Volume 37, Issue 2 (March 2014)

    Continuous Monitoring of Bender Element Shear Wave Velocities During Triaxial Testing

    (Received 11 December 2011; accepted 23 October 2013)

    Published Online: 2014

    CODEN: GTJOAD

      Format Pages Price  
    PDF 13 $25   ADD TO CART


    Abstract

    Bender element testing is used to measure shear wave velocities (VS) across soil specimens in the laboratory. Conventional bender element testing is carried out at a few discrete points during an experiment. This paper presents a method which uses bender elements to monitor VS continuously throughout a triaxial test. The method is based on monitoring the change in phase angle between a continuous trigger signal and a received signal. It allows the phase velocity at multiple selected frequencies to be monitored throughout a test. The method is described in detail and its use is illustrated for triaxial tests on loose specimens of Fraser River sand prepared by water pluviation. The variation of shear wave velocity is demonstrated during consolidation, ageing, and shearing to failure along a conventional stress path. Potential difficulties of interpretation are presented and discussed. In addition, the potential for continuous excitation of the specimen to alter the test results is considered and dismissed based on a comparison of samples tested without benders and with continuous benders at a range of excitation voltages. The proposed method for continuously monitoring bender element shear wave velocities does not use special or unique equipment. It results in a continuous VS from a trigger and receiver element installed on opposite ends of a triaxial specimen. This method provides a measure of VS during dynamic phases of an experiment that have not previously been observed. For example, this paper includes measures of VS at the onset of creep, the onset of shearing, and over the phase transformation from contractive to dilative behaviour. The relationship between fundamental soil behaviour and VS can now be more easily explored.


    Author Information:

    Styler, Mark A.
    Univ. of British Columbia, Department of Civil Engineering, Vancouver, BC

    Howie, John A.
    Univ. of British Columbia, Department of Civil Engineering, Vancouver, BC


    Stock #: GTJ20120098

    ISSN: 0149-6115

    DOI: 10.1520/GTJ20120098

    ASTM International is a member of CrossRef.

    Author
    Title Continuous Monitoring of Bender Element Shear Wave Velocities During Triaxial Testing
    Symposium , 0000-00-00
    Committee D18