Design and optimization of an innovative lining structure for high-pressure water transmission tunnels subjected to strike-slip fault creep

Long-distance water transmission tunnel projects face significant challenges in crossing active faults. This paper presents a novel multi-layer flexible lining (MFL) structure for high-pressure tunnels that can accommodate fault creep deformation. Finite element numerical analysis was utilized to validate the feasibility of the MFL structure under the actual conditions of a particular engineering project. Additionally, the effects of various parameters on the tunnel structure were examined. The results indicated that shorter concrete segments and longer flexible joints are better able to accommodate fault dislocations and reduce concrete damage. A thicker cushion layer, with a thickness ranging from 0.1 to 0.4 m, is more advantageous for the tunnel lining to adapt to fault dislocations. However, an excessively thick cushion layer will have a negative impact on the lining's stress. Appropriate use of bellows joints can improve the tunnel resistance to fault displacement. The number of bellows joints needed for effectiveness and the potential failure of the joints at the edge of the fault zone were examined. The research findings can provide valuable guidance for the structural design of high-pressure water transmission tunnels in dealing with fault creep deformation.