Compression characteristics and index properties of tills and intertill clays in southern Saskatchewan, Canada

Abstract

Compression characteristics and index properties of unweathered tills and clays from repeated glaciations follow a predictable pattern at 10 sites along a 1300-km transect across southern Saskatchewan. A surface ablation melt-out till of the Battleford Formation is normally consolidated, a basal melt-out till of the Battleford Formation is moderately overconsolidated (σp′ = 400–750 kPa), and the older (pre-Battleford) tills and intertill clays are heavily overconsolidated (1800 ± 200 kPa). Variation in lithology, as indicated by Atterberg limits, is small within formations which reflected in the compression index. The older tills of the Sutherland Group are highly plastic compared with the younger tills of the Saskatoon Group. The in situ dry density of the youngest (Battleford) till is slightly above 100% maximum Proctor density. The in situ dry density of the older (pre-Battleford) tills is at or above the 100% maximum modified Proctor density. At these high densities the in situ degree of saturation is 94.5 ± 4.8%; as compared with Proctor optimums at 80.3 ± 3.8%. It is not practical to increase bearing capacity of the tills by compaction. Disturbance by compaction equipment could cause a decrease in density. Key words : preconsolidation, tills, intertill clays, Proctor density, multiple glaciations.