STP1014

    Comparison of In-Situ Vane, Cone Penetrometer, and Laboratory Test Results for Gulf of Mexico Deepwater Clays

    Published: Jan 1988


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    Abstract

    Site investigations were recently performed offshore at three prospective plat-form sites in water depths between 400 and 500 m in the Gulf of Mexico. Soil conditions at the sites generally range from very soft clays near the seafloor to very stiff clays at 120- to 150-m penetration. Analyses of stress history indicate the soils at these locations are generally normally consolidated. Laboratory tests were performed on recovered specimens to deter-mine the undrained shear strength. Standard laboratory miniature vane shear tests and unconsolidated-undrained triaxial tests were performed in addition to consolidated-undrained tests using stress history and normalized soil engineering properties (SHANSEP) procedures. Tests performed in the field included in-situ vane and cone penetrometer. Cone factors Nk were computed using in-situ vane shear strengths as the reference strength.

    This paper compares the results of consolidated-undrained (SHANSEP) laboratory and in-situ tests to determine a relationship that may be used to correlate these results. The effects of soil strength and plasticity are examined and used to correlate shear strength with the liquidity index. A comparison is also made between peak and residual in-situ vane strengths.

    This paper further describes how a combination of these in-situ and laboratory tests can be used to characterize a deepwater site for foundation design. Recommendations for future site investigations are also discussed.

    Keywords:

    clays, site investigation, in-situ vane, cone penetrometer, SHANSEP, liquidity index, plasticity index, normalized shear strength


    Author Information:

    Johnson, GW
    Geotechnical engineer, Browning-Ferris Industries, Houston, TX

    Hamilton, TK
    Project manager, McClelland Engineers, Inc., Houston, TX

    Ebelhar, RJ
    Engineering department manager, S&ME, Inc., Fairfield, OH

    Mueller, JL
    Ocean engineer, Conoco, Inc., Houston, TX

    Pelletier, JH
    Senior civil engineer, Shell Oil Company, Houston, TX


    Paper ID: STP10337S

    Committee/Subcommittee: D18.02

    DOI: 10.1520/STP10337S


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