LAUSR

Abstract In this work, the three-dimensional failure mechanism of a deep soil-tunnel is established based on the nonlinear Mohr-Coulomb criterion and the upper bound theorem of the limit analysis subjected to the effects of pore water pressure. The formulas of the height, width and upper bound surface of a three-dimensional collapse of a deep soil-tunnel are derived from the three-dimensional failure mechanisms. The correctness and effectiveness of the proposed method is confirmed by comparing the results with those of existing studies. Then, the change rule of the geotechnical and geometrical parameters on the influence of the collapsing range and weight are studied. The results indicate that the pore water pressure has a significant influence on the range and weight of a tunnel collapse, but the initial cohesion determines the change rule of the pore pressure coefficient on the influence of the collapsing weight. The work in this study provides a reliable theoretical method for the optimization of the support designs of deep soil-tunnels.