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首页> 外文期刊>Earth Surface Processes and Landforms: The journal of the British Geomorphological Research Group >Experimental study of rill bank collapse
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Experimental study of rill bank collapse

机译：河岸塌陷的实验研究

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Rill bank collapse is an important component in the adjustment of channel morphology to changes in discharge and sediment flux. Sediment inputs from bank collapse cause abrupt changes in flow resistance, flow patterns and downstream sediment concentrations. Generally, bank retreat involves gradual lateral erosion, caused by flow shear stress, and sudden bank collapse, triggered by complex interactions between channel flow and bank and soil water conditions. Collapse occurs when bank height exceeds the critical height where gravitational forces overcome soil shear strength. An experimental study examined conditions for collapse in eroding rill channels. Experiments with and without a deep water table were carried out on a meandering rill channel in a loamy sand and sandy loam in a laboratory flume under simulated rainfall and controlled runon. Different discharges were used to initiate knickpoint and rill incision. Soil water dynamics were monitored using microstandpipes, tensiometers and time domain reflectometer probes (TDR probes). Bank collapse occurred with newly developed or rising pre-existing water tables near rill banks, associated with knickpoint migration. Knickpoint scour increased effective bank height, caused positive pore water pressure in the bank toe and reduced negative pore pressures in the unsaturated zone to near zero. Matric tension in unsaturated parts of the bank and a surface seal on the 'interrill' zone behind the bank enhanced stability, while increased effective bank height and positive pore water pressure at the bank toe caused instability. With soil water contents > 35 per cent (sandy loam) and > 23 per cent (loamy sand), critical bank heights were 0-11-0-12 m and 0-06-0-07 m, respectively. Bank toe undercutting at the outside of the rill bends also triggered instability. Bank displacement was quite different on the two soils. On the loamy sand, the failed block slid to the channel bed, revealing only the upper half of the failure plane, while on the sandy loam the failed block toppled forwards, exposing the failure plane for the complete bank height. This study has shown that it is possible to predict location, frequency and magnitude of the rill bank collapse, providing a basis for incorporation into predictive models for hillslope soil loss or rill network development. Copyright (c) 2006 John Wiley & Sons, Ltd.
机译：堤岸塌陷是调节河道形态以适应流量和泥沙通量变化的重要组成部分。堤岸塌陷产生的泥沙输入会引起流阻，流型和下游沉积物浓度的突然变化。通常，河岸退缩涉及流量剪切应力引起的逐渐的横向侵蚀，以及河道流量与河岸和土壤水分状况之间复杂的相互作用所触发的河岸突然坍塌。当堤岸高度超过重力克服土体抗剪强度的临界高度时，会发生坍塌。一项实验研究检查了侵蚀的小河通道坍塌的条件。在有模拟降雨和受控流明的条件下，在实验室水槽中的壤质砂质壤土和砂质壤土中的曲折河道上进行了有或没有深水位的实验。使用不同的放电来开始形成拐点和小切口。使用微型立管，张力计和时域反射计探头（TDR探头）监测土壤水分动力学。河岸倒塌是由于小溪岸附近新开发的或已有的地下水位上升而引起的，与拐点迁移有关。拐点冲刷增加了有效堤岸高度，导致堤岸脚趾处的孔隙水压力为正值，而非饱和区的孔隙水压力为负值，降低到接近零。堤岸不饱和部分的基质张力和堤岸后面“中间钻孔”区域的表面密封增强了稳定性，而有效堤岸高度的增加和堤岸脚趾处的正孔隙水压力导致了不稳定。当土壤含水量> 35％（沙壤土）和> 23％（壤土）时，临界河岸高度分别为0-11-0-12 m和0-06-0-07 m。小溪弯曲处外侧的脚趾底切也引发了不稳定。在这两种土壤上，河岸位移大不相同。在壤质砂土上，破裂的块体滑入河床，仅露出破裂面的上半部分，而在砂质壤土上，破裂的块体向前倾倒，使破裂面露出整个堤岸高度。这项研究表明，有可能预测河岸塌陷的位置，频率和大小，为将其纳入山坡土壤流失或河网发展的预测模型提供基础。版权所有（c）2006 John Wiley＆Sons，Ltd.

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