Tunnel Face Stability Study in Soft Shallow Tunnel

Abstract

With Xiamen Jiaheyuan underground access as the project background, tunnel face stability of soft shallow tunnel was analyzed under the condition of no pre-reinforcement by means of three-dimensional finite element method. The results indicated that the ground was relaxed because the tensile stress appeared in front and top of tunnel face after excavation, at the same time, the ground into the plastic state around the tunnel face. From the point of view of deformation, the displacement of tunnel face were such as the longitudinal horizontal displacement reached the maximum, the vertical deposition following by, and the lateral horizontal displacement being the least. Further analysis showed that the longitudinal horizontal displacement in front of tunnel face mostly produced at 1.0D (one excavation width) distance before tunnel face, the maximum displacement was located at the center of tunnel face. The conclusions remind that engineers also pay attention to the tunnel face reinforcement in front and top of tunnel face to minimize the impact of surface environment during tunnel construction in soft shallow tunnels.