STP874: Laboratory Testing of Cement-Bentonite Mix for Proposed Plastic Diaphragm Wall for Complexe LaGrande Reservoir Caniapiscau, James Bay, Canada

    Gill, SA
    Chief engineer and principal engineer, STS Consultants, Ltd., Northbrook, IL

    Christopher, BR
    Chief engineer and principal engineer, STS Consultants, Ltd., Northbrook, IL

    Pages: 15    Published: Jan 1985


    Abstract

    A comprehensive laboratory investigation was carried out to determine a suitable mix of cement-bentonite for a slurry trench cutoff wall for Caniapiscau Reservoir project in James Bay, Canada in 1980. Specifications required the mix to have a permeability of less than 0.01 μm/s and to be able to sustain a plastic deformation of 10% without fissuring as measured at 90 days in a triaxial compression test with a lateral pressure of 196 kPa. Laboratory samples were prepared with different mixes of cement, bentonite, sand, and water and kept in a curing chamber of 100% humidity. Permeability determination and triaxial compression tests were performed after curing periods ranging from 10 to 120 days. Over 84 specimens were tested. The compression tests included unconfined tests, unconsolidated-undrained tests at a constant rate of strain, unconsolidated-drained tests with varying strain rates and at a controlled rate of stress, and a consolidated-drained test. Permeability tests were performed before and, in some cases, after loading. The specimens were examined for fissures and cracks after a strain of 10%. It was concluded that a mixture of 6% (by weight) Ultra Gel 180 bentonite and 160 kg of cement in each cubic metre of the mixture would meet the required specifications. Recommendations for standardized test procedures are made.

    Keywords:

    bentonite, cement, slurry trenches, permeability, test procedures, triaxial test, cutoff wall, strain, strain rate, deformation, plasticity, stress-strain curve


    Paper ID: STP34569S

    Committee/Subcommittee: D18.05

    DOI: 10.1520/STP34569S


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