STP670

    Field Evaluation of Caisson-Shale Interaction

    Published: Jan 1979


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    Abstract

    Load tests were conducted on ten full-sized cast-in-place drilled caissons (bored piles, drilled shafts) of varying diameter. Three caissons were tested to evaluate end-bearing on the surface of fissile shale; five caissons were tested to evaluate side shear of shale sockets; one caisson was tested to evaluate end-bearing below weathered shale; and one caisson was tested to evaluate side shear in soil. Nine of the shale-bearing caissons tested exhibited subgrade failure, observed as excessive settlement, while the remaining shale-bearing caisson, drilled to end-bearing below the weathered shale, failed by shearing of the concrete shaft. The end-bearing test values exceed commonly employed empirical design values by factors ranging from 3 to 23. The shale sockets supported loads of at least one-third of and in some cases exceeding the ultimate end-bearing load.

    Keywords:

    axial load, bored piles, construction, drilled piers, field tests, foundations, load testing, shafts, shale


    Author Information:

    Spanovich, M
    Principal and project engineer, Engineering Mechanics, Inc., Pittsburgh, Pa.

    Garvin, RG
    Principal and project engineer, Engineering Mechanics, Inc., Pittsburgh, Pa.


    Paper ID: STP33750S

    Committee/Subcommittee: D18.11

    DOI: 10.1520/STP33750S


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