Abstract
This study aims to characterize the effect of microbial-induced calcite precipitation (MICP) on the desiccation cracking behaviors of compacted calcium bentonite soils. We prepare six groups of samples by mixing bentonites with deionized water, pure bacteria solution, pure cementation solution, and mixed bacteria and cementation solutions at three different percentages. We use an image processing tool to characterize the soil desiccation cracking patterns. Experimental results reveal the influences of fluid type and mixture percentage on the crack evolution and volumetric deformation of bentonite soils. MICP reactions effectively delay the crack initiation and remediate desiccation cracking, as reflected by the decreased geometrical descriptors of the crack pattern such as surface crack ratio. The mixture containing 50% bacteria and 50% cementation solutions maximizes the MICP treatment and works most effectively in lowering the soil cracking potential. This study provides new insights into the desiccation cracking of expansive clayey soils and shows the potential of MICP applications in the crack remediation.
Highlights
Geological waste disposal is a globally preferred method focusing on the storage of high-level radioactive waste
This study aims to characterize the effect of microbial-induced calcite precipitation (MICP) on the remediation of desiccation cracking in compacted bentonite soils
Our study indicates that MICP treatment can delay the crack initiation and suppress the soil desiccation cracking significantly at high initial water content, because of the remarkable water stability of calcite mineral produced in the MICP process
Summary
Geological waste disposal is a globally preferred method focusing on the storage of high-level radioactive waste. Municipal waste landfills remain the most common method of waste treatment worldwide. The resulting progressive formation of desiccation cracks imposes substantial negative impacts on the mechanical and hydraulic behaviors of clayey soils. These cracks undermine the mechanical integrity of the soil structure and cause considerable weakening in soil strength [3,4]. The extensive crack network formed by crack propagation and coalescence provides the dominant conductive pathways for fluid migration, resulting in an increase in the hydraulic conductivity of clayey soils by several orders of magnitude [5,6], which is critical to the isolation functionality of the geostorage system [7]. The degradation of clayey soil properties due to the presence of desiccation cracks under climate changes is responsible for many other geohazards, such as slope failure [8], embankment failure [9], and foundation and dam failure [10]
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