抄録
To evaluate the effects of various static stress conditions and stress histories on shear modulus and damping of sand under cyclic loadings, a comprehensive series of cyclic torsional shear tests on hollow cylindrical specimens of a clean sand was performed. All the tests were performed and the constant value of mean principal stress =1.0 kgf/cm2 (about 100 kN/m2) under fully drained condition. From the test results, the followings were found. For a wide range of shear strain amplitude (γ=5×10-5∼5×10-3), the effect of stress ratio on shear modulus is minor in the triaxial compression case but considerable in the triaxial extension case. Initial shear stress decreases shear modulus especially for the triaxial compression case. Although shear modulus is affected by various static stress conditions, its strain-dependency is insensitive to those static stress conditions. The effects of stress ratio and initial shear stress on damping ratio are less important than shear strain amplitude γ and mean principal stress p. It was found that the effects of overconsolidation history and previous larger cyclic shear stress history on G and η are also less important than γ and p.
