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

Author(s): Franco M.Francisca*, Marcos A.Montoro, Pablo M.Nieva

Physic and chemical properties of liquids 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 fluidswith different chemical properties: deionizedwater, 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. Results show 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 observed behavior. On the other hand, the hydraulic conductivity of fine soils (silts and bentonite-sand mixtures) shows a dispersion of five orders ofmagnitude when tested at the same dry density but with different permeating fluids.

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