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Development and validation of the downhole freestanding shear device (DFSD) for measuring the dynamic properties of clay.
  • Published Date:
    2008-12-01
  • Language:
    English
Filetype[PDF-34.78 MB]


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Development and validation of the downhole freestanding shear device (DFSD) for measuring the dynamic properties of clay.
Details:
  • Corporate Creators:
    University of California, Berkeley. Dept. of Civil and Environmental Engineering ; California. Dept. of Transportation. Division of Research and Innovation ;
  • Report Number:
    CA03-0024
  • Resource Type:
  • Geographical Coverage:
    California
  • OCLC Number:
    502291920
  • Corporate Publisher:
    California. Dept. of Transportation. Division of Research and Innovation
  • Format:
    PDF
  • Description:
    The Downhole Freestanding Shear Device (DFSD) is an innovative tool developed for in situ measurement of dynamic

    properties (modulus and damping) of clay soils over a broad range of strains. The device essentially performs

    laboratory-quality torsional shear testing on a “freestanding” column of soil carved below the bottom of a borehole.

    Other shear testing modes may also be accommodated. The DFSD design and testing procedure minimizes sample

    disturbance by maintaining estimated values of the original in situ effective stress throughout the sample preparation,

    instrumentation, and testing processes. As a result, the sample is not significantly unloaded, and therefore does not

    experience the stress-relief disturbance associated with the removal and re-application of stresses.

    This report documents design, development and validation work that has yielded a field-capable prototype DFSD tool

    that is capable of meeting or exceeding the best current laboratory testing capabilities for measurement of dynamic

    properties of clay soils used in earthquake site response analysis. Mechanical, pneumatic, electrical and sensor

    systems used to remotely create a test specimen, maintain continuous control of its anisotropic stress state, and test the

    specimen over a wide strain range of shear strain are described. Validation tests comparing DFSD results to state-ofthe-

    art laboratory results are presented as well as results from a series of tests that quantify and compare reduced

    sample disturbance caused by the DSFD relative to conventional high-quality sampling methods.

  • Funding:
    65A0014
    DRI Research Task No. 0024
  • Supporting Files:
    No Additional Files
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