A Comprehensive Study on Swelling Potential of Yazd Clay

Some of the structures founded on clay soils in the desert area of the country، especially in Yazd، have suffered damages، most probably due to swelling of the soil. The ambiguity in the interpretation of the mechanisms and causes of these damages has necessitated studying swelling characteristics of these soils. Thirty soil samples، taken from 1. 5m to 3. 0m below the ground surface، were tested. Tests included: (a) physical tests including determination of Atterberg Limits، hydrometer method gradation، natural dry density، water content، and swelling pressure/percentage; (b) chemical tests for determining chemical substances and cations of the samples and (c) XRD tests to determine the soil mineralogy. According to the indirect methods of swelling assessment، most of the samples lie in the medium to low swelling potential catgories. The direct oedometer test support this notion. The prevailing minerals present in the soil samples are illite and calcium montmorillonite. The paper also presents the relationships between the swelling potential and the Atterberg Limits، clay fraction، sodium and calcium contents of the soil.