Strength and permeability parameters of compacted partially saturated silty and sandy soils

This Technical note summarizes some experimental results concerning the effective strength parameters (c’ – ϕ’) and the saturated coefficient of hydraulic conductivity (k) of silty and sandy soil specimens that have been compacted at different compaction degrees. The tested soils were used for the construction/refurbishment of existing levees. The effective strength parameters were obtained from conventional triaxial loading compression tests. Specimens were compacted at different percentages of the maximum (optimum) dry density and at the optimum water content. The maximum dry density and optimum water content were determined according to the Modified Proctor method. Specimens with different percentages of the maximum dry density at the optimum water content were obtained in the Proctor mold by using different compaction energy. Levees (and more generally any type of earthworks) can increase their water content because of intense rainfall or repeated floods. Therefore the strength parameters of fully saturated specimens have also been experimentally determined. The saturated coefficient of hydraulic conductivity has been inferred from variable head permeability measurements that were performed in specially equipped oedometers. This coefficient has been measured in the case of specimens compacted at different compaction degrees and at different initial water contents (i.e. saturation degrees). The effect of compaction degree on strength and permeability parameters has been shown. As for the strength parameters, the effect of partial saturation (suction) has also been shown.