On slope instability induced by seepage erosion

This paper is focused on seepage erosion causing liquefaction processes and rapid slope failures. One case history, which occurred along an old fluvial terrace in the Po Plain (northern Italy), is presented. The failure was the final consequence of a concentrated flow induced by the incisions due to tractor edged-blade-wheels cutting through the soil layer sealing the bottom of a flooded rice field. To clarify the evolution of the seepage and the erosion phenomena which preceded and characterized the collapse, numerical analyses and some experimental tests on small-scale models have been performed. The problems associated with the hydraulic and mechanical description of localized water flows in unsaturated soils, the three-dimensional conditions of the failure mechanism, and the liquefaction phenomenon are discussed.