Dynamic evolution of three-dimensional cracks in expansive soil under wet-dry cycles: insights from resistivity monitoring

This study investigates the dynamic evolution of cracks in expansive soil under varying wet-dry cycles, employing a self-developed three-dimensional spatiotemporal crack evolution model testing system. The research includes experiments, spatial moisture migration analysis, resistivity monitoring, and crack distribution inference to elucidate the crack development mechanisms. The findings reveal distinct stages in moisture evaporation at different soil depths, characterized by initiation, stability, deceleration, and residual phases. The influence of wet-dry cycles on evaporation rates is pronounced, particularly in deep soil layers. Resistivity changes in expansive soil during moisture evaporation display specific phases, demonstrating their potential to characterize crack development. The study validates the feasibility of assessing crack development through soil resistivity changes. Crack formation initiates at weak points on the soil surface, with subsequent elongation and secondary crack development, resulting in a crack network. Further moisture evaporation and volume shrinkage widen cracks, while wetting leads to crack healing. Total crack length, average width, and area crack ratio decrease exponentially with soil depth, but increase at different depths with more wet-dry cycles. Volume crack ratio initially rises and then stabilizes, while volume shrinkage capacity diminishes until equilibrium. Wet-dry cycles promote crack development, modifying particle arrangements. This research underscores that soil cracking and crack development result from the evolving balance of moisture-induced stresses in space, stemming from non-uniform moisture distribution. In conclusion, this study sheds light on crack development mechanisms in expansive soil under wet-dry cycles, offering valuable insights for soil engineering and geotechnical applications.