Pseudo-dynamic analysis of asymmetric collapse mechanism in shallow tunnels

In order to solve the collapse failure problem of overlying rock mass in shallow tunnels during earthquake, and to guide the design of tunnels safety width and the reinforcement of overlying rock mass, the prediction method of collapse failure curve under earthquake is studied. The main means is to simulate the seismic wave action on the overlying rock mass by the pseudo-dynamic method, establish the virtual power equation in the upper bound theorem based on the Hoek-Brown criterion, and solve it by the variational method of the variable endpoint problem. The effects of seismic wave parameters, rock mass strength parameters and engineering parameters on the predicted collapse area are analysed. The results show that the horizontal seismic acceleration affects the shape of the collapsing rock block, while the vertical seismic acceleration affects the size; the rock mass with weak strength and high density has a small size of collapsed rock block. By referring to the influence of engineering parameters, reducing the depth of the tunnel and uniform load on the surface and increasing the supporting pressure on the overlying rock mass can help to restrain the occurrence of collapse.