Geotechnical aspects of Thunder Bay Terminals

CIM Bulletin, Vol. 72, No. 808, 1979

J. L SEYCHUK Principal, Golder Associates, J. H. A. CROOKS, Associate, Golder Associates, Toronto, Ontario

McKellar Island, the site of the Thunder Bay Terminals coal handling facility, is situated in a low-lying delta area. The ground surface across the island, which is relatively flat at between 1 and 5 ft above lake level, is underlain sequentially by surficial peat materials, extensive lacustrine strata and glacial till deposits which overlie shale bedrock. Each of these major stratigraphic units significantly influenced the design and construction of major features of the facility.Coal is to be stored in 60-ft-high stockpiles placed directly on the surficial peat deposits. The assessment of the potential for basal instability of the stockpiles involved determining the nature and engineering characteristics of the peat deposits, together with observations of the behaviour of instrumented sections of a loop railway embankment which was also constructed directly on the surficial peat. Deep-seated instability through the underlying lacustrine clay deposits was also considered. The requirement for minimal deformation of the dock structure for Slip No. 2 necessitated consideration of the stability of the combined fill and dredged slopes in this area. Finally, the nature of the glacial till deposits and underlying shale bedrock was important in two aspects, namely the capability of these materials as a founding stratum for driven piles and for the construction of the dumperhouse and conveyor tunnel crossing of the McKellar River to a thermal generating facility on Mission Island.This paper describes the nature and engineering properties of the various stratigraphic units underlying the site and their effect on the design and construction of the major features of the terminal. The results of monitoring programs and observations of the geotechnical aspects of the performance of these major features are also described.
Keywords: Thunder Bay Terminals Ltd., Geotechnical engineering, McKellar Island, Terminals, Design, Construction, Geomorphology, Lacustrine deposits, Foundations, Stockpiles, Coal, Slope stability, Conveyors, Tunnels, Monitoring