Experimental investigation of the effects of suffusion on physical and geomechanic characteristics of sandy soils

This paper reports the measured effects of suffusion, a type of internal erosion, on the physical and geo-mechanical properties of soils including permeability, volume change, compressive strength, and soil grains gradation. A poorly graded river sand with the addition of 10 % kaolinite clay was used to create three gap-graded soils and an unaltered poorly graded "original soil." Testing was performed using a modified triaxial apparatus that permits seepage through compacted specimens and allows collection of effluent and eroded soils. The specimens, 5.1 cm in diameter and 10.2 cm in length, were monitored for changes in volume and permeability during the suffusion tests. After erosion, the specimens were compressed using the consolidated-undrained (CU) test. The collected effluent samples were dried to determine the erosion rate and eroded soil particle gradations with respect to effluent volume. Companion control specimens were tested without erosion. The results revealed that suffusion may affect some physical and geo-mechanical properties of soils. Permeability reduction was generally observed in all soils, indicating fine grains migration and clogging within the specimens. The three gap-graded soils each exhibited a greater degree of internal erosion (suffusion), permeability reduction, and volume change than the original soil. The experimental setup and testing protocol also provided a feasible methodology for further research on the effects of suffusion on the physical and geo-mechanical properties of soils. Limitations of this research and future research recommendations on this topic are provided at the end of this paper.