Influence of Soil-Arching Effect on Tunnel Face Stability

Abstract

Based on the slip line theory and the upper-bound limit analysis theorem, a three-dimensional (3D) slip–rupture mechanism to design the shield tunnel face stability is proposed. This model is defined by using a spatial discretization technique. According to the stress arching theory, the vertical earth pressure at the top of the slip zone is calculated. The critical support tunnel face pressure is then deduced by using this additional load on the upper part of the slip damage zone. A series of finite difference numerical calculations based on the limit shear strain theory were performed to find the slip failure surface and obtain the critical support pressure. The results indicate that the soil-arching effect significantly affects the magnitude and the vertical stress distribution on front of the tunnel face. The good concordance obtained by the comparison of the results with the numerical simulations and other existing researches shows that the proposed model has a good applicability in both purely cohesive and frictional soils. At the same time, the critical tunnel face failure pattern is close to the numerical calculations one.