Study On Probabilistic Demand Models Of Tunnel Linings Subjected To Transverse Seismic Load

Several cases of severe damage or even collapses to tunnels have been reported in the past earthquakes,such as the Wenchuan earthquake and the 1995 Osaka-Kobe earthquake.The seismic safety of tunnel structures has attracted extensive attention from scholars at home and abroad.Seismic demand is one of the main contents in seismic vulnerability analysis and reliability theory research.At present,there have been a lot of researches on the seismic demand model of overground buildings.Influenced by factors such as soil nonlinearity is difficult to consider and soilstructure interaction is difficult to simulate,there is little research on the seismic demand model of tunnel structures.The main purpose of this paper is to give the probability demand models of bending moment,axial force and deformation of tunnel linings subjected to transverse seismic load.The main research contents are as follows:(1)In order to make the models have definite physical meaning,this paper obtains the seismic demand models of tunnel structures by adding linear correction term and random term to the analytical models.Therefore,the analytical method for calculating seismic demand is firstly discussed.Due to the small dynamic amplification effect of tunnel structure,this paper adopts pseudo-static numerical analysis data to calibrate the demand parameters.(2)In order to obtain displacement loading data in pseudo-static analysis,a site nonlinear analysis model is established based on the measured soil mass data.A set of actual horizontal ground motions are used to calculate the soil displacement corresponding to the maximum dynamic shear strain at the tunnels depth.In view of the fact that maximum free-field shear strain at tunnel depth is an important parameter in analytical methods,this paper presents a probabilistic model of maximum shear strain based on site seismic response analysis data.(3)In order to consider the uncertainties of ground motion,site conditions,tunnel depth,tunnel size,concrete strength and other factors,sample points are generated based on uniform design method.Stepwise regression is used to optimize the model correction term,and the least square method is used to estimate the model parameters.Three accurate and unbiased probability demand models for bending moment,axial force and deformation are established.Based on the analysis results in this paper,the probability distributions of bending moment,axial force and deformation of tunnel linings under lateral horizontal earthquake can be obtained.This result is of great significance for seismic vulnerability analysis and design based on reliability of tunnel structures.