An elastoplastic mechanical constitutive model for microbially mediated cemented soils

Microbially induced calcite precipitation (MICP) is an innovative bio-mediated soil improvement technique that develops cementation within originally loose and potentially collapsible soils. This method utilizes biogeochemical processes with microbes. It has the advantage of being friendly to the environment and sustainable. In spite of the current interest in the MICP technique, the mechanical modeling of MICP-treated soils is still limited. In this paper, a constitutive model for MICP-treated sands is presented. The core components of the proposed approach include: a critical state yield surface, sub-loading concepts, a mechanism to account for the MICP-induced cementation enhancement, and an evolution law to consider bonding degradation effects during shearing. The mathematical framework is presented in detail. The model is then applied to analyze recently published experiments involving MICP-treated samples, with different calcite contents, and tested under different conditions (i.e., various confining pressure and loading paths). The model was able to properly capture the main features of MICP-treated sands behavior observed in the tests. It also assisted to interpret the response of this type of soil under different loading conditions.