Characterization of a Complex Soil Foundation

December 10, 2020

This paper summarizes the geotechnical characterization of a complex soil foundation below an earthfill embankment and how it was managed in design. Preliminary investigations in the area revealed a sequence of clays and interbedded sands and silts underlain by an irregular bedrock surface. Of particular interest to embankment stability was the presence of a narrow bedrock trough within the embankment footprint which was infilled with soft clays and loose sands and silts. Site investigations were conducted to delineate the extent of the trough and characterize the geotechnical properties of the soils present within. Methods comprised: cone penetration tests (CPTs), standard penetration tests (SPTs), shear vanes, test pits, drilling and sample collection for index and advanced laboratory testing. The investigations confirmed the presence of normally and overconsolidated clay and a previously unidentified and potentially liquefiable interbedded sand and silt unit. Data collected were used to develop a geologic model and soil strength parameters which were incorporated into design analyses. Quinn. J., J. Casey, L. Murray and R. Friedel. 2017. “Characterization of a Complex Soil Foundation,” in GeoOttawa 2017 70 Years of Canadian Geotechnics and Geoscience, 70th Canadian Geotechnical Conference, Ottawa, Ontario, October 1 – 4, 2017. Toronto: Canadian Geotechnical Society.