EFFECT OF MINERAL PARTICLE SIZE HETEROGENEITY ON MECHANICAL PROPERTIES IN PFC^2D SIMULATION

As aggregates of mineral particles, the macroscopic mechanical behaviors of rock are obviously affected by mineral particle size and size heterogeneity. The effect of size heterogeneity on rock macroscopic mechanical behaviors(elasticity modulus, peak strength and poisson's ratio) is studied using the software of particle flow code PFC^2D. Different kinds of particle sizes are included in a model and size ratio are used to reflect particle size heterogeneity. Six size heterogeneous scenarios are designed and conducted in the numerical uniaxial compression tests. The type numbers of particle sizes included in a model are respectively continuous distribution, ten kinds, eight kinds, five kinds, three kinds and two kinds. Each scenario includes five mean grain sizes and four size ratios. The results show that particle size and size heterogeneity play an important role in the macro-mechanical properties of these numerical tests. Elasticity modulus and peak strength of samples decrease with the increase of average particle size. With the increase of the size heterogeneity, elasticity modulus and peak strength also show a decreasing trend overall, but during some local change stages show an increasing trend affected by the number and content of fine particles. The effect of particle size and size heterogeneity on Poisson's ratio is smaller. The effect mechanism of particle size on elastic modulus is mainly achieved by influencing the porosity of the model. The achieved results disclose that the change of rock macroscopic properties is the combined action of particle size effect and size heterogeneity effect, and supply references for studying the influence of particle size parameters on strength and deformation feature of rock materials.