USE OF ROTATIONAL EROSION DEVICE ON COHESIVE SOILS

Water erosion of cohesive soils is a complex phenomenon that includes different processes. A classification of erosion processes is proposed and examples are given in relation to highway construction. In the case of the scour resistance of solid clays, available prediction methods proposed relatioships between physical or mechanical parameters and the critical hydraulic shear stress that defines a boundary between erosion and no erosion, whereas erosion rates usually are not estimated. These methods have been questioned because it appears that the physicochemical parameters of both the clay and the eroding water control the erosion process. Subsequent research on these parameters has yet to yield reliable predictions based on indirect measurements. Consequently, it is deemed necessary to test the clay and eroding water for each case. In order to study the erodibility of solid cohesive soils, a rotational erosion device has been improved. Either intact or remolded samples can be tested, physicochemical parameters can be controlled, and the hydraulic shear stress and the erosion rate can be adequately determined. A relatively complete and accurate graph of erosion rate versus hydraulic shear stress, including erosion rate-values for hydraulic shear stress-values lower than critical, can be established. The influence of water quality or of any stabilizing treatment of the cohesive soil may be quantitatively analyzed.