Modelling of the elastoplastic behaviour of the bio-cemented soils using an extended Modified Cam Clay model

An elastoplastic constitutive model based on the Modified Cam Clay (MCC) model is developed to describe the mechanical behaviour of soils cemented via microbially induced calcite precipitation (MICP). It considers the increase of the elastic stiffness, the change of the yield surface due to MICP cementation and the degradation of calcium carbonate bonds during shearing. Specifically, to capture the typical contraction-dilation transition in MICP soils, the original volumetric hardening rule in the MCC model is modified to a combined deviatoric and volumetric hardening rule. The model could reproduce a series of drained triaxial tests on MICP-treated soils with different calcium carbonate contents. Further, we carry out a parametric study and observe numerical instability in some cases. In combination with an analytical analysis, our numerical modelling has identified the benefits and limitations of using MCC-based models in the simulation of MICP-cemented soils, leading to suggestions for further model development.