Interaction of reverse fault creep and rock creep and its effects on tunnels

Deeply buried tunnels crossing faults may suffer both fault creep and rock creep. However, the present design of a tunnel crossing a creep fault is based on the fault creep rate, where the rock creep effects are not considered. This study performs a series of numerical models to explore the interaction of reverse fault creep and rock creep and their effects on tunnel responses. The three-dimensional numerical model is validated both by a faulting test and creep tests. The responses of surrounding rocks and the behaviors of tunnels are presented and discussed. The results show that there are apparent interactions between the reverse fault creep and the rock creep. The reverse fault creep causes an increase in differential stress in the fault zone, which further results in continuous and accelerated creep strain in the surrounding rock. It further leads to more severe damage and earlier failure of the tunnel in the fault zone. The rock creep leads to larger strain of the rock at the tunnel bottom in the fault zone, which fills in the gap or loose zone caused by tunnel deformation. It results in larger tunnel axis displacements and cross-sectional deformation in the fault zone. The results suggest that the stiffness of the tunnel cross-section should be further enhanced in the design.