基于椭球模型的圆砾堆积特性分析

堆积特性是颗粒形状、大小等因素的综合体现，也在一定程度上反映了颗粒集合体的力学特性。以河流冲积型圆砾土中主要占比的10～50 mm圆砾为对象，利用数字图像技术，通过对大样本圆砾颗粒的形态特征分析，选取轴向系数作为圆砾的形状特征参数，并据此提出了圆砾颗粒的椭球模型构建方法，建立了与实际圆砾料在形状和大小上同分布的圆砾椭球模型数据库，进而通过数值堆积试验分析了单粒组圆砾料的堆积特性，并与室内圆筒堆积物理试验进行对比。有以下结论：圆砾的形态特征主要体现在宏观轮廓形状，棱角特性不明显；圆砾堆积数值模拟结果表明，不同大小粒组圆砾堆积孔隙比变化较小；颗粒间摩擦系数对于堆积孔隙比有显著影响，摩擦系数介于0～0.4时，孔隙比变化剧烈，随后逐渐趋于平缓；室内圆筒堆积试验结果验证了椭球模型模拟圆砾堆积的有效性，标定了重力堆积条件下圆砾料颗粒间摩擦系数约为0.3。

Ellipsoid model based packing characteristics analysis of round gravels

Packing characteristics are the comprehensive embodiment of particle shape, size and other factors. It also reflects the mechanical properties of particle aggregates to an extent. Round gravels of river alluvial gravel soil with size range of 10-50 mm is used as research objects. By using the digital image technology and analyzing the morphology of large quantities of round gravels, aspect ratios of round gravels are taken as the shape parameters and the method to build the ellipsoid models is formed. Based on the above, the ellipsoid model database is established with the same distribution in shape and size as the actual round gravels, and the models are used to numerically simulate the packing tests of single set round gravels. By comparing with the physical packing experiments, the following conclusions are made: The morphological features of the round gravels are mainly reflected in the macroscopic contour shape, and the angular characteristics are not obvious. The numerical simulation results show that the void ratios of packing test in different size groups vary little. The coefficient of interparticle friction has significant effect on the void ratios. The void ratio increases rapidly when the friction coefficient is 0.0-0.4 and then becomes flat. The physical experiments results verify the validity of the ellipsoid model simulation, and the coefficient of interparticle friction under gravity is calibrated to be approximately 0.3.