Effects of Fine Particles on the Suffusion of Cohesionless Soils. Experiments and Modeling

Internal erosion has long been a major problem associated with earthen structures, and its field investigation has been limited because of its complexity. Laboratory experiments provide a potential insight into the induced processes. Soils suitable to suffusion involve an easy movement of fine particles between the coarse ones. In this study, suffusion experiments were performed on a laboratory column packed with different sand-fines mixtures and subjected to controlled flow conditions. The mixtures are made of Fontainebleau sand (NE34) and fines (kaolinite or illite or silt). The initiation and the progression of soil suffusion were investigated for soil mixtures, and the hydraulic conductivity variation was derived from pressure measurements. Attempts are made to assess the influence of the type and content of fine particles on mixtures suffusion. The results show that among the tested fine particles, illite exhibits a great resistance against suffusion. Fine content increase involves less suitability to suffusion till a threshold value. Recorded pressures indicate that detachment of fines may be followed by clogging in the soil matrix, leading to a decrease of hydraulic conductivity. Furthermore, analytical solutions of simplified mathematical model based on the mass conservation of eroded particles (Govindaraju et al., J Hydrol 172:331-350, 1995) were used to simulate the recorded soil suffusion curves, and the model performance was evaluated. Comparisons between numerical and experimental results indicated a quite good agreement, and allowed the estimation of the model parameters.