粗粒料颗粒形状对材料宏观力学性能的影响?

粗粒料的颗粒形状是影响材料宏观力学性能的重要因素,大型三轴试验的局限性限制了粗粒料微观结构对力学性能影响的研究。基于二维颗粒流理论,利用PFC2D建立4种不同形状的颗粒簇,进行了双轴实验的颗粒流数值模拟,建立形状与宏观力学性能和变形特征的相互关系。结果表明:颗粒形状系数与材料内摩擦角近似呈线性关系,随着形状系数的增加内摩擦角递减;材料强度峰值和残余强度随着颗粒形状系数的增加而减小;材料初始切线模量随着形状系数的增加而减小;数值模型在加载过程中先出现剪缩效应,后产生剪胀效应,且同一形状颗粒的试样,围压越大,剪胀变形越明显;不同形状颗粒的试样达到最终应变软化状态之前,形状系数越小,剪缩效应越不明显,反之,剪胀效应越明显。

Influence of Particle Shape on the Macroscopic Mechanical Properties of Coarse Aggregate

The shape of coarse aggregate is an important impact factor that determines the macroscopic mechanical properties of materials. The limitation of large-scale triaxial tests restricts the study on the influence of microstructure on mechanical properties of the coarse aggregate. Based on two-dimensional particle flow theory, four different shapes of clumps are built by PFC2D, and biaxial tests are simulated. The relationships of macroscopic mechanical properties and deformation behaviour with coarse aggregate shape are established, respectively. The results of particle flow numerical simulation show that the relationship between the particle shape coefficient and the friction angle of material is approximately linear, and the internal friction angle decreases with the increment of shape coefficient. Both the peak strength and the residual strength of coarse aggregate decrease with the increment of particle shape coefficient, and the initial modulus shares the same law. The shear contraction appears firstly in the process of loading, and then the dilatancy effect is observed. For the samples with the same shape of particles, the greater the confining pressure is, the more obvious the shear dilatancy is. Before samples with different shapes reach the final states of strain softening, the smaller the shape coefficient is, the more inconspicuous the shear contraction is. On the contrary, the shear dilatation is more significant.