Influences of normal fault dislocation on response of surrounding rock and lining system based on discrete-continuous coupling simulation

The seismic damage records show that the destruction of tunnel structure mostly occurs in the fault zone with surrounding rock mass of poor quality and great changes in stratigraphic conditions. In order to study the influences of fault dislocation on the response characteristics of surrounding rock and tunnel, an analytical method based on 3D discrete-continuous coupling theory is proposed, and the existing indoor model tests are introduced into the comparative tests to verify the validity of the coupling method. Based on the coupling model, the process of micro cracks gathering to form fracture and the evolution of shear zone are explored. The deformation mechanism and mechanical response characteristics of a cross-fault tunnel are studied. Besides, the influences of thickness of linings, elastic modulus of concrete and burial depth of the tunnel on its mechanical response and deformation characteristics are analyzed. The results show that the tensile cracks accumulate at the bottom of the tunnel in the hanging wall to form an inverted triangle shear zone, and shear cracks are distributed in strip on the fault plane. Meanwhile, a sharp deformation of linings emerges near the fault plane. In the hanging wall, the top arch is under pressure and the floor is under tension, while, in the footwall, the top arch is under tension and the floor is under pressure. In addition, increasing the thickness and concrete elastic modulus of the linings within a reasonable range is conducive to improving the anti-fault capability of the tunnel. And deep buried tunnel is protected by surrounding rock under fault dislocation to reduce the damage. The research results can provide a certain reference for the stability evaluation of surrounding rock mass and the anti-fault design of tunnels.