Measurement of shear modulus using bender elements and resonant-column

Abstract

In recent times, new demands in geotechnical engineering, mainly in transportation geotechnics, require the use of advanced characterization techniques in order to accurately assess soil stiffness parameters. From this perspective, seismic wave-based techniques have received significant attention, since these allow performing the same basic measurement in the laboratory and field. With an enormous potential, bender elements are currently one of the most popular techniques used to measure reference soil properties in the very small strain range, namely the shear modulus. Bench and triaxial tests conducted on a wide range of geomaterials already demonstrated the applicability of this technique. However, the combined use of bender elements with other testing techniques, as the resonant column, is quite important in order to compare and validate some of the procedures used. In this context, bench bender elements tests were carried out on stiff sandy silt/silty sand specimens and the interpretation of seismic wave velocities was performed using time domain methods under a variety of excitations. Resonant column tests were also conducted on the same material to validate the obtained results with the bench bender elements setup. A critical discussion is made on the advantages and limitations of bender elements usage in contrast with the resonant-column for the assessment of the shear modulus, as well as some insights regarding damping. Additional tests were carried out in two distinct BE setups, one of which installed in the resonant column device, as well as ultrasonic measurements, with the purpose of validating the BE procedure and results interpretation. From this research, it was possible to compare and analyze the results obtained with the three different bender element setups and derive recommendations towards achieving reliable measurements.