MPM-FEM based numerical analysis on responses of stratum and twin tunnels to water-soil gushing

Water-soil gushing presents significant challenges in shield tunnel engineering, notably large soil deformations and complex interactions between the tunnel structure and surrounding strata. Hence, this study proposed a comprehensive numerical analysis procedure using MPM and FEM to examine the whole-process responses of strata and twin tunnels to water-soil gushing. To tackle the difficulties in simulating large soil deformations, a two-phase MPM approach is first introduced and validated through a detailed case study, and then soil and water pressures obtained from the MPM model are transferred to a FEM model for tunnel structures by utilizing a data interface. The findings of a case study reveal that the gushing significantly affect the surrounding soils, particularly in terms of variations in pore pressure and soil stress within the flow zone, which could lead to significant changes in shear forces and bending moments of tunnel lining. A parametric study investigated the influence of gushing location on the tunnel. The results indicate that lower gushing locations in the tunnel lead to larger variations in the effective soil stress distribution and flow zone patterns, causing a more dramatic joint opening and dislocation. This study provides key insights into the evolutionary responses of the strata and tunnels due to the water-soil gushing, offering valuable guidance for designing and maintaining shield tunnels in water-rich sandy layers.