A novel hydro‐mechanical coupled multiphysics model for slurry penetration in sand with application to face stability analysis of shield tunnel

The slurry penetration in tunnels driven by the slurry TBM in the highly permeable water‐bearing ground is a complicated multiphysics process, which significantly affects the stability of the excavation face but has not been fully modelled. This study establishes a novel hydro‐mechanical coupled multiphysics modelling approach for face stability analysis. Different from existing methods, the proposed one is able to quantify simultaneously the spatial and temporal variation of slurry concentration, viscosity, stagnation gradient, soil porosity and pore pressure, as well as the soil skeleton deformation induced by the transferred slurry pressure in two or three‐dimension. The spatial and temporal pressure transfer from slurry suspension to soil skeleton during slurry penetration can be obtained. The coupled formulations are implemented into a finite element package for initial and boundary value problems at the engineering scale and enhanced by the Petrov‐Galerkin weighted residual stabilisation technique. After being validated through the experimental slurry infiltration tests, it is applied to a field case analysis to predict the excess pore pressure in front of the tunnel face, which shows good agreement with the field measurement. The efficiency of the applied slurry pressure and the pressure transfer mechanism are thus verified. Comparative calculations about the influence of the pressure transfer model are presented to further improve the understanding of the pressure transfer mechanism. The proposed approach is also verified applicable to estimate the optimum slurry pressure.