ABSTRACT:

We enhance the Modified-Cam-Clay (MCC) Model to capture the stress-level dependency of mudrock mechanical properties observed in recent experimental work. The MCC model assumes that the internal friction angle (?), the slope of the normal compression curve (?), the undrained strength ratio (Su/s’vo), and the lateral stress ratio (K0) are constant. However, recent lab tests on resedimented mudrocks from Eugene Island, Gulf of Mexico, document that these properties vary substantially over the stress range of 1-100 MPa. We enhance the linear form of the critical state and compression curves in the MCC model to a power-law form to fit the observed variation of ? and ? with the stress level. The enhanced MCC model is then used to predict Su/s’vo and K0 ratios over the stress range of 1-100 MPa. The enhanced model successfully predicts the variation of these variables. The enhanced model also predicts that the shape of the state boundary surface varies significantly with the stress level. The successful performance of the enhanced model suggests that the MCC model, developed for soils at low stress levels, has the potential to predict the nonlinear behavior of resedimented mudrocks over large stress ranges encountered in the geologic systems.The Modified-Cam-Clay (MCC) model is the most commonly used model for clays in geotechnical engineering, where stresses are typically lower than nearly 1 MPa. The main advantage of this model is its satisfactory performance in simulating the complicated behavior of clays with a minimal number of parameters (Roscoe and Burland 1968). The MCC model is an elastic-plastic model, where the total strain tensor,

e

, is decomposed into elastic,

ee

, and plastic strain tensors,

ep

:

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