| Alternate deformations in the expansive Regina clay has crippled civil infrastructure such as water supply and sewage collection systems, transportation networks, and residential, industrial, and commercial facilities in southern Saskatchewan. In a predominantly semi-arid (BSk) region, volume changes in this glaciolacustrine deposit are governed by seasonal climatic variations. The purpose of this research was to develop a fundamental understanding of the swell, shrink, and consolidation behaviour of Regina clay. The soil is comprised of expansive clay minerals such as smectite (32%), illite (7%), and chlorite (3%), the combined effect of which is manifested in a high water adsorption and retention capacity. The swelling pressure (Ps ) and the swelling potential (SP) were determined to be 120 kPa and 1.5 kPa, respectively. The estimated heave in the top 1.0 m layer of the soil was found to be 33 mm. The S-shaped swell-shrink path correlated well with the consistency limits such that the bulk of the volume change was found to be in between the plastic limit (S = 80%) and the shrinkage limit (S = 60%). Between these consistency limits, the Ps increased 12 times (from 2% to 24%) and the SP increased by two orders of magnitude (from 27 kPa to 2500 kPa). The air-entry value and the residual water content were determined to be 313 kPa and 7%, respectively. Likewise, the hydraulic conductivity changed by eleven orders of magnitude (from 10-9 m/s to 10-20 m/s) with a change in saturation from 100% to 0%. Results of numerical modelling indicated that the generation of SP was negligible in winter and became quite active in the summer and early fall. The highest SP was predicted to be 37% in September. The degree of saturation and the SP data widely fluctuated at the ground surface and these fluctuations gradually reduced with depth. The top 1.0 m soil layer was found to be the active zone susceptible to changes in atmospheric conditions. |
