Erosion in a granular medium interface

If stratified soil structures are not designed according to conventional filter criteria, a flow of ground water may erode and transport an underlying, finer material through the pore system of the coarser stratum above. A constitutive equation for interfacial transport rate is derived from physical principles and verified through laboratory experiments. The relationship is incorporated in a mathematical formulation for interfacial erosion processes analogous to the one commonly applied to alluvial streams. Both analysis and experiments indicate that interfacial erosion depends strongly on variation in the grain size ratio between the two strata and the porosity of the coarser stratum. A simulation example demonstrates a case in which the core in an earth-fill dam is subjected to overflow and the crest of the core is eroded.