Bio-remediation of desiccation cracking in clayey soils through microbially induced calcite precipitation (MICP)

Abstract

Desiccation cracking is a common natural phenomenon in clayey soils, considerably degrading their mechanical and hydraulic properties. Typical remediation methods are associated with high labor costs, high maintenance costs, or the usage of environment-unfriendly chemicals. Microbially induced calcite precipitation (MICP) has emerged as a green and sustainable soil improvement technique. The application of MICP in clayey soils remains poorly investigated due to the presence of microscopic pores among clay soil particles that restrain the free passage of bacteria. In this study, we carry out cyclic wetting-drying tests to characterize the effect of MICP on the desiccation cracking behaviors of clayey soils. We prepare four groups of soil samples sprayed with deionized water, bacteria solution, cementation solution, and both bacteria and cementation solutions, respectively. Soil desiccation cracking behaviors captured by a high-resolution camera are quantified using image processing. We resort to optical microscopy and scanning electron microscopy for microstructural characterizations. Experimental results reveal the effects of fluid type and treatment cycle number on the crack evolution and volumetric deformation of soils. Comparatively, the MICP treatment involving both bacteria and cementation solutions work most effectively in lowering the soil cracking potential. Geometrical parameters featuring the crack pattern such as surface crack ratio, average crack width, total crack length, crack width distribution range and the most probable value of crack width decrease significantly with the increasing treatments. This study is expected to improve the fundamental understanding of desiccation cracking mechanisms in the MICP-treated soils and provide insights into the potential application of MICP for cracking remediation in clayey soils.