本文選題：坡面流 + 挾沙力�。� 參考：《西北農林科技大學》2017年碩士論文

【摘要】：坡面流挾沙能力被定義為在給定流量、地形、表面特征、沉積物的密度和大小的情況下,水流所能帶走的沉積物的最大數量。坡面流在順坡流動過程中會產生土壤顆粒的分離、泥沙的輸移和泥沙的沉積。若來水的含沙量小于該水流條件下的挾沙力,坡面水流就會從本段坡面上挾帶更多同類型泥沙,從而造成坡面侵蝕和水土流失;反之,若來水的含沙量大于該水流條件下的挾沙力,水流中過剩的泥沙就會在該段坡面發(fā)生淤積。坡面處于不沖不淤平衡輸沙時水流搬運泥沙的最大通量即為水流挾沙力,它是確定泥沙是否分離或沉積的控制因子。因此,挾沙能力的精確估計是許多基于過程的土壤侵蝕模型的關鍵,研究坡面水流的挾沙能力對建立適合于我國實際情況的土壤侵蝕過程模型具有重要的理論意義,并為我國黃土高原坡面水土流失治理提供重要科學依據。本文通過室內水槽輸沙模擬試驗,系統研究了3種坡度(6°、9°、12°),7種流量(0.042L/s、0.083L/s、0.125L/s、0.167L/s、0.208L/s、0.250L/s、0.333L/s)組合沖刷試驗條件下坡面流水動力學特性。綜合其他學者的試驗數據共計355組,采用無量綱化分析坡面流挾沙能力與無量綱平均流速、無量綱水流剪切力、無量綱水流功率、無量綱單位水流功率、無量綱有效水流功率等水力參數的耦合關系,最后基于無量綱有效水流功率建立統一挾沙力公式。取得了以下主要結論:(1)本試驗數據分析表明,坡面流挾沙力隨著坡度和流量的增加而增加,平均流速、水流剪切力、水流功率、單位水流功率、有效水流功率均與坡面流挾沙力呈正相關關系。(2)揭示了坡面流挾沙能力與水動力學參數的耦合關系。為了消除量綱對挾沙力的影響,對水動力參數和挾沙力進行無因次化。在本試驗的基礎上,結合其他學者的試驗數據,共計355組進行分析,經過回歸分析得出:不同粒徑、流量及坡度下,坡面流挾沙能力對平均流速、水流剪切力、水流功率、單位水流功率、有效水流功率等水力參數的響應關系均可以用冪函數方程描述。(3)闡明了坡面流挾沙能力變化的動力學機理。綜合355組各學者試驗數據得出,坡面流挾沙能力對主要水動力參數響應的決定系數大小順序為:有效水流功率(R2=0.9785)水流功率(R2=0.9701)水流剪切力(R2=0.9662)單位水流功率(R2=0.8770)平均流速(R2=0.8428)。由此表明,有效水流功率是與坡面水流挾沙能力變化關系最密切的水動力學指標,是描述坡面水流輸沙能力變化最好的動力學參數。(4)建立了具有動力學意義的坡面流挾沙能力數學模型。選擇無量綱有效水流功率作為模擬挾沙力的水動力學指標并引入相關因子,最后基于無量綱有效水流功率建立了坡面流統一挾沙能力模型。
[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 擄/ 9 擄/ 12 擄/ 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.
【學位授予單位】：西北農林科技大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：S157

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