We describe compaction, induced by weak tapping of a powder, as a process where a grain can jump into a hole, only if the hole is large enough. The distribution of hole sizes is taken to be the Poisson type, with a certain characteristic free volume. For macrodisperse powders, this leads to a classical logarithmic law of compaction, already derived by Knight et al. Here we focus our attention on the case of mixtures, between two populations: large grains (L) and small grains (S) with very different sizes, so that the (S) grains may fill the interstices of the (L) grains. Geometrically, these mixtures can exist as ''gravels'' (where the interstices are not completely filled) or ''puddings'' (where the L grains are not tightly packed). Dynamically, we expect a cross over curve between L-type compaction and S-type compaction, which is different from the geometrical boundary. This implies that, for certain material ratios rho = L/S, the plot of density versus number of tappings should show two distinct branches. [References: 13]
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机译：我们将由粉末的弱攻引起的压实描述为只有在孔足够大的情况下晶粒才能跳入孔的过程。孔尺寸的分布被认为是具有一定特征自由体积的泊松型。对于大分散粉末，这导致了Knight等人已经推导的经典对数压实定律。在这里，我们将注意力集中在两个种群之间的混合物的情况上：大晶粒（L）和小晶粒（S），它们的尺寸非常不同，以便（S）晶粒可以填充（L）晶粒的空隙。从几何学上讲，这些混合物可以“砾石”（空隙未完全填充）或“布丁”（L粒未紧密堆积）的形式存在。在动力学上，我们期望L型压实和S型压实之间有一条交叉曲线，这与几何边界不同。这意味着，对于某些材料比率rho = L / S，密度与攻丝数量的关系图应显示两个不同的分支。 [参考：13]
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