Suffusion of sand–clay mixture by three-staged change of ionic strength

The suffusion of particles classified as coarse-grained soils in the Unified Soil Classification System has been relatively well investigated in previous studies, whereas suffusion of clay particles has not been thoroughly explored. For clay particles, the surface interaction energy between clay and sand can be a critical factor in conjunction with hydraulic gradient. Therefore, this paper presented a series of designed soil-column experiments for assessing the reduction of ionic strength on suffusion of clay particles in the sand–clay mixture. The three most typical clay particles (kaolinite, illite, and montmorillonite) were selected and the ionic strength was decreased during the injection. The results indicate that the sequence of decreasing ionic strength induced substantial suffusion of clay particles, mainly attributed to the decreased attraction between sand grains and clay particles. In addition, among three types of clay particles, the high swelling potential of montmorillonite particles led to the most substantial increase in relative hydraulic conductivity caused by suffusion.