甘肃黄土的粒度分维特征及意义

依据分形理论分析了甘肃黄土粒度分布的分形结构特征。黄土具有良好的统计自相似性。随着空间位置和黄土形成时代的不同,黄土的分形结构特征有明显的变化特征,其分维值介于2.29至2.56之间;且粒度分维值的大小与分选好坏密切相关,即:分选系数大则分维值大,反之则分维值小。这表明黄土的粒度分维在一定程度上可以反映黄土的形成演化特征。在此基础上进一步研究了黄土粒度分维与干密度、孔隙比、湿陷系数之间的定量关系,指出黄土分维值可以定量表征黄土的物理、水理性质。与地形地貌、水文和气候等因素一样,它也可作为自然区划的一个主要指标。

Science and Technology Press. 52-69.GRAIN-SIZE FRACTAL DIMENSION OF THE LOESS IN GANSU AND ITS SIGNIFICANCE

Based on the fractal theory, the fractal dimension (D) of the grain-size of the loess in Gansu province was calculated. The results showed that the statistical self-similarity of grain-size distribution existed in the loess. With the varying of space and deposited time, the characteristics of fractal dimension (D) of the loess grain-size changed obviously. The fractal dimension values in the loess ranged from 2.29 to 2.56. In addition, the fractal dimension related closely with the degree of sorting. The higher the sorting coefficient, the bigger the fractal dimension. All these proved that fractal dimension values reflected the characteristics of deposition and evolution of the loess. Furthermore, the relationship between fractal dimensions and physical, hydraulic and mechanical properties of the loess, namely, the engineering geological property of the loess, was analyzed. All these suggested that this parameter could also serve as an index for climatic zoning, just as the indexes of topography, landform, hydrology, climate, and so on.