当卡水电站下游冲刷坑形态的试验研究

发布时间：2018-06-12 00:08

本文选题：局部冲刷 + 冲刷坑形态　；参考：《西北农林科技大学》2014年硕士论文

【摘要】：水电是一种清洁能源，在我国能源结构中占有非常重要的地位。近年来，我国经济发展迅速，社会对水、电的需求日益增加，低水头电站开发应时代要求迅速崛起，成为十分重要的水电开发方向。低水头电站具有水头低、流量大、弗氏数低、深尾水及消能率低等特点，过闸水流经过消能设施后仍具有比较大的余能，因此会冲刷带走下游河床上的大量泥沙，在下游形成形态各异的冲刷坑，甚至造成已建和在建工程部分或整体遭到严重破坏。所以，正确认识冲刷坑形态，对保障水利枢纽的安全稳定具有重要意义。本文结合当卡水电站模型进行了不同流量及不同床沙级配的试验，分析研究了影响下游局部冲刷坑的因素以及下游冲刷坑的形成机理，得到的成果主要有：（1）通过收集整理试验数据，对冲刷坑的形成机理、形态变化等进行分析，得到了冲刷坑形态与下泄流量、下游河床泥沙粒径、消力池护坦末端水流流态、消力池底板高度及闸门开度等影响因素的关系；在护坦末端水流佛氏数相近的时冲刷坑内坡面坡度比较一致的规律。（2）采用抽板法对泥沙休止角进行测量，拟合求出试验所用泥沙的静水休止角公式和空气休止角公式。以试验数据为依托，采用量纲分析和多元回归分析相结合的方法，推导求出冲刷坑下游坡面动水休止角与流速v、水深h，泥沙中值粒径d50的关系式，经试验资料验证，该公式具有较高的预测精度。（3）利用力学原理，推导出冲刷坑下游坡面泥沙在滑动起动和滚动起动两种模式下的起动流速公式。对比分析两个公式，，发现两种起动模式下的公式结构形式基本一致，并利用模型试验证明了公式的可行性。
[Abstract]:Hydropower is a kind of clean energy, which occupies a very important position in the energy structure of our country. In recent years, with the rapid development of economy and the increasing demand for water and electricity, the development of low-head hydropower station has become a very important direction of hydropower development. The low-head power station has the characteristics of low head, large discharge, low Friehlet number, low deep tail water and low energy dissipation rate. After passing through the energy dissipation facilities, the sluice flow still has a relatively large residual energy, so it will wash away a large amount of sediment on the downstream riverbed. Various scour pits are formed downstream, even causing serious damage to the part or whole of the built-in project. Therefore, it is of great significance to correctly understand the shape of scour pits to ensure the safety and stability of water conservancy projects. This paper, combined with the Dangka Hydropower Station model, has carried out tests of different flow rates and different bed sand gradation. The factors affecting the local scour pit downstream and the formation mechanism of the scour pit downstream are analyzed. The main results are as follows: 1) the formation mechanism and morphological change of the scour pit are analyzed by collecting and finishing the experimental data. The relationship between the shape of the scour pit and the discharge, the sediment diameter of the downstream river bed, the water flow state at the end of the stilling tank, the height of the bottom plate of the stilling pool and the opening degree of the gate are obtained. The slope gradient of the slope in the scour pit is consistent when the Fowler number of the flow is similar at the end of the dam. (2) the sediment repose angle is measured by the method of pumping plate, and the formula of the static water angle of repose and the air angle of repose of the sediment used in the experiment are obtained by fitting out the formula of static water angle of repose and air angle of repose. Based on the test data and using the method of dimensional analysis and multiple regression analysis, the relationship between the angle of repose of dynamic water and velocity v, water depth (h) and sediment median particle size (d50) on the slope of the downstream of the scour pit is derived and verified by the experimental data. The formula has high prediction accuracy. (3) based on the principle of mechanics, the formula of the starting velocity of sediment on the slope of the downstream of the scour pit under the two modes of sliding start and rolling start is derived. By comparing and analyzing the two formulas, it is found that the formula structure is basically the same under the two starting modes, and the feasibility of the formula is proved by the model test.
【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】：2014
【分类号】：TV147

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