Primary Research On The Stability Of The Xi'an Subway Through The Ground Fissure

Ground fissure is main environment disaster in Xi'an city construction. All of the lines of the Xi'an metro pass across the ground fissure vertically or obliquely, therefore the ground fissure has caused many difficulties to the construction of the Xi'an metro.On the basis of the geological situation of the south gate to Nanshao gate tunnel of the Xi'an metro, this paper analyzed the influence of the ground fissure on the country rock stability of the metro tunnel in the term of different lining structures. The excavation and support process of the metro tunnel was simulated by the finite difference software-FLAC3D in this paper. After comparing the ground surface settlement, crown displacement, the change of the stress of the country rock-support system, and the distribution of the plastic zone in the term of unsupport, initial support, and secondary lining, it confirmed that the tunnel would slump in the term of unsupported, but if the initial support is applied to the tunnel, the settlement of the ground surface and the crown displacement would reduce largely. But the displacement doesn't satisfy the requirement of the engineering. After the secondary lining beening applied to the tunnel, the displacement satisfies the requirement of the engineering and the support system is advantageous to the stability of tunnel. Next, it studied primarily the different excavation methods adopted by the tunnel in the area of ground fissure, and analyzed the influence on the stability of the metro tunnel by using the infinite difference software-FLAC3D. This paper researched the influence of the full face excavation method and bench excavation method. It analyzed the ground surface settlement, crown displacement, the change of the stress of the country rock-support system, and the distribution of the plastic zone in the term of unsupported, initial support, and secondary lining. By comparing and analyzing, it concluded that the bench excavation is better than full face excavation.The result from this subject can instruct construction, it supplies the reference value and pratical significance to the construction of the Xi'an metro.