EXPERIENCES WITH ALLUVIAL FOUNDATIONS FOR EARTH DAMS IN THE PRAIRIE PROVINCES

The foundations for numerous dams in proglacial and interglacial valleys in the Prairie provinces of Canada consist of soft alluvial soils. The deposits are up to 60 m deep, and contain thick layers of clay interspersed with lenses and layers of silt, sand, and gravel. This paper describes the damsite investigation and laboratory testing required, the design methods and construction procedures used, and the foundation performance observed during and after construction. A number of empirical relationships between index tests and physical properties of the soils, which provide useful guidelines for preliminary design are presented. Safe economical dams have been constructed in spite of large deformations and high pore pressures. Two case histories illustrate the wide range in dam design for alluvial foundations. Refs.