soft rock tunnels;  finite element method;  anchor spray support;  3D numerical simulation

In order to verify the feasibility of a national defense tunnel engineering design and construction scheme. According to the Drucker-Prager criterion of underground structure design and rock yield, considering the self-bearing capacity of the surrounding rock, ANSYS9.0 software was used to simulate the excavation and support process of the tunnel in <>D finite element, verify the design parameters, and comprehensively analyze the deformation and initial support effect of the surrounding rock, and conclude that the design scheme is feasible, the initial support meets the requirements, and the hoard rock can stabilize by itself. The numerical analysis results are consistent with the on-site measurement results, which can provide theoretical guidance for related engineering design and on-site construction.