Compression and shear wave propagation in cemented-sand specimens

Abstract

Ultrasonic and bender element tests in the laboratory are typically used to measure elastic modulus and damping ratio. However, interpretation of the results is challenging for a variety of reasons, including the influence of experimental details, geometrical effects and the analytical techniques used for data processing. It is therefore convenient to cross-check results by performing several independent measurements. Three different types of measurements were performed on cementedsand specimens. Longitudinal waves or constrained compressional waves in a cylindrical specimen were generated in a high-frequency range (20-70 kHz) using a newly designed transducer interface. Full dynamic characterisation was made possible by independent measurement of the transducer response. Pure unconstrained compressional waves or simply compression waves were measured in the same specimens with high-frequency transducers. The shear modulus was computed and used to predict the arrival of shear waves on independent bender element measurements. The predicted arrival was close to first-break estimates, and bender measurements were therefore confidently employed to track cement curing effects on a different set of specimens. The specimen frequency response function obtained from the longitudinal wave measurements was examined in detail and damping ratios were estimated for the compression vibration modes in a rod.

Numerical Methodology to Minimize Resolution and Sensitivity Effects in P-Wave Measurements

“…This index was first presented by Consoli et al (2007) to analyze unconfined compression tests, later proving to be quite adequate to represent small strain stiffness (e.g., Consoli et al 2009;Amaral et al 2011a) from seismic wave measurements as included in this paper.…”

“…In geotechnical engineering, several authors (e.g., Viggiani and Atkinson 1995;Brignoli et al 1996;Greening and Nash 2004;Leong et al 2005;Arroyo et al 2006;Alvarado and Coop 2012) have reported difficulties in signal interpretation for soil dynamics purposes, using bender elements (BE) tests. On the other hand, other authors (e.g., Khan et al 2006Khan et al , 2011Tallavó et al 2009Tallavó et al , 2011Amaral et al 2011a) have implemented signal transformation techniques to evaluate soil dynamic properties using piston-type ultrasonic transducers. In any case, most of these works report the effect of the subjective interpretation on the obtained results, and, therefore, the operator experience has an important role in these analyses.…”

“…Changes in the received signal because of the signal energy were evaluated by the divided differences method (DDM) of first and second order. In addition, an index proposed by Consoli et al (2007) and used by Viana da Fonseca et al (2009a), Consoli et al (2009), Amaral et al (2011a, and Rios et al (2012), was applied, which relates porosity and cement content. In that sense, the values of the longitudinal or P-wave modulus (M 0 ) obtained with and without the DDM were plotted against that index.…”

Simplifying calibration of bonded elasto-plastic models

“…This is a well characterized soil and extensive geotechnical data has been gathered both for the parent soil alone [20] and for its mixtures with cement ( [21], [22], [23] and [24]). …”

Indexation of dynamic and static geomechanical properties of a cemented aggregate for transportation engineering

“…Since the used cement is a rapid curing agent, no significant differences were observed in the results obtained in the specimens tested at 28 days of curing and after this period (Amaral et al, 2011). V P and V S values are presented in Table 4 as well as the elastic moduli computed from these values (M 0 , E 0 , G 0 , and m 0 ).…”