Dynamic Shear Modulus and Damping Ratio of Recently Deposited Soils in the Coastal Region of Jiangsu Province
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.
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DYNAMIC SHEAR MODULUS AND DAMPING RATIO OF RECENTLY DEPOSITED SOILS IN THE COASTAL REGION OF JIANGSU PROVINCE Guoxing Chen Institute ofGeotechnical Engineering, Nanjing University ofTechnology, Nanjing 210009, China Binghui Wang, Jianda Liu Institute ofGeotechnical Engineering, Nanjing University ofTechnology, Nanjing 210009, China Jiangsu Province Institute 0/Earthquake Engineering, Nanjing 210014, China 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 / Gm", - r and damping ratio A - 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.
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INTRODUCTION
The dynamic shear modulus and damping ratio are important parameters of dynamic characteristics ofsoils and they are indispensable basic data for the seismic response analysis of important project sites. The coastal region of Jiangsu province mentioned in this paper is stand for 3 cities, namely Nantong city, Yancheng city and Lianyungang city, where exist the marine deposited stratums. The Chinese researchers generally considered that there are 3 times transgressions after late Pleistocene Epoch, and the marine deposited stratum which
deposited in Holocene Epoch is the thickest. Based on the research of Wang qiang et ai, the whole thickness of marine soil stratum approach 80m in the southern Dongtai city area, and gradually reduce in the northern Dongtai city area, as shown in Figure 1. It is impossible to classify all soil samples into marine deposited or continental deposited in that the information of the distribution of marine soil stratum in the coastal region of Jiangsu province is insufficient. However, some of marine dep
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