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A heavy intruder in a locally-shaken granular solid.
Soft Matter ( IF 2.9 ) Pub Date : 2020-04-29 , DOI: 10.1039/c9sm02498k
Diego Berzi 1 , Stefano Buzzaccaro 2
Affiliation  

We experimentally investigate the gravitational-driven motion of a heavy object inside a vertical 2D assembly of identical, plastic cylinders arranged in a regular, triangular lattice. The bottom of the assembly is in contact with a rough plate whose horizontal, sinusoidal motion induces the formation of shear bands in the granular solid, aligned with the edges of the lattice. The intruder sinks when the width of the shear band is as large as its size and halts once the regular configuration of the grains is recovered. The resulting vertical motion of the intruder is random and intermittent, as in disordered granular or colloidal systems near jamming, with alternate flows and blockades. We show, in analogy with earthquakes, that the relation between the size and the duration of the flowing events follows a power-law with an exponent larger than one, and that the statistics of their size is compatible with the Gutenberg-Richter law. We also show that the probability density function of times between flowing events is similar to the Omori law governing the distribution of aftershock sequences following large earthquakes. Finally, the analysis of the velocity fluctuations of the intruder points to a transition from a strong to a weak contact network in the ordered granular assembly, similar to the transition from jammed to fragile states in disordered systems.

中文翻译:

局部晃动的颗粒状固体中的重型入侵者。

我们通过实验研究了重力物体在垂直2D组件中的重力驱动运动,该组件由规则的三角形晶格排列的相同塑料圆柱体构成。组件的底部与一块粗糙的板接触,该板的水平正弦运动会导致在粒状固体中形成剪切带,该剪切带与晶格的边缘对齐。当剪切带的宽度与其尺寸一样大时,入侵者就会下沉,一旦恢复到正常的晶粒形状,入侵者就会停止。入侵者所产生的垂直运动是随机的和间歇性的,例如在干扰附近的无序颗粒或胶体系统中,交替流动和阻塞。与地震类似,流动事件的大小和持续时间之间的关系遵循指数大于一个的幂律,并且事件大小的统计量与古腾堡-里希特定律兼容。我们还表明,流动事件之间时间的概率密度函数类似于大森定律,后者控制着大地震后余震序列的分布。最后,对入侵者速度波动的分析表明,在有序的颗粒状组件中,从强接触网络到弱接触网络的过渡类似于在无序系统中从阻塞状态变为脆弱状态的过渡。我们还表明,流动事件之间时间的概率密度函数类似于大森定律,后者控制着大地震后余震序列的分布。最后,对入侵者速度波动的分析表明,在有序的颗粒状组件中,从强接触网络到弱接触网络的过渡类似于在无序系统中从阻塞状态变为脆弱状态的过渡。我们还表明,流动事件之间时间的概率密度函数类似于大森定律,后者控制着大地震后余震序列的分布。最后,对入侵者速度波动的分析表明,在有序的颗粒组件中,接触网络从强到弱接触网络过渡,类似于无序系统中从阻塞状态到脆弱状态的过渡。
更新日期:2020-03-19
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