Research on comprehensive analysis and control method of surrounding rock stability in submarine tunnel crossing fault fracture zone by drilling and blasting method

The stability control of surrounding rock is crucial when the submarine tunnel passes through poor geological conditions like fault fracture zone. In this paper，a numerical analysis method of surrounding rock stability is proposed，which requires the stability of the surrounding rock in the whole area of the tunnel to be calculated first，and then the refined hazard process of high-risk area is analyzed. Numerical simulation with FLAC3D and DEM methods are carried out respectively based on the F9 fault and weathering trough section of the Shantou Bay Submarine Tunnel Project. The high-risk sections of the tunnel were evaluated. The control effect of different grouting reinforcement area thicknesses on the deformation of the tunnel surrounding rock was compared by simulation. Based on the comparison results，a scheme of joint grouting on the sea surface and inside the tunnel was proposed. The reliability of the proposed scheme was verified through numerical simulations and measurements of Shantou Bay Tunnel. The implementation of the grouting scheme ensured the safety of tunnel construction. The relevant conclusions offer valuable insights for controlling the stability of surrounding rock and optimizing grouting schemes during the construction of submarine tunnels under similar conditions.