Stability on the Excavation Surface of Submarine Shield Tunnel Considering the Fluid-Solid Coupling Effect and the Equivalent Layer

The support pressure on an excavation surface is a critical factor in the ground deformation and excavation stability of a submarine shield tunnel. The shield tail gap and the disturbance zone of grouting behind the tunnel wall are also important influencing factors. However, the effects of these factors on excavation stability are difficult to quantify. Consequently, a homogeneous, elastic, and annular equivalent layer is employed to simulate the thin layer behind the tunnel wall. Using COMSOL Multiphysics software, the effects of the water level depth, the thickness of the equivalent layer, the diameter of the shield tunnel, and the internal friction of soil and tunnel burial depth on the excavation deformation and ground surface subsidence of a submarine tunnel are considered with regard to the fluid-solid coupling effect. The result show that the surface subsidence of the case with respect to the fluid-solid coupling effect and the equivalent layer is larger than that without interstitial fluid and the equivalent layer, indicating that the present model can better simulate the stability of tunnel excavation. Therefore, it is important to consider the impact of the fluid-solid coupling effect and the equivalent layer on the deformation of the excavation face and ground surface subsidence.