The Infiltration characteristics of expansive soil subjected to drying-wetting cycles under surchage

This study investigates the infiltration characteristics of expansive soil subjected to drying–wetting cycles under surcharge. Infiltration tests are conducted on undisturbed expansive soil over four drying–wetting cycles. Additionally, the permeability coefficient under loading is determined prior to any drying–wetting cycles. Within the context of this study, the sample heights after drying and after wetting are monitored to determine the natural swelling and shrinkage deformations. Experimental results show that the infiltration rate decreases as the pressure increases. The sample’s swelling–shrinkage deformation decreases with each progressive drying–wetting cycle, whereas the infiltration rate consistently increases. The infiltration curve under the drying–wetting cycle can be divided into three stages according to the infiltration characteristics, which is significantly different from the infiltration curve of the sample without the drying–wetting cycle. Moreover, the proposed model can fit the infiltration curves well, and its fitting parameters are described using dimensionless pressure and the number of drying–wetting cycles. The drying of the expansive soil produces cracks that are advantageous for infiltration. Additionally, the microscopic connection between aggregates reflects changes in the internal structure of the soil during successive drying–wetting cycles. As the number of drying–wetting cycle increases, small particles aggregate into large aggregates, and the contact relationship between the aggregate changes from face–face to point–point contact, reducing the swelling potential and increasing the porosity and infiltration capacity of the soil.