New Apparatus for Assessing Soil Suffusion Susceptibility Under Two Flow Directions

Suffusion is the process of selective erosion of fine particles within the matrix of coarse soil particles under the effect of seepage flow. Suffusion can induce important modifications in the hydraulic and mechanical characteristics of the soil in different flow directions. Thus, to ensure the safety assessment of hydraulic earth structures, the experimental models need to match the reality of the body of dikes or dams with horizontal flow. In this paper, a new multi-directional flow apparatus is described for characterizing soil sensibility for the suffusion process and to study the effect of flow direction. A series of suffusion tests was performed using this new device with vertical flow or horizontal flow on both gap graded soils and widely graded soils. All tested specimens were subjected to a multi-stage hydraulic gradient. The comparison of the results of the new device with results obtained from another device in vertical flow was realized. The specimens have the same initial hydraulic conductivity and suffusion susceptibility classification with both devices. Furthermore, for specimens characterized by limited soil anisotropy, the suffusion susceptibilities of these soils are quite identical under vertical flow and horizontal flow. These results permit to validate the new device and the experimental method.