A Study on Tunnel Stability with Tunnel Construction by Finite Element Method

During excavation of shallow tunnels in soft ground, failure zones around the tunnel face have major influences on the stability of tunnels. In order to solve these problems, the failure mechanism of tunnel faces and the appraisal method of tunnel stability are very important. Therefore numerical models are applied to the simulation of tunnel collapse in typical longitudinal cross sections at tunnel heading. A first aspect is introduced with respect to tunnel shape and the second aspect with respect to an unsupported tunnel length. The results has shown that the stability increases as the length of unsupported tunnel heading decreases, and also that circular cross section is more stable than the other cross section shapes. The stability of tunnel has been investigated in terms of critical shear strain occurring in failure zone around the tunnel. A case study has shown good results in the appraisal of tunnel stability.