Simulation Analysis of Mechanical Behavior during Treatment Construction of Tunnel Collapse

Combined with Shenjiashan tunnel collapse accident in Guanggan highway, the paper analyzes the construction simulate the mechanical behavior of rock collapse segment caused stress field, displacement field and variation of the plastic zone calculated by FLAC3D numerical software. The conclusions are as follows: (1) The maximum tensile stress occurs in the vault 60 degrees range and the central backplane while the maximum compressive stress occurs in the middle part of the foot of the tunnel arch; (2) Vault subsidence maximum displacement is mainly distributed in the range of 60 degrees vault, floor uplift maximum displacement is mainly distributed in the 1/3 of the central bottom. (3) As the excavation proceeds, the central cavity collapse begins to appear plastic zone (tensile yield based), the arch plastic zone (shear yield based) significantly increase the scope and depth of rock to develop. If unchecked, the arch part of shear failure may occur. The results show that the support system of advance pipe shed support + cavity grouting reinforcement + steel arch played an active role in the collapse of governance throughout the process, and the foot of the tunnel arch and vault 60 degrees range are the focus of the site in support of this collapse treatment construction.