Failure Investigation of Braced Excavation in Soft Clays: Case Study on the Collapse of Nicoll Highway

Abstract

Deep excavation in clay normally causes large soil movement, which may induce basal heave failure. In this study, the three-dimensional finite element analysis with the strength reduction method was employed to evaluate the typical failure mechanism of braced excavation in soft clays. The collapse of Nicoll Highway was selected as a failure case history and further conducted by considering the full elastoplastic structural behavior. The results showed that the computed wall displacements were successfully verified through the observation data. It was also found that the excavation failure was initiated by the yielding of the strut-waler connection, which was similar to that of the field observation. Finally, the proposed finite element model adopted in this study can be used as a design recommendation to evaluate the failure mechanism and further prevent possible braced excavation failure in soft clays.