Mechanics Characteristics of Expressway Tunnel Through Fault Fracture Zone at the Entrance

Guandoushan tunnel in the Yibin - Luzhou expressway passes through fault fracture zone at the entrance. Structure internal force are complex during or after the construction. It challenges the safety during construction and operation. Plane finite element model was used to calculate internal force of primary support in the cases of different buried depths and three dimensional finite element model was applied to calculate stress distribution of primary support and secondary lining of the tunnel through fault fracture zone. The results indicate: with the increasing of buried depth, the loads acting on the structure will increase. It leads to uneven stress distribution in longitudinal direction, especially in the border of fault zone. It is suggested to increase the longitudinal reinforcement to improve overall longitudinal shearing resistance capacity and set deformation joint in the intersection to strengthen the longitudinal deformation ability of structure.