当卡水电站下游局部冲刷坑深度试验研究

发布时间：2018-09-06 18:59

【摘要】：枢纽下游局部冲刷问题是影响水工建筑物安全的重要因素，随着水利枢纽建设的加快，人们对枢纽下游局部冲刷问题的研究越来越重视。本文通过收集已有的水利工程资料，结合当卡模型进行了不同流量及不同床沙粒径的模型试验，分析了枢纽下游冲刷坑的主要影响因素及形成机理，从不同角度推导了当卡下游河床局部冲刷深度的计算公式，得到以下主要结论：（1）下游河床受到水流横向和纵向流速冲刷形成局部冲刷坑。冲刷坑形成过程主要有三个阶段：开始强烈冲刷阶段、随时间推移不断扩展阶段、冲刷稳定阶段，前期发展迅速，后期发展缓慢。（2）枢纽下泄流量和下游泥沙中值粒径是影响水工建筑物下游局部冲刷坑深度与范围的主要因素，随着流量的增加，冲刷坑深度、范围也随之增大；随着下游泥沙中值粒径的增加，，冲刷坑的深度和范围逐渐变小。（3）在二元水流基础上，通过水流连续性方程推导得到了下游局部冲刷坑深度计算公式，利用冲刷坑观测资料，对本文公式及现有的枢纽下游局部冲刷坑深度计算公式进行验证表明，现有的公式计算值与实测值误差较大，本文公式与实测值误差较小；在此基础上，通过分析误差原因，对推导的公式进行了修正，得到了当卡水电站下游冲刷坑深度计算公式，为当卡下游局部冲刷深度的计算提供了依据。（4）在连续方程的基础上，考虑了水流平面扩散特性、回流等因素对下游局部冲刷深度的影响，推导了下游局部冲刷深度公式，依据水流扩散情况，回流强弱程度对公式的适用条件进行分类。
[Abstract]:Local scour problem is an important factor that affects the safety of hydraulic structures. With the acceleration of the construction of hydro-junction, people pay more and more attention to the problem of local scour downstream. In this paper, by collecting the existing water conservancy engineering data and combining the Dangka model to carry out the model tests of different discharge and different bed sand particle size, the main influencing factors and formation mechanism of the downstream scour pit of the project are analyzed. The formula for calculating the local scour depth of the downstream river bed is derived from different angles. The main conclusions are as follows: (1) the downstream riverbed is washed by the lateral and longitudinal flow velocity to form a local scour pit. There are three main stages in the formation of the scour pit: the beginning of the intense scour stage, the continuous expansion of the scour pit over time, the stable scour stage, and the rapid development of the early stage. The later development is slow. (2) the discharge down of the hub and the median particle size of the sediment downstream are the main factors affecting the depth and range of the local scour pit in the downstream of the hydraulic structure. With the increase of the discharge, the depth and the range of the scour pit also increase; The depth and range of the scour pit become smaller with the increase of the median particle size of the downstream sediment. (3) on the basis of binary flow, the formula for calculating the depth of the local scour pit is derived through the flow continuity equation. Based on the observation data of scour pits, the formulas of this paper and the existing formulas for calculating the depth of local scour pits in the downstream of the hub are verified. The results show that the errors between the existing formulas and the measured ones are large, and the errors between the formulas and the measured values are small. By analyzing the error reasons, the derived formula is modified, and the formula for calculating the depth of the scour pit downstream of Dangka Hydropower Station is obtained, which provides the basis for the calculation of the local scour depth in the downstream of Dangka Hydropower Station. (4) on the basis of the continuous equation, Considering the influence of flow plane diffusion and reflux on the local scour depth of downstream, the formula of local scour depth is derived, and the applicable conditions of the formula are classified according to the condition of flow diffusion and the degree of backflow.
【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】：TV131.61;TV147

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