近直下型断层的地铁车站结构地震响应

Seismic response of subway station structures under straight-down near-fault

目前在近断层场地中地下地铁车站抗震性能水平认识方面相对匮乏,鉴于此,提出了一种考虑发震断层-地下结构全过程地震响应的IBE-FEM联合求解分析方法。首先,基于运动学有限断层模型,采用间接边界元方法(IBE)求解直下型走滑断层错动作用下上覆软土沉积层场地内的地震波场,并验证了有限元法(FEM)间接求解地震波场的可行性;在此基础上,通过建立土-地下连续墙-主体结构非线性静-动力耦合的二维整体时域有限元模型,初步探究了断层-软土场地耦合效应对地铁车站抗震性能的影响规律。结果表明:在近断层区域,地铁车站结构震害具有典型的断层上盘效应和震害集中效应,更容易进入塑性变形发展阶段;在远断层区域,由于断层-场地效应耦合作用,断层下盘场地内地震波场衰减较缓,其内车站结构整体震害略大于断层上盘。本文研究方法为近断层场地条件下地下结构地震响应分析开辟新思路,也可为相关场地区域内的地下结构抗震设计提供技术参考。

Given the deficiencies of knowledge on the seismic performance level of shallow-buried subway station structures in the near-fault site,the indirect boundary element method and the finite element method(IBE-FEM)integrated solution approach that considers the seismic response of the whole process of seismogenic fault-underground structures is proposed.First,based on the kinematic finite fault model,the IBE is used to solve the seismic wave field in the overlying soft soil site under the dislocation of straight-down strike-slip fault,and the feasibility of indirectly solving the seismic wave field by using the FEM is verified.On this basis,the influence laws of the fault-soft soil site coupling effects on the seismic performance of the subway station are preliminarily investigated by establishing a two-dimensional finite element model for the soil-diaphragm wall-underground structure nonlinear static dynamic coupling interaction system.The results show that in the near-fault region,the seismic damage of the subway station structures has typical hanging wall effects and concentration effects,and it's more likely to enter the stage of plastic deformation development.In the far-fault region,due to the fault-site coupling effects,the seismic wave field attenuation is slower in the footwall site,and the overall seismic damage of the station structures in the footwall is slightly larger than that in the hanging wall.This study may provide a new idea for the seismic response analysis of underground structures under near-fault site conditions,and it is of great significance for the seismic design of underground structures in the related site.