Relation between flow through and volumetric changes in natural expansive soils

Abstract

Geology and climate govern the evolution and behavior of natural expansive soils in the semi-arid Canadian Prairies. The Regina clay deposit has a flat topography, a homogenous composition, and contains hair-line fissures. This research focuses on understanding the relation between flow through and volumetric changes in the natural expansive soil. Based on analysis of test data, it is concluded that flow occurs through macro-pores or fissures (5 × 10−8 m/s) during structural volume change and through micro-pores or matrix (10−9 m/s) during normal and residual volume changes. The hydraulic conductivity decreases by several orders of magnitude and becomes asymptotic vapor flow (2 × 10−14 m/s) during residual volume change. A complete assessment of soil behavior requires water retention, swell-shrink, and hydraulic conductivity curves. The proposed straight-line representation of the functions' components is useful for predicting field response of expansive soils.