Abstract
The effect of solution composition on unsaturated hydraulic conductivity of Houston Black clay, Beaumont clay, Katy fine sandy loam, Nacogdoches fine sandy loam and Troup sand was determined. Samples representing defined horizons of these soils were equilibrated with several salt concentration levels and various SAR values. The soil-water diffusivity of the different electrolyte treated samples was measured using the pressure plate outflow apparatus. The modified one-step method was used. Calculation of the diffusivity values was based on Doering's procedure. The corresponding hydraulic conductivity data were calculated from the soil-water diffusivity by taking the slope of the soil-water characteristic curves at the water contents represented by the diffusivity values. In order to analyze the hydraulic conductivity values obtained, the various electrolyte treated soils were characterized with regard to swelling, dispersion and exchangeable sodium percentage. The concentration and chemical nature of the solution used for the hydraulic conductivity measurement are of extreme importance. The most important factor contributing to differences in behavior of soils under saline and alkaline conditions is mineralogy. The effect of solution composition is caused by ion-exchange phenomena of the colloidal fraction of the soil. The variations in swelling, flocculation or dispersion of the soil aggregates are a result of the degree to which sodium will occupy exchange positions on clay surface. At a high salt concentration, the soils exhibited a minimum swelling and dispersion because of the collapsed condition of the electrical double layer. Swelling, dispersion (the disintegration of aggregates), and flow of solid material and the weakened aggregates under local shearing stress (aggregate failure) usually occurred simultaneously. Swelling was usually accompanied by a reduction in macropore volume due to the distortion of the soil aggregates that are subjected to anisotropic confining pressure. ...
Saffaf, Adham Yassin (1969). The effect of solution composition on unsaturated hydraulic conductivity of some Texas soils. Doctoral dissertation, Texas A&M University. Texas A&M University. Libraries. Available electronically from
https : / /hdl .handle .net /1969 .1 /DISSERTATIONS -175486.