Pore-scale flow measurements at the interface between a sandy layer and a model porous medium: Application to statistical modeling of contact erosion

Contact erosion is potentially initiated at the interface between two soil layers by a groundwater flow within the coarser material. Once eroded by the flow, particles from the finer soil are transported through the pores of the coarser layer. Fluvial dykes are often exposed to this phenomenon. Small-scale experiments, combining Refractive Index Matching medium, Planar Laser Induced Fluorescence, and Particle Image Velocimetry, were carried out to measure the flow characteristics in the vicinity of an interface between a model granular medium and a fine graded sandy layer. Longitudinal velocities and shear-stresses distributions were obtained in Darcy flow conditions. They reveal a long tail towards large values which reflects the spatial variability of the constrictions in the pores network. Taking account of these distributions can improve the modeling of contact erosion by going beyond the simple use of mean quantities, like Darcy velocity, as usually proposed in the literature. Author-produced version of the article published in Journal of Hydraulic Engineering , 2013, 139, 1-11 Original publication available at http://cedb.asce.org doi : 10.1061/(ASCE)HY.1943-7900.0000641