Laboratory experimental study on dynamic shear modulus ratio and damping ratio of soils

The averaeine curves, recommended values and envelopes of dynamic shear modulus ratio and damping ratio λ versus dynamic shear strain γ for 6 types of soils in China are presented in the paper using the free vibration method by resonant column apparatus. The refitted resonant column apparatus in the Institute of Engineering Mechanics is employed for the experimental investigation and its accuracy and reliability have been verified by the tests.The undisturbed soil samples, including clay, silty clay, silt, sand, muck and mucky soil, come from about ten different regions in China. The relation of -γ is fitted by two hyperbolic equations and the relation of λ-γ is also fitted by two hyperbolic equations. The parameters a and b in the equations are obtained from regression analysis of each testing data by the least squares method. For the same type of soil, the mean values, are gotten by averaging all a and b for the same type of soil. The relations of and λ-γ for each ype of soil are then derived using the mean parameters and finally, the averaging curves and recommended values of -γ and λ-γ for the 6 types of soils are obtained.Because the laboratory test is performed under consolidation pressures, the presented results in the paper are suitable respectively for two depths of soil, less than 10 meters as well as between 10 meters and 20 meters.