Influence of sand type on pipe development in small- and medium-scale experiments

摘要

Up to now, the phenomenon of backward erosion piping in uniform sands covered by a cohesiverntop layer has been predicted using a 2D approach. The Sellmeijer model (Sellmeijer 1988) includes the 2D-flowrntowards the pipe, Poiseuille flow in the infinitely wide pipe and equilibrium of grains on the pipe bottom tornpredict the critical head.Arecent series of experiments indicates that the original Sellmeijer model fails to predictrnthe critical head correctly for coarser sand types, and an empirical correction has been proposed to correct forrnthis (Sellmeijer et al. 2011).A theoretical solution is not presently forthcoming. In this study the pipes formed inrnsmall- and medium-scale experiments have been analysed for different sand types. It was found that the width ofrnthe pipe increases with increasing grain size. This indicates that a 3D-approach is required to correctly model thernpiping process and to solve the influence of grain size on critical head. 3D numerical simulations of the pipingrnexperiments provide insight in the pipe hydraulics and difficulties encountered upon modeling of piping.