Characterizing drying-induced clayey soil desiccation cracking process using electrical resistivity method

Desiccation cracking process negatively impacts both mechanical and hydraulic properties of clayey soils. Traditional methods applied for the characterization of soil cracking behaviors are mainly based on visual inspections or destructive approaches. The electrical resistivity method provides a non-destructive, sensitive and continuous evaluation of the spatiotemporal variations of many soil physical properties. In this study, an integrated experimental setup is configured to simultaneously capture the evolution of temperature, relative humidity, water content, crack morphology, and apparent electrical resistivity in clay during continuous drying. Apparent electrical resistivity measurements at 1.0 cm electrode spacing are carried out to detect the initiation, propagation and coalescence of desiccation cracks. Image processing quantitatively describes the geometrical characteristics of shrinkage surface crack patterns. Experimental results indicate the strong correlation between the measured apparent electrical resistivity and cracking behavior of soil. As water content decreases during drying, the apparent electrical resistivity of initially saturated clayey soil decreases first before the onset of desiccation cracking, and then transits into the increasing trend. The evolution of apparent electrical resistivity in clayey soil is dominated by two competing effects, with one originated from the volumetric shrinkage-induced closer packing of soil fabric and higher concentration of ions in pore fluids, and another from the evaporation induced water loss associated with hydration film contraction and desiccation crack insulation. The electrical resistivity method is an effective technique to characterize the development of desiccation cracks, and particularly reliable to map their positions. This study is expected to improve the fundamental understanding of desiccation cracking mechanisms in soils and provide insights on soil characterizations for enhanced stability and performance of earthwork structures.