MODELLING GROUND RESPONSE FOR DEEP EXCAVATION IN SOFT GROUND

Abstract

Due to its simplicity in use and input parameters can be straightforwardly determined (from
in-situ tests, laboratory tests and empirical correlations), linear elastic perfectly-plastic Mohr-Coulomb (MC)
model remains a favourite constitutive modelling choice to Geotechnical engineers. Non-linear Hardening
Soil (HS) model is an improvement of MC model. It is not commonly used mainly due to lack of appropriate
non-linear drained stiffness parameters from laboratory tests and field calibrations. Using a deep excavation
project as a case study, this paper presents a comparison of MC and HS models in assessing wall deflection.
The numerical models are established based on soil parameters interpreted from available soil investigation.
It was found from back analysis of a case history that laboratory tests and empirical correlations grossly
underestimated the drained stiffness parameters. In order to close the gaps between predicted and observed
deflections, the drained stiffness parameters have to be increased by six-fold and more than eight-fold for
MC Model and HS Model, respectively.