Face stability of slurry-driven shield with permeable filter cake

The hydraulic resistance of the filter cake on a tunnel face is an important factor in the stability of slurry-driven shield tunnels. However, the effect of the filter cake is not well understood. The study presented in this paper explores the dynamic and periodic features of the filter cake on the tunnel face through infiltration column tests. A three-dimensional numerical model with a permeable filter cake was developed to investigate the hydraulic head field in sandy soil from which the seepage forces were computed as well as a new calculation approach for the limit excess pressure based on a limit equilibrium analysis. The influences of the hydraulic conductivity of the filter cake on the limit excess pressure were also studied. Our results show that the limit excess pressure increased with an increase in the hydraulic conductivity of the filter cake and also show that the limit excess pressure, when calculated using the current approaches in the literature, was underestimated.