Physical approaches of erosion by water flows: roles of transport and reactions in mass-transfers – PhysErosion

Erosion is defined as the loss of mass of a solid phase under the action of a flow in a fluid. Two physical mechanisms are distinguished. Chemical erosion occurs, when the molecules and minerals forming the solid are dissolved into the liquid. Mechanical erosion acts when the flow is fast enough to transport grains extracted from the solid. These phenomena explain, for example, the weathering and corrosion of building materials. Erosion is also essential in geomorphology, describing at different scales the formation of landscapes under the action of wind, rainfalls and rivers. The transport of grains in the river beds thus corresponds to a process of mechanical erosion, while the dissolution of soluble rocks such as salt or limestone by water forming a cave network is a matter of chemical erosion. In general, chemical weathering and mechanical transport are combined. In this project, we propose to study from a physical point of view the different mechanisms of erosion by water flows by associating several complementary areas of expertise. The dynamics and forms of erosion will be studied experimentally in different hydrodynamic configurations, at IPGP (Olivier Devauchelle) for granular transport and at MSC (Michael Berhanu) for fast dissolving materials, then the combination of chemical and mechanical erosion. The reactive mechanisms at the interfaces will be physically characterized at ILM (Jean Colombani). Finally, these experimental inputs will be used to propose at ISTO (Cyprien Soulaine) a general model involving several space and time scales that will be integrated in cutting-edge multi-scale simulators for hydro-geochemical processes. It will thus be possible to offer long-term predictions of the evolution of landscapes under the action of erosion phenomena.