Macro And Micro Study On The Mechanism Of Particle Breakage And Mechanical Response Of Sand

With the state increasing investment in the major infrastructure,more and more super-project will be put into construction and use.Sand as a bulk material,is widely used in roads,earth and rock dams,port engineering and other foundations.Due to the irregular shape of the particles,in the deposition process anisotropy will be inevitably produced.The mechanical properties of sand will be different.Under special conditions or high stress,sand will appear the characteristics of particle fragmentation,threatening the safety of the building.Researchers at home and abroad have already learned about the mechanical properties of sandy crushing and have carried out laboratory tests,numerical simulations,microstructures and constitutive models to study the mechanism of particle crushing.However,in the current research on the anisotropy and particle,the results show that there are few documents on the macroscopic mechanical properties of sand.Because the discrete element numerical test can provide detailed data of macroscopic and microscopic two scales at the same time,it can quantitatively study the mechanical properties of sand and become a powerful tool for multi-scale research of granular materials.Therefore,this paper adopts laboratory test and discrete element test combined with the contrast method.In this paper,the anisotropy of the particles is combined with the particle crushing in the order of horizontal,vertical and staggered arrangement,and compares with the simulation results of the discrete element software.The following conclusions are obtained: In the anisotropy in the "sand",the horizontal arrangement is more prone to particle breakage than the other arrangement,because this arrangement,the single particles are more by the role of shear stress,and the elastic particles of the shear strength which is lower than its compressive strength and tensile strength.In the other anisotropic "sand",the larger the coordination value of the particles is,the more stable the deformation is.The shear strength of sand under high stress is obtained by referring to the documents of direct shear test in sandy soils.The results show that the particle crushing does not increase linearly with the vertical pressure,but increases with the vertical increase.And then through the discrete element software to prepare the same characteristics with the indoor test sample,the value of the sample parameters assigned to the value of the other samples of the sample.The samples were prepared according to the different gradation,gradation concentration,gradation loss and particle size.The direct shear test was carried out by applying different vertical loads by servo,and the macro Microparameter characteristics:(1)Under the same gradation condition,the vertical stress is larger,and the stress-displacement curve of the specimen gradually exhibits the characteristics of stress softening.The particle size is a single specimen,and the stress softening phenomenon is more obvious with the vertical force increasing.(2)Under the same vertical pressure,the volume strain corresponding to the good sample is smaller than that of other gradation samples.The characteristics of the body-displacement curve corresponding to different gradations are different.Provided that there is the same gradation sample,the greater the vertical stress,the smaller the volume strain in the shear process.(3)The size of the contact force is related to the distribution of the particle size.Under the same vertical pressure,the higher the proportion of the large particle size in the sample,the higher the proportion of the strong chain.(4)When the particle model is an unbreakable model,the effect of the displacement cloud is smaller with the increase of the vertical pressure.When considering the particle crushing,the mechanical properties of the model are closer to the indoor direct shear test.The displacement curve of the sand is smaller and the shear strength index of the sand is lower,which is in accordance with the conclusion of the indoor direct shear test.(5)In the same vertical pressure under different gradation conditions,the C group with good gradation under the shear contact under the direction of the main direction of the minimum deflection,which is due to the better graded particles between the more compact and the resistance to deformation Ability to be large.(6)During the shearing process,when the vertical stress is small,the anisotropy of the normal contact force increases,but when the vertical stress is large,the coordination number increases and the particle contact force distribution is more uniform but the normal contact force anisotropy has been reduced.