Physical model test of seepage and deformation characteristics of shallow expansive soil slope

Abstract

Large-scale physical model test on expansive soil slope at a shallow depth is conducted with the aim of monitoring moisture content and swelling deformation. In this paper, a wedge-shaped model box with a bevel at the bottom was developed to reflect the actual channel slope in the South-to-North Water Transfer Project. The results provide an improved understanding of the physical behavior and failure mode of a saturated-unsaturated expansive soil slope subjected to moisture content variation. Showing that, after rainfall, the surface soil quickly became saturated, with the deeper soil moisture remaining unchanged. Infiltration depth, speed, and saturation region reduced with the increasing height along the slope. Surface displacement increased from slope foot to slope shoulder, and significantly attenuated towards the depth. Horizontal displacement was about 1/3–1/2 of the vertical displacement. The larger the increment of the soil moisture, the greater the surface deformation. Soil showed dehydration shrinkage with fissures first appearing in the soil surface and expands downward with continuing evaporation. The junction of saturated-unsaturated zone and the wet-dry interface were the areas of stress concentration. Swelling effect led to stress field redistribution in the expansive soil slope, and it was the most important factor causing expansive soil shallow slope failure.