颗粒形状对不良级配碎石集料剪切特性的影响

Effect of particle shape on the shear behavior of open-graded crushed aggregate

碎石颗粒的形状对于集料的整体剪切性能有很大的影响,而现有的研究缺乏对于不规则块体颗粒形状的定量评价指标。利用离散元软件PFC2D(Particle flow code,2D)研究,提出了不规则块体的生成方法,建立了平面双轴剪切试验条件,通过对比室内试验结果完成了对模型的验证以及细观参数的选择。通过对块体进行分割后得到的多边形相邻顶角的差值进行分析,改进了棱角度指数的概念,在此基础上分析了颗粒形状对于级配不良的碎石集料的力学性质的影响,研究结果表明:棱角度指数受划分边界数的影响较大,随着划分密度的增加,棱角度指数不断减小并趋于稳定;随着轴向应变的增加,碎石集料的剪应力呈现出明显的非线性增加,曲线的形态受颗粒形状影响较大,除球形颗粒外,其他形状颗粒集料均呈现出应变硬化的特性。在棱角度指数较低时,抗剪强度和内摩擦角缓慢增加,而当棱角度较大时,抗剪强度指标则增加较快,可以通过幂函数进行拟合。

The shape of crushed rock particle greatly influences the shear behavior of crushed aggregate. However few quantitative evaluation indices were proposed. PFC2D （Particle flow code, 2D） was utilized in this paper to simulate the biaxial shear condition and the randomly shaped polygon particle generation method was studied based on clump logic. By comparing with the experimental results, the numerical model was validated and the parameters were determined. The angularity index was modified based on current research by dividing the clumped particles into polygons. The effect of particle shape on the shear behavior of open-graded crushed aggregate was analyzed. The results showed that, the dI （Angularity Index） was greatly influenced by the partition density, AI increased and became stable with partition density. The shear strength increased nonlinearly with the axial strain and the morphological characteristics of the curve was obviously affected by particle shape, except ball particle, all the aggregate showed shear hardening. The shear strength and friction angle increased slowly when AI was relatively small before pronouncedly increased with dl, the relationships can be fitted with power function.