Dynamic Properties of Gravelly Materials

This paper studies the dynamic characteristics (i.e. shear modulus and damping ratio) of modeled gravelly soils used as construction materials in some rock-fill dams in Iran by conducting large-scale triaxial testing. Tested specimens were compacted to more than 95% maximum dry density, according to Modified Proctor, and tested according to ASTM D 3999. Accurate monitoring of strains by means of non-contact type displacement transducers to infinitesimal strains as small as 0.0001% enabled us to obtain G(max) with some extrapolation. Based on the available experimental results the ranges for G/G(max) - gamma and D - gamma are defined for materials with > 30% fine content and materials with < 15% fine content. The results clearly indicate the need for modification in previously proposed G/G(max) - gamma curves, particularly for gravels with > 30% fine content. Also, the suggested D - gamma curves lay out of the bounds of data reported by previous researchers, which may be due to the effects of testing frequency, fine content, and confining pressure. In addition, a predictive hyperbolic model for estimating normalized shear modulus (G/G(max)) versus shear strain (gamma) is presented. Effects of the number of cyclic loadings over the shear modulus and damping ratio are also investigated.