Dynamic Triaxial Test And DEM Simulation Of Transparent Sand

Transparent soil is a new type of geotechnical test material synthesized artificially.It is combined with particle image velocimetry(PIV)technology.In recent years,it has been applied in civil engineering model test and achieved good results.Transparent soil technology is different from traditional deformation measurement technology.It can monitor soil deformation from a mesoscopic point of view and obtain the mechanism of soil deformation.At present,the research on mechanical properties of synthetic transparent soil mainly focuses on static aspects,and the research on mechanical properties of transparent soil under dynamic action is less.Based on the laboratory dynamic triaxial test of transparent sand made of fused quartz sand,the dynamic strength and dynamic deformation of transparent soil are obtained,and then the dynamic characteristics of transparent soil are analyzed by discrete element method.The effects of confining pressure,frequency,relative density and deviation stress amplitude on dynamic strength and dynamic deformation are studied.The conclusions are as follows:(1)The dynamic triaxial tests of transparent sand samples made of fused quartz sand under undrained conditions were carried out,and the dynamic stress-strain relationships of nonlinearity,hysteresis and accumulation of deformation of transparent sand were obtained,reflecting the elastic-plastic and strain-hardening characteristics of the material.The accumulative plastic deformation curves of the samples were fitted,and it was found that the trend of deformation development was stable.In addition,the effects of relative density,confining pressure,frequency and deviating stress amplitude on dynamic strength and deformation of transparent soil are analyzed.(2)The discrete element analysis model of transparent sand is established by PFC 2D software.The model parameters and contact-sliding constitutive relationship are determined according to the law of influence of meso-parameters on macro-mechanical properties.The change of meso-characteristics of transparent sand under dynamic loading is analyzed.The comparison with the indoor dynamic triaxial test results verifies the rationality of the established discrete element model and calculation.(3)The influence of relative density on displacement field and contact force under static load is obtained by comprehensive analysis of indoor dynamic triaxial test and discrete element analysis results;the influence of deviating stress amplitude,confining pressure and initial void on the deformation of transparent sand specimens under cyclic load is analyzed,and the sensitivity of these parameters is analyzed,and the dynamic load action is obtained from the micro-point of view.The variation of contact force chain,coordination number and porosity of the sample under use reveals the deformation evolution characteristics of the transparent sand sample.The above results of dynamic triaxial tests and discrete element analysis of transparent sand provide a scientific reference for the application of transparent sand to the relevant model tests of soil dynamics.