模拟径流条件下坡长对工程堆积体坡面土壤侵蚀的影响

发布时间：2018-05-08 15:24

本文选题：工程堆积体 + 细沟形态　；参考：《西北农林科技大学》2017年硕士论文

【摘要】：生产建设项目挖填不平衡产生的工程堆积体已成为近20年来新增人为水土流失的主要泥沙策源地。根据“因害设防,生态优先”的原则,在工程堆积体坡面布设合理的防治措施以提高坡面的水土保持功能,进而改善生态环境,为对黄土区工程堆积体坡面防治措施进行最优化配置,使坡面防护措施发挥最大效益。本文以坡长为研究对象,就坡长对工程堆积体坡面土壤侵蚀的影响进行研究,在野外对模拟工程堆积体径流小区进行径流冲刷试验,设置5个坡长、3个坡度来探讨坡长对工程堆积体坡面土壤侵蚀的影响。得出主要结论如下:(1)工程堆积体坡面产流率随放水时间持续呈现波动性增大,随着坡长增大,产沙率波动振幅也变大。径流含沙量随着放水时间的持续呈现先减小而后保持稳定变化,随着坡长增大,含沙量呈递增变化。工程堆积体坡面累积产流量随放水时间的变化可以用线性函数表达,累积产沙量与放水时间呈极显著幂函数关系,累积产沙量和累积产流量均随着坡长的增大呈现递增变化。试验坡度、坡长均对坡面累积产流产沙量具有重要的影响,坡长对坡面累积产流产沙的影响大于坡度,坡长对累积产流产沙量产生正效应,坡度对累积产流产沙量产生负效应。(2)细沟沟宽和沟深均随放水时间的持续呈现增大变化,沟宽随放水时间的变化可以很好地用对数函数进行描述,沟宽随坡长的增大呈现递增变化,沟深随放水时间的变化可用线性函数很好地描述。细沟宽深比均随着放水时间的持续呈现先减小后逐渐稳定的变化,细沟断面积随冲刷历时的持续呈现不断增大的趋势,断面积随放水时间的变化可以很好地用线性方程进行描述。不同坡度、坡长条件下,沟宽的沿程分布情况并不一致,呈现多样性;在小坡长情况下,沟深的波动性较大,整体上来看,沟深均随着坡面沿程向下呈现逐渐递减并趋于稳定的分布规律。(3)流速随着放水时间的持续呈现先减小后逐渐趋于稳定,坡面水流流速与时间之间的关系可以很好地用对数函数进行描述。雷诺数随着时间的持续呈先增大后减小的趋势,随着坡长增加而减小,雷诺数随放水时间的变化可以很好地用二次函数关系进行描述,二次函数开口向下,表明雷诺数在试验过程中存在最大值。佛汝德数随着放水时间的持续呈现先骤降后趋于稳定的变化,这表明坡面径流流态在不断地向缓流发展。坡面阻力系数随着时间的增大呈现不断增大的趋势,阻力系数总体介于0.017~12.14,随着坡长增大而增大,佛汝德数、阻力系数与时间的关系均可以很好地用幂函数进行描述。(4)土壤剥蚀率与水流剪切力和水流功率均存在显著的线性函数,对应的土壤可蚀性参数为3.5×10-3s/m,临界水流剪切力为5.57Pa,剥蚀率与水流剪切力的拟合效果最好。(5)含沙量与坡长存在良好的对数函数关系,累积产流量与坡长的关系可以很好地用幂函数进行描述,累积产沙量与坡长存在二次函数关系。细沟形态指标沟深与坡长并不存在显著的函数关系,细沟沟宽与坡长存在显著的二次函数关系。流速与坡长存在显著的线性函数关系,佛汝德数、阻力系数、粗糙系数、水流挟沙力与坡长均存在显著的指数函数关系。
[Abstract]:In the past 20 years, the accumulation of Engineering accumulation has become the main sediment source of artificial soil erosion in the construction projects. According to the principle of "fortification and ecological priority", reasonable prevention and control measures are set up on the slope surface of the project in order to improve the soil and water conservation function of the slope and to improve the ecological environment. In this paper, the slope length is the research object, the influence of slope length on the soil erosion of the slope surface of the engineering accumulation body is studied in this paper. The runoff scour test of the runoff plot in the simulated engineering accumulation body is carried out in the field, and 5 slope lengths and 3 slopes are set up in the field. The main conclusions are as follows: (1) the flow rate of the slope surface of the engineering accumulating body increases with the water release time, and the fluctuation amplitude of sediment yield increases with the increase of the slope length. The cumulative yield of the slope on the slope of the engineering accumulation can be expressed with linear function with the change of the time of water release. The cumulative sediment yield and the discharge time have a very significant power function relationship. The cumulative sediment yield and the cumulative yield are all increasing with the increase of the slope length. The slope and the length of the slope are all accumulated on the slope surface. The effect of the sediment yield on the sediment yield is more important than that of the slope. The slope length has a positive effect on the cumulative yield and sediment yield, and the slope has a negative effect on the cumulative runoff and sediment. (2) the width of the trench groove and the depth of the ditch vary with the duration of the water release, and the width of the ditch can be used well with the change of the water release time. The logarithmic function is described with the increase of the width of the ditch with the increase of the length of the slope. The depth of the ditch is well described with the linear function. The width to depth ratio of the rill is gradually reduced with the continuous presentation of the water release time. The variation of water time can be well described by linear equation. Under the condition of different slope and length, the distribution of groove width is different and presents diversity. In the case of small slope length, the depth of the ditch has a large fluctuation. On the whole, the depth of the ditch shows a gradual decreasing and stable distribution along the slope along the slope. (3) flow The relation between the flow velocity and the time can be described well with the logarithmic function. The number of Reynolds number increases first and then decreases with the time, which decreases with the increase of the slope length, and the Reynolds number can be used two times with the change of the water release time. The function relation is described, and the two function opening downward indicates that the Reynolds number has the maximum value during the experiment. The resistance coefficient is generally in 0.017~12.14, with the increase of the slope length. The relationship between the Froude number, the resistance coefficient and the time can be well described with power function. (4) there is a significant linear function between the soil erosion rate and the flow shear force and the flow power, and the corresponding soil erodibility parameters are 3.5 * 10-3s/m, and the critical flow shear is cut. Force of 5.57Pa, the best fitting effect of the erosion rate and the flow shear force is best. (5) there is a good logarithmic function relationship between the sediment content and the slope length. The relationship between the cumulative yield and the slope length can be well described with the power function, and the cumulative sediment yield and the slope length have two functional relationships. The trench shape index does not have a significant function in the depth of the ditch and the slope length. There is a significant two function relationship between the width of the rill ditch and the length of the slope. There is a significant linear function relationship between the velocity and the slope length, and there is a significant exponential function relationship between the Froude number, the drag coefficient, the roughness coefficient, the sediment carrying capacity and the slope length.

【学位授予单位】：西北农林科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S157.1

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