With the rapid development of heavy haul railway transportation technology,tunnel foundation defects and their effects on structural performance have attracted wide attention.This paper systematically investigates the...With the rapid development of heavy haul railway transportation technology,tunnel foundation defects and their effects on structural performance have attracted wide attention.This paper systematically investigates the evolution mechanism of tun-nel foundation defects in heavy haul railway tunnels and their impact on structural stiffness degradation through experiments and numerical simulations.A heavy haul train-ballasted track-tunnel basement-surround rock dynamic interaction model(TTTR model)is constructed.Firstly,the study reveals the four-stage evolution process of initial defects in the tunnel base-ment under complex environmental conditions.Experiments were conducted to measure the load-bearing capacity and stiff-ness degradation of the tunnel basement structure under different defect states.It is found that foundation defects,especially under the coupling of loose fill in the basement with the water-rich environment of the surrounding rock,significantly reduce the stiffness of the tunnel bottom structure and increase the risk of structural damage.Then,based on refined simulation of wheel-rail interaction and multi-scale coupled modeling technology,the TTTR dynamic interaction model was successfully constructed,and its validity was proven through numerical validation.A time-varying coupling technique of constrained boundary substructures(CBS technique)was adopted,significantly improving computational efficiency while ensuring calculation accuracy.The study also analyzes the effects of different degrees of void defects on the dynamic behavior of the train and the dynamic characteristics of the tunnel structure.It finds that foundation defects have a significant impact on the train’s operational state,track vibration displacement,and vibration stress of the tunnel lining structure,especially under the coupling effect of basement voids and the water-rich environment,which has the greatest impact.The research results of this paper provide a theoretical basis and technical support for the maintenance and reinforcement of tunnel foundation structures.展开更多
In order to effectively prevent the spread of novel coronavirus pneumonia and ensure the orderly development of teaching tasks,colleges and universities have launched online teaching activities.As a new teaching metho...In order to effectively prevent the spread of novel coronavirus pneumonia and ensure the orderly development of teaching tasks,colleges and universities have launched online teaching activities.As a new teaching method,how to reasonably carry out teaching design,teaching organization and ensure teaching quality has become a new problem in front of educators.Taking the“Subway”course as an example,this paper summarizes and introduces the online teaching methods and personal experience under the epidemic situation from the aspects of the overall framework design,specific implementation scheme,effect investigation and reflection of the online teaching mode based on MOOC platform,so as to enrich the experience of online teaching activities in colleges and universities during the epidemic period.展开更多
Graduation project(thesis)is an important practice part in undergraduate education,which forms an organic whole with theoretical teaching link,and it is the continuation,deepening and examination of the theoretical te...Graduation project(thesis)is an important practice part in undergraduate education,which forms an organic whole with theoretical teaching link,and it is the continuation,deepening and examination of the theoretical teaching part.This paper focuses on the constitution that the lack of quality standards for undergraduate graduation design,resulting in different depth and breadth standards;the graduation design materials are scattered and lack of standardization,which leads to the lack of systematic reference materials for students,taking the tunnel and underground engineering major as an example,this paper carries out the practice research on the standardization of the graduation design of tunnel and underground engineering through investigation and combining the teaching resources accumulated in the past decades.Through the study of practice,the content of undergraduate graduation design of tunnel and underground engineering is standardized,the breadth and depth of graduation design is defined,and the“Guide for undergraduate graduation design of tunnel and underground engineering”is organized and compiled,which can provide reference for the standardization and guidance of undergraduate graduation design of tunnel and underground engineering.展开更多
Outwash deposit is one of the major threats to the safety and stability of railway transit engineering in the Sichuan–Tibet area.In this paper,different samples of outwash deposits were prepared based on the random s...Outwash deposit is one of the major threats to the safety and stability of railway transit engineering in the Sichuan–Tibet area.In this paper,different samples of outwash deposits were prepared based on the random structure method,and a series of large-scale direct shear tests were carried out under different normal stresses.The influence of stone content and the spatial distribution of stone blocks on the physical and mechanical properties of outwash deposits were studied.The results show that with the increase of stone content,the shear stress-displacement curve changs from strain softening to strain hardening.The shear zone is larger,and its shape is more tortuous due to the movement and rotation of stone blocks.The internal frictional angle increases linearly while the cohesion diseases with the increase of stone content.The main influence of the spatial distribution of stone blocks on the mechanical properties of outwash deposits is the peak stress.The shear zone is mainly determined by the distribution of the stone blocks near the shear zone.展开更多
