Journal of Geotechnical and Geoenvironmental Engineering · 1998 · 491 citations · 14 references
Geotechnical EngineeringShear StrainBecker Penetration TestsEarthquake EngineeringDamping RatioEngineeringGeotechnical ProblemMechanicsDamping RelationshipsMechanical EngineeringGeographyCivil EngineeringSoil-structure InteractionGeomechanicsGeotechnical PropertySediment TransportSoil Mechanic
Shear modulus and damping ratio are key dynamic soil parameters that vary with strain, and fifteen studies—including this one—have produced test results on diverse gravels. The study compiles existing data to derive best‑fit relationships among shear wave velocity, normalized shear modulus, and damping ratio versus shear strain and penetration test values. They fit empirical curves to the compiled data linking shear wave velocity to Becker penetration test N60, normalized shear modulus to shear strain, and damping ratio to shear strain. Normalized shear modulus curves for gravel closely match those for sands and depend mainly on confining pressure, while damping ratio curves lie in the lower range of previous data and also depend primarily on confining pressure, with little influence from disturbance, density, gradation, or other factors.
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.
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