坡面水流流速对贴地植被的响应特性试验研究
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摘要
坡面上植被对坡面流流速有着显著影响,进而对坡面的输沙特性起着重要作用,而覆盖度是植被影响坡面粗糙度的一个重要因素。以往研究多集中在植被覆盖度相对较小的范围。为进一步探明植被覆盖度与坡面流流速间的相关关系,基于坡面流系列概化变坡水槽试验,采用人工塑料草模拟贴地植被,设置了在0～80%范围之间的9种不同的贴地植被覆盖度、3种不同的坡度(10°、20°、25°)以及6个不同的流量级(0.286～1.058 L/s)条件下的共计162组清水径流试验,对坡面流流速特性进行了定量研究。试验结果表明:随着贴地植被覆盖度的增大,流速沿坡长由增大变为减小;当覆盖度小于30%时,流速受流量的影响较大;当覆盖度大于30%后,流速受流量的影响较小。将植被覆盖度引入坡面流流速计算公式,采用生长模型中常见的e–x表达形式反映植被对坡面粗糙度的影响,对公式中的k进行修正,应用非线性回归的方法对试验数据进行回归分析,确定参数k、a、b、c分别为10.06、–1.71、0.22、0.4,所得公式的计算效果良好(R~2=0.96)。将公式应用于其他文献中提及的实验室水槽试验条件,所得的计算值与文献中的实测值符合较好(R~2=0.73)。公式对实验室试验具有良好的适应性,而其对野外条件的适用性仍有待于进一步检验。
Vegetation has significant effects on overland flow velocity and plays an important role in sediment transportation on a slope. The land coverage is an important factor to affect the roughness of the slope. The previous researches have focused on a relatively small range of vegetation coverage. To reveal the relationship between vegetation coverage and overland flow velocity, a series of flume experiments are carried out by using artificial grass to study quantitatively the characteristics of the overland flow velocity under different vegetation coverage. The experiments are set under the conditions of 9 different vegetation coverage from 0 to 80%, 3 slope gradients(10°,20°,25°) and 6 flow discharge(0.286～1.058 L·s–1), which are 162 groups in total. The result shows that the velocity along the slop changes from increase to decrease with the increase of the vegetation coverage. The discharge has a great effect on velocity when the coverage is less than 30% and has small effect when the coverage is more than 30%. The vegetation coverage is introduced in the velocity formula of overland flow, using the common form e–x in the growth model to reflect the influence of vegetation on slope roughness. Applying the nonlinear regression to the experiment data, the parameters k, a, b, c are determined as 10.06, –1.71, 0.22, 0.4 respectively. The formula obtained matches well with the measurement(R~2=0.96). Applying the formula to the lab experiments in other literatures, the results agreed with the experiment data reasonably well(R~2=0.73). It seems that the formula has good adaptability to laboratory tests, although its applicability to field conditions needs further testing.
Vegetation has significant effects on overland flow velocity and plays an important role in sediment transportation on a slope. The land coverage is an important factor to affect the roughness of the slope. The previous researches have focused on a relatively small range of vegetation coverage. To reveal the relationship between vegetation coverage and overland flow velocity, a series of flume experiments are carried out by using artificial grass to study quantitatively the characteristics of the overland flow velocity under different vegetation coverage. The experiments are set under the conditions of 9 different vegetation coverage from 0 to 80%, 3 slope gradients(10°,20°,25°) and 6 flow discharge(0.286～1.058 L·s–1), which are 162 groups in total. The result shows that the velocity along the slop changes from increase to decrease with the increase of the vegetation coverage. The discharge has a great effect on velocity when the coverage is less than 30% and has small effect when the coverage is more than 30%. The vegetation coverage is introduced in the velocity formula of overland flow, using the common form e–x in the growth model to reflect the influence of vegetation on slope roughness. Applying the nonlinear regression to the experiment data, the parameters k, a, b, c are determined as 10.06, –1.71, 0.22, 0.4 respectively. The formula obtained matches well with the measurement(R~2=0.96). Applying the formula to the lab experiments in other literatures, the results agreed with the experiment data reasonably well(R~2=0.73). It seems that the formula has good adaptability to laboratory tests, although its applicability to field conditions needs further testing.
引文
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[8]Wang Diyuan,Yang Fan,Zhang Kuandi,et al.Discharge and slope on hydraulic characteristics of overland flow under vegetated coverage[J].Yellow River,2017,39(6):86-89.[王柢渊,杨帆,张宽地,等.流量和坡度对植被水流水动力学特性的影响[J].人民黄河,2017,39(6):86-89.]
[9]Li Mian,Yao Wenyi,Chen Jiangnan,et al.Experimental study on the effect of different grass coverages on the overland flow velocity[J].Transactions of the CSAE,2005,21(12):43-47.[李勉,姚文艺,陈江南,等.草被覆盖对坡面流流速影响的人工模拟试验研究[J].农业工程学报,2005,21(12):43-47.]
[10]Yang Fan,Zhang Kuandi,Ma Xiaoling,et al.Effect of vegetation coverage on relative hydrodynamics of overland flows[J].Journal of Hydroelectric Engineering,2017,36(2):29-39.[杨帆,张宽地,马小玲,等.植被覆盖度对坡面流相对水动力学特性的影响[J].水力发电学报,2017,36(2):29-39.]
