Effect of Desiccation Cracking on the Swell and Swell Pressure of Expansive Clay

Significant effort has been placed on the determination of swelling properties of expansive soils, such as swell pressure and swell potential. However, there are only a limited number of studies of expansive soil response that include the effect of desiccation cracking; most studies and methods of analysis have simply neglected the effect of cracks. At the same time that cracks provide a path for flow of water under positive head, the crack network in an expansive soil functions as swell-absorbent media (due to open spaces within the soil) which can reduce the total amount of vertical swell that the soil would experience. In this study, a laboratory investigation was carried out to quantitatively evaluate the effect of cracks on swell potential and swelling pressure. The presence of desiccation cracks was found to reduce the amount of swell and also reduce the swell pressure compared to intact, uncracked, specimens. The percentage reduction of swell potential and swell pressure was found to be a function of the volume of cracks and the applied net normal stress.