Modeling Bio-Cemented Sands: Shear Strength and Stiffness with Degradation

Over the past decade, recent developments between the geotechnical and life science disciplines have establish microbial induced calcite precipitation (MICP) as a novel ground improvement method. This method improves the static and dynamic mechanical properties of the soil while maintaining its environmentally friendly characteristics. Its application process lends itself to increased compatibility with varying infrastructure where other methods pose issues due to constraints. Currently, there are no established methods to properly assess the level of improvement, or adequately predict the expected performance for a given level of cementation. It is envisioned that numerical simulations will hold the key. With this in mind, a model was developed that incorporates the key aspects of the improved biomaterial for the purpose of comparing the lightly cemented and the original uncemented soils to illustrate the potential of the MICP method. Specifically, the model incorporates the ability to capture the behavior and transition from the cemented state to the uncemented state while maintaining adherence to the controlling factors of void ratio and confining stress. This paper focuses on the changes of shear stiffness and shear strength as a result of the degradation of the calcite (CaCO₃) cementation in the MICP soils.