Evolution of mechanical properties of shield tunnels induced by water-soil gushing

Water and soil gushing in shield tunnels pose a significant risk to tunnel structure safety. However, it is challenging to fully capture the evolution of the mechanical response of tunnel structures due to the limitations of conventional numerical methods in simulating large soil deformations around the tunnel due to gushing. This paper develops a coupled material point method (MPM) and finite element method (FEM) approach for water and soil gushing, where MPM is for modelling the soil deformation and FEM is for modelling the tunnel response. The developed approach is utilized to conduct the gushing-induced large deformation analyses and generate the varying soil and water pressures acting on the tunnel lining. Meanwhile, structural internal forces and joint deformations are identified based on the load-structure method. The findings suggest that the gushing process can be categorized into three stages: initial developing, rapid developing and stable developing stages. The soil and water pressures around the gushing point decreased abruptly during the “rapid developing stage”, but the soil pressures on the tunnel crown and tunnel invert increase, causing a sharp rise in the bending moment of the lining and severe joint deformations, particularly at joints No. 2 and No. 3. Finally, the parametric analyses show that a lower gushing location, deeper tunnel depth, and higher soil shear strength will all exacerbate the influence of water-soil gushing on tunnel structural response, due to variations in the soil and water pressures acting on the tunnel lining throughout the whole process of gushing. These findings underscore the importance of revealing the evolution of tunnel responses to water-soil gushing for maintaining tunnel safety.