Mechanical Property Simulation Of Rockfill Materials Based On The Energy Dissipation Mechanism

In recent years,requirements for the macro-mechanical properties of rockfill have increased with the construction of high earth-rockfill dams in the coastal and mid-west regions of China.The discreteness,brittleness,dilatancy,and anisotropy of rockfill make the existing design theory and constitutive model unable to meet the actual engineering requirements.This study investigates micro-mechanical behavior,such as crushing,shape,translation,rotation,and contact composition,during the cutting of rockfill particles on the destruction mechanism of rockfill dam deformation,by which the macro-mechanical behavior and micro-mechanical properties are established.This study serves as a reference for a complete understanding of the multi-scale mechanical properties of rockfill materials.The main physical and geometric characteristics of rockfill materials are composed of fragmentation behavior,particle shape,and particle surface texture at the micro scale.In this study,breakable rockfill particles are generated by using a particle tangential clustering method and the outer contour of an irregularly shaped particle.An improved contacting constitutive model that simulates the texture of the surface of rockfill particles is described by using custom shape factor parameters.The influence of different particle shapes,rotation effects,and physical features on the macro-mechanics and micro-mechanics of rockfill is discussed in detail.The internal mechanism of the influence is described in accordance with a particle set system energy allocation mechanism by using quantitative statistical analysis to explain the destruction mechanism of rockfill dam deformation.The following conclusions are drawn.(1)Particle crushing is constantly dominated by shear failure in the entire cutting process on the basis of the evaluation on the changing process of particles during cutting with the introduction of broken rate b combined with the evolution of an energy distribution mechanism.For small deformation,the total input energy(external work)is stored in the form of elastic strain energy between particles.The frictional energy consumption(sliding friction energy and rotational friction energy consumption)and kinetic energy are relatively small,and the crushing energy consumption is 0.For the large deformation,the elastic strain energy is converted into other forms of energy consumption,such as storage release,which results in an increase in friction energy(sliding friction energy and rotational friction energy consumption)and crushing energy consumption.(2)For the irregular shape of rockfill,a shape factor that properly describes the outer contour of particles is proposed.A more rounded shape of the particles corresponds to less biting interaction between the particles and less obvious friction resistance effect.The biting force between the particles increases the sliding friction degree at the indirect contact points of particles and contributes to shear strength.The crushing rate is decreased with the increase in shape factor,and the final gradation curve tends to the particle crushing grading curve proposed by Einav.(3)The shear strength of rockfill materials is significantly increased through the anti-rotation effect,and the external work is mainly consumed through the storage of elastic rotational potential energy at the indirect contact points of particles.The particle coordination number is reduced,the force chain transmission capability is enhanced,and the structure becomes stable through the anti-rotation effect.Different anti-rotation effects cause rockfill materials to completely exhibit different mechanical properties in the shearing process due to different micro-mechanisms.Specifically,the peak internal friction angle and anisotropy feature are obvious under the peak deviatoric stress.(4)A fractal model based on the number of particles is established on the basis of a linear contact constitutive model.A numerical test platform that can simulate the boundary conditions,axial displacements,and stress loading modes of the indoor specimen are constructed to extract the macro-mechanical parameters of the specimen.The scale effect has a significant influence on the mechanical properties of rockfill materials.The filling relationship between coarse and fine particles is significantly improved,the corresponding peak strength increases,and the deviatoric stress curve of the scaled specimen possesses strain softening characteristics with the increase in the content of fine particles.(5)The energy distribution mechanism of the particle set system is constantly applied in the shearing process due to the bond of the macro and micro-mechanical behavior of rockfill materials.The microscopic scale is mainly based on particle mechanics and motion parameters,and energy statistical analysis is used to explain the internal mechanism of the macroscopic mechanical behavior of rockfill materials.Generally speaking,the mechanical properties of rockfill are systematically studied in this paper by the PFC2D software.The effects of particle breakage,particle shape,rotational friction coefficient,and scale on mechanical properties of rockfill during shearing are discussed in detail.The relationship between macro and micro mechanical behaviors of rockfill materials is established by means of energy analysis.The purpose of this paper is to study the internal mechanism of deformation and destruction of rockfill during shearing process,and to provide theoretical guidance for deformation of rockfill dam,and ultimately to serve in geotechnical engineering construction.