Evaluation of submergence effects on the stability of slopes

Abstract

This work presents a numeric study of the effects of submergence on the stability of slopes. Submergence is a hydraulic condition under which water levels are the same outside and inside the slopes. Cases that have been studied show that safety factors change according to submergence levels. This phenomenon is observed even when the slopes are composed of granular materials that obey the linear Mohr-Coulomb law. The numerical analysis enables identifying the causes of said effect. The safety factors reach their maximum values for totally submerged slopes, both cohesive and granular. Minimum safety factors are not observed at zero submergence but rather at the intermediate submergence level. These minimum factors can be as low as 25% less than those computed at zero submergence, and in most of the cases studied they are between 20% and 50% of slope height. The maximum reduction in the safety factor and the submergence level at which it is presented depend on several variables, such as shearing resistance, the volumetric weight of soils, slope inclination and conditions of the slope's foundation. Without the consideration of submergence effects, safety factors can be considerably overestimated in many cases.