Finite element analysis of excavation in soft clay using cross walls

Abstract

The performance of braced excavation is often evaluated by the maximum lateral deflection of the sheetpile or diaphragm wall. This project will evaluate the performance of cross walls and struts in reducing the lateral deflection of the diaphragm wall in soft clay, using finite element analysis software. This study will investigate the viability of the use of cross walls in Singapore by simulating an excavation in soil properties found in Kallang formation, using advanced soil models such as the Hardening soil model. For this study, the parameters of the excavation, and the earth retaining wall system will be varied to investigate the relationship between these parameters and their ability to influence the lateral wall deflection. Some of the parameters that will be varied, are the length of the excavation, embedment depth of the cross wall, cross wall interval, and the location of the cross wall bay in relation to the diaphragm wall corner. A numerical comparison will then be done between cross walls and struts to access their performance. In numerical finite element analysis of excavation models, it is common practice to conduct the analysis under plane strain conditions to save computation time. However it is found in previous parametric studies that a plane strain analysis would produce a more conservative result compared to a three-dimensional one. Hence this study would also aim to access the degree of divergence between a plane strain analysis and a three-dimensional one under soft clay conditions found in Singapore soils.