Evaluation of factors affecting the deformation behaviour of braced excavation

Abstract

Deformation behavior of braced excavation is influenced by some factors related to soil behavior and the wall as well as interface between the wall and the soil. The objective of this study is to evaluate the relative importance of these factors through a series of numerical experiment performed using finite element method coded in PLAXIS. A hypothetical model was established as a reference in this study. Subsequently, parametric study was performed by varying the soil modulus and interface reduction factor. Two constitutive models: Hardening Soil model (HS) and Mohr-Coulomb model (MC) were used in the study to compare the capability of the models to capturing the deformation response of the braced excavation. The analysis result shows that the choice of the constitutive model has a significant effect on the deformation response of braced excavation. More specifically the magnitude of soil modulus used in the constitutive model affects the deformation behavior of braced excavation. Assigning 50% of HS model soil stiffness to MC model gave closely matched wall deflection at the final level of excavation. Assigning one-third of HS model soil stiffness to MC model gave close match in ground surface settlement. This results shows the incapability of MC model to predict actual modulus of the soil at any stage of excavation and unloading conditions. On the other hand, HS model with the capability to assign suitable soil modulus at any stress level is expected to give more realistic prediction of wall deflections and surface deformation. The results also show that the ground surface settlement and wall deflection of braced excavation is significantly sensitive to the variation of interface factor at the active side of the wall.