Progressive and asymmetric active and passive mechanisms of shallow tunnels under the effect of seismic forces

Abstract

Abstract To investigate the effect of the seismic force on asymmetric failure mechanisms of shallow tunnels, progressive and asymmetric active and passive failure mechanisms of shallow tunnels were discussed in this paper. In each of these failure mechanisms, the lower stratum was inclined, and there were four different detaching curves. Based on the nonlinear yield criterion and the upper bound theorem of limit analysis, the expressions of detaching curves for describing the active and passive failure mechanisms of shallow circular tunnels were first derived by the variational method. Then the equations for calculating the range and weight of the failure blocks were obtained. After sensitivity analysis of parameters, the range and weight of the failure blocks under different parameters were computed. According to the results of this study, the rock stratum inclination has a decisive effect on the symmetry of both active and passive failure mechanisms of shallow circular tunnels. Besides, the seismic force is an important factor affecting the stability of the tunnel roof.