Macroscopic properties of soils controlled by the diffuse double layer around particles

Abstract

Physic and chemical properties ofliquids and particle-fluid interaction (PFI) mechanisms control relevant soil properties. Chemical properties of pore fluids affect mainly the structure and hydraulic conductivity of fine soils with high specific surface. In this work, the hydraulic conductivity of three different soils (sand, silt and a bentonite-sand mixture) was measured using fluids with different chemical properties: deionized water, kerosene, 1N Sodium chloride solution and a solution with 20% of ethylic alcohol. The hydraulic conductivity was determined by following the falling head test procedure and using three different rigid-wall permeameters. Resultsshow that the hydraulic conductivity of coarse granular soils does not depend on fluid chemistry since PFI have negligible effect on soil behavior. In this case, the dry density of soils and viscosity of fluids determine the ob- served behavior. On the other hand, the hydraulic conductivity of fine soils (silts and bentonite-sand mixtures) shows a dispersion of five orders of magnitude when tested at the same dry density but with different perme- ating fluids.