Effect of Slope Steepness, Void Ratio, and Intensity of Rainfall on Seepage Velocity and the Stability of Slopes

Rainfall has been considered as one among the major causes of shallow slope failures. Infiltration of rainwater increases pore water pressure, changes degree of saturation and causes the loss of strength in soil, which all attribute to the reduced factor of safety of the slope. A series of physical model tests were conducted on slopes prepared at different soil void ratios and steepness. The slopes were subjected to three different rainfall intensities – 0.28 mm/min, and 0.55 mm/min until the soil reached saturation and time-wise variation in seepage velocity, spatial variation of soil suction, and soil deformation were measured. The study results showed that pore water pressure and the velocity of movement of wetting front increase with an increase in void ratio, and increase in the intensity of rainfall. Deformation analysis results of the slope materials were performed with the measured location of wetting front and soil suction for different time period and matched well with the experimental results. This study was useful to quantify the effect of void ratio, and intensity and duration of rainfall on slope.