Study on tunnel support stability considering rock mass expansion effect in fault fracture zone

Abstract This study explores a variety of mountain settlements and stress-strain problems caused by tunnels passing through mountain fault zones. Based on the research background of the Lianfeng Mountain tunnel project, the expansion pressure of the rock mass was introduced through the Kastner formula using ABAQUS finite element simulation software. A mountain structure model was established, and the structural stress state of the mountain after tunnel excavation and the stability law of the secondary lining were studied. The results showed that for the double-layer steel frame, the inner steel frame of the tunnel bore more stress. In the normal section, the settlement of the tunnel vault was similar to the amount of bottom uplift. However, in the broken section, the settlement of the vault was significantly greater than the amount of bottom uplift. The excavation of the second tunnel during the construction of the double tunnel caused the strain in the first tunnel to increase. This study provides a theoretical reference for the safety analysis of similar mountain tunnels.