Particle transport over rough hillslope surfaces by dry ravel: Experiments and simulations with implications for nonlocal sediment flux
Particle transport over rough hillslope surfaces by dry ravel: Experiments and simulations with implications for nonlocal sediment flux
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干散布在粗糙山坡表面上的颗粒传输：对非局部沉积物通量影响的实验和模拟
DOI：
10.1029/2011jf002229
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发表时间：
2012
影响因子：
--
通讯作者：
Morgan K. Mendoza
中科院分区：
文献类型：
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作者：
E. Gabet;Morgan K. Mendoza
[1] 过去对山坡演化的研究通常假设土壤蠕变过程受局部山坡角度和迁移距离之间的线性关系控制。 “线性扩散”的假设已经失宠，因为当与质量连续性的表达相结合时，它会产生不切实际的山坡剖面。因此，需要更好地了解沉积物输送的机制。在这里，我们报告了一系列水槽实验的结果，这些实验旨在研究干拉尔沉积物的输送，这是干旱和半干旱环境中常见的土壤蠕变过程。我们发现，在缓坡上，运输距离遵循当地运输的分布特征。随着梯度变陡，一部分粒子开始表现出非局域传输，并且该部分随着斜率迅速增加。将有效摩擦项与冲击项耦合的随机离散元模型再现了水槽实验的结果，表明它可用于探索粗糙表面上颗粒传输的性质。该模型预测，缓坡上传输距离的指数分布会演变成陡坡上的准均匀分布，并且当斜坡接近休止角时会发生转变。我们的结果支持之前的发现，即休止角代表摩擦和惯性状态之间的阈值。此外，我们提出休止角代表局部和非局部传输之间的模糊边界。
[1] Past studies of hillslope evolution have typically assumed that soil creep processes are governed by a linear relationship between local hillslope angle and transport distance. The assumption of “linear diffusion” has fallen out of favor because, when coupled with an expression of mass continuity, it yields unrealistic hillslope profiles. As a consequence, a better understanding of the mechanics of sediment transport is needed. Here we report results from a series of flume experiments performed to investigate sediment transport by dry ravel, a common soil creep process in arid and semiarid environments. We find that, at gentle slopes, transport distances follow distributions characteristic of local transport. As gradients steepen, a fraction of the particles begins to exhibit nonlocal transport, and that fraction increases rapidly with slope. A stochastic discrete element model that couples an effective friction term with a shock term reproduces the results from the flume experiments, suggesting that it can be used to explore the nature of particle transport on rough surfaces. The model predicts that exponential distributions of transport distances on gentle slopes evolve into quasi-uniform distributions on steep slopes, and the transition occurs as slopes approach the angle of repose. Our results support previous findings that the angle of repose represents a threshold between friction and inertial regimes. In addition, we propose that the angle of repose represents a fuzzy boundary between local and nonlocal transport.