A coupled hydromechanical modelling of internal erosion around shield tunnel

Tunnel leakage is one of the most important factors of the ground movement (Zhang et al. 2017). However, the effect of the loss of fines has not been deeply discussed in the previous study. The leakage of underground water through the cracks and joints of lining commonly carries fines in the form of silt and clay from the surrounding ground, i.e. internal erosion (Bonelli and Marot 2011). The change of porosity due to loss of fines affects the mechanical behaviour of the surrounding soil (Yin et al. 2014; Yin et al. 2016). Conversely, the change of porosity influences the permeability of the sand and, therefore, its hydraulic conductivity. In this study, the effect of leakage on the tunnel in sand layer was investigated numerically with a coupled hydro-mechanical continuum approach, considering the internal erosion phenomenon induced by the local flows of underground water