Combined effects of wet-dry cycles and interacting fluid on desiccation cracks and hydraulic conductivity of compacted clay

Abstract

Compacted clays are used as barriers in landfills mainly due to their low hydraulic conductivity and self healing properties. These clays are subjected to moisture fluctuations and simultaneously exposed to leachates. Besides swelling, the shrinkage and cracks developed during drying get altered due to their exposure to contaminants and control their hydraulic behaviour. Therefore, this paper quantifies the volumetric behaviour and cracks pattern of compacted clay exposed to salt solutions during wet-dry cycles using X-ray computed tomography (XCT) imaging experiments. The results showed that the cracks volume of clay specimen interacted with 4 M NaCl solution is significantly greater than the specimens interacted with distilled water (DW) and 0.4 M NaCl solution at the end of drying cycles. XCT and digital camera imaging experiments showed that the cracks did not develop at same locations in specimen interacted with DW, indicating the self healing property of clay. However, the development of cracks at same locations in specimen interacted with 4 M NaCl solution indicates the complete deterioration of self healing property of clay. This resulted in significantly higher hydraulic conductivity of compacted specimen interacted with 4 M NaCl solution than the specimens interacted with DW and 0.4 M NaCl solution at the end of different wetting cycles.