Shallow tunnelling in partially saturated soil numerical analysis of the contribution of dewatering to the enhancement of face stability

Abstract

Partially saturated soils exhibit higher shear strength than saturated soils. Shallow tunnels are often driven closely to or inside the saturated layers. The water table is sometimes lowered to excavate the tunnel in a partially saturated condition. In doing so, the face stability is improved and the necessary support pressure can be reduced. In this paper a numerical study is performed to assess the effect of dewatering on the face stability of shallow tunnels. The analyses are performed with an advanced constitutive model for partially saturated soil. The model is implemented in a commercial software using the Bishop’s effective stress for the equilibrium equation.