滚动推移质运动的统计规律

发布时间：2018-10-14 08:56

【摘要】：推移质运动规律的研究是泥沙运动力学及河流动力学的基本课题之一。认识和掌握山区河流卵石推移质的运动规律对水利工程的安全以及预测河道演变趋势意义重大。推移质的运动形式一般可分为滚动、滑动和跃移。一般认为跃移是推移质运动的主要形式。然而，当水流强度较低时，颗粒运动形式以滚动为主；即使跃移颗粒，通常在跃起之前需要先滚动一段距离。因此，有必要进行泥沙颗粒滚动机理的研究。本文针对滚动型推移质，从泥沙颗粒典型受力出发，建立了其运动的力学模型。该力学模型引入相对暴露度，考虑了泥沙位置对其运动的影响；将单步滚动步划分为接触步和自由步，具体脱离点位置取决于其相对暴露度和水流强度。本文首先分析了泥沙的起动，在推导起动流速时，考虑了流速的脉动和泥沙颗粒的相对暴露度这两个随机变量，，经推导得到了单颗粒泥沙的起动概率和考虑起动概率的泥沙起动流速公式，且用实测资料进行了验证。接着通过数值求解和回归分析的手段，求解了滚动推移质运动的力学模型，求出单步运动参数如单步步长和单步运动时间等的数学表达式。最终利用爱因斯坦的思想，修正了其中的冲刷概率和单步步长，结合概率论推导出输沙率表达式，并用实测卵石输沙率资料进行了验证，表明其适用于低水流范围内的推移质运动，且与韩其为低输沙率公式相比，适用的水流范围更广。
[Abstract]:The study of bed load motion is one of the basic subjects of sediment movement mechanics and river dynamics. It is of great significance to understand and master the movement law of pebble bed load in mountain rivers for the safety of water conservancy projects and to predict the trend of river channel evolution. Bedload motion can generally be divided into rolling, sliding and jumping. It is generally considered that jumping is the main form of bed load movement. However, when the flow intensity is low, the motion of particles is mainly in the form of rolling, and even if the particles leap, they usually need to roll a distance before jumping up. Therefore, it is necessary to study the rolling mechanism of sediment particles. In this paper, according to the rolling bed load and the typical force of sediment particles, a mechanical model of its motion is established. In this model, the relative exposure degree is introduced, and the influence of sediment position on its motion is considered, and the single step rolling step is divided into contact step and free step, and the location of the breakaway point depends on the relative exposure degree and the flow intensity. In this paper, the incipient velocity of sediment is analyzed, and the fluctuation of velocity and the relative exposure of sediment particles are taken into account in the derivation of the incipient velocity. The incipient probability of single sediment and the formula of sediment incipient velocity considering the starting probability are derived and verified by the measured data. Then by means of numerical solution and regression analysis, the mechanical model of rolling bedload motion is solved, and the mathematical expressions of single step motion parameters such as single step length and single step motion time are obtained. Finally, by using Einstein's thought, the erosion probability and the single step length are corrected, and the expression of sediment transport rate is deduced with probability theory, and verified by the measured data of cobble sediment transport rate. It shows that it is suitable for the bedload movement in the range of low water flow, and compared with the formula of low sediment transport rate in Korea, the applicable range of flow is wider.
【学位授予单位】：天津大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TV142.2

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