Journal Published Online: 26 December 2019
Volume 43, Issue 6

Selecting an Appropriate Shear Plate Configuration to Measure Elastic Wave Velocities

CODEN: GTJODJ

Abstract

The (small-strain) elastic moduli of soil can be determined from stress wave velocity measurements. Bender/extender elements are widely used in laboratory experiments; however, discussion on how to accurately determine wave velocities using this method continues. Planar piezoelectric transducers (sometimes called shear plates) are a relatively new technology, whose use is not yet widely established, that appear to offer some advantages in comparison with bender/extender elements for laboratory geophysics tests. This contribution critically assesses the use of planar piezoelectric elements experimentally and using discrete element method (DEM) simulations. Planar piezoelectric elements capable of generating and receiving either shear or compression waves were placed in the top and base caps of a triaxial apparatus. Samples of glass ballotini were used so that stress wave propagation simulations could be performed on equivalent virtual samples using DEM. The appropriate shear plate configuration to effectively measure the shear wave velocity is explored. Considering both time- and frequency-domain responses, it is revealed that shear plate signals are sensitive to the surface area and thickness of the piezoelectric elements and to the lateral boundary conditions. Using a shear plate with the widest possible surface area exposed to the soil specimen is recommended to increase the signal-to-noise ratio and to produce more planar shear waves, resulting in a more accurate measurement of shear wave velocity.

Author Information

Otsubo, Masahide
Institute of Industrial Science, The University of Tokyo, Tokyo, Japan
O’Sullivan, Catherine
Department of Civil and Environmental Engineering, Imperial College London, London, United Kingdom of Great Britain and Northern Ireland
Ackerley, Steven
Department of Civil and Environmental Engineering, Imperial College London, London, United Kingdom of Great Britain and Northern Ireland
Parker, Duncan
Department of Physics, Imperial College London, London, United Kingdom of Great Britain and Northern Ireland
Pages: 22
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Details
Stock #: GTJ20180146
ISSN: 0149-6115
DOI: 10.1520/GTJ20180146