Processes in model slopes made of mixtures of wettable and water repellent sand: Implications for the initiation of debris flows in dry slopes
Processes in model slopes made of mixtures of wettable and water repellent sand: Implications for the initiation of debris flows in dry slopes
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DOI：
10.1016/j.enggeo.2015.06.021
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发表时间：
2015-09
影响因子：
7.4
通讯作者：
S. Lourenço;Gong-hui Wang;T. Kamai
中科院分区：
文献类型：
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作者：
S. Lourenço;Gong-hui Wang;T. Kamai
最初干燥的山坡上的泥石流，如野火后的泥石流，是由地表径流和由于渗透减少而产生的沉积物膨胀引起的。土壤防水性、极端干燥的土壤和松散、无粘性的材料会影响它们的引发。这些特征之间的确切联系，由此产生的渗透过程和泥石流的启动机制仍然不清楚。在这里，我们研究土壤颗粒润湿性和物理模型中的斜坡过程之间的关系。水槽试验中进行了10%的增量的质量比，防水砂，进行人工降雨监测土壤含水量，孔隙水压力，泥沙和水流量和故障模式。到目前为止，润湿性只被认为是防水的一端，因为它减少了渗透，增加了表面径流。这项研究表明，轻微的润湿性变化，在充分的防水范围内，影响各种斜坡过程。两个极端，充分渗透和防水给出了相反的反应，倒退幻灯片的入渗开始在流沙和侵蚀的表面径流在防水砂。过渡主要由地表径流和优先流，产生的组合侵蚀和幻灯片。根据试验，由拒水性产生的连续覆盖效应是侵蚀和砂膨胀的必要条件，即，径流引发的泥石流的产生。模型的斜率响应人工降雨的敏感性是特别尖锐的高比例的防水砂。对于混合物以上的临界比例的防水砂，指数测试的测量结果显示，尽管渗透，饱和度和孔隙水压力建立的趋势的差异，一个完全防水材料。野火后的泥石流和泥石流的斜坡最初干燥的影响进行了讨论。
Debris flows in slopes initially dry, such as post-wildfire debris flows, are initiated by surface runoff and sediment bulking due to reduced infiltration. Soil water repellency, extreme dry soils, and loose, cohesionless materials influence their initiation. The exact link between these features, the resulting infiltration processes and the initiation mechanism of a debris flow remains unclear. Here, we examine the relation between soil particle wettability and slope processes in physical models. Flume experiments were conducted in 10% increments of mass ratios of wettable to water repellent sand, subjected to artificial rainfall with monitoring of soil water content, pore water pressure, sediment and water discharge and failure mode. To date, wettability was considered only for the water repellent end, because it reduces infiltration, enhancing surface runoff. This study demonstrates that slight wettability changes, in the full wettable to water repellent range, impact a variety of slope processes. The two extremes, fully wettable and water repellent gave opposite responses, retrogressive slides for infiltration-initiated in wettable sand and erosion by surface runoff in water repellent sand. The transition was dominated by surface runoff and preferential flow, yielding a combination of erosion and slides. From the tests, a continuous capping effect generated by water repellency was a necessary condition for erosion and sand bulking i.e., the generation of runoff-initiated debris flows. The sensitivity of the model slope response to artificial rainfall was particularly acute at high ratios of wettable to water repellent sand. For mixtures above a critical ratio of wettable to water repellent sand, the measurements with an index test revealed a fully wettable material despite differences in the infiltration, saturation and pore water pressure built-up trends. Implications for post-wildfire debris flows and debris flows in slopes initially dry in general are discussed.