饱和紫色土初始态和稳定态细沟水力学特征研究
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国家自然科学基金项目(41571265)和重庆市技术创新与应用示范(社会民生类重点研发)项目(cstc2018jscx-mszdX0061)资助


Hydraulic Characteristics of Rills of Non-eroded and Eroding on Saturated Purple Soil
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National Natural Science Foundation of China (No.41571265) and the Key Research and Development Project of Social Livelihood in Chongqing (No. cstc2018jscx-mszdX0061)

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    摘要:

    细沟水力学特征是影响坡面土壤侵蚀的重要动力因素。不同侵蚀阶段细沟形态影响水流动力学特征,进而影响细沟侵蚀发育与形态演变。试验以饱和紫色土为研究对象,在测量得到不同流量(2,4,8 L·min-1)及坡度(5°,10°,15°,20°)下初始态细沟和稳定态细沟径流流速的基础上,计算得到初始态和稳定态细沟水力学参数,包括平均径流深,雷诺数,弗劳德数,达西阻力系数,曼宁糙率系数等,对其特征进行对比分析。结果表明,在不同细沟侵蚀阶段,初始态细沟流速介于0.170~0.778 m·s-1之间,稳定态细沟流速介于0.156~0.619 m·s-1之间,在同一流量和坡度条件下,初始态细沟流速>稳定态细沟流速,且流量和坡度在不同细沟侵蚀阶段对流速和平均径流深的贡献率存在差异。流态以过渡流居多,均属于急流,弗劳德数在稳定态细沟阶段受到流速和平均径流深的调节保持相对稳定且趋近于1。达西阻力系数受流速和平均径流深的影响发生改变,在初始态细沟中流速的影响占主要作用,稳定态细沟中平均径流深的影响占主要作用。饱和紫色土细沟从初始态到稳定态的发育过程中,流速逐渐减小,平均径流深增大,雷诺数增大,弗劳德数减小,达西阻力系数和曼宁糙率系数增大。研究结果有利于明确饱和紫色土坡面不同细沟侵蚀阶段水力学特征,对建立土壤侵蚀物理模型具有一定参考价值。

    Abstract:

    [Objective] Rill hydraulics is an important dynamic factor affecting slope soil erosion. Rill morphology affects flow dynamics characteristics at all erosion stages, and further on development and morphology evolution of rill erosion.[Method] Scouring experiments were conducted on flumes packed with saturated purple soil for determination of runoff velocity in non-eroded and eroding rill, relative to flow discharge (2, 4, and 8 L·min-1) and slope gradient (5°, 10°, 15°, and 20°). The electrolyte pulse boundary model method was used to measure rill flow velocity (V), On such a basis, calculation was done of the hydraulic parameters of rills of non-eroded and eroding (including mean flow depth (h), Reynolds number (Re), Froude number (Fr), Darcy-Weisbach friction coefficient (f) and Manning roughness coefficient (n)), and then comparison was made of the hydraulic characteristics between the rills of the two states.[Result] Results show that the flow velocity in the rills of non-eroded state (VN) ranged from 0.170 to 0.778 m·s-1, and that in the rills of eroding state (VE) did from 0.156 to 0.619 m·s-1. VN varied with flow discharge to the power of 0.524 and with slope gradient to the power of 0.601, while VE varied with flow discharge to the power of 0.474 and with slope gradient to the power of 0.530, and their determination coefficient was 0.910 and 0.905, respectively. The mean flow depth of the rills of non-eroded state (hN) ranged from 0.078 to 0.413 cm, and that of the rills of eroding state (hE) did from 0.107 to 0.450 cm. hN varied with flow discharge to the power of 0.502 and with slope gradient to the power of -0.505, while hE varied with flow discharge to the power of 0.558 and with slope gradient to the power of -0.415, and their determination coefficients were both 0.942. When the flow discharge was 2 L·min-1, Re was < 500, and when the flow discharge was 4 or 8 L·min-1, Re varied between 500 and 2 000. Fr was always >1 regardles of working conditions, and ranged from 1.237 to 6.026 in the rills of non-eroded (FrN), and from 1.079 to 4.274 in the rills of eroding state (FrE). f ranged from 0.079 to 0.856, n did from 0.011 to 0.035, fN (in the rills of non-eroded state) did from 0.079 to 0.592, and fE (in the rills of eroding state) did from 0.156 to 0.856.[Conclusion] The parameter h is positively related to flow discharge in the power function, but negatively to the slope gradient. The influences of flow discharge and slope gradient on V decrease in all the rills regardless of state, and that of the former on h increases, while that of the latter on h decreases. The flow regime is dominated by transition flow and rarely by laminar flow, all belonging to rapids. Re does not differ much between rills different in state; FrEremaints almost a constant while approaching 1; f varies as affected by the interaction between V and h, in which V is the dominant one in the rill of non-eroded state, while h is in the other rills. During the development of the rills from the non-eroded state to the eroding state, V decreases, while h increases, so that Re increases, Fr decreases, and both f and n increase, and the erosion of the rills of eroding state caused by rill flow is lower than that of the rills of non-eroded state in intensity. This is because variation of the rills in morphology promotes energy dissipation, which in turn retards rill flow, reduces flow velocity, but increases the mean flow depth, thus eventually leading to changes in flow regime and resistance. All the findings in this study may hopefully help determine hydraulic characteristics of saturated purple soils with rills different in state and be of certain reference value to the establishment of a physical model for researches on soil erosion.

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陶婷婷,陈晓燕,陈仕奇,韩珍,李彦海,顾小杰,叶鸿铭.饱和紫色土初始态和稳定态细沟水力学特征研究[J].土壤学报,2022,59(1):129-138. DOI:10.11766/trxb202005280259 TAO Tingting, CHEN Xiaoyan, CHEN Shiqi, HAN Zhen, LI Yanhai, GU Xiaojie, YE Hongming. Hydraulic Characteristics of Rills of Non-eroded and Eroding on Saturated Purple Soil[J]. Acta Pedologica Sinica,2022,59(1):129-138.

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  • 收稿日期:2020-05-28
  • 最后修改日期:2020-08-16
  • 录用日期:2021-03-01
  • 在线发布日期: 2021-03-19
  • 出版日期: 2022-01-11
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