Dynamic Response And Micro-experimental Research Of Qiantang River Silt

This article takes the silt along the Qiantang River as the research object,considers the dual effects of the excavation of foundation pits and the dynamic load of the pavement and the underground operating subway,and focuses on the analysis of the dynamic characteristics and micropore structure of the silt along the Qiantang River.Based on previous research foundations,this article first introduces the working principles of electromagnetic resonance columns and nuclear magnetic resonance analyzers in detail;second,based on the GDS-RCA resonance columns,the random modulus of shear and damping ratio of silt along the Qiantang River are studied.Confining pressure,porosity ratio and water content change law.Finally,using NMR technology,from the perspective of microscopic pore structure,the mechanism of changing the stiffness of silt along the Qiantang River under different physical parameters was revealed.The specific research content is as follows:(1)The composition structure,basic principle,sample preparation method,test procedure and test accuracy of the electromagnetic resonance column and nuclear magnetic resonance analyzer are introduced in detail,and a set of test equipment suitable for micro-pore test of granular soil is provided.(2)A shear modulus test study was carried out on the silt along the Qiantang River to analyze the variation of confining pressure,porosity and water content on the stiffness of the soil.Based on Hardin's formula,considering the influence of moisture content on soil stiffness under the influence of precipitation in foundation pit engineering,a new empirical formula for calculating the dynamic shear modulus of Qiantang River silt.(3)A damping ratio test study was carried out for silt along the Qiantang River,which simulates the change of soil stiffness under dynamic traffic loads.The dynamic shear modulus ratio and damping ratio of the Qiantang River silt under different physical parameters follow the variation of shear strain is studied in detail.Based on the ideal Hardin-Drnevich model,considering the normalized dynamic shear modulus ratio and damping ratio of silt along the Qiantang River and the dynamic shear strain,the new empirical formulas of G/G0-? and D-? are further modified.(4)The T2 cutoff value of the soil under different physical parameters was determined for the NMR test,and the content and distribution of pore water were quantitatively described,and the change mechanism of soil stiffness from a micro perspective were revealed.The accuracy of the test results was verified by the NMR calibration curve,which extended the NMR technology widely used in the field of geotechnical engineering.Figure[34]table[11]reference[105]...