床面粗糙特性的综合分析研究

发布时间：2018-05-08 15:54

本文选题：卵砾石粗糙床面 + 统计分析　；参考：《重庆交通大学》2017年硕士论文

【摘要】：粗糙床面在自然界中广泛存在,床面粗糙特性与河流动力学中的许多问题(如泥沙起动、河床阻力、推移质运动等)密切相关,但床面粗糙特性的科学量化一直是河流动力学的难点,也是目前尚未有效解决而又充满挑战的课题。本文在对天然卵砾石床面进行深入调查的基础上将其分类概化,基于床面激光扫描试验资料,应用统计分析方法和分形几何理论开展人工铺制散叠型卵砾石床面粗糙特性研究。取得如下主要研究成果:(1)卵砾石床面高程的中数、众数约等于平均高程;相对高程频率分布呈负偏态、高狭峰,其负值跨度区远大于正值跨度区。(2)均匀颗粒床面高程的标准差随粒径的增大而增大,可作为均匀颗粒床面粗糙特性的优良量化指标。(3)卵砾石床面的变异特征与球状模型最为接近,球状模型可作为卵砾石床面变异性分析的最优模型。(4)卵砾石床面横纵向剖面轮廓平均变异函数与床面特征方向平均变异函数的基台值和块金常数基本相同,而变程却存在较大差异。(5)剖面轮廓和粗糙床面的分形尺度区宽度与床面颗粒中值粒径d50有关,上临界尺度可分别取为(0.5~1.5)d50和(0.8~2.1)d50,平均宽分别约为d50和1.5d50。(6)粗糙床面分形维数与覆盖基准面位置有关,当覆盖基准面取平均床面时,分形维数取得真实值,且随床面变化较为敏感,可有效量化和区分床面粗糙特征。(7)不同方向剖面轮廓的分形维数差异较大,剖面轮廓具有不同程度的各向异性;剖面轮廓分形维数的频率分布具有双峰特征。(8)均匀砾石颗粒床面粒径越大,床面高程标准差越大,偏度越小,分形维数越小。(9)非均匀卵砾石颗粒床面级配组成相同时,中值粒径越大,分形维数越小;中值粒径相同时,颗粒组成越不均匀,分形维数越大;床面高程极差、标准差、偏度(绝对值)和峰度越大,分形维数越小。(10)床面整体分维随剖面轮廓分维的增大而增大,数值上略大于局部分维;粗糙床面分维的变异性明显小于剖面轮廓分维,两者异性指数相差一个数量级,粗糙床面分维具有良好的稳定性,可作为粗糙床面特征的综合量化参数。
[Abstract]:Rough bed surface exists widely in nature. The roughness of bed surface is closely related to many problems in river dynamics (such as sediment starting, bed resistance, bed load movement, etc.). However, the scientific quantification of bed roughness has been a difficult point in river dynamics, which has not yet been effectively solved and is full of challenges. In this paper, the natural gravel bed surface is classified and generalized on the basis of in-depth investigation. Based on the laser scanning test data of the bed surface, the statistical analysis method and the fractal geometry theory are used to study the roughness characteristics of the artificial scattered gravel bed surface. The main research results are as follows: (1) the median height of the gravel bed surface, the mode of which is equal to the average height, the relative elevation frequency distribution is negative skewed, the high peak is high, The standard deviation of the height of uniform particle bed increases with the increase of particle size. It can be used as an excellent quantitative index for the roughness characteristics of homogeneous granular bed surface. The variation characteristics of gravel bed surface are most close to the spherical model. The spherical model can be used as the best model for the analysis of the variation of the gravel bed surface. 4) the average variation function of the profile of the cross and longitudinal profile of the gravel bed surface is basically the same as the base table value and the block gold constant of the average variation function of the characteristic direction of the bed surface. However, there is a great difference between the variation range and the profile of the profile and the width of the fractal scale area of the rough bed surface, which is related to the median particle size d _ (50) of the bed surface. The upper critical scale can be taken as 0.5U / 1.5 / d50 and 0.82.1d50, respectively. The average width is about d50 and 1.5d50.60) the fractal dimension of rough bed surface is related to the position of covering datum level. When the coverage datum is taken as average bed surface, the fractal dimension can get real value, and it is sensitive to the change of bed surface. The fractal dimension of profile in different directions is different, and the profile has anisotropy in different degree. The frequency distribution of fractal dimension of profile has bimodal feature. (8) the larger the particle size of uniform gravel bed, the greater the standard deviation of bed height, the smaller the deviation, the smaller the fractal dimension, and the smaller the fractal dimension. The larger the median particle size is, the smaller the fractal dimension is; the more uneven the particle composition is, the larger the fractal dimension is when the median particle size is the same, the greater the height of bed, the standard deviation, the deviation (absolute value) and the kurtosis, The smaller the fractal dimension is, the larger the overall fractal dimension of bed surface is with the increase of profile fractal dimension, and the greater the numerical value is, the greater the variation of fractal dimension of rough bed surface is than the fractal dimension of profile, and the difference of heterogeneity index between them is one order of magnitude, and the variation of fractal dimension of rough bed surface is obviously smaller than that of profile fractal dimension. The fractal dimension of rough bed surface has good stability and can be used as a comprehensive quantization parameter of rough bed surface feature.
【学位授予单位】：重庆交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U617;TV882.2

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