Study On The Mechanism Of Tunnel Damage And Geotechnical Failure Propagation Due To Fault Rupture

Fault movements and overlaying soil rupture cause direct damage to the ground and underground buildings across the fault, therefore, the tunnel across the fault and embedded in the overlaying soil must take the faults into account.Newly built Chengdu-Lanzhou railway contains some long tunnels, some of which go through high intensity area, some tunnels even have to cross the active fault. This paper is based on nonlinear finite element theory, introduce the plastic damage model of concrete tunnel structure to analysis the damage, and establish three-dimensional finite element model of the tunnel across fault and the fault-overlaying soil system according to specific site condition to study the mechanism of active fault's effect.On the basis of previous theoretical studies, the paper study on the crossing-fault tunnel's response mechanism under the fault rupture, the failure and damage of the tunnel structure are also considered. The roles of the fault rupture mode, fault obliquity, fault dislocation distance, tunnel diameter size and other related factors are analyzed separately. Based on the study of the mechanism, we put forward and analyze the effects of the anti-breaking measures. Finally, the rupture process of the overlaying soil caused by the fault movement is simulated, the impact of the rupture on the embedded tunnel is also studied.Based on the above analysis, the following conclusions can be obtained. The longitudinal range caused by the fault rupture is only about 10-20m. Fault rupture mode, fault obliquity, fault dislocation distance, tunnel diameter size and other related factors play an important role on the tunnel's response. The impact of joints on the anti-breaking is obvious, which can effectively reduce the strain within the tunnel structure; lining enhancement can't effectively improve the anti-breaking performance. Buffer layer changes the interaction between the linings of tunnel, which is beneficial to reduce the impact of the fault rupture to the second lining. Overlaying soil rupture caused by active fault began from the soil and bedrock interface and extend up, when the dislocation distance reaches a certain value, the soil surface rupture appears, With the progress of the dislocation increases, the rupture zone is formed through. Compared with case of tunnel across fault, the tunnel affected by fault expanded a lot, and the impact is reduced accordingly.