Basal stability analysis of braced excavations with flexible embedded walls in undrained clay

Abstract

An upper bound mechanism for the basal stability analysis in non-homogeneous undrained clay is presented. The current streamline-based velocity field formulas are extended into broader forms, allowing for the deformation compatibility between the wall and the soil. The proposed mechanism, comprising three shear zones, integrates consideration of the plastic bending moment of the embedded wall. The present study is validated by comparisons with solutions from the finite element limit analysis and elastoplastic finite element analysis. Results demonstrate that the proposed mechanism yields lower upper bounds compared to existing analytical methods, with predicted failure surfaces aligning well with elastoplastic finite element analysis and finite element limit analysis outcomes. Furthermore, a novel dimensionless number is proposed to quantify the relative strength of the plastic bending moment to soil undrained strength. Investigation into the influence of wall plastic bending moment, soil non-homogeneity, and wall penetration depth reveals beneficial effects. Following the analysis of case studies, it becomes evident that the proposed mechanism offers more dependable predictions compared to the existing circular upper bound mechanism.