Dynamic Shear Modulus and Damping Ratio of Recently Deposited Soils in the Coastal Region of Jiangsu Province

Abstract

Many important engineering projects such as digital strong-motion observation stations, ports or wharfs, wind power stations have been constructed because of the unique locations and rapid development of economy in the coastal region of Jiangsu province. And the dynamic shear modulus and damping ratio of soil are indispensable basic data for the seismic design on important engineering projects. For the construction of these important engineering projects, the free vibration column tests of 134 undisturbed soil samples were conducted which took about 3 years and the free vibration column test system developed by Nanjing University of Technology was used. Those undisturbed soil samples are 5 type soils of muddy soils, clay, silt clay, silt and fine sand. Due to the transgressions after the late Pleistocene Epoch, the marine deposited soils have existed in the coastal region of Jiangsu province extensively. Therefore, 3 type marine deposited soils of silt clay, silt and fine sand were also screened. The results show that it is suitable to use the Martin-Davidenkov model and the damping ratio empirical formula recommended by Chen Guoxing et al to fit the results of the normalized dynamic shear modulus ratio G/Gmax - γ and damping ratio λ - γ curves respectively. By comparing marine deposited soils with continental deposited soils, the following results can be found. For silt clay, the dynamic shear modulus ratios and damping ratios are very close to each other. And for silt and fine sand, however, the dynamic shear modulus ratios and damping ratios have obvious differences.