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    Improved Determination of Preconsolidation Pressure of a Sensitive Clay

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    Poor agreement between calculated and measured consolidation settlement in the Leda (Laurentian) clay of eastern Canada suggested that either the classical consolidation theory might not apply to this soil or that present testing techniques were not yielding the correct consolidation characteristics of the soil. An underestimation of the preconsolidation load was found to result from tests using normal procedures. An investigation of various techniques to improve the determination of the preconsolidation pressure are outlined in this paper.

    Increment loading tests with various increment sizes and increment durations were investigated as well as continuous loading tests under various controlled rates of stress application and various controlled rates of strain. It was found that small increment tests best defined the pressure - void-ratio curve, but required much time. A method of determining the point of 100 per cent primary consolidation on the log time - deflection plot of small increment tests was developed. Constant rate of strain tests show promise as possible rapid testing techniques.

    Author Information:

    Hamilton, J. J.
    Research Officer, National Research Council, Ottawa, Ont.

    Crawford, C. B.
    Head, National Research Council, Ottawa, Ont.

    Committee/Subcommittee: D18.05

    DOI: 10.1520/STP44323S