Contact erosion is a type of internal erosion which occurs at the interface between two soil layers of different particle sizes. Particles from the fine soil (sand, silt, clay…) are pulled and driven by the flow through the pores of the surrounding coarse soil (gravel ...). Although its presence is suspected in many earthfill embankments, this process has been little studied so far. The aim of this thesis was to better understand and, possibly, to model contact erosion. At pore scale, the flow at the interface between two porous media was characterized thanks to an experimental device, developed in Cemagref, combining Planar Laser Induced Fluorescence, PIV method and Refractive Index Matching. The spatial variability of flow shear stress has been emphasized. At sample scale, several tests on real and reconstituted soils were carried out in LTHE, in order to identify the phenomena involved in contact erosion. Erosion rates as a function of flow magnitude have also been measured for different types of fine and coarse soils. Then, a stochastic model was proposed to account for these experiments. Finally, large scale tests were conducted in the laboratory of Compagnie National du Rhône, to study the influence of scale effects as well as the consequences of contact erosion on global behavior and integrity of the embankment structure. The possibility of piping initiation by contact erosion was underlined. This thesis is part of the project ERINOH project and was funded by EDF-CIH.
