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Evaluation of the shear modulus of soil is of great importance in understanding both the fundamental soil behavior and its practical application in dynamic geotechnical problems as well as accurate analysis of seismic response of soil deposit and soil-structure interaction. There are traditionally several available techniques in measuring shear modulus of soil using laboratory tests. In this paper, calculation methods to evaluate shear modulus were reviewed from previously published works. A simple procedure was established using the previous equations. This procedure successfully obtained shear modulus of a sand deposit used for dynamic centrifuge tests. It also captured non-linear shear modulus with shear strain and effect of confining pressure. The shear modulus and normalized shear modulus versus shear strain curves from the experiment are compared with empirical curves proposed in literature. The shear modulus curves from the centrifuge tests are in reasonable agreement with the previous curves.

Coarse granular geomaterials containing large gravels are broadly used for construction of large geotechnical systems such as dams, levees, railways and backfills. It is necessary to evaluate deformation characteristics of these materials for dynamic analysis, e.g. seismic design. This study presents evaluation of dynamic deformation characteristics of coarse materials using large scale resonant column testing apparatus, which uses specimens with 200 mm in diameter and 400 mm in height, and the effects of gradation characteristics on maximum shear modulus, shear modulus reduction curve and damping characteristics were investigated. From experimental study using rock-fill materials for a dam, we could see that the largest or mean particle size affects the shape of shear modulus reduction curve. When the specimens are prepared under the same conditions for maximum particle size, the coefficient of uniformity affects the confining stress exponent of maximum shear modulus. It could be concluded that the maximum particle size is an factor which affects shear modulus reduction curve, and that the coefficient of uniformity is for small strain shear modulus, especially for the sensitivity to confining stress.

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