Disruption and destruction mechanism of cross-active fault tunnels based on 3D discrete-continuous coupling method

In the large-scale water conservancy projects built in strong earthquake regions in western China, the water conveyance tunnels inevitably crosse multiple regional active faults. Affected by the movement of the active faults, these water conveyance tunnels are faced with a serious threat of dislocation. The traditional anti-breaking numerical simulation methods for tunnels mostly consider the surrounding rock as the equivalent continuum, and they cannot simulate the fracture process from microscale and large deformation phenomenon of the surrounding rock when the fault is dislocated. The 3D discrete-continuum coupling method is used to study the anti-dislocation problem in a tunnel crossing active faults, and the mechanical response of the linings and the micro fracture characteristics of the surrounding rock mass under the action of fault dislocation are studied. In this analysis method, the discrete element spherical particles are used to model the surrounding rock mass, simultaneously, the lining structure of the tunnel is considered as a continuous zone. The compatibility and continuity of the coupling force at the contact boundary are verified, at the same time, the discrete region is consistent with the macroattributes of the continuous region through parameter calibration. On this basis, a 3D discrete-continuous coupling numerical model for tunnels crossing active faults is established. Using this method, the displacements and mechanical responses of the tunnels due to fault dislocation under different movement quantities of fault as well as the failure characteristics of the surrounding rock mass are discussed from the microscale. The conclusions may provide some reference for the anti-fault design of tunnels crossing active faults.