Two-dimensional experimental assessment of interaction energy-induced suffusion in sand–clay mixtures

Suffusion can be defined as the loss of relatively small soil particles in gap-graded soils without any volume change. In this study, the susceptibility of interaction energy-induced suffusion in sand–clay mixtures is investigated using a laboratory-scale two-dimensional flow cell. The filtrated clay during the injection was measured at three outlets to assess the gravity and reattachment effects as a function of clay type (kaolinite, illite and bentonite) and sand grain size. It was found that the settling of detached clay particles and the reattachment effect during their transport through the sand medium is a strong function of the swelling potential of clay and the size ratio between sand and clay. In addition, observed particle size distributions of clay at the outlet demonstrated that the relatively small and large clay particles are susceptible to suffusion for non-swelling and swelling clay, respectively. The comparison of total filtrated clay between a two-dimensional flow cell and the typical soil-column experiments (one-dimensional flow) revealed a high chance of underestimating suffusion using soil-column experiments to assess the suffusion of sand–clay mixtures.