染色石膏颗粒一维压缩破碎与粒径迁移

Breakage and migration of dyed gypsum particles under one-dimensional compression

为研究粒状岩土材料粒组层面的破碎与粒径迁移规律,采用人工制备的染色石膏颗粒,进行不同应力和级配的单粒组及多粒组等比例混合试样的一维压缩试验。采用人工识别和图像识别软件相结合的方法进行破碎后的颗粒分离,得到各粒组破碎后的级配,据此分析颗粒破碎过程中的粒径迁移模式、粒组的破碎概率以及破碎重叠效应。分析结果表明,颗粒破碎与粒径迁移模式为分步多次破碎、依粒组次序迁移,因而破碎后粒组的级配是连续不间断的。与单粒组级配试样中颗粒破碎概率随粒径减小而减小不同,多粒组级配试样中颗粒的破碎概率随粒径减小而增大(窄级配试样)或先增后减(宽级配试样),但较单粒组级配试样整体上有所下降。破碎重叠效应表现为各粒组颗粒的绝对破碎量远大于相对破碎量,且随着应力的增加和粒径的减小更加明显。最后基于粒度熵的概念,建立了可以反映破碎重叠效应的绝对破碎率。该试验结果亦可为颗粒破碎的数值模拟提供参考。

To study the breakage and migration of soil and rock granular materials from the aspect of grain group,a series of one-dimensional compression tests with different vertical stresses and particle size distributions(PSD) were carried out on dyed gypsum particles. Particles of different groups were separated according to their sizes and colors by combining artificial recognition and image recognition software,and the particle breakage and migration mode,the particle breakage percentage and the breakage overlap effect were analyzed. It is found that particles undergo more than one generation of breakage with broken particles migrating from bigger size intervals to the adjacent smaller ones,and thus,the PSDs of each-color particles are ungapped. With decreasing the particle size,the particle breakage percentage of the better-graded particles increases(for samples with a relatively narrow PSD) or increases first and then decreases(for samples with a relatively wide PSD),but is lower than that of the uniformly graded particles in general. The breakage overlap is described as the phenomenon that the mass of survived particles within a size interval decreases obviously after crushing while the overall mass of the size interval drops little or even increases. In addition,an absolute particle breakage index considering breakage overlap is established based on the concept of grading entropy. The test results can also provide a reference for the numerical simulation of particle breakage.