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针对传统方法刻画粗糙床面总体特征存在缺陷的问题,将分形几何理论引入非均匀卵砾石粗糙床面特征研究,以卵砾石床面激光扫描试验资料为基础,探讨了分形尺度区宽度与中值粒径d50的关系,分析了覆盖基准面对分形维数的影响,研究了床面整体与局部分形维数的特征与联系,获得了分形维数随床面颗粒组成及高程统计参数的变化规律。结果表明:分形尺度区宽度与床面颗粒中值粒径d50有关,上临界尺度可取为1.5d50;分形维数与覆盖基准面位置有关,覆盖基准面距平均床面的距离越大,分形维数越大且逐渐失真,为有效量化和区分床面粗糙特征,覆盖基准面宜取平均床面;粗糙床面分形维数具有良好的稳定性,局部分形维数变异性很小,并与整体分形维数接近;粗糙床面的分形维数与颗粒大小、级配组成及床面高程统计参数有关,中值粒径越大,颗粒组成越均匀,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。
Aiming at the problem of the traditional method of characterizing the general characteristics of the rough bed, the fractal geometry theory is introduced into the study of the characteristics of the rough bed of heterogeneous pebbles. Based on the laser scanning test data of the gravel bed, the relationship between the width and median of the fractal dimension The relationship between the coverage datum and the fractal dimension was analyzed. The characteristics and relations between the whole and the local fractal dimensions of the bed were studied. The fractal dimension was obtained according to the change of bed particle composition and elevation statistical parameters law. The results show that the width of the fractal dimension zone is related to the median diameter d50 of the bed particles, and the upper critical dimension is about 1.5d50. The fractal dimension is related to the position of the cover datum. The larger the distance from the datum plane to the average bed, the fractal dimension The larger the number and the more distorted, in order to effectively quantify and distinguish the bedside rough features, the cover datum should be averaged. The fractal dimension of rough bed has good stability and the variability of local fractal dimension is very small, The fractal dimension is close to the whole; the fractal dimension of the rough bed is related to the particle size, gradation composition and bed height statistical parameters. The larger the median diameter is, the more uniform the particle composition is, the higher the bed elevation is, the standard deviation is The greater the degree (absolute value) and kurtosis, the smaller the fractal dimension.