陡坡林地加速侵蚀的水动力学及能耗机制研究
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国家重点基础科学(973)研究发展计划“粗沙风—洪产输物理过程及模拟”(2011CB403302),“黄土坡面土壤养分流失特征与控制机理”(2011CB411903);国家科技支撑计划课题“农田水土保持工程与耕作关键技术研究”(2011BAD31B01)


Hydraulic Characteristics and Flow Enemy Consumption of Accelerated Erosion on Steep Slope Woodland
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    摘要:

    利用野外原位模拟降雨试验,对陡坡林地加速侵蚀下的薄层水流水力学参数和能耗特征进行了研究.结果表明,林地原状延缓径流作用显著,流速维持在0.05~0.09m/s,加速侵蚀后流速均增加,且自上坡面至下坡面有增大的趋势.原状林地处理的雷诺数(Re)为160.8,属于层流;加速侵蚀后坡面Re显著增加,处于层流与紊流之间的过渡流状态.与原状相比,去除枯枝落叶层和除地上部分处理的Re分别增加了114.9%~245.1%和322.2%~1 012.9%,阻力系数(f)分别减少了5.2%~90.6%和42.6%~270.3%;除枯枝落叶层处理的中下段和下段弗汝德数(Fr)均大于1,为急流,坡上和中上段Fr均小于1,为缓流.翻耕处理的径流流速减缓,Re减小;Fr在坡中上、中下段、下段增加了181.6%~72.3%,f减少了41.3%~66.8%,坡上Fr减少了67.3%,但f表现为增加.在降雨初期动能较低,随降雨历时增加呈缓慢上升,最后趋于稳定,且径流势能远大于径流动能.坡面除枯枝落叶层、除地上部分和翻耕加速侵蚀后,坡面能耗增大,侵蚀量与能耗相关性较好.

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    The hydraulic characteristics and flow energy consumption of runoff on steep slope woodland were studied under accelerated erosion condition with simulated rainfalls. The results show that the natural soil surface had a significantly effect on reducing flow velocity, which remained very slow as 0.05 to 0.09 m/s. The flow velocity increased under manmade accelerated erosion. Furthermore, the increasing amplitude was greater on the lower slope position than the upper one. The Reynolds number Re of the runoff on natural soil surface of the woodland was 160.8, which can be recognized as laminar flow. Under manmade accelerated erosion, the flow shifted to a transition state between laminar and turbulent flow condition. Compared with natural soil surface, the Froude number Fr of the middle and lower slope position with litter removal in-creased by 114.9%~245.1% and 322.2%~1 012.9%, and the friction coefficient f increased by 5.2%~90.6% and 42.6%~270.3%, respectively. The flow velocity on the bottom and mid-lower slope sections were rapid with Fr>l, and slow on the upper and mid-upper slop sections with Fr<1. The treatment of till-age increased Fr and f by 181.6G~72.3G and 41.3%~66.80% on the bottom, mid-lower and mid-upper slope sections. In the upper section, Fr decreased by 67.3~ while f increased by 8 times. The potential en-ergy of the surface flow was greater than kinetic energy, the kinetic energy level of the flow was low in early stage of simulation rainfall and then increased and finally stabilized over the experiment time. Compared with the natural soil surface, the energy consumption of the slope surface increased in all the treatments of forest litter removal, cutting above ground parts and tillage. The intensity of soil erosion was closely related to en-ergy consumption of the slope surface.

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陈磊,李占斌,李鹏,徐国策,宋炜.陡坡林地加速侵蚀的水动力学及能耗机制研究[J].水土保持通报,2012,(4):5-9

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  • 收稿日期:2011-05-22
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  • 在线发布日期: 2014-11-25
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