A Study of the Failure Mechanism of Braced Excavations Using 3D Finite-Element Analysis

Abstract

This study aims to investigate the failure mechanism of structural support systems in braced excavations. The three-dimensional finite-element method (FEM) was used to model the complexity of real geometry by considering the elastoplastic structural support system. Because failure could occur at the connection between walls and struts, a new model of a strut–wall connection was considered in the analysis to represent the actual condition of excavation failure. Three failure case histories were studied to investigate the performance of strut–wall connections by calibrating their strength parameters until the factor of safety was close to unity. It was found that a good result of stability analysis could be obtained in the FEM by considering this model. The yielding of the strut–wall connection model initiated the collapse of the bracing system in all case histories, followed by the yield of struts and failure of soils. A robust failure mechanism was also obtained, in which the yielding of the structural support system at failure initially developed at the middle section toward the corner of excavation geometry.