Analysis of Excavation Support Systems Considering the Influence of Saturated and Unsaturated Soil Conditions

Abstract

A well-established framework for the design of excavation support systems (ESSs) is not available in the literature. Several guidelines that have evolved from engineering practice are conventionally used in the design of ESSs. The key indicators for judging the performance of ESSs are wall deformation, internal wall stresses, and surface soil settlement information. There is evidence from several case studies that the measured wall deformations are typically lower than the predicted values. Such behavior may be attributed to ignoring the influence of capillary suction. The key objective of the study presented in this paper is twofold; the first is highlighting limitations in the current design practice and the second is to pave the way for comprehensive design of ESSs. This is achieved by undertaking numerical analysis on a silty clay taking account of the influence of saturated and unsaturated soil conditions to investigate the performance of ESSs based on a rational design approach. In addition, the proposed approach is validated based on wall deflections information using the published results of a case history. The proposed approach is promising for implementing the mechanics of unsaturated soils in geotechnical engineering practice for the rational design of ESSs. The paper also highlights some limitations of the present study and the need for future studies to provide verifications using more case histories.