Modeling of Weather-Induced Volumetric Changes in Cracked Expansive Clays

Abstract

The main objective of this research was to develop a model for predicting weather-induced volumetric changes. Based on the unique soil properties of cracked expansive clays, the model included flow-through estimations and heave-settlement predictions. The water content and volume change were trained using long-term monitoring data (1960–1968) in Regina (Canada). The water flux was found to increase from − 0.3 mm/day to − 0.05 mm/day (1960–1963), followed by a further increase to 0.1 mm/day (1964–1965), and then by a bounce back to − 0.2 mm/day (1966–1968). The monthly flux-in and flux-out closely matched one another because evaporation equalled infiltration whereas snowmelt resulted in runoff. The water content varied during summer following a cyclic trend with an initial decrease in April–June and a subsequent rebound in July–October. This delay is due to the slow advance of the wetting front through the soil profile that subdued large variations in surface saturation below 0.5 m depth. The fluctuations were high (28% to 15%) in 1960–1963 and gradually decreased (35% to 33%) in 1964–1965 and remained similar in the subsequent dry years (1966–1968). Volume changes were found to be ± 20 mm in water deficient years (1960–1963) and decreased to half (± 10 mm) in water surplus years (1964–1965) and subsequent water deficient years (1966–1968). The large surface variations gradually decreased with depth and were found to be negligible at 3.1 m below the surface due to the lower cumulative values at depth. The model was successfully validated for compacted soils with respect to depth (1.2 m and 2.0 m) as well as asphalt cover and grass cover using 2006–2007 and 2009–2010 field data.