COMPRESSION CHARACTERISTICS AND INDEX PROPERTIES OF TILLS AND INTERTILL CLAYS IN SOUTHERN SASKATCHEWAN, CANADA

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 surfac e ablation melt-out till of the Battleford Formation is normally conso lidated, a basal melt-out till of the Battleford Formation is moderate ly overconsolidated (sigma(p)' = 400-750 kPa), and the older (pre-Batt leford) tills and intertill clays are heavily overconsolidated (1800 /- 200 kPa). Variation in lithology, as indicated by Atterberg limits, is small within formations which is reflected in the compression inde x. The older tills of the Sutherland Group are highly plastic compared with the younger tills of the Saskatoon Group. The in situ dry densit y of the youngest (Battleford) till is slightly above 100% maximum Pro ctor density. The in situ dry density of the older (pre-Battleford) ti lls 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 c ompared with the Proctor optimums at 80.3 +/- 3.8%. It is not practica l to increase bearing capacity of the tills by compaction. Disturbance by compaction equipment could cause a decrease in density.