A Coupled Hydro-Mechanical Modeling of Tunnel Leakage in Sand Layer

The tunnel leakage in sand layer plays an important role in the evolution of the lining stresses and the ground movement. The phenomenon of internal erosion occurs when underground water leaks into the tunnel from the damaged joints or the cracks of the linings. Fines in sand are pulled off by seepage forces and transported throughout the soil matrix into the tunnel. The loss of fines due to seepage flow affects the mechanical behavior of the soil around the tunnel. Conversely, the change of porosity influences the permeability of the soil and, therefore, its hydraulic conductivity. In this study, the effect of tunnel leakage in sand layer is investigated numerically with a coupled hydro-mechanical approach, considering the internal erosion phenomenon induced by the local flows of underground water, using the continuous porous medium theory and a critical-state based constitutive model. Simulation results show that the loss of fines as well as the leakage locations have significant impacts on the tunnel lining and the ground movement