A Study on Excavation Effect of Tunnel Based on Using 3-D FEM

The excavation of the tunnel induces the changes of the stress state of the surrounding rock,such changes alter the mechanical property of the surrounding rock.On the basis of a detailed 3-D finite-element analysis,the near-field stress path and displacement changing law during the progressive advancement of a tunnel face and the state of stress,displacement around the tunnel after the excavation finished are studied and analyzed.According to the study results,some conclusions can be drawn out.The surrounding rock of the tunnel undergoes a stress path from loading to unloading during the excavation.The unloading effect of the excavation has more evident expression on the bottom than on the arch crown of the tunnel,and insignificant expression on the side wall of the tunnel.The region affected by excavation on the surrounding rock is from 1B before the tunnel face to 1B behind the tunnel face at the tunnel axis and 2B around the tunnel perpendicular to the tunnel axis.B represents the tunnel span.The results of the analysis and engineering practice are compared and studied qualitatively in this paper.