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This study reports on the significance of particle shape on the small-strain damping ratio of dry sands in shear (D s,min ) through a comprehensive set of torsional resonant column tests. Sands with a variety of grain shapes prepared at variable initial densities are studied. The samples are subjected to torsional resonant column tests under isotropic confining pressures ( p′) ranging from 50 to 800 kPa. Small-strain damping ratios are derived based on the free-vibration decay mode of the samples and the results are compared with the half-power bandwidth method. The effects of grain size distribution, particle shape and effective confining stress on D s,min are thoroughly discussed, and a new model for the prediction of small-strain damping ratio of dry sand is proposed.

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The influence of gradation and particle shape on the small-strain Young's modulus of dry sands is investigated through a comprehensive set of resonant column tests in the flexural mode of vibration. Experiments are performed on an array of sands with different coefficients of uniformity and particle shapes. The effect of gradation is investigated using tests on sands with similar particle shapes. The effect of particle shape is then examined through the experimental results on sands with a range of particle shapes. A new model is developed to incorporate the effects of gradation and particle shape into the prediction of the small-strain Young's modulus. The proposed model is verified and compared with the existing models in the literature using the state parameter in the critical state soil mechanics framework. It is shown that the proposed model outperforms the previous ones considering the significant effect of particle shape on the small-strain Young's modulus. Using the theory of elasticity, a model is developed for the prediction of Poisson's ratio for sands taking into account the effects of particle shape and gradation.