Effects of Silt Content and Void Ratio on the Saturated Hydraulic Conductivity and Compressibility of Sand-Silt Mixtures

The hydraulic conductivity, the coefficient of consolidation, and the coefficient of volume compressibility play major roles on the pore pressure generation during undrained and partially drained loading of granular soils with fines. This paper aims to determine how much these soil parameters are affected by the percentage of fines and void ratio of the soil. The results of a large number of flexible wall permeameter tests performed on 60 specimens of two poorly graded sands with 0, 5, 10, 15, 20, and 25% nonplastic silt are presented and discussed. Hydraulic conductivity measurements were done at effective confining stresses of 50–300 kPa. The evaluation of the data shows that the hydraulic conductivity and the coefficient of consolidation of sands with 25% silt content are approximately two orders of magnitude smaller than those of clean sands. The coefficient of volume compressibility of the sand-silt mixtures is affected in a lesser degree by void ratio, silt content, and confining stress. The influence of the degree of saturation on the laboratory-measured k values is also discussed.