Journal Published Online: 19 July 2013
Volume 36, Issue 5

Combined Time and Frequency Domain Approach to the Interpretation of Bender-Element Tests on Sand



Shear wave velocities are obtained from bender-element tests on laboratory specimens by analyzing the trigger and response signals. The response signal is a highly distorted translation of the trigger signal, obscuring the identification of the shear wave arrival. This has led to the publication of many criteria to guide subjective decisions on the selection of trigger waveform and frequency and of applicable interpretation methods. Current methods of interpretation result in determination of either the group or phase velocity. As soil and bender-element responses are dispersive, and as the group velocity is only valid in non-dispersive systems, the phase velocity should be measured. A combined time and frequency domain method is presented to allow interpretation of the phase velocity, minimizing subjective input to the interpretation. The method is first demonstrated using simplified synthetic signals and is then applied to laboratory test data. The reproducibility of the results is demonstrated from measurements on ten triaxial specimens of saturated Fraser River sand. The group velocities are shown to be very sensitive to dispersion, not reproducible, and contingent on the selected frequency window, whereas the phase velocities are considerably more repeatable. The combined time and frequency domain method results in the interpretation of a phase velocity using only measured parameters.

Author Information

Styler, Mark
Dept. of Civil Engineering, University of British Columbia, Vancouver, BC, CA
Howie, John
Dept. of Civil Engineering, University of British Columbia, Vancouver, BC, CA
Pages: 11
Price: $25.00
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Stock #: GTJ20120081
ISSN: 0149-6115
DOI: 10.1520/GTJ20120081