Full scale test of periodic irrigation infiltration in a cracked and intact clay slope

Near-surface clays can experience substantial volume change as matric suction changes in response to imposed changes in environmental conditions. A decrease in soil suction can cause swell of soils, which can be damaging to structures founded in or supported on these soils. Furthermore, when drying progresses, clays may begin to crack as matric suction increases because of the low confining pressures near the ground surface. Light structures founded on clay soils are often subject to infiltration from nearby irrigation systems on landscaping installed near the surface. Infiltration of water into the supporting clay can be very difficult to estimate for several reasons, including the difficulty in estimating the surface flux in a sloped condition, the difficulty associated with predictions of conductivity in the presence of secondary permeability through surface cracks, and the difficulties associated with modeling a wetting front moving into an initially dry soil. In this study, full-scale infiltration testing was performed on a soil bed subjected to periodic irrigation over an extended time frame. Tests were conducted for a flat surface and for a surface sloped at a 10% grade. Two surface soil conditions were studied, intact soil and soil with artificially introduced cracks, resulting in a total of four tests. The depth and extent of wetting will be presented for each test. Significant differences were observed between the four cases. The results can be used to calibrate existing models for movement of the wetting front and to develop improved algorithms for modeling the movement of the wetting front.