Influence of Soil Type on the Effect of Strain Rate on Small-Strain Cyclic Shear Modulus

Abstract

ABSTRACT Sixteen different soils were tested in an NGI type simple shear device to examine the effect of strain rate, γ . , on cyclic secant shear modulus, Gs, at very small to small cyclic shear strain amplitudes, γc ≈ 0.0003-0.01%. The effect of γ . on Gs was characterized by strain-rate shear modulus parameter, αG, and strain-rate shear modulus factor, Nγ-G. Parameter αG describes the slope of Gs-log γ . data for a given γc, while Nγ-G is αG normalized by reference Gs. For the clayey soils and their conditions tested αG ≈ 1.0-6.5% MPa and Nγ-G ≈ 2.0-6.0% were obtained. For the sandy soils αG ≈ 0.3-1.2 MPa and Nγ-G ≈ 0.5-3.0% were obtained. Data revealed that αG decreases with increasing γc, while Nγ-G either slightly decreases with increasing γc or stays about constant. The trends of Nγ-G with plasticity indes, Ip, liquid limit, wL, clay content, and activity were examined. It was found that at a given γc, Nγ-G generally increases with increasing all of these properties and indices. Most consistent and strongest correlations were obtained between Nγ-G and Ip and Nγ-G and wL. These two correlations can be useful for the soil dynamics engineering practice and are presented in the paper