Critical hydraulic gradient and suffusion of sand-clay mixtures under a gradual increase in flow rate

초록

Suffusion is the loss of relatively small particles from the soil matrix due to high hydrodynamic forces acting on them. This study investigates critical hydraulic gradient and hydraulic-induced suffusion of sand-clay mixtures as a function of clay type, the size ratio between sand and clay, and ionic concentration using a two-dimensional flow cell in the laboratory. The breakthrough curves, particle size distribution (PSD) of filtrated clay, flow rate, and mass of filtrated clay at the top, middle, and bottom outlets of the flow cell were measured as the hydraulic gradient increased. It was found that the critical hydraulic gradient of sand-clay mixtures is a function of ionic concentration, clay type, and size ratio. In addition, the order of critical hydraulic gradient and the mass of filtrated clay during the injection implies that the earlier initiation of suffusion does not lead to more significant suffusion. Furthermore, the flow rate during the injection indicates that the flow rate can be a good indicator of assessing critical hydraulic gradient at low ionic concentrations. Overall, the results shown in this study suggest the need for coupling the interaction energy between sand and clay and hydrodynamic forces in assessing the susceptibility of suffusion for clay-containing soils. (c) 2026 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/bync-nd/4.0/).

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