Aspects of soft clay behaviour important for correct prediction of spudcan foundation penetration

Abstract

An advanced hypoplastic constitutive model for soft clay has been developed with the following features: pre-yield non-linearity, strength anisotropy (different critical state friction angles in compression and in extension), stress- and OCR-dependency of undrained shear strength and soil structure and its degradation during loading. The model features are explored here through simulation of spudcan foundation penetration into a carbonate silty clay that was obtained from the Timor Sea. As different parameters control individual features of the model, model properties that are relevant to spudcan bearing pressure predictions can be separated from the properties that do not affect the results substantially. As expected, it is confirmed that pre-yield non-linearity is among the properties not important for the predictions. On the contrary, strength anisotropy, stress- and OCR-dependency of undrained shear strength and structure degradation are shown to be important aspects to be considered, indicating limitations of the use of simple elasto-plastic models for spudcan bearing pressure predictions. The conclusions can be adopted in the definition of a suitable experimental programme targeting the features of soil behaviour relevant to this geotechnical problem.