Shear and compression strain development in sandy model slope under repeated rainfall

Repeated rainfall on natural slope may cause repeated loading and unloading of pore pressure in the slope. The deformation behavior and soil-water conditions in a model slope were monitored under repeated rainfall to examine the influence of repeated rainfall on the deformation of the slope. The results show that the shear and compression deformation of the soil layer developed not only during the wetting process but also during the drying process. The surface and vertical displacement of the slope increased as the groundwater level (G.W.L.) increased during the first wetting process and remained constant during the subsequent drying process. The displacements showed small progress until the maximum G.W.L. of the first wetting process and then increased significantly at the next wetting process. The shear and compression strain remained constant as the suction decreased during the wetting processes and increased with the increase of suction during the drying processes; the strains significantly increased with a small decrease in the suction and then significantly increased with the generation of the pore pressure at the final rainfall event. The relationship between the shear strain and the compression strain was not affected by the repeated loading and unloading of suction. The relationship between the surface displacement and the vertical displacement was also free from the variation of the suction due to the repeated rainfalls. Strain increased with the increase in the pore pressure and the maximum pore pressure at a deeper layer was larger than at a shallower layer. The increase in the vertical displacement to the increase of the surface displacement approaches zero with the increase in the shear strain at the soil layer, denoting a failure state of the soil layer.