Abstract:In order to study the parameters of the initial support structure of the subway tunnel in the soil-rock composite stratum in Qingdao, this paper relies on the Qingdao Metro Line 1 tunnel project, combined with orthogonal test design method, and uses FLAC 3D to carry out numerical simulation. The construction method, anchor length, initial The influence of support stiffness, initial support thickness on tunnel deformation, optimal initial support structure parameters, and anchor forces are analyzed. The comparison between field measurements and numerical calculations verifies the correctness of the numerical calculations. The research shows that when the tunnel is located in the strongly weathered granite stratum, the construction method has the most significant effect on the tunnel deformation, and changes in factors such as the length of the anchor cause the tunnel deformation to be insignificant; the full section method is used for construction, and the optimal initial support structure parameter combination is the anchor The length of the rod is 2 m, the thickness of the initial support is 30 cm, and the concrete strength grade is C25. The axial compression of the anchor above the vault may affect the support of the anchor, mainly due to the relative slip between the ground and the anchor. Shift deformation. The research conclusions have certain theoretical significance and engineering value for "upper and lower hard" areas such as Chongqing and Xiamen.