Impact of Rainfall Variation on Slope Made of Expansive Yazoo Clay Soil in Mississippi

Yazoo clay soil is highly expansive in nature and extends over central Mississippi, Alabama, and Southern Louisiana. Shallow slope failure is frequent in embankments constructed using Yazoo clay due to rainfall volume and climatic variation. This study investigates the effect of different intensities and volumes of rainfall on slopes constructed of Yazoo clay soil in Mississippi. The coupled flow-deformation analysis was conducted using the finite element method (FEM) in PLAXIS to investigate the unsaturated hydromechanical behavior of the slopes. Weathered Yazoo clay soil samples were collected and tested in laboratory conditions to investigate the soil index properties, soil strength parameters, and soil water characteristics curve. The historical rainfall pattern of Mississippi from National Oceanic and Atmospheric Administration (NOAA) is evaluated at different intensities (2 to 50 mm/h) and duration of rainfall (30 min to 7 days) based on return periods of 50, 100, and 500 years. Three fill slopes constructed using Yazoo clay soil, with slope ratios of 2H:1V, 3H:1V, and 4H:1V, are investigated. The rainfall pattern is applied to the top boundary of the slope in PLAXIS. The investigation results indicated that rainfall water infiltrated the top part of the slope, near the crest, resulting in the reduction of both the matric suction and the factor of safety of the slope.