Suffusion behavior under fluctuated hydraulic gradient conditions focusing on amount and size of soil particles contained in drainage

Suffusion is the detachment and migration of fine particles through voids connected by the matrices of coarse particles. Although water storage structures are known to be affected by fluctuations in seepage flow, due to fluctuations in the water storage levels brought about by rainfall and agricultural activities, the suffusion behavior when the hydraulic gradient is fluctuated is unclear. In this study, one-dimensional downward water-passing experiments with suffusion were performed using a cylindrical column device, and the changes in the amounts of the discharged water and soil particles, as well as the turbidity of the drainage over time, were examined. The behavior of suffusion was investigated from two viewpoints: the quantitative changes in the amount of discharged drainage and the amount of discharged soil particles due to the progress of suffusion, and the qualitative changes in the particle size composition of the discharged soil particles. A unique feature of this study was the tracing of the changes in the particle size composition of the discharged soil particles from the relationship between the turbidity and the concentration of drainage during suffusion. As a result, it was found that not only the amount of soil particles discharged by suffusion, but also the particle size composition of the discharged soil particles changed under both constant and fluctuated hydraulic gradient conditions.