Reduction of Shear Modulus at Small Strains in Simple Shear

Cyclic tests were conducted to study the secant shear modulus, Gs, of two reconstituted sands and three laboratory-made clays at small cyclic shear-strain amplitudes γc≈ 0.0006%–0.02%. A recently developed direct simple shear device for small-strain testing was employed. The effects of cyclic strain amplitude (γc), type of soil and plasticity index (PI), vertical effective consolidation stress (σvc′), and overconsolidation ratio (OCR) were investigated. The results show that the ordinates of the normalized shear modulus reduction curve, Gs/Gmax−γc, generally increase as σvc′ and OCR increase. However, these effects of σvc′ and OCR become smaller and may eventually disappear as the PI of the soil increases.

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