花岗岩红壤坡地沟头高度对沟床跌穴发育过程的影响
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广西大学林学院

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S157.1??????

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中央引导地方科技发展资金项目(桂科ZY21195022), 国家自然科学基金项目(42107350,42007055)


Influence of Headcut Height on the Developmental Processes of Downstream Plunge Pool on a Granite Red Soil Slope
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Forestry College of Guangxi University

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    摘要:

    沟床跌穴发育是溯源侵蚀的关键过程。为明确沟头高度对沟床跌穴发育过程和动力机制的影响,研究探讨了花岗岩红壤坡地不同沟头高度(25 cm、50 cm、75 cm、100 cm和125 cm)下沟床跌穴发育过程及动力机制。结果表明:(1)随着沟头高度的增加,流经沟床部分水流的雷诺数、径流剪切力、径流功率和射流参数:触底流速、射流剪切应力、瞬时动能、跌穴径流能耗均表现为增加的趋势。(2)红土层冲刷后以形成“V”型的小跌穴为主,随着流量的增加跌穴形态逐渐增大,但难以形成面积较大的跌穴。而砂土层在冲刷过程中,沟床跌穴发育较为明显,当流量增大到120 L/min后,沟床破碎化程度逐渐剧烈,跌穴轮廓逐渐清晰,横截面积增大。(3)研究通过横截面积来表征跌穴的侵蚀程度,利用随机森林算法和沙普利值构建模型并表征各参数的关系。红土层沟床径流的弗罗德数、径流功率、水平出射动能、雷诺数与横截面积呈负相关;砂土层沟床径流的弗罗德数和跌穴径流能耗与横截面积呈负相关。随机森林算法可用于沟床跌穴侵蚀程度的预测(LCCC=1.02,R2adjusted=0.876和0.868)。研究可为揭示沟头溯源侵蚀机理和沟蚀防治提供理论依据。

    Abstract:

    The development of plunge pool is a key process of headcut erosion. To clarify the effect of headcut height on the developmental processes and dynamical mechanisms of plunge pool. The study investigated the developmental processes and dynamical mechanisms of plunge pool under different headcut heights (25 cm, 50 cm, 75 cm, 100 cm, and 125 cm) on a granite red loam slope. The results show that: (1) As the height of the headcut increases, the Re, τ, ω and the jet parameters: Vbottom, , Ekbottom, and show an increasing trend. (2) After the laterite soil layer scouring to form a "V" type of small plunge pool mainly, with the increase in the flow of the form of plunge pool gradually increased, but it is difficult to form a large area of the plunge pool, and the laterite soil layer is more stable than the sandy soil layer. During the scouring process of the sandy soil layer, the development of headcut bed drop points was more obvious, and when the flow rate increased to 120 L/min, the degree of headcut bed fragmentation was gradually drastic, and the outline of the drop points was gradually clearer, and the cross-sectional area increased (3) The study characterizes the degree of erosion of drop caves through cross-sectional area. Random forest algorithm and Shapley values are used to construct the model and characterize the relationship between the parameters. The results showed that in the laterite layer, Fr, ω, Ekbrink, and Re were negatively correlated with the cross-sectional area; and in the sandy soil layer, Fr and were negatively correlated with the cross-sectional area. Higher accuracy of predictive models constructed by the random forest algorithm (LCCC=1.02, R2adjusted=0.876 and 0.868). The study provides a theoretical basis for revealing the mechanism of plunge pool development, improving the theoretical system of gully erosion, and preventing and controlling soil erosion in the red soil area.

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  • 收稿日期:2023-12-06
  • 最后修改日期:2024-01-12
  • 录用日期:2024-01-15
  • 在线发布日期: 2024-04-29
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