Research On The Influence Of Particle Gradation And Density On Dynamic Deformation Characteristics Of Sand

The study of dynamic deformation characteristics such as soil dynamic modulus and damping ratio is an important issue in geotechnical engineering analysis and design,which is affected by many factors.Based on the improved resonant column instrument,this paper starts from the two different influencing factors of particle gradation and relative compactness,and studies the change law of soil dynamic characteristic parameters in a small strain range.The instrument can simultaneously measure the dynamic shear and elastic modulus changes of sand in a small strain range through the improvement of the drive plate and the laser displacement sensor.The main research contents and conclusions of the full text are as follows:1.Through the resonance column test,the dynamic shear modulus,dynamic elastic modulus,damping ratio and other parameters are obtained along with the coarse particle content,relative density and other factors.The results show that as the strain increases,the shear modulus and elastic modulus of the soil gradually decrease;when the strain is fixed,as the coarse-grain content increases,the shear modulus and elastic modulus of the soil appear It increases first and then decreases,and reaches the maximum when the coarse-grain content is about 50%-60%;when the coarse-grain content is fixed,as the relative density increases,the shear modulus and elasticity of the soil The modulus gradually increases.The maximum dynamic modulus obtained by extrapolation method can better reflect the change law of shear modulus and elastic modulus with the change of gradation and compactness.2.The shear modulus and elastic modulus are normalized to obtain the normalized attenuation curve of shear modulus and elastic modulus.It is found that the shear modulus and elastic modulus are both higher than the coarse particle content.The attenuation rate is greater when it is high,and the maximum attenuation rate is about70% coarse grain content.3.The dynamic damping ratio changes with strain under different conditions are analyzed,and it is found that the damping ratio increases with the increase of strain.The greater the strain,the greater the growth rate of the damping ratio.At the same time,the damping ratio increases faster when the content of coarse particles is high,and increases slowly when the content of coarse particles is small;when the content of coarse particles is constant,the greater the relative density,the smaller the damping ratio,and the slower the increase of the damping ratio.4.Based on the above-mentioned dynamic modulus change law considering different coarse grain content ratios Rc and relative density Dr,a dynamic constitutive model considering both Rc and Dr modulus is proposed,and the model parameters are analyzed and verified.At the same time,according to the change characteristics of dynamic shear and elastic modulus with strain,a new method for solving dynamic Poisson's ratio is proposed,which can obtain the value of Poisson's ratio under arbitrary strain conditions through iterative cycles.