| Ground fissures,as a typical geological disaster,are commonly happened in many counties.Not only could make serious ecological problems,but also it can cause catastrophic failure to the major city construction project,traffic and lifeline engineering.If space avoidance measures are strictly implemented,available land resources cannot be used efficiently,and the urban construction and economic development could be limited.Therefore,it is of great theoretical significance and practical value to carry out the research on the catastrophic behavior of engineering structures and control measures under the ground fissure site with high intensity.In this paper,shaking table tests on a subway station structure crossing the ground fissure with or without considering the surface structure were performed.In addition to practical experiments,a comprehensive numerical model was established to investigate the seismic response and failure model of the subway station on the site with the ground fissure.Based on the mechanical properties of the textile reinforced ECC composite,the disaster control measures on the subway station in the ground fissure site were proposed.The conclusions are summarized as follows:(1)Shaking table tests were conducted on the model of subway station crossing the ground fissure-soil and the model of the subway station crossing the ground fissure-soil-surface structure.Based on the analysis of acceleration response,ground settlement deformation,dynamic characteristics and acceleration response of the underground structure and the change of strain response at different measuring points,the dynamic response of the hanging wall and footwall and the distorted deformation were studied.The influencing factors of the surface structure on the seismic response of the underground structure were analyzed.Then the dynamic response and failure characteristics of the underground structure crossing the ground fissures under different earthquakes were revealed.An important basis for the study of the interaction mechanism between the ground fissure site and the underground structure and its seismic response characteristics were provided.(2)Based on the numerical modelling of soil-structure,a scale model of ground fissure soil-underground structure interaction,and the prototype structure models of the subway station structure in the site with and without ground fissure were established respectively.The feasibility of the numerical simulation analysis method was verified by comparing the simulation results with the experimental results.Meanwhile,the differences in the dynamic response of the subway station structure in the site with and without ground fissure under different earthquakes were discussed.The influence factors such as burial depth,site soil characteristics,and adjacent surface structure on the dynamic seismic response of the subway station in the ground fissure environment were analyzed.The law of seismic response of underground structure was obtained.The research results could provide some references for guiding the design and construction of underground structures in the ground fissure site.(3)By analyzing the deformation and internal force distribution characteristics of the station at different locations in the ground fissure site and combining with the plasticity distribution characteristics of the site soil,the failure mechanism of the station in the ground fissure site was studied.Results indicated that the hanging wall and footwall of the ground fissure site were distorted and deformed under earthquake,resulting in central column boring a larger vertical load.Under the combined action of the gravity of the overlying soil,the shear action of the hanging wall and footwall of the ground fissure site and the earthquake,the compression-shear failure appeared on the central columns.(4)Model tests on the mechanical properties of textile reinforced ECC composite retrofitted concrete column were conducted,and the reinforcement effectiveness of textile reinforced ECC composite on concrete columns was studied.The dynamic response of the subway structure crossing the ground fissure and failure modes of columns were studied by numerical modelling,in terms of the unreinforced structure and the structure under different retrofitting schemes.The feasibility and effectiveness of the retrofit method on the central column to improve the seismic performance of subway station structure in the ground fissure site were validated.The research provided some references of the control measures for underground structures in the ground fissure site. |
