Measurement of small-strain shear modulus G_max of dry and saturated sands by bender element, resonant column, and torsional shear tests

Abstract

The bender element method is an experimental technique used to determine the small-strain shear modulus (Gmax) of a soil by measuring the velocity of shear wave propagation through a sample. Bender elements have been applied as versatile transducers to measure the Gmax of wet and dry soils in various laboratory apparatuses. However, certain aspects of the bender element method have yet to be clearly specified because of uncertainties in determining travel time. In this paper, the bender element (BE), resonant column (RC), and torsional shear (TS) tests were performed on the same specimens using the modified Stokoe-type RC and TS testing equipment. Two clean sands, Toyoura and silica sands, were tested at various densities and mean effective stresses under dry and saturated conditions. Based on the test results, methods of determining travel time in BE tests were evaluated by comparing the results of RC, TS, and BE tests. Also, methods to evaluate Gmax of saturated sands from the shear-wave velocity (Vs) obtained by RC and BE tests were investigated by comparing the three sets of test results. Biot’s theory on frequency dependence of shear-wave velocity was adopted to consider dispersion of a shear wave in saturated conditions. The results of this study suggest that the total mass density, which is commonly used to convert Gmax from the measured Vs in saturated soils, should not be used to convert Vs to Gmax when the frequency of excitation is 10% greater than the characteristic frequency (fc) of the soil.

Dynamic Characterization of Cohesive Material Based on Wave Velocity Measurements

“…Nevertheless, there are still some differences between the first arrival of the S-wave and the preferred input wave. Therefore, the BE technique still needs to be verified with respect to how reliable it is, when it comes to calculation of the arrival time [2,22].…”

“…The small strain and elastic moduli, such as the shear modulus (G max ) and Young's modulus (E max ), are key parameters during, for example, the site response analysis of an earthquake, the design of machine foundations and soil dynamics problems [2]. Burland et al [3] even emphasized the significance of G max in static deformation analysis of geotechnical problems.…”

Settlement Prediction of Footings Using VS

“…The V S was calculated after determining the first arrival time of received shear wave signals and the tip-to-tip distance between the two corresponding bender elements [24]. Interpolation based on a regression analysis was conducted to produce continuous V S profiles for precise predictions because the shear wave was detected by point-based measurements.…”

Water-induced granular decomposition and its effects on geotechnical properties of crushed soft rocks

“…Only a few studies are known to exist like, Neves and Pinto (1988) and Nakano et al (1998), concerning the effects of slaking-induced degradation of soil grains on its engineering properties. Many researchers reported negligible influence by the presence of water on mechanical behaviour of standard sands like, Fioravante and Capoferri (1997), Wichtmann et al (2005), and Youn et al (2008). Such an approach is essentially true for most of the standard laboratory sands consisting of durable grains.…”