A New 2D Failure Mechanism for Face Stability Analysis of a Pressurized Tunnel in Spatially Variable Sands

This paper presents a method to consider the spatial variability of the soil shear strength parameters for determining the critical collapse pressure of a pressurized tunnel face. Only the case of a cohesionless soil is considered in the analysis. The present method is based on the kinematic theorem of limit analysis. A new 2D kinematically admissible collapse mechanism whose shape depends on the spatial distribution of the soil friction angle (φ) is proposed. In this mechanism, the normality condition imposed by limit analysis is enforced everywhere along the slip surfaces of the failure mechanism. The results obtained using the present approach are presented and compared to those based on common numerical methods such as the Finite Element Method (FEM) or the Finite Difference Method (FDM). The proposed method is computationally more efficient and has significant potential for simulation studies involving random fields.