Influence of the Grain-Size Distribution Curve of Quartz Sand on the Small Strain Shear Modulus G_(max)

摘要

The paper presents a study of the influence of grain-size distribution curve on the small strain shear modulus G_(max) of quartz sand with subangular grain shape. The results of 163 resonant column tests on 25 different grain-size distribution curves are presented. It is demonstrated for a constant void ratio that while G_(max) is not influenced by variations in the mean grain-size d_(50) in the investigated range, it significantly decreases with increasing coefficient of uniformity C_u = d_(60)/d_(10) of the grain-size distribution curve. Well-known empirical formulas (e.g., Hardin's equation with its commonly used constants) may strongly overestimate the stiffness of well-graded soils. Based on the RC test results, correlations of the constants of Hardin's equation with C_u have been developed. The predictions using Hardin's equation and these correlations are in good accordance with the lest data. Correlations of the frequently used shear modulus coefficient K_(2, max) with C_u and empirical equations formulated in terms of relative density, are also given in the paper. A comparison of the predictions by the proposed empirical formulas with G_(max)-data from the literature and a micromechanical explanation of the experimental results are provided. Correction factors for an application of the laboratory data to in situ conditions are also discussed.