Comparison of shear wave velocity measurements in a soft clay specimen using time and frequency domain techniques

Bender elements have been used to determine shear wave velocity in specimens of soft Bothkennar clay using two different techniques. Tests have been carried out in a stress-path triaxial cell equipped with bender elements mounted in three orthogonal directions enabling anisotropy of small strain stiffness to be determined. Phase-delay methods have been used to determine travel time in addition to the more common first arrival technique. The phase delay readings show that the soils are dispersive resulting in variations of velocity with frequency. Of much more significance is the finding that the frequency domain method consistently produces an estimate of shear wave velocity which is lower than that from traditional time domain readings. The paper describes observations made as a sample of natural Bothkennar clay was first consolidated to in-situ stress conditions and then destructured by subjecting it to undrained shear. The automated data acquisition system has enabled shear wave velocity determinations by the two methods throughout the test, which provide a useful and unusual data set. The shear wave velocities are compared and the evolving anisotropy is discussed.

Bender elements …

AUTORI: Nash D., Sukolrat J., Greening P., Benahmed N.
Numero di pagine: 56

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