Effects of Hydraulic Loading History on Suffusion Susceptibility of Cohesionless Soils

Suffusion is a selective erosion of fine particles under the effect of seepage flow within the matrix of coarser particles. This complex phenomenon appears as a combination of three processes: detachment, transport, and possible filtration of finer fraction. It can induce a change in particle size distribution, porosity, and hydraulic conductivity of the material. With the objective to characterize suffusion susceptibility, downward seepage flow tests were conducted. Four different cohesionless soils were tested under hydraulic-gradient controlled conditions or under flow-rate controlled conditions. This study shows the significant effect of hydraulic loading history on the value of critical hydraulic gradient. Moreover, the method characterizing the erosion susceptibility based on rate of erosion does not lead to a unique characterization of suffusion process for different types of hydraulic loading. The new analysis is based on energy expended by the seepage flow and the cumulative eroded dry mass. The results demonstrate that this approach is more effective to characterize suffusion susceptibility for cohesionless soils.