On the physicochemical aspects of compacted clay compressibility

The effects of the clay-water-electrolyte system and the temperature on soil compressibility due to primary consolidation and secondary compression are investigated. The method used for the alteration of the exchange complex yielded a single species of cation (Na+, Ca++, or K+) to dominate the exchange complex, representing more than 87% of the total exchangeable cations present. The potassium (K+) dominated exchange complex caused fundamental changes in the behavior of the tested soil: from the untreated soil to the K-soil, there was a decrease in the plasticity index (PI) from 66 to 13%, a decrease in free swell from 10.5 to 1.74%, and about a 10-fold increase in the coefficient of permeability. The virgin compression index (C-c) is found to be strongly related to the soil dry density and can be accurately modeled accordingly. Temperature significantly affects the behavior of the untreated soil: the measured coefficient of permeability was increased by about 100% for a temperature change from 26 to 40 degrees C; whereas temperature has almost no influence on the K-treated soil.