关键词: 黄土, 分维, 粒度分布, 公路自然区划

Abstract: Highway construction greatly develops in China nowadays, but the regional classification of highways is highly macroscopical and the classification standards are hard to employ, especially in the loess areas of China. The study aims to search for the idea classification scheme and standards. Results of analysis on the fractal dimension (D) of the grain size of loess in Gansu province show that loess has close statistical self-correlation, with fractal dimension values from 2.15 to 2.705. The fractal dimension (D) of soil grain size can not only reflect the sediment environment but also decide the soil physical, mechanical and hydraulic properties. That is, the higher fractal dimension the higher dry density is, also the higher specific surface area, the higher soil cohesion and the higher internal friction angle is; simultaneously, the more micropores are. Whereas, the higher fractal dimension indicates the smaller average aperture, smaller void ratio, smaller collapsibility coefficient and smaller permeability coefficient, thus the stable engineering geology nature of soil. Analyzing results also show that the fractal dimension (D) of loess grain size has obvious spatial variation law, well reflecting the differentiation among the five sub-regions of Gansu second-grade highway classification. All these suggest that the parameter of fractal dimension (D) of the soil grain size could serve as an index for highway regional classification same as the indexes of topography, landform, hydrology, climate and etc.

Key words: loess, fractal dimension, grain size distribution, regional classification of highway