Experimental study on the design of a fault-resistant buffer layer for diversion tunnels traversing active faults

Abstract

The anti-fault effect and the failure characteristics of tunnel lining when the buffer layer is set up in a tunnel that crosses an active fault zone is examined on the basis of the Xianglushan diversion tunnel in Dianzhong. The indoor model test method is used to study the stress characteristics of the buffer layer on the tunnel crossing the active fault zone when the fault is dislocated and the anti-fault effect on the tunnel crossing the fault. Results show that S-shaped displacement pattern of the lining can serve as a quantitative index for evaluating structural damage severity. With the increase of buffer layer thickness under the same dislocation magnitude, the high-fault-risk area reduces in size and moves upward, leading to less sliding and lining dislocation. After dislocation, the lining contour becomes elliptical, while the collapse at junctions and the bending deformation of the steel mesh are alleviated, as the buffer layer absorbs dislocation energy effectively. The tunnel structures of the hanging wall, upper fault-influenced zone, and their interfaces are most vulnerable to fault dislocation, being key areas for anti-fault reinforcement. Notably, buffer layers can significantly weaken lining damage in these vulnerable areas, greatly enhancing the anti-fault performance of cross-fault tunnel linings.