坡面流挟沙能力计算方法

发布时间：2018-05-30 19:55

本文选题：坡面流 + 挟沙力　；参考：《西北农林科技大学》2017年硕士论文

【摘要】：坡面流挟沙能力被定义为在给定流量、地形、表面特征、沉积物的密度和大小的情况下,水流所能带走的沉积物的最大数量。坡面流在顺坡流动过程中会产生土壤颗粒的分离、泥沙的输移和泥沙的沉积。若来水的含沙量小于该水流条件下的挟沙力,坡面水流就会从本段坡面上挟带更多同类型泥沙,从而造成坡面侵蚀和水土流失;反之,若来水的含沙量大于该水流条件下的挟沙力,水流中过剩的泥沙就会在该段坡面发生淤积。坡面处于不冲不淤平衡输沙时水流搬运泥沙的最大通量即为水流挟沙力,它是确定泥沙是否分离或沉积的控制因子。因此,挟沙能力的精确估计是许多基于过程的土壤侵蚀模型的关键,研究坡面水流的挟沙能力对建立适合于我国实际情况的土壤侵蚀过程模型具有重要的理论意义,并为我国黄土高原坡面水土流失治理提供重要科学依据。本文通过室内水槽输沙模拟试验,系统研究了3种坡度(6°、9°、12°),7种流量(0.042L/s、0.083L/s、0.125L/s、0.167L/s、0.208L/s、0.250L/s、0.333L/s)组合冲刷试验条件下坡面流水动力学特性。综合其他学者的试验数据共计355组,采用无量纲化分析坡面流挟沙能力与无量纲平均流速、无量纲水流剪切力、无量纲水流功率、无量纲单位水流功率、无量纲有效水流功率等水力参数的耦合关系,最后基于无量纲有效水流功率建立统一挟沙力公式。取得了以下主要结论:(1)本试验数据分析表明,坡面流挟沙力随着坡度和流量的增加而增加,平均流速、水流剪切力、水流功率、单位水流功率、有效水流功率均与坡面流挟沙力呈正相关关系。(2)揭示了坡面流挟沙能力与水动力学参数的耦合关系。为了消除量纲对挟沙力的影响,对水动力参数和挟沙力进行无因次化。在本试验的基础上,结合其他学者的试验数据,共计355组进行分析,经过回归分析得出:不同粒径、流量及坡度下,坡面流挟沙能力对平均流速、水流剪切力、水流功率、单位水流功率、有效水流功率等水力参数的响应关系均可以用幂函数方程描述。(3)阐明了坡面流挟沙能力变化的动力学机理。综合355组各学者试验数据得出,坡面流挟沙能力对主要水动力参数响应的决定系数大小顺序为:有效水流功率(R2=0.9785)水流功率(R2=0.9701)水流剪切力(R2=0.9662)单位水流功率(R2=0.8770)平均流速(R2=0.8428)。由此表明,有效水流功率是与坡面水流挟沙能力变化关系最密切的水动力学指标,是描述坡面水流输沙能力变化最好的动力学参数。(4)建立了具有动力学意义的坡面流挟沙能力数学模型。选择无量纲有效水流功率作为模拟挟沙力的水动力学指标并引入相关因子,最后基于无量纲有效水流功率建立了坡面流统一挟沙能力模型。
[Abstract]:The sediment carrying capacity of slope flow is defined as the maximum amount of sediment that can be carried away by flow under given flow, topography, surface characteristics, density and size of sediment. The separation of soil particles, the transport of sediment and the deposition of sediment will occur in the process of slope flow. If the sediment content of the incoming water is less than the sediment carrying capacity under the condition of the flow, the slope water will carry more sediment of the same type from the slope of this section, resulting in erosion and soil erosion on the slope. If the sediment content of the incoming water is greater than the sediment carrying capacity under the flow condition, the excess sediment in the water flow will be silted up on the slope. The maximum flux of sediment transport on slope is the sediment carrying capacity, which is the controlling factor to determine whether the sediment is separated or deposited. Therefore, the accurate estimation of sediment carrying capacity is the key of many process-based soil erosion models. It is of great theoretical significance to study the sediment carrying capacity of sloping water flow in order to establish a soil erosion process model suitable for the actual situation in China. It also provides important scientific basis for soil and water loss control on slope of Loess Plateau in China. In this paper, the hydrodynamic characteristics of the slope surface under the combined scour test conditions are systematically studied by means of the simulation test of sediment transport in the indoor flume. The flow dynamics of three kinds of slope (6 掳/ 9 掳/ 12 掳/ 7) are studied under the combined scour test of 0.042L / s 0.083L / s 0.125L / s 0.167L / s 0.208L / s = 0.208L / s ~ (0.250) L / s ~ (0.333L / s). By synthesizing the experimental data of other scholars, 355 groups were used to analyze the sediment carrying capacity of slope flow and the dimensionless average flow velocity, dimensionless flow shear force, dimensionless flow power, dimensionless unit flow power, dimensionless flow capacity, dimensionless mean velocity, dimensionless flow shear force, dimensionless flow power and dimensionless flow power. Finally, a unified sediment carrying capacity formula is established based on dimensionless effective flow power. The main conclusions are as follows: (1) the analysis of the experimental data shows that the sediment carrying capacity increases with the increase of slope and flow rate, and the mean flow velocity, flow shear force, flow power, unit flow power, flow velocity, flow shear force, unit flow power, mean flow velocity, flow shear force, flow power and unit flow power increase. There is a positive correlation between the effective flow power and the sediment carrying capacity of the slope flow. 2) the coupling relationship between the sediment carrying capacity of the slope flow and the hydrodynamic parameters is revealed. In order to eliminate the influence of dimensionality on sediment carrying capacity, hydrodynamic parameters and sediment carrying capacity are dimensionless. On the basis of this experiment, combined with the experimental data of other scholars, 355 groups were analyzed. Through regression analysis, it was concluded that under different particle size, flow rate and slope degree, the capacity of sediment carrying on slope surface affects average velocity, shear force and power of flow. The response relationship of hydraulic parameters such as unit flow power and effective flow power can be described by power function equation. According to the experimental data of 355 groups of scholars, the order of determining coefficient of sediment carrying capacity to the main hydrodynamic parameters is as follows: effective flow power (R2N) 0.9785) flow power (R2N) 0.9701) flow shear force (R2N) 0.9662) (unit flow power (R2N) 0.8770) average flow velocity (R20.8428N). It is shown that the effective flow power is the most closely related hydrodynamic index to the change of sediment carrying capacity on the slope surface. It is the best dynamic parameter to describe the change of sediment transport capacity of slope flow. The mathematical model of sediment carrying capacity of slope flow with dynamic significance is established. The dimensionless effective flow power is chosen as the hydrodynamic index to simulate the sediment carrying capacity, and the correlation factor is introduced. Finally, based on the dimensionless effective flow power, the unified sediment carrying capacity model of slope flow is established.
【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

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