Spontaneous stratification in granular mixtures

被引:306
作者
Makse, HA
Havlin, S
King, PR
Stanley, HE
机构
[1] BOSTON UNIV,DEPT PHYS,BOSTON,MA 02215
[2] BAR ILAN UNIV,MINERVA CTR,RAMAT GAN,ISRAEL
[3] BAR ILAN UNIV,DEPT PHYS,RAMAT GAN,ISRAEL
[4] BP EXPLORAT OPERATING CO LTD,SUNBURY TW16 7LN,MIDDX,ENGLAND
关键词
D O I
10.1038/386379a0
中图分类号
O [数理科学和化学]; P [天文学、地球科学]; Q [生物科学]; N [自然科学总论];
学科分类号
07 ; 0710 ; 09 ;
摘要
Granular materials(1-5) segregate according to grain size when exposed to periodic perturbations such as vibrations(6-12). Moreover, mixtures of grains of different sizes can also spontaneously segregate in the absence of external perturbations: when such a mixture is simply poured onto a pile, the large grains are more likely to be found near the base, while the small grains are more likely to be near the top(13-20). Here we report another size-separation effect, which arises when we pour a granular mixture between two vertical plates: the mixture spontaneously stratifies into alternating layers of small and large grains whenever the large grains have larger angle of repose than the small grains. We find only spontaneous segregation, without stratification, when the large grains have smaller angle of repose than the small grains. The stratification is related to the occurrence of avalanches: during each avalanche, the grains separate into a pair of static layers, with the small grains forming a sublayer underneath the layer of large grains.
引用
收藏
页码:379 / 382
页数:4
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