双分散粒状流中与尺度有关的过程和冲出:实验室实验的启示及对岩石/碎石崩塌的影响

IF 3.5 2区 地球科学 Q1 GEOSCIENCES, MULTIDISCIPLINARY
S. Makris, I. Manzella, A. Sgarabotto
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引用次数: 0

摘要

岩石雪崩和火山碎屑雪崩(岩石/碎屑雪崩)的颗粒大小分布具有双分散性,这被认为是造成雪崩长期失控的一个因素。小规模模拟实验研究证实了这一点,这些研究观察到,小部分细颗粒与较粗颗粒混合在一起会增强颗粒雪崩的冲出力。然而,这种现象的产生机制及其与岩石/碎屑雪崩的相似性尚未得到直接评估。在此,我们利用二元混合物颗粒雪崩实验来确定双分散性在实验中增强颗粒雪崩冲出的过程和条件。结构运动摄影测量法用于测量质心位移和评估能量耗散。随后,本研究评估了实验室和野外的动态缩放和流动机制,以评估失控增强机制是否适用于岩石/碎屑崩落。在小规模实验中,颗粒质量在碰撞机制下传播,实现了动力学筛分和尺寸分离。细颗粒迁移到基底,减少了粗颗粒与基底之间的摩擦面积,促进了滚动。能量耗散的减少增加了动能转换和雪崩流动性。然而,岩石/碎屑雪崩不太可能获得纯粹的碰撞机制;相反,它们会在摩擦机制下传播。从岩石/碎屑雪崩沉积物的沉积学中可以明显看出,在实验室尺度下观察到的过程所必需的尺寸分离被摩擦机制所禁止。将双分散性作为一种流出增强机制的建议忽略了自然事件的规模依赖行为在小规模实验中往往被忽略。
本文章由计算机程序翻译,如有差异,请以英文原文为准。

Scale-Dependent Processes and Runout in Bidisperse Granular Flows: Insights From Laboratory Experiments and Implications for Rock/Debris Avalanches

Scale-Dependent Processes and Runout in Bidisperse Granular Flows: Insights From Laboratory Experiments and Implications for Rock/Debris Avalanches

The bidispersity observed in the particle-size distribution of rock avalanches and volcanic debris avalanches (rock/debris avalanches) has been proposed as a factor contributing to their long runout. This has been supported by small-scale analog experimental studies, which observe that a small proportion of fine particles mixed with coarser particles enhances granular avalanche runout. However, the mechanisms enabling this phenomenon and their resemblance to rock/debris avalanches have not been directly evaluated. Here, binary mixture granular avalanche experiments are employed to constrain the processes and conditions under which bidispersity enhances the runout of granular avalanches in experiments. Structure-from-motion photogrammetry is used to measure center of mass displacement and assess energy dissipation. Subsequently, this study evaluates the dynamic scaling and flow regimes in the lab and field to assess whether the runout-enhancing mechanism is applicable to rock/debris avalanches. In small-scale experiments, the granular mass propagates under a collisional regime, enabling kinetic sieving and size segregation. Fine particles migrate to the base where they reduce frictional areas between coarse particles and the substrate and encourage rolling. The reduced energy dissipation increases the kinetic energy conversion and avalanche mobility. However, rock/debris avalanches are unlikely to acquire a purely collisional regime; instead, they propagate under a frictional regime. The size segregation which is essential for the process observed at the lab-scale is prohibited by the frictional regime, as evident by the sedimentology of rock/debris avalanche deposits. The proposal of bidispersity as a runout-enhancing mechanism overlooks that scale-dependent behaviors of natural events are often omitted in small-scale experiments.

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来源期刊
Journal of Geophysical Research: Earth Surface
Journal of Geophysical Research: Earth Surface Earth and Planetary Sciences-Earth-Surface Processes
CiteScore
6.30
自引率
10.30%
发文量
162
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