Experimental Study on Dynamic Shear Modulus and Damping Ratio of Recently Deposited Soils

Owing to the special geographic location and the rapid development of economy in coastal region of Jiangsu province,many important projects have been constructed such as digital strong ground motion observation sta- tions,ports or wharfs,wind power stations.The dynamic shear modulus and damping ratio of site soils are basic and necessary data for the seismic design of important projects.Based on the construction of those important projects,ex- perimental studies on dynamic shear modulus and damping ratio of 134 undisturbed soil samples are accomplished in about 3 years,using the free vibration column test system developed by Nanjing University of Technology.Those un- disturbed soil samples are muddy soils,clay,silt clay,silt and fine sand.The marine deposited soils in coastal re- gion of Jiangsu province are existed extensively due to three times of transgression after the late Pleistocene Epoch. Therefore,marine deposited silt clay,silt and fine sand are also screened.The results show that it is suitable to use Martin-Davidenkov model and the damping ratio empirical formula recommended by Chen Guoxing to fit the results of the normalized mean dynamic shear modulus ratio G/G_(max)～γ_(?) and damping ratioλ～γ_(?) curves respectively.The ref- erence values of regression coefficients are also given.By comparing the dynamic shear modulus ratio and damping ra- tio of marine deposited soils with continental deposited soils,the following results can be found:for silt clay,the dy- namic shear modulus ratio and damping ratio of marine and continental deposited soils are much dosed with each oth- er,for silt and fine sand,however,the dynamic shear modulus ratios and damping ratios of marine and continental deposited soils are obviously different.