Shear Modulus and Damping Relationships for Gravels

Two of the most important parameters in any dynamic analysis involving soils are the shear modulus and the damping ratio. Because both shear modulus and damping are strain dependent, curves must be developed to define their variation with shear strain. Fifteen studies (including this one) now provide results from tests on a wide variety of gravels. This paper combines the results of available investigations to develop best-fit relationships between (1) shear wave velocity and equivalent N60 from Becker penetration tests; (2) normalized shear modulus and shear strain; and (3) damping ratio and shear strain. The mean curve for the normalized shear modulus reported for gravelly soil in this study falls near the mean curve reported for sands by Seed and Idriss (1970). The normalized shear modulus curve is dependent on confining pressure, but essentially independent of sample disturbance, relative density, and gradation. The mean damping ratio curve falls toward the lower range of the data reported by Seed and Idriss (1970). The damping ratio curve is dependent on confining pressure but essentially independent of other factors.