Thermo-bio-chemo-hydro-mechanical coupled model framework investigating factors influencing strength and failure of microbial induced carbonate precipitation (MICP) treated soils

Microbially induced carbonate precipitation (MICP) is a promising, sustainable soil-improvement technique. However, comprehensive models that simultaneously predict the extent of cementation and the associated strength and failure characteristics of treated soils are still lacking. This study presents a novel coupled Thermo-Bio-Chemo-Hydro-Mechanical (TBCHM) model integrated with a statistical damage constitutive model to overcome the limitations of previous elastoplastic approaches for MICP-treated soils. By representing the initial microelement strength through a Weibull distribution, the formulation enables a realistic simulation of progressive failure mechanisms in bio-cemented soils. Following successful validation against experimental data for both reactive transport and mechanical response, the model was applied to investigate the influence of treatment temperature, bacterial concentration, and chemical concentration on the mechanical behaviour of MICP-treated soil under both static and cyclic loading conditions. The results demonstrate that bacterial concentration has the most pronounced influence on mechanical performance. The proposed framework effectively predicts the mechanical improvement level and highlights that achieving a desirable calcite distribution is as critical as the total precipitation amount for optimizing strength and cyclic resistance. The proposed model serves as a mechanistic framework for quantifying and optimizing the interplay between bio-cementation processes and soil mechanical performance for specific geotechnical applications.