River currents, wind, and waves drive bed-load transport, in which sediment particles collide with each other and Earth's surface. A generic consequence is impact attrition and rounding of particles as a result of chipping, often referred to in geological literature as abrasion. Recent studies have shown that the rounding of river pebbles can be modeled as diffusion of surface curvature, indicating that geometric aspects of impact attrition are insensitive to details of collisions and material properties. We present data from fluvial, aeolian, and coastal environments and laboratory experiments that suggest a common relation between circularity and mass attrition for particles transported as bed load. Theory and simulations demonstrate that universal characteristics of shape evolution arise because of three constraints: (i) Initial particles are mildly elongated fragments, (ii) particles collide with similarly-sized particles or the bed, and (iii) collision energy is small enough that chipping dominates over fragmentation but large enough that sliding friction is negligible. We show that bed-load transport selects these constraints, providing the foundation to estimate a particle's attrition rate from its shape alone in most sedimentary environments. These findings may be used to determine the contribution of attrition to downstream fining in rivers and deserts and to infer transport conditions using only images of sediment grains.

中文翻译：

---

床载切屑导致颗粒形状演变的普遍特征。

河流，风和海浪驱动着床层运输，沉积物中的颗粒彼此碰撞，并与地球表面发生碰撞。一般的结果是由于碎裂而造成的冲击磨损和颗粒变圆，在地质文献中通常将其称为磨损。最近的研究表明，可以将河卵石的倒圆建模为表面曲率的扩散，这表明冲击磨损的几何特征对碰撞细节和材料特性不敏感。我们提供了来自河流，风沙和沿海环境以及实验室实验的数据，这些数据表明了圆形度和质量损耗之间的共同关系，这些颗粒作为床载运输。理论和仿真表明，形状演化的普遍特征是由于三个约束而产生的：（i）初始粒子是轻微拉长的碎片，（ii）粒子与大小相似的粒子或床层碰撞，并且（iii）碰撞能量小到足以使碎屑占主导地位，但大到足以使滑动摩擦忽略不计。我们表明，床荷运输选择了这些约束条件，为在大多数沉积环境中仅根据颗粒的形状估算颗粒的磨损率提供了基础。这些发现可用于确定损耗对河流和沙漠下游精细化的贡献，并仅使用沉积物颗粒的图像来推断运输条件。（iii）碰撞能量足够小，以致碎屑比碎屑占支配地位，但又足够大，以至于滑动摩擦可以忽略不计。我们表明，床荷运输选择了这些约束条件，为在大多数沉积环境中仅根据颗粒的形状估算颗粒的磨损率提供了基础。这些发现可用于确定损耗对河流和沙漠下游精细化的贡献，并仅使用沉积物颗粒的图像来推断运输条件。（iii）碰撞能量足够小，以致碎屑比碎屑占支配地位，但又足够大，以至于滑动摩擦可以忽略不计。我们表明，床荷运输选择了这些约束条件，为在大多数沉积环境中仅根据颗粒的形状估算颗粒的磨损率提供了基础。这些发现可用于确定损耗对河流和沙漠下游精细化的贡献，并仅使用沉积物颗粒的图像来推断运输条件。