Study On Failure Characteristics And Seismic Performance Of Tunnel Crossing Strike-Slip Fault

Since the Reform and Opening Up,with the rapid development of China’s social and economic level,the scale and level of infrastructure construction has correspondingly entered a new historical stage.However,compared with the coastal cities in southeast China,some parts of the central and western regions still have problems of insufficient economic development and relatively backward infrastructure construction.In order to solve the "contradiction between the people’s growing needs for a better life and unbalanced and inadequate development",it is particularly important to increase the scale of infrastructure construction in the central and western regions,among which mountain tunnel plays an important role.However,the geological activities in the central and western regions are very strong,and tunnel structures frequently cross active faults,which can easily lead to large-scale destruction of tunnel structures.Relying on KD tunnel of CZ Railway,the methods of data investigation,theoretical analysis and numerical simulation are adopted to analyze the mechanical response of tunnel structure in the case of fault dislocation。The main achievements are as follows:(1)The literature and engineering cases about crossing active faults and the influence of earthquake on tunnel structures are collected and investigated.The typical failure modes of tunnel structures crossing faults and the characteristics of existing tunnel fortification systems across faults are summarized.(2)Based on the specific situation of KD tunnel crossing a strike-slip fault,the effects of different dislocation angles,different dislocation directions and different fortifying methods on the displacement,stress and plastic zone of surrounding rock are studied by establishing numerical models.At the same time,according to the stress and strain characteristics of tunnel structure,the anti-stagger failure mode and the range of fortification zone are proposed.(3)Based on the concrete damage plastic constitutive model,the numerical model of tunnel crossing yulongxi strike-slip fault is established,and the failure characteristics of lining under different dislocation modes and different fortification modes are studied.Combined with the damage range of lining structure under different staggered distance,the corresponding longitudinal fortification length of tunnel is proposed.(4)Based on the seismic fortification level of the site,the dynamic response model of the tunnel is established,and the dynamic characteristics of the lining acceleration,stress response and lining damage of the tunnel structure under the action of different seismic waves are compared and analyzed.By comparing with the failure characteristics of tunnel structure under strike-slip fault dislocation,it is shown that fault dislocation plays a major role in tunnel failure.