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

Abstract

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 determination 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.

The role of compaction energy on the small strain properties of a compacted silty sand subjected to drying–wetting cycles

“…This can either be accessed by visual inspection or using an automated procedure that detects small changes in the amplitude of the received signal for cases where visual inspection is difficult (e.g. Leong et al, 2009). In this study it was found that the arrival of the compressional wave is relatively independent of the testing frequency, although the wave propagation mode seems to change for lower excitation frequencies (i.e.…”

Dynamic Characterization of Cohesive Material Based on Wave Velocity Measurements

“…Over the years, bender elements have become increasingly popular in order to determine the S-wave velocity [9,10] through experiments. Nowadays, they are commonly available [11,12].…”

“…Because of this fact, it acts as a signal transmitter. Being subjected to mechanical excitation causes the emission of an electrical output by another bender element, which is, in this way, acting as a signal receiver [9].…”

“…They allow calculating Gmax at small strains on the basis of the wave velocity [6]. Some of the laboratory tests and field studies, such as cross-hole seismic [7,8], down-hole seismic [9], suspension logging [10], seismic cone [11], seismic flat dilatometer [12] and spectral analysis of seismic waves [13], are indirect tests [14]. Compared to direct tests, the indirect tests enable measuring quantities different from the more desired ones and relate them to each other through mathematical relationships.…”

Using small-strain stiffness to predict the load-settlement behaviour of shallow foundations on sand

“…The most common techniques are measuring the time between the onset of the sender driving signal and detecting the first arrival at the receiver element (visual picking), travel time between two receivers some distance apart along the ray path detecting the same seismic event, as well as cross-correlation and cross-power spectrum methods (Leong et al 2005). For this project, the method of visual picking of the first arrival was used.…”