Coupled Soil-Atmosphere Modeling for Expansive Regina Clay

Abstract

Alternate deformations in the expansive clay have crippled civil infrastructure systems in and around the city of Regina that lies in a semi-arid zone. The main objective of this paper was to develop a soil-atmosphere model for predicting the net water flux and the corresponding volume change in the local expansive soil. A one-dimensional hydrologic model was developed, for a homogeneous soil and no ground water table, by coupling material properties with atmospheric parameters. The use of site coordinates ensured material continuity in a strain-independent framework and soil volume changes were calculated using model results in conjunction with laboratory data. Results showed high water absorption and retention capacities for the investigated soil deposit. Conducive atmospheric conditions during summer gradually desatuarted the top 2.5 m layer of the clay that imbibed sporadic rainfall water thereby resulting in volume increases. Cyclic variations in the degree of saturation and the corresponding swelling potential were highest at and near the ground surface and gradually decreased with depth. The highest swelling potential was predicted for late summer and equaled 37%. The model reasonably estimated the soil-atmosphere interactions for the investigated expansive clay and was found to depend on an effective capture of site conditions and material properties. An increased modeling duration can ensure steady state with respect to antecedent moisture.