基金funded by the National Natural Science Foundation of China (Grant No. 52178402 & 52378468)the Open Foundation of MOE Key Laboratory of Engineering Structures of Heavy Haul Railway (Central South University) (Grant No. 2022JZZ01)+1 种基金the National Engineering Research Center for High-Speed Railway Construction Technology for their project supportthe support from the MOE Key Laboratory of Engineering Structure of Heavy Haul Railway (Central South University)
文摘With the rapid development of heavy haul railway transportation technology,tunnel foundation defects and their effects on structural performance have attracted wide attention.This paper systematically investigates the evolution mechanism of tun-nel foundation defects in heavy haul railway tunnels and their impact on structural stiffness degradation through experiments and numerical simulations.A heavy haul train-ballasted track-tunnel basement-surround rock dynamic interaction model(TTTR model)is constructed.Firstly,the study reveals the four-stage evolution process of initial defects in the tunnel base-ment under complex environmental conditions.Experiments were conducted to measure the load-bearing capacity and stiff-ness degradation of the tunnel basement structure under different defect states.It is found that foundation defects,especially under the coupling of loose fill in the basement with the water-rich environment of the surrounding rock,significantly reduce the stiffness of the tunnel bottom structure and increase the risk of structural damage.Then,based on refined simulation of wheel-rail interaction and multi-scale coupled modeling technology,the TTTR dynamic interaction model was successfully constructed,and its validity was proven through numerical validation.A time-varying coupling technique of constrained boundary substructures(CBS technique)was adopted,significantly improving computational efficiency while ensuring calculation accuracy.The study also analyzes the effects of different degrees of void defects on the dynamic behavior of the train and the dynamic characteristics of the tunnel structure.It finds that foundation defects have a significant impact on the train’s operational state,track vibration displacement,and vibration stress of the tunnel lining structure,especially under the coupling effect of basement voids and the water-rich environment,which has the greatest impact.The research results of this paper provide a theoretical basis and technical support for the maintenance and reinforcement of tunnel foundation structures.
文摘In order to effectively prevent the spread of novel coronavirus pneumonia and ensure the orderly development of teaching tasks,colleges and universities have launched online teaching activities.As a new teaching method,how to reasonably carry out teaching design,teaching organization and ensure teaching quality has become a new problem in front of educators.Taking the“Subway”course as an example,this paper summarizes and introduces the online teaching methods and personal experience under the epidemic situation from the aspects of the overall framework design,specific implementation scheme,effect investigation and reflection of the online teaching mode based on MOOC platform,so as to enrich the experience of online teaching activities in colleges and universities during the epidemic period.
文摘Graduation project(thesis)is an important practice part in undergraduate education,which forms an organic whole with theoretical teaching link,and it is the continuation,deepening and examination of the theoretical teaching part.This paper focuses on the constitution that the lack of quality standards for undergraduate graduation design,resulting in different depth and breadth standards;the graduation design materials are scattered and lack of standardization,which leads to the lack of systematic reference materials for students,taking the tunnel and underground engineering major as an example,this paper carries out the practice research on the standardization of the graduation design of tunnel and underground engineering through investigation and combining the teaching resources accumulated in the past decades.Through the study of practice,the content of undergraduate graduation design of tunnel and underground engineering is standardized,the breadth and depth of graduation design is defined,and the“Guide for undergraduate graduation design of tunnel and underground engineering”is organized and compiled,which can provide reference for the standardization and guidance of undergraduate graduation design of tunnel and underground engineering.
基金supported by the Open Research Fund of State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin(China Institute of Water Resources and Hydropower Research),Grant No.IWHRSKL-KF202016Natural Science Foundation of Hunan Province(CN),Grant No.2020JJ5732+3 种基金National Natural Science Foundation of China(Grant No.51679069)National Key R&D Program of China,Grant No.2017YFC1501100Open Fund of State Key Laboratory of Hydraulics and Mountain River Engineering(Sichuan University),Grant No.SKHL1725Water Conservancy Science and Technology Research and Extension Project of Shanxi Province,Grant No.2021LS034.
文摘Outwash deposit is one of the major threats to the safety and stability of railway transit engineering in the Sichuan–Tibet area.In this paper,different samples of outwash deposits were prepared based on the random structure method,and a series of large-scale direct shear tests were carried out under different normal stresses.The influence of stone content and the spatial distribution of stone blocks on the physical and mechanical properties of outwash deposits were studied.The results show that with the increase of stone content,the shear stress-displacement curve changs from strain softening to strain hardening.The shear zone is larger,and its shape is more tortuous due to the movement and rotation of stone blocks.The internal frictional angle increases linearly while the cohesion diseases with the increase of stone content.The main influence of the spatial distribution of stone blocks on the mechanical properties of outwash deposits is the peak stress.The shear zone is mainly determined by the distribution of the stone blocks near the shear zone.
