Numerical study on the influence of excavation slope on the structural behavior of ground penetrating shield tunnels

Abstract

The ground penetrating shield technology (GPST) is a fast shield tunnelling method, wherein the shield is launched and received at the ground surface without constructing deep and large working shafts. With regard to the notable sloping excavation characteristics of the GPST, this study established a three-dimensional numerical model to analyze the impact of the excavation slope on the structural response of the tunnel lining based on the South Longshui Road Cross-river Tunnel project in Shanghai. The results indicate that the circumferential earth pressure acting on the lining is determined by both the buried depth and decomposition angle induced by the change in the excavation slope. The distribution of the earth pressure along the longitudinal direction may be affected by the excavation slope, and this subsequently affects convergence deformation of the tunnel. An increase in the excavation slope equalized the distributed force acting on the lining. In addition, the existence of circumferential joints exaggerates the impact of the excavation slope on the differential convergence between adjacent rings. A larger excavation slope resulted in a decrease in the proportion of convergence deformation caused by the longitudinal joints. These findings can provide important guidance for controlling the ovalization and dislocation behaviors of GPST.