Shear wave velocity and permeability evolution of MICP-treated carbonate bearing sand

Microbially induced calcite precipitation (MICP), a promising method developed for soil stabilization, demonstrates potential as an eco-friendly approach capable of significantly improving the geotechnical properties of soil. However, research indicating the evolution of permeability requires further investigation to substantiate the effectiveness of MICP treatment in enhancing permeability. In this aspect, this study investigates the evolution of shear wave velocity (Vs) and permeability (k) in MICP-treated carbonate bearing sands. Compacted specimens were subjected to MICP-treatment using 5ml/min and 10ml/min injection flow velocities. Injection velocities of 5ml/min produced heterogeneous CaCO3 precipitation across the sample, with maximum precipitation near the injection point after 6 cementation cycles. This led to clogging near the injection point, resulting in a decrease in k by an order of magnitude and a constant Vs, showing a maximum value of 554.2m/s. On the other hand, specimen subjected to a 10ml/min injection velocity showed a relative homogeneous CaCO3 distribution throughout. This resulted in a consistent permeability and Vs continued to increase beyond 6 cementation cycles and reached a constant value of 950m/s after 13 cementation cycles. Thus, injection flow velocity is an important variable to be considered when investigating permeability modifications in MICP treated soils.