Apparatus design for suffusion characterization

The internal erosion of soil results from seepage flow. It appears to be the main cause of severe hydraulic failure for dams and dikes. All around the world, 46% of dams present a risk of internal erosion. In France, 70 critical cases have already been detected. When internal erosion is suspected, the delay to failure is hardly predictable. Then, authorities should be able to develop effective emergency action plans to prevent casualties. Previously, it is necessary to understand phenomena of internal erosion. Three main processes can be identified: backward erosion, concentrated leak and suffusion. Suffusion is the process where the fine particles of the soil are eroded. A state of the art can be found in the literature and several laboratory studies have been carried out on the subject of suffusion but mainly with the development of the Hole Erosion Tests (HET). In this paper, we present a new experimental device named Cross Erosion Test (CET), which is devoted to the measurement of the initiation of the suffusion. The test consists of the injection, in a first drilling, of clear water and the recovery, in another drilling, of water charged with particles. In a first part, this experiment is calibrated with a numerical simulation. In a second part some preliminary experimental results are analysed. Concluding remarks show the possibility to characterize internal suffusion into a specific soil. This technique can be transposable, in-situ, to consider risks of internal erosion on dams and dikes. Keywords— Cross erosion test, Internal erosion, Numerical calibration, Suffusion.