingling, DUAN Jiaying, YAO Jian
Research purposes: Railway passenger stations are high-density large public places and energy consuming large households. In order to implement the national "dual carbon" strategy, focusing on passenger stations is an important breakthrough point for the green transformation of railways. At present, passenger stations prioritize "energy conservation" over "clean energy", and weaken "empowerment". The development of "digitalization, greening, and low-carbon" is each focused on, which restricts the pace of green transformation. The new theory and method of "new green digital intelligent passenger stations" proposed in this article fills the industry gap, to break through the evolution of " Three modernizations and Three energies" from "clear differentiation" to "integrated symbiosis", and promote the green and high-quality development of stations, providing guidance, reference, and demonstration.
Research conclusions: (1) The characteristic model and transformation path of "Three Modernizations and Three Energies" provide new ideas for strengthening the supply of digital intelligence empowerment technology. (2) The operational principles of "Three Modernizations Collaboration, Digital Intelligence Empowerment, Green Traction, and Low Carbon Drive" and the theory of "Three Elements" synergy provide new methods for the transformation of green stations. (3) The BMCEO comprehensive balance optimization control algorithm proposed has been validated to improve efficiency by 20%~40% compared to traditional single factor optimization, providing a technical means to solve the problem of efficient operation of station balance under multi-objective constraints and dynamic uncertain complex influencing factors.
2024 Vol. 41 (7): 87-92 [Abstract] ( 3 ) HTML (0 KB)  PDF  (897 KB)  ( 0 )
       Urban Rail Construction
93 The Technology of Block Stone Detection and Treatment for Shield Tunnel in Complex Site
YE Xiangqian, CEN Yangrun, CAI Hairong, WANG Linjun, LIN Rong
Research purposes: The presence of boulder clusters in the overburden layer has a significant impact on shield tunneling construction for subway sections. Conventional drilling or geophysical exploration methods are not very effective in investigating boulder clusters, and selecting appropriate exploration methods and clearance techniques is a major challenge for similar projects. Based on the section from Wushan Square Station - Jiangcheng Road Station of Hangzhou Metro Line 7, this paper systematically introduced the comprehensive exploration technology of block stones in the overburden under complex site conditions, and analyzed the related technologies of block stone removal for subway shield tunnels based on advanced grouting reinforcement and blasting pretreatment.
Research conclusions:（1）Under the condition of a large number of existing surface buildings, it is necessary to combine drilling with geophysical prospecting for the detection of block stone.（2）Microtremor detection has a distinct advantage in detecting boulders in overburden layers. （3）The blasting pretreatment shall be adopted in the site with conditions, and the advanced grouting reinforcement pretreatment shall be adopted in case of encountering block stones in the absence of blasting site conditions. After the shield tunneling, the soil around the segment shall be reinforced by long pipe grouting. If necessary, the warehouse should de cleaned under pressure. （4）The research results can provide reference for the investigation, design and construction of shield tunnel engineering under similar complex site conditions.
2024 Vol. 41 (7): 93-98 [Abstract] ( 2 ) HTML (0 KB)  PDF  (1922 KB)  ( 0 )
99 Research on the Seismic Behavior of Strut-waling-diaphragm Wall Joint
MAI Jiaer, LU Xiaozhi, HE Guanhong, PEI Xingkai
Research purposes: Prefabricated construction technology has advantages such as low material consumption and high production efficiency. In China, prefabricated construction technology has gradually been applied to the construction of metro stations. To adapt to the common internal support and protection system in Guangzhou, Guangzhou Metro has proposed a new form of prefabricated metro station. The temporary support structure of this metro station will serve as a permanent structure of the station, adopting a "two-in-one wall" design. Therefore, this project places high demands on the connection accuracy and mechanical performance of the strut-waling-diaphragm joint. Based on this project, low-cycle loading tests were conducted on the full-scale joints to explore the applicability and safety of two connection schemes: steel plate and mechanical coupler connection used in this project. The seismic performance differences between the two full-scale joints were also compared.
Research conclusions: (1) The test results showed that both types of connection methods can meet the seismic performance requirements for the design of prefabricated metro station structures. (2) The failure locations of both joints were at the interface between the waling beam and the strut. During the design phase, the connection strength at this location should be reinforced. (3) Compared to the coupler-connected joint, the steel plate-connected joint behaved with less strength degradation, higher stiffness, better ductility, and superior seismic performance. Therefore, steel plate connection joints should be prioritized as the preferred connection method for this type of prefabricated metro station. (4) The research results can provide reference for seismic design of prefabricated metro station nodes.
