Shape and dynamics of seepage erosion in a horizontal granular bed.
Shape and dynamics of seepage erosion in a horizontal granular bed.
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水平颗粒床渗流侵蚀的形状和动力学。
DOI：
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发表时间：
2012
期刊：
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通讯作者：
D. Rothman
中科院分区：
文献类型：
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作者：
M. Berhanu;A. Petroff;O. Devauchelle;A. Kudrolli;D. Rothman
我们研究了在水平颗粒床上观察到的侵蚀模式，这种侵蚀模式是由在更大尺度的陆地形式中观察到的海滩小沟和河道生长引起的水的渗透引起的。我们的实验装置由一个装满玻璃珠的宽矩形盒子组成，在侧壁上有一个狭窄的开口，被侵蚀的颗粒可以从里面出来。利用激光辅助地形技术获得了图案形状和侵蚀动力学的定量数据。研究表明，地下水来源的空间分布对观测模式的形状有显著影响。当地下水注入与保持恒定高度的水库相邻的边界时，观察到一条细长的河道向上游生长。当均匀的降雨渗入颗粒床以维持地下水位时，观察到圆形（半圆形）形状。随着地下水的作用，沟渠的生长可以观察到分叉。我们进一步发现，随着颗粒床高度在毛细上升之上的增加，通道通过离散雪崩生长，导致较深的通道具有较粗糙的锋面。当床层部分饱和导致颗粒间黏聚时，雪崩的时空分布随床层高度的增加而增加。然而，观察到通道的整体形状没有受到影响，这表明渗透侵蚀对侵蚀锋的扰动是强大的。
We investigate erosion patterns observed in a horizontal granular bed resulting from seepage of water motivated by observation of beach rills and channel growth in larger scale land forms. Our experimental apparatus consists of a wide rectangular box filled with glass beads with a narrow opening in one of the side walls from which eroded grains can exit. Quantitative data on the shape of the pattern and erosion dynamics are obtained with a laser-aided topography technique. We show that the spatial distribution of the source of groundwater can significantly impact the shape of observed patterns. An elongated channel is observed to grow upstream when groundwater is injected at a boundary adjacent to a reservoir held at constant height. An amphitheater (semicircular) shape is observed when uniform rainfall infiltrates the granular bed to maintain a water table. Bifurcations are observed as the channels grow in response to the groundwater. We further find that the channels grow by discrete avalanches as the height of the granular bed is increased above the capillary rise, causing the deeper channels to have rougher fronts. The spatiotemporal distribution of avalanches increase with bed height when partial saturation of the bed leads to cohesion between grains. However, the overall shape of the channels is observed to remain unaffected indicating that seepage erosion is robust to perturbation of the erosion front.