卵砾石床面的统计粗糙特性

中文摘要: 针对代表粒径法难以准确量化床面总体粗糙特性的问题，引入统计学理论研究卵砾石床面的粗糙特性，采用不同粒径组成的天然卵砾石颗粒人工铺制了多种散叠型床面，基于床面激光扫描试验资料并结合他人试验成果，探讨床面粗糙统计参数随颗粒组成的变化关系，分析剖面轮廓及粗糙床面的高程变异特征。结果表明：床面高程频率分布呈负偏态，形态较正态分布陡峭，为峰度 K u>3的高狭峰；高程标准差 σ z随中值粒径 d 50的增大而增大，偏度 S k随 d 50的增大而减小；在 d 50相同的情况下，人工铺制床面的 σ z和 S k值均小于清水冲刷粗化床面，而 K u值并明显差异。剖面轮廓的1维结构函数满足变异函数球状模型，模型参数包括变程、块金值和基台值，变程随 d 50和 σ z均呈先减小后增大的趋势变化，块金值、基台值随 d 50和 σ z均呈单调递增变化，变化趋势可用2次多项式曲线拟合。床面2维结构函数的分布形态与抽样尺度 h x、 h y密切相关， h x、 h y与 d 50相当时，2维结构函数分布形态接近圆形，床面粗糙具有各向同性，与清水冲刷粗化床面的结构函数分布规律一致；随着 h x、 h y的增大，2维结构函数分布形态复杂性明显增加，不同象限的结构函数值差异较大，且不再具有清水冲刷粗化床面结构函数的分布规律，床面粗糙出现各向异性。
Abstract:In order to slove the problem that the representative particle size method is difficult to accurately quantify the roughness of the gravel bed surfaces (GBS), the statistical theory was introduced to study the roughness properties of natural GBS. A series of loose-stacked GBS were prepared by using particles with different size and composition. Based on the analysis of the laser scanning data of the above GBS and the existing test results, the relationship between the statistical parameters of bed roughness and particle size was discussed, and the elevation variation characteristics of gravel bed profiles (GBP) and GBS was analyzed. The results showed that the frequency distribution of bed elevation had a negative skewness, the curve shape was steeper than the normal distribution, and the kurtosis K u is greater than 3 which belongs to high narrow peak. The standard deviation σ z increased with the increase of the median particle size d 50, and the skewness S k decreased with the increase of d 50. In the case of the same particle size d 50, the standard deviation σ z and skewness S k of unworked GBS were less than that of water-worked GBS, but there was no significant difference in kurtosis K u. The one-dimensional structure function of GBP satisfied the variogram spherical model, whose parameters included the range, nugget and abutment value. The range showed a trend of first decrease and then increased with the increase of d 50 and σ z, and nugget and abutment value increase with the increase of d 50 and σ z. The trend couied be fitted with second order polynomial curves. The distribution pattern of two-dimensional structure function was closely related to sampling scale h x and h y. When h x, h y and d 50 were equivalent, the distribution of the two-dimensional structure function was close to the circular shape and the rough GBS was isotropic, with the distribution law of the structural function being consistent with that of the water-worked GBS. With the increase of