2024 Vol. 41 (7): 99-105 [Abstract] ( 3 ) HTML (0 KB)  PDF  (2634 KB)  ( 0 )
       Engineering Materials
106 Effect of Cement on the Mechanical and Crack Resistance of Railway Bridge Pier Concrete
LI Shuming, DENG Qingshan, XIE Yongjiang, LIU Jing, ZHANG Chi, YU Peiyun
Research purposes: Portland cement was the main cementitious material for railway concrete. In order to study the performance of anti-cracking cement and improve the anti-cracking performance of plateau railway bridge pier concrete from the perspective of cement, the differences between anti-cracking cement and general silica cement in working performance, hydration performance, mechanical properties, drying shrinkage properties and anti-cracking properties were systematically compared, and a comparative test was carried out in the solid pier. Through the study of the internal temperature and strain change law of pier concrete, the effect of cement on crack resistance of the plateau bridge pier concrete is evaluated comprehensively.
Research conclusions: (1) Compared with general silica cement, the water requirement of crack resistant cement is lower, the hydration rate slows down and the hydration heat decreases in the early stage, the hydration activity decreases in the early stage, and the strength decreases slightly in the early stage, but the strength develops stably and exceeds that of general silica cement in the late stage. The bending ratio of crack resistant cement at the same age is obviously higher than that of general silica cement, showing better toughness. (2) The dry shrinkage rate of concrete prepared with anti-cracking cement is significantly lower than that of general silicon cement, and the anti-cracking property of concrete is significantly improved. (3) The application of crack resistant cement in pier concrete can reduce the core temperature of pier concrete, the temperature peak of core can be reduced by 5.0 ℃, and the strain of core concrete and surface concrete can be significantly reduced, the strain of core can be reduced by 50%, and the strain of surface concrete can be reduced by 40%, thus improving the crack resistance of plateau pier concrete. (4) The application of crack resistant cement can be used as an effective means to improve the crack resistance of railway bridge pier concrete.
2024 Vol. 41 (7): 106-112 [Abstract] ( 3 ) HTML (0 KB)  PDF  (1696 KB)  ( 0 )
113 Study on Intelligent Prediction Model for Energy Consumption Characteristics of Rubber-sand Concrete
MEI Xiancheng, MA Yalina, LI Jianhe, DING Changdong, CHEN Xingqiang, CUI Zhen, BAI Qiangqiang
Research purposes: Aseismic layer design is important to ensure the stability of underground engineering structures in strong earthquake area in the western China. The development and application of aseismic materials are the key to enriching the design of aseismic layer structures and ensure their performance. A comprehensive understanding of the energy consumption characteristics of rubber-sand concrete lays the foundation for its effective application in underground engineering aseismic layers. In this paper, the energy consumption characteristics of rubber-sand concrete were tested by Hopkinson pressure bar test, and four different swarm intelligence optimization algorithms were used to optimize the back-propagation neural network algorithm based on the test results, so as to build four hybrid intelligent prediction models.
Research conclusions: (1) The importance of affecting the energy consumption performance of rubber-sand concrete ranges from high to low, with rubber content > cement content > rubber particle size. (2) The optimal population numbers for the hybrid intelligent models are 150 (PSO-BPNN), 75 (FOA-BPNN), 75 (LSO-BPNN), and 80 (SSA-BPNN). (3) The LSO-BPNN hybrid intelligent model has the highest prediction accuracy for the proportion of transmission energy of rubber-sand concrete, while the other models have prediction performance of PSO-BPNN, FOA-BPNN, and SSA-BPNN. (4) The proposed hybrid intelligent model can be used to develop suitable rubber-sand concrete for aseismic layer materials in underground engineering such as railway tunnelling, and provide guidance for aseismic design to ensure safe construction and stable operation for railway tunnelling.
2024 Vol. 41 (7): 113-120 [Abstract] ( 2 ) HTML (0 KB)  PDF  (1576 KB)  ( 0 )
       Risk Management and Research
121 Research on the Progressive Decision-making Method of Investment Risks in Overseas High-speed Railway Construction Projects
QU Daoyuan, MENG Chuncheng, MENG Yang, DUAN Xiaochen
Research purposes: Aiming at the problems of high investment failure rate and lack of scientific and effective investment decision-making methods for China's high-speed railway "Go-Global" under the background of "Belt and Road Initiative", based on the perspective of enterprises and on the basis of risk decision-making, combined with the investment characteristics of overseas high-speed railway construction projects, it establishes a progressive decision-making model of investment risk, which provides a new way of thinking for the investment decision-making of overseas high-speed railway construction projects.
Research conclusions: (1) Breaking through the limitations of the single object, method and form of the previous research, it adopts a more rigorous longitudinal progressive decision-making framework to study the risk of China's high-speed railway enterprises' overseas investment. (2) The method of Grounded Theory is adopted to refine decision-making indicators, and a two-layer decision-making indicator system is established for macro-location environment and micro-project characteristics. (3) The methods such as ELM and Nonlinear Combination Empowerment Cloud Model are introduced into investment risk decision-making of overseas high-speed railway construction projects, to effectively reduce the influence of experts' subjectivity and enhance the dynamics and accuracy of decision-making. (4) The research results can provide realistic support for China's high-speed railway "Go-Global" enterprises to make scientific and effective investment decisions in the international engineering market.
2024 Vol. 41 (7): 121-126 [Abstract] ( 7 ) HTML (0 KB)  PDF  (1057 KB)  ( 0 )
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