Small-strain stiffness properties of soils, such as shear wave velocity,shear modulus and material damping, play a key role in the adequate design/analysisof unsaturated earth structures subject to staticon-static loading. Most conventionalgeotechnical testing techniques, however, cannot capture this small-strain behaviorand, hence, vastly underestimate the true soil stiffness, mainly due to inaccuracies insmall-strain measurements. Bender element technique has proved to be a viable wayto investigate soil stiffness at very small strains, albeit mostly under dry or saturatedconditions. Hence, there is a great need for assessing the feasibility of bender elementtechnique in unsaturated soils as compared to fully standardized procedures, such asthe resonant column and simple shear test methods. This paper introduces a suctioncontrolledproximitor-based resonant column device featuring self-contained benderelements for simultaneous testing of soils using both techniques. A comprehensiveseries of RC and BE tests were conducted on samples of silty sand at 50, 100, 200and 400-kPa matric suction states via the axis-translation technique. Results show areasonable good agreement between RC and BE test results. Both techniques showedthe critical influence of matric suction on soil’s small-strain stiffness response.
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