隧道纵向地震反应的三维数值仿真及行波效应研究

At present, the seismic response analysis and simplified design methods for underground tunnel cross section have been developed comparatively perfect, while less research works have been carried out dealing with the longitudinal seismic response of tunnels under asynchronous earthquake input, of which the theory and method are not perfect, resulting in the difficulties in effectively judging the influence of travelling wave effect on the security of tunnel structures. Aiming at these problems, by hackling both the 1D time domain finite element method used to calculate the free field wave motion in elastic layered half space and the theory of wave input, the three dimensional numerical simulation technique for the site asynchronous earthquake response is consummated and then the soil-tunnel structure interaction model is established. On this basis, systematic numerical analysis of tunnel longitudinal seismic response is conducted for both the conditions of oblique seismic incidence of P, SV and SH waves from the bedrock to layered soils and the propagation of Rayleigh wave at the shallow ground. The influence factors of producing the most unfavorable longitudinal seismic response of tunnels are discussed and the improvements on the simplified seismic design methods are also suggested. Based on the background of the immersed tube tunnel project, the nonlinear meticulous numerical analysis of its longitudinal seismic response is conducted, through which the integral seismic response mechanism is studied. The seismic performance of the immersed tunnels is evaluated, and the research work provides a reference for similar projects.

目前，针对地下隧道横断面的地震反应分析及简化设计方法已发展得较为完善，但对于非一致地震作用下隧道纵向的地震反应研究仍较少，有关理论和方法尚不完善，因而在抗震评估中难以有效判断隧道纵向行波效应对地下结构安全性的影响。针对上述问题，本课题计划通过梳理成层地基非一致地震反应的一维化时域算法和波动输入理论，完善非一致地震反应场地的三维数值模拟技术，据此建立地基-地下隧道系统纵向动力反应数值模型。在此基础上，分别针对由基岩向成层土地基斜入射的P波、SV波、SH波，以及地表附近形成的Rayleigh波条件下隧道纵向地震反应特性进行系统的数值分析，综合讨论产生隧道纵向最不利地震反应的影响因素，对已有隧道结构抗震简化设计方法提出改进建议。结合具体沉管隧道结构进行纵向地震反应非线性精细化数值模拟，研究沉管隧道结构的整体地震反应机理，对其抗震性能做出评价，并对类似沉管隧道工程提供参考。

非一致地震作用下隧道纵向地震反应研究是进行隧道纵向行波效应对地下结构安全性影响的抗震评估的重要内容。针对上述问题，本课题系统梳理了隧道纵向非一致地震反应的数值计算方法。通过梳理了成层地基非一致地震反应的一维化时域算法和波动输入理论，完善非一致地震反应场地的三维数值模拟技术，据此建立地基-地下隧道系统纵向动力反应数值模型。通过数值算例验算了该方法的有效性。本项目同时考虑到饱和地基土两相介质的特点基于u-U方程研发了用于动力问题的粘弹性传输边界。运用上述方法分别针对由基岩向成层土地基斜入射的P波、SV波、SH波条件下隧道纵向地震反应特性进行系统的数值分析，综合讨论产生隧道纵向最不利地震反应的影响因素。本课题成果对进一步开展隧道纵向地震反应非线性精细化数值模拟，研究沉管隧道结构的整体地震反应机理等工程问题具有重要的参考意义。