Slope Stability Under Extreme Rainfall Conditions

It is known that natural or cut slopes are usually unsaturated soils. A slope may lose its current stability because of the decrease in matric suction due to the increase in water content. One of the reasons that can cause an increase in water content is rainfall, which is an environmental issue. The failure of a natural and/or cut slope triggered by a rainfall may cause environmental disasters resulting in fatal loses and injuries as well as economic damages. This study covers the stability of natural slopes under extreme rainfall conditions. During the stability analysis, a numerical analysis program was used which utilizes finite difference formulations. The slope model used in the study was designed to represent a classical natural slope dimensions and two different soil types were selected to compare; both are silty soils but having different suction characteristics and hydraulic conductivities. Three rainfall intensities have been selected and the two were from the recorded past events. The first is a long-term precipitation with low intensity, and the second and the third ones are short-term intensive precipitations, and all the rainfall models were acted individually with the same antecedent saturation degree. The factor of safety values was calculated for each situation and compared as well. As a result of the analysis, it has been seen that slope stability analysis of the unsaturated soils are very depended on their suction characteristics and hydraulic conductivities even though they have similar mechanical properties.