The prediction of total heave of a slab-on-grade floor on Regina clay

Abstract

Several analytical methods for the prediction of total heave of desiccated, expansive soils have been proposed for various geographic regions. The proposed method herein is based on a general theory for unsaturated soil. The in situ stress conditions, as assessed from the corrected swelling pressure and the required soil moduli, are deduced from the constant volume oedometer test.Verification of the proposed method was accomplished using data accumulated from the monitoring of movements of a floor slab in a light industrial building in north-central Regina, Saskatchewan. A leak in a water line buried under the floor slab resulted in a maximum heave of about 106 mm. Of the three final pore-water pressure distributions assumed, the one where pressure is constant with depth and equal to atmospheric pressure appears to be representative of the field conditions corresponding to the maximum measured heave. The measured heave represents 89% of the predicted heave for the zero pore-water pressure distribution. It is concluded that the proposed method of analysis, based upon a general theory for unsaturated soils, provides a practical method to accurately assess total heave.