用改进的伏尔米流变学解释岩崩体积和冲出量之间的比例关系

IF 2.8 2区 地球科学 Q2 GEOGRAPHY, PHYSICAL Earth Surface Dynamics Pub Date : 2024-01-23 DOI:10.5194/esurf-12-219-2024
Stefan Hergarten
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引用次数: 0

摘要

摘要。岩石崩塌的冲出长度远远大于库仑摩擦力的预测值。虽然人们早就知道崩落长度会随体积的增加而增加,但如何定性地解释这种增加仍然是一个难题。本研究对广泛使用的 Voellmy 流变学进行了重新解释和修改。修改后的流变学不再添加库仑摩擦项和速度相关项,而是将这两个项分配给不同的速度状态。假设在给定速度下库仑摩擦和流动之间的转换是最简单的方法,而对现有随机粒子运动动能模型的重新解释则预测了交叉速度与岩崩厚度的关系。对简单的一维地形上的块状质点的分析解显示,在流动体系中存在坡度主导和高度主导体系。在坡度主导机制中,坡脚处的动能主要取决于坡度角,而相对于谷底的绝对高度影响不大,反之亦然。根据流变学得出的长度尺度与地形的长度尺度之比可以区分这两种状态。在高度占主导地位的情况下,会出现较长的径流。结合体积、厚度和高度之间的经验关系,基于随机动能模型的方法很好地再现了自然界中观察到的流出长度与体积的比例关系。
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Scaling between volume and runout of rock avalanches explained by a modified Voellmy rheology
Abstract. Rock avalanches reach considerably greater runout lengths than predicted by Coulomb friction. While it has been known for a long time that runout length increases with volume, explaining the increase qualitatively is still a challenge. In this study, the widely used Voellmy rheology is reinterpreted and modified. Instead of adding a Coulomb friction term and a velocity-dependent term, the modified rheology assigns the two terms to different regimes of velocity. While assuming a transition between Coulomb friction and flow at a given velocity is the simplest approach, a reinterpretation of an existing model for the kinetic energy of random particle motion predicts a dependence of the crossover velocity on the thickness of the rock avalanche. Analytical solutions for a lumped mass on a simple 1D topography reveal the existence of a slope-dominated and a height-dominated regime within the regime of flow. In the slope-dominated regime, the kinetic energy at the foot of the slope depends mainly on the slope angle, while the absolute height relative to the valley floor has little effect, and vice versa. Both regimes can be distinguished by the ratio of a length scale derived from the rheology and the length scale of the topography. Long runout occurs in the height-dominated regime. In combination with empirical relations between volume, thickness, and height, the approach based on the random kinetic energy model reproduces the scaling of runout length with volume observed in nature very well.
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来源期刊
Earth Surface Dynamics
Earth Surface Dynamics GEOGRAPHY, PHYSICALGEOSCIENCES, MULTIDISCI-GEOSCIENCES, MULTIDISCIPLINARY
CiteScore
5.40
自引率
5.90%
发文量
56
审稿时长
20 weeks
期刊介绍: Earth Surface Dynamics (ESurf) is an international scientific journal dedicated to the publication and discussion of high-quality research on the physical, chemical, and biological processes shaping Earth''s surface and their interactions on all scales.
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