Experimental Study On Dynamic Characteristics Of Marine Sandy Soil In Zhoushan

Lots of marine sandy soil are distributed in the sea area of Zhoushan islands in China.Reasonable foundation design is the key for the safe and efficient use of marine sandy soil foundation.Therefore,it is necessary to select reasonable and accurate dynamic parameters of marine sandy soil to ensure the safety of marine engineering construction.The research of dynamic parameter characteristics under dynamic loading is the key for the design of marine engineering foundation.In this paper,marine sandy soil in a certain sea area of Zhoushan was selected as the testing sample,and a series of experiments on dynamic parameters under different boundary conditions were carried out through Wille resonant column test.The main research work is as follows:1.Tests were conducted on marine sandy soil samples with the same saturation degree to investigate the relationship within damping ratio,different effective confining pressures,dynamic shear modulus,and shear strain.And the relationship within the dynamic shear modulus,effective confining pressures and the damping ratios would be revealed.2.The maximum dynamic shear modulus tests under different saturation degree were conducted for marine sandy soil samples with the same effective confining pressure.The influence of different saturation degree on the maximum dynamic shear modulus of the sample was investigated,and the optimal saturation degree was obtained,which correspond to the maximum dynamic shear modulus of the sample.The effects of different effective confining pressures and pore ratio on the maximum dynamic shear modulus of samples were analyzed by using the theoretical model proposed by Hardin and the theoretical model proposed by Nanjing water science institution.The relationship between the maximum dynamic shear modulus and effective confining pressures and pore ratio was revealed.3.Martin-Davidenkov's three parameters of experience modelwas used to fit and analyze the normalization of dynamic shear modulus and shear strain,and the relationships between the normalized dynamic shear modulus and shear strain were got.Then the theory prediction equations of dynamic shear modulus are given under different boundary conditions.The empirical model of damping ratio proposed by Chen was used to fit and analyze the damping ratio and the normalized dynamic shear modulus in this paper.The relationship between the damping ratio and the normalized dynamic shear modulus was obtained.And the theory prediction equations of damping ratio are also given under different boundary conditions at the same time.4.Based on the dynamic parameters obtained from Sherif's experimental data of dry sand sample,Iwasaki's experimental data of Toyoura sand sample,Hardin's experimental data of saturated sandy soil and dynamic parameters of Rollins for saturated sandy soil,the dynamic parameters of Zhoushan marine sandy soil are compared with them,and the rationality and reliability of the testing data are also verified in this paper.5.Using the initial Hardin theoretical model to fit the testing data of the normalized dynamic shear modulus and shear strain in this paper under different boundary conditions.On the base of the shortcomings of initial Hardin theoretical model,this paper proposes a new modified Hardin model with three parameters.This modified Hardin model was used to analyze the experiment data and reveal the modified Hardin model is more accurate and reasonable than the initial Hardin theoretical model for the dynamic parameters of Zhoushan marine sandy sand.At the same time,the prediction equations of the modified Hardin theoretical model under different boundary conditions are given,which provide certain reference value for the later marine engineering construction and scientific research.