Development and Validation of the Downhole Freestanding Shear Device (DFSD) for Measuring the Dynamic Properties of Clay

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 reapplication 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.

Language

  • English

Media Info

  • Media Type: Print
  • Edition: Final Report
  • Features: Appendices; Figures; References; Tables;
  • Pagination: v.p.

Subject/Index Terms

Filing Info

  • Accession Number: 01150473
  • Record Type: Publication
  • Source Agency: UC Berkeley Transportation Library
  • Report/Paper Numbers: CA03-0024
  • Contract Numbers: 65A0014
  • Files: CALTRANS, TRIS, STATEDOT
  • Created Date: Feb 2 2010 3:14PM