ABSTRACT
Slope instability in unsaturated residual soils and loose fills has attracted increasing attention in recent years around the world in such countries as Brazil, South Africa, Japan and in the Far East. Rain-induced failures are the most common failures. Rainfall leads to the development of a perched water table, increasing the main groundwater level and soil erosion (due to concentrated water flow), resulting in an increase in pore water pressure or a reduction in soil matrix suction. This, in turn, results in a decrease in shear strength on the potential failure surface to a point where equilibrium can no longer be sustained in the slope and then failures occur. However, the present understanding of the influence of transient seepage in unsaturated soils, due to water infiltration under various boundary and ground conditions, and hydrogeological regimes on slope stability, is still relatively poor compared with other elements of geomechanics.
