Most smaller asteroids ($<$1 km diameter) are granular material loosely bound together primarily by self-gravity known as rubble piles. In an effort to better understand the evolution of rubble-pile asteroids, we performed bulk measurements using granular simulant to study the effects of the presence of fine grains on the strength of coarse grains. Our laboratory samples consisted of fine–coarse mixtures of varying percentages of fine grains by volume of the sample. We measured the material’s angle of repose, Young’s Modulus, angle of internal friction, cohesion, and tensile strength by subjecting the samples to compressive and shear stresses. The coarse grains comprising the fine–coarse mixtures ranged from 1 mm to 20 mm (2 cm) and the fines were sieved to sub-millimeter sizes ($<$1 mm). The measured angles of repose varied between 32$°$–45$°$ which increased with increasing fine percentage. In compression, samples generally increased in strength with increasing fine percentage for both confined and unconfined environments. In all cases, the peak strengths were not for purely fine grains but for a mixture of fine and coarse grains. Shear stress measurements yielded angles of internal friction ranging between 25$°$ and 45$°$ with a trend opposite that of the angle of repose, 300–550 Pa for bulk cohesion, and 0.5–1.1 kPa for tensile strength. Using other published works that include data from telescopic and in-situ observations as well as numerical simulations, we discussed the implications of our findings regarding rubble-pile formation, composition, evolution, and disruption. We find that the presence of fine grains in subsurface layers of regolith on an asteroid (confined environment) aids the avoidance of disruption due to impact. However these same fines increase an asteroid’s chance to disrupt or deform from high rotation speeds due to reduced grain interlocking. In surface layers (unconfined environments), we find that the presence of fine grains between coarse ones generates stronger cohesion and aids in the prevention of mass loss and surface shedding.

大多数较小的小行星（直径 $<$ 1 公里）是颗粒状物质，主要通过自身重力松散地结合在一起，称为碎石堆。为了更好地了解碎石堆小行星的演化，我们使用颗粒模拟物进行了批量测量，以研究细颗粒的存在对粗颗粒强度的影响。我们的实验室样品由细粒-粗粒混合物组成，其中细粒占样品体积的比例不同。我们通过使样品承受压缩应力和剪切应力来测量材料的休止角、杨氏模量、内摩擦角、内聚力和拉伸强度。粗颗粒由细粗混合物组成，尺寸范围为 1 毫米至 20 毫米（2 厘米），细颗粒筛分至亚毫米尺寸（ $<$ 1 毫米）。测量的休止角在 32 $°$ –45 $°$ 之间变化，随着细粒百分比的增加而增加。在压缩过程中，无论是受限环境还是非受限环境，样品的强度通常会随着细度百分比的增加而增加。在所有情况下，峰值强度并非针对纯细晶粒，而是针对细晶粒和粗晶粒的混合物。剪切应力测量得出的内摩擦角范围在 25 $°$ 和 45 $°$ 之间，其趋势与休止角相反，体内聚力为 300–550 Pa，内聚力为 0.5–1.1 kPa 为拉伸强度。利用其他已发表的作品，包括来自望远镜和现场观测以及数值模拟的数据，我们讨论了我们的研究结果对碎石堆形成、组成、演化和破坏的影响。 我们发现小行星（密闭环境）的地下风化层中存在细颗粒有助于避免因撞击而造成的破坏。然而，由于颗粒互锁减少，这些相同的细粉增加了小行星因高旋转速度而破坏或变形的机会。在表面层（无约束环境）中，我们发现粗颗粒之间存在细颗粒会产生更强的内聚力，有助于防止质量损失和表面脱落。