农业工程学报Issue(4)：118-124,7.DOI:10.3969/j.issn.1002-6819.2014.04.015
华北冲积平原壤质潮土的土壤粒径分形空间尺度分析
Analysis of fractal magnitude of soil particles in loamy Chao soils in North China Plain
摘要
Abstract
It is widely accepted that soils have fractal characteristics in certain spatial scales. However, the exact magnitude of this spatial self-similarity is often neglected when doing fractal related researches. In this study, 43 sets of soil particle size distribution data of the Chao soil in North China Alluvial Plain were collected, and their particle size distributions with 93 levels were determined by laser diffraction analysis method (Beckman Coulter LS 13-320).The spatial magnitude orders of soils can be taken as fractal objectives and their affecting factors were analyzed based on the particle size distribution data. For determining the fractal magnitude of the soils, we used a typical scale method:1) calculate the differential fractal dimensions in all the 93 particle size levels (Di, i=1, 2,…, 93) according to the definition fractal; 2) choose a typical scale which is supposed to follow self-similarity (however, the measured Di values may still fluctuate in a certain range); 3) suppose Di in the typical scale is normally distributed, and calculate the corresponding distribution characteristics; 4) use the distribution characteristics to find out the lower and upper limits of Di which follows the same normal distribution in the whole range from the lower to upper limit (in the study, 0.5%and 99.5%of the accumulation curve were taken as the lower and upper limits, respectively);5) fit Di in the entire fractal magnitude, and the slope is supposed to be the fractal dimension of the soil.The results showed that the Chao soils in the study area mostly had good gradations, and they only had rigorous fractal structure at small to medium particle sizes (large clay to fine silt), but didn’t show spatial self-similarity in coarse sand scale. Soils with more clay particles usually had larger fractal dimensions, and the extents of fractal reduced with the increasing of clay fraction. Soils with good graduations usually had wider fractal extents. The fractal dimension values were significantly affected by soil gradation uniformity coefficient, the small particle fractions (<50 μm except for 5-20 μm) and effective particle size (p<0.01). However, fractal dimension was not significantly correlated with bulk density and saturated hydraulic conductivity. The reason could be that soil bulk density and saturated conductivity are greatly impacted by the soil characters in coarse particle scale;however, the Chao soils are not self-similar and the fractal dimension cannot reflect the soil characters in this scale. Therefore, it is recommended that the fractal magnitude orders of soil particles should be firstly analyzed before applying it to solve soil structure and hydraulic related problems.关键词
土壤/分形维数/颗粒大小分析/潮土/分形尺度/激光衍射粒径分析法Key words
soils/fractal dimension/particle size analysis/Chao soil/fractal magnitude/laser diffraction particle size analysis分类
农业科技引用本文复制引用
李晓鹏,刘建立,张佳宝,王伟鹏,辛文文..华北冲积平原壤质潮土的土壤粒径分形空间尺度分析[J].农业工程学报,2014,(4):118-124,7.基金项目
国家自然科学基金资助项目（41001127）；国家自然科学基金资助项目（41171179）；南京土壤研究所知识创新工程领域前沿项目（ISSASIP1102）。 （）
