In light of the surrounding rock mass of class V of Fenggang tunnel

a three-dimensional nonlinear simulation for it has been carried out. The cavity effect and the damage softening effect induced by excavating the tunnel in soft rock mass

have been presented. And the fitting of convergent deformation is effectively established by using the parameters softening method for plastic zone. Finally

the space effect

reinforcing effect as well as the optimizing construction scheme are also discussed; and the stability of the tunnel is demonstrated too.