[11]Yan Xufeng,Zhou Sufen,Huang Er,et al.Experimental study on the effects of vegetation on hydraulic characteristics of overland flow[J].Journal of Sichuan University(Engineering Science Edition),2012,44(2):26-30.[闫旭峰,周苏芬,黄尔,等.植被条件下坡面薄层水流动力学特性试验研究[J].四川大学学报(工程科学版),2012,44(2):26-30.]
[12]Foster G R,Huggins L F,Meyer L D.Laboratory study of rill hydraulics.I:Velocity relationships[J].Transactions of ASAE,1984(3):790-796.
[13]Nearing M A,Simanton J R,Norton L D,et al.Soil erosion by surface water flow on a stony,semiarid hillslope[J].Earth Surface Processes and Landforms,1999,24(8):677-689.
[14]Zhang K D,Wang Z G,Wang G Q,et al.Overland-flow resistance characteristics of nonsubmerged vegetation[J].Journal of Irrigation and Drainage Engineering,ASCE,2017,143(8):04017021.
[2]Emmett W W.The hydraulics of overland flow on hillslopes[R].Washington D.C.:United States Government Pringing Office,1970.
[3]Dunkerley D.Estimating the mean speed of laminar overland flow using dye injection uncertainty on rough surfaces[J].Earth Surface Processes and Landforms,2001,26(4):363-374.
[4]Sun Juying,Zhang Lu,Zhao Lu,et al.Experimental study of the effects of different height flexible vegetation on hydraulic characteristics of overland flow[J].Mechanics in Engineering,2016,38(3):283-289.[孙菊英,张璐,赵璐,等.不同高度柔性植被对坡面流水动力特性的影响[J].力学与实践,2016,38(3):283-289.]
[5]Wang Xiekang,Liu Tonghuan,Ye Long,et al.Experimental study on the effects of flexible vegetation on hydraulic characteristics and local head losses of overland flow[J].Journal of Sichuan University(Engineering Science Edition),2013,45(2):22-27.[王协康,刘同宦,叶龙,等.坡面柔性植被阻水效应及其局部水头损失特性试验研究[J].四川大学学报(工程科学版),2013,45(2):22-27.]
[6]Ye Long,Wang Yulin,Liu Xingnian,et al.Experimental study on effects of different artificial vegetation distribution on overland flow[J].Journal of Sichuan University(Engineering Science Edition),2014,46(2):42-48.[叶龙,王玉林,刘兴年,等.不同人工植被分布条件下坡面水流动力学特性试验研究[J].四川大学学报(工程科学版),2014,46(2):42-48.]
[7]Cao Ying,Zhang Guanghui,Tang Keming,et al.Experiment on the effect of simulated surface cover on the overland flow velocity[J].Journal of Mountain Science,2011,29(6):654-659.[曹颖,张光辉,唐科明,等.地表覆盖对坡面流流速影响的模拟试验[J].山地学报,2011,29(6):654-659.]
[8]Wang Diyuan,Yang Fan,Zhang Kuandi,et al.Discharge and slope on hydraulic characteristics of overland flow under vegetated coverage[J].Yellow River,2017,39(6):86-89.[王柢渊,杨帆,张宽地,等.流量和坡度对植被水流水动力学特性的影响[J].人民黄河,2017,39(6):86-89.]
[9]Li Mian,Yao Wenyi,Chen Jiangnan,et al.Experimental study on the effect of different grass coverages on the overland flow velocity[J].Transactions of the CSAE,2005,21(12):43-47.[李勉,姚文艺,陈江南,等.草被覆盖对坡面流流速影响的人工模拟试验研究[J].农业工程学报,2005,21(12):43-47.]
[10]Yang Fan,Zhang Kuandi,Ma Xiaoling,et al.Effect of vegetation coverage on relative hydrodynamics of overland flows[J].Journal of Hydroelectric Engineering,2017,36(2):29-39.[杨帆,张宽地,马小玲,等.植被覆盖度对坡面流相对水动力学特性的影响[J].水力发电学报,2017,36(2):29-39.]
[11]Yan Xufeng,Zhou Sufen,Huang Er,et al.Experimental study on the effects of vegetation on hydraulic characteristics of overland flow[J].Journal of Sichuan University(Engineering Science Edition),2012,44(2):26-30.[闫旭峰,周苏芬,黄尔,等.植被条件下坡面薄层水流动力学特性试验研究[J].四川大学学报(工程科学版),2012,44(2):26-30.]
[12]Foster G R,Huggins L F,Meyer L D.Laboratory study of rill hydraulics.I:Velocity relationships[J].Transactions of ASAE,1984(3):790-796.
[13]Nearing M A,Simanton J R,Norton L D,et al.Soil erosion by surface water flow on a stony,semiarid hillslope[J].Earth Surface Processes and Landforms,1999,24(8):677-689.
[14]Zhang K D,Wang Z G,Wang G Q,et al.Overland-flow resistance characteristics of nonsubmerged vegetation[J].Journal of Irrigation and Drainage Engineering,ASCE,2017,143(8):04017021.
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