Numerical Analysis on Stability of Excavation Support for Certain Gneiss Tunnel

In the process of tunnel construction, the instability of surrounding rock may induce tunnel landslide disaster, causing casualties and damage to the construction machinery and resulting loss to property, which has adverse impact on the society. Based on the research background of Dongshan Tunnel of Chengzhang Expressway, the stability analysis has been made on states in three surrounding rocks of horizontal gneissic schistosity, slanted gneissic schistosity and vertical gneissic schistosity, as well as two working conditions of excavation + initial lining and excavation + initial lining + anchoring with the FLAC3D model in this paper. The results show that the tunnel has the best stability under the condition of the horizontal surrounding rock, followed by the moderate stability under the condition of the slanted surrounding rock, and has the worst stability in the state of the vertical surrounding rock. Under the condition of excavation + initial lining, it is in a relatively stable state, while under that of excavation + initial lining + anchoring, is in a stable state.