An equivalent salt solutions method for predicting hydraulic conductivities of soils for different salt solutions

Abstract

Equivalent salt solutions are defined as solutions with combinations of sodium absorption ratio (SAR) and electrolyte concentration producing the same extent of clay swelling in a given soil. It is suggested that in the presence of different equivalent salt solutions a given soil will have the same pore geometry, the same saturated and unsaturated conductivities at specific pressure heads, and hence the same capacity to transmit such solutions under specific boundary conditions. This concept of equivalent salt solutions was used to develop a method for predicting the saturated hydraulic conductivities of soils for different salt solutions. The basic data required for such predictions in a given soil are the equivalent salt solution values and the relationship between saturated conductivity and electrolyte concentration at a given SAR. Saturated conductivities of a red-brown soil and an alluvial soil for salt solutions of SAR 20 and 10 and different electrolyte concentrations predicted by this method were fairly close to measured values. The significance of this concept to field problems involving flow of the salt solutions through soils is briefly discussed.