Case Study of Mohr–Coulomb and Hardening Soil Models in PLAXIS Using Field Monitoring Data for Excavation and Lateral Support Works

Abstract

This paper presents the analysis of finite element modelling using PLAXIS 2D, to evaluate the predicted performance of two modelling methods — Mohr-Coulomb model and Hardening soil model — against the monitoring data obtained in the excavation and lateral support works in project in Kwai Chung, New Territories. On-site monitoring data, including the ground movement monitoring and inclinometer readings throughout the staged excavation, were collected and reviewed in this study. The Mohr-Coulomb model, that assumed as linearly-perfectly plastic soil behaviour, has limitations in using the linear relationship in stress and strain in soil to predict the ground movement during the excavation. The model is unlikely to illustrate the plasticity before failure, and strain hardening is not captured. In contrast, the Hardening soil model reflects the deformation behaviour under different stress, and the increase in soil stiffness at depth. It simulates a more realistic stress- strain relationship under different loading conditions. The numerical analyses using the MC and HS models were presented and compared with the site monitoring data. The comparison showed that the HS model better reflected the actual wall deflection shape and presented closer location of maximum wall deflection with the site data. These findings highlight the significance of adopting advanced constitutive models to enhance the accuracy of estimation in designing excavation and lateral support (ELS) systems and the limitation of the modelling methods will be discussed.