Author(s): Gijs Hoffmans; Leo Van Rijn Emeritus Professor
Keywords: Backward erosion; Darcy’s law; incipient motion; laminar pipe flow; piping; shear-stress concept of Grass; Shields diagram
Abstract: This paper discusses a piping model that fundamentally differs from Sellmeijer’s model in relation to the structure of the formula used to calculate the critical hydraulic gradient at which backward erosion leads to dike failure. In this model, the laminar groundwater flow in the sand layer is schematized by characteristic discharges, which are estimated by Darcy’s Law. The laminar pipe flow and the incipient motion of the particles are described using equations of Hagen–Poiseuille, Darcy–Weisbach and Shields. The shear-stress concept of Grass is used to include the effects of the non-uniformity of the sand mixture on pipe erosion. Sellmeijer’s piping equations and the proposed piping model are compared using over 100 laboratory experiments and some field observations.