Abstract
For water transmission tunnels constructed in high-risk seismic regions of western China, active faults pose threats of serious ruptures to the tunnels. To overcome this issue, a 3D discrete-continuum coupling approach is introduced into the study. By this approach, spherical discrete-element-method (DEM) particles are used to represent the surrounding rock mass, and the tunnel is considered to be the continuous finite-difference-method (FDM) zone. In this way, a 3D coupling model was established to study the longitudinal displacement profile and stress response of the tunnel lining under various fault dislocations. The failure pattern of the surrounding rock mass was investigated from a micro perspective. Meanwhile, the design strategy of flexible joint was investigated with the present numerical model. The results from a parametric study show that the smaller segment length, wider width and weaker strength of the flexible joints are beneficial to the anti-dislocation performance of the tunnel. Moreover, an orthogonal array test technique was utilized to investigate the influence level of the main design parameters of the flexible joint on the lining internal stress. With the obtained knowledge, the optimal combination for flexible joint design was presented. Findings may provide references for the anti-dislocation issue of tunnels across active faults.
Highlights
Active faults, which exist in the weak parts of the earth’s crust, are potential sources of seismic activity
When a tunnel inevitably crosses a fault zone, it is directly subjected to strong impacts due to the dislocation of the two parts of an active fault, which leads to the failure of the tunnel lining [1,2]
The results showed that the mechanical response of an essentially infinite-length tunnel could be predicted
Summary
Active faults, which exist in the weak parts of the earth’s crust, are potential sources of seismic activity. Anastasopoulos et al [10] investigated the mechanical response of a 70 m-deep immersed tunnel crossing a normal fault in Greece, based on a nonlinear finite element model. Several studies have revealed that the continuum method is efficient and accurate, it is suitable for the study of a continuous medium and for small deformation problems With these models, the failure pattern cannot be investigated from a micro perspective. Researchers have been investigating the response of cross-active-fault tunnels with various discrete element models. A 3D discrete-continuum coupling method was first introduced to study the failure mechanism of cross-active-fault tunnels. The longitudinal displacement profile and stress response of the tunnel lining under various fault dislocations were investigated.
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