The solution on problem of soft soil layer's collapse in Xin Kailing Tunnel and evaluations on its effect

This paper presents the solution on the soft soil layer's collapse of Xin Kailing Tunnel in China based on the analysis on its causes. The effect of the solution is evaluated by site survey and finite element analysis. The results show that the geological factor mainly leads to collapse; the crucial factor of preventing the collapse from happening is to give a better description of the tunnel face, to analyze and predict conditions of wall rocks which are in front of the tunnel face in time and to evaluate precisely whether the wall rocks and supporting system are strong enough or not; effective ways to solve the collapse problem is to strengthen supporting system of the being influenced parts in the tunnel, to seal wall rocks in collapsed possibly part as well as to add supporting system in time; the minimum safety factor of the solution in this project is about 3.1 which meets official standards of the tunnel construction; the solutions on the soft soil layer's collapse of Xin Kailing Tunnel is effective, safe and reliable.