Effects of particle size ratio on the macro- and microscopic behaviors of binary mixtures at the maximum packing efficiency state

摘要

The effects of particle size ratio on themechanical behaviors of binary mixtures are investigated using three-dimensional discrete element method. The samples with three types of particle size ratios (SR, SR = 3.0, 4.5 and 6.0) are prepared at the maximum packing efficiency state, which appears at 70% of the large particle volume content. The results demonstrate that the maxima of peak deviator stress are obtained at the sample with SR = 4.5. The initial elastic modulus, E-0, increases with increasing SR. The value of deviator stress increases with increasing SR at the softening stage, whereas an opposite trend is observed at the critical state. The evolutions of the effective particle ratio can capture the differences among the evolutions of the deviator stress of different samples during the softening stage and the critical state to some degree. In addition, different SRs generate different packing structures of the binary mixtures and have apparent influences on the force chain networks in the binary mixtures. With increasing SR, the strong force chains become stronger, and the weak force chains become weaker. The deviator stress contributed by the contacts between large particles and between large and small particles constitutes a major part of the overall deviator stress of the binary mixtures at the maximum packing efficiency state. Furthermore, the positions of the critical state lines of binary mixtures in the p-q plane and v-ln p plane are sensitive to SR, and the lubrication effect of small particles in the binary mixtures is enhanced with increasing SR.