A Bio-Hydro-Mechanical Model for Propagation of Biogrout in Soils

Conventional soil improvement techniques can lead to permanent soil pollution or emission of carbon dioxide. It is therefore a challenge for engineers to design alternative sustainable and cost-effective grouting techniques. In Microbial Induced Calcite Precipitation (MICP), bacterial activity leading to calcite precipitation is created and the precipitated calcite acts as a cementing agent in the soil. Bacterial strains producing urease can indeed have a major impact on the natural calcite precipitation process when supplied with nutrients and urea. The miscible and reactive biogrout injection in saturated, deformable soil need to be better described to more effectively design this innovative grouting technique. A comprehensive research work is therefore carried out on this topic. The field equations for biogrout transport are established based on the understanding of the complex processes involved: bio-hydro-mechanical couplings, transport, miscibility, bacterial growth and decay and bacterial attachment and detachment. The resulting set of field equations is discretized and implemented into an advanced finite element code. Finite element modelling of column injection tests is carried out to validate the formulation and demonstrate the potentiality of the developed model. The simulation results emphasize the significant role of bio-hydro-mechanical processes in the global MICP response of the soil.