Study On The Influence Of Particle Fabric On The Macro And Micro Mechanical Properties Of Rockfill

Rockfill dams are the fastest-growing and most widely used dam types in China since the 1950 s.As a kind of earth-rock dam,it has the advantages of low cost,convenient material acquisition,and high stability.However,as the dam body engineering becomes more and more high,it has to consider the safety issues caused by the force and deformation of the dam body.The fundamental cause of the deformation of rockfill dams lies in the internal particle interaction and changes in the microstructure of the dam body under the external load.That is to say,the macroscopic deformation of the dam body is a macroscopic expression of the internal particle movement and particle interaction.As the main filling material for dams,rockfill materials have extremely important macro-mechanical properties.The structural characteristics such as particle shape,size,and content of fine particles have a significant effect on the macro-and micro-mechanical properties and deformation of rockfill materials.Based on extensive reading of literature at home and abroad,this paper uses polyvinyl chloride materials to make artificial rockfill particles,combines them into rockfill samples with different structural characteristics,and conducts biaxial loading tests under four different confining pressures.PFC2 D is used to simulate the biaxial loading test,the relevant calculation parameters are calibrated,and the evolution process of the contact force chain during loading is analyzed to reveal the evolution mechanism of the macro-mechanical properties of the rockfill material during the biaxial loading process from the particle level.The main work of this article is as follows:(1)Using artificial rockfill materials made of polyvinyl chloride as the research object,the visual biaxial loading test system developed by ourselves is used to carry out biaxial loading tests under different confining pressures,and all indoor tests are simulated by using the PFC2 D discrete element program in order to study the influence of various fabric factors on the macro-mechanical properties and deformation of rockfill materials.The numerical experiments in this paper can better fit the indoor physical experiments,and the laws presented are consistent.(2)Using artificial rockfill materials with different particle sizes(10mm,20 mm,and 30mm),carry out biaxial loading indoor tests and numerical tests at four confining pressures(100kPa,200 kPa,300kPa,and 400kPa)to study the effect of particle size on macromechanical properties of rockfill.It is found that the larger the particle size,the higher the peak value of the eccentric stress-axial strain curve,the larger the initial elastic modulus,and the stronger the sample strength.(3)Randomly mixing artificial rockfill materials of two particle sizes(10mm and 20mm)and conducting biaxial loading laboratory tests and numerical tests under four confining pressures in order to study the effect of fines content on macro-mechanical properties of rockfill.It is found that the higher the fine particle content,the lower the peak value of the partial stress-axial strain curve,the lower the initial elastic modulus,and the smaller the sample strength.(4)The clump unit in the PFC2 D particle flow program is used to establish three different-shaped heterogeneous polygonal particles with complex boundaries.Four biaxial loading laboratory tests and numerical tests under four different confining pressures are conducted to study the effect of particle shape on macro-mechanical properties of rockfill.It is found that the larger the number of polygon sides,the lower the peak value of the bias stress-axial strain curve and the lower the strength.