Measuring shear and compression wave velocities of soil using bender-extender elements

Piezoceramic elements have been used for laboratory measurement of wave velocity in soil and rock specimens. Shear-wave piezoceramic elements (bender elements) are commonly used to measure shear wave velocity for the determi-nation of small-strain shear modulus. Compression-wave piezoceramic elements (extender elements), on the other hand, are less commonly used as compression wave velocity is less frequently measured. In this paper, the performance of a pair of bender-extender elements for the determination of both shear and compression wave velocities is examined with respect to the resolution of the recorder, bender-extender element size. and excitation voltage frequency. The evaluation showed that the performance of the bender-extender elements test can be improved by considering the following conditions: (i) the digital oscilloscope used to record the bender-extender element signals should have a high analog to digital (A/D) conversion resolution; (ii) the size of the bender-extender elements plays an important role in the strength and quality of the receiver signal, especially for compression waves; and (iii) using a wave path length to wavelength ratio of 3.33 enables a more reliable determination of shear wave velocity.