Limit support pressure on tunnel face at different construction line slopes by slip line method

Abstract

Tunnels in urban areas typically have complex geological conditions, and sufficient support pressure is necessary to guarantee the safety of tunnel excavations and prevent damage to adjacent structures. In this study, the slip line method is employed to obtain the limit support pressure on the tunnel face and analyze the effects of the internal friction angle, cohesion of the soil, interface friction angle, cover layer thickness and tunnel construction line slope on tunnel face stability. The soil is idealized as a rigid plastic material. The slip line method assumes that the soil satisfies the plastic equilibrium state specified by the Mohr-Coulomb criterion. Moreover, a mathematical model of the static equilibrium with a solvable limit equilibrium boundary is established. The limit support pressure distribution and failure mechanism of the tunnel face are obtained by the finite difference method. The results show that the limit support pressure decreases when the internal friction angle and cohesion of the soil increase, whereas limit support pressure increases when the interface friction angle increases. When comparing the derived results with those found in related references, it is observed that the slip line method for calculating the limit support pressure on the tunnel face is reliable. Furthermore, it is particularly suitable when the interface friction angle and tunnel construction line slope are considered.