Geological Eras

The geologic time scale subdivides the 4.6 billion years of the earth history into a hierarchy of time periods corresponding to the history of the earth formation (Canada 2010). The Precambrian era began with the formation of the Earth and followed by the Paleozoic, Mesozoic, and Cenozoic eras. Each of these eras is divided into periods, the periods into epochs, and epochs into ages (Canada 2010). Geologically, Canada is one of the oldest countries in the world, and Precambrian rocks extend over more than half of Canada (Wallace 1948). Three significant geological events governed the geological formation of Canada, namely the shield formation, mountains formation from sediments accumulated in basins in the region of the margins of the Shield,

The upper lacustrine drift deposit within Glacial Lake Regina consists mainly of highly plastic clay, known as Regina clay, which extends to variable depths depending on the location. The lacustrine deposit occasionally encounters a lower section that is very silty, low plastic, saturated and less stiff than the upper clay. Previous geotechnical studies identified two different layers of the glacial clay till deposits (Christiansen and Schmid 2005). The upper clay till was characterized to be relatively thin, weathered (brown) glacial clay till of the Battleford Formation. However, the lower layer was identified to be unoxidized (grey) glacial clay till of the Floral Formation. The Battleford till was found to have lower shear strength than the Floral till. In some areas, the two till layers are directly connected, in other areas are separated by layer comprised of sand and gravel or sandy silty clay with variable thickness. Both the glacial clay till and the clay lacustrine soil deposits are a part of a distinct geological unit known as the Saskatoon

The amount of swelling-shrinkage movements is determined by the water content of the near-surface zone, the zone of seasonal fluctuations, or the active zone, which extends to a depth of 3 m below the ground surface and more in the case of the presence of tree roots (Driscoll 1983). According to Nelson et al. (2001), the active soil zone can be defined as follows, (i) the area of soil that significantly contributes to soil expansion at any particular time, (ii) the zone of seasonal moisture fluctuation in which the soil moisture changes due to climatic changes near the ground surface, (iii) the depth of wetting in which water contents have changed due to the water supply from external sources, and (iv) the depth of potential heave in which the overburden vertical stress equals or exceeds the swelling pressure of the soil. The active soil zone is of particular importance to be used to estimate heave by integrating the strain produced over the zone in which water contents change (Walsh et al.