基于分形理论研究土壤结构及其水分特征关系

The Relationship between Soil Structure and Water Characteristics Based on Fractal Theory

为定量获得土壤结构对其水力性质的指示作用,室内实验选用华北平原子牙河流域原状土样为研究对象,用张力计法和激光粒度分析仪分别测定土壤水分特征曲线和样品粒度分布,基于分形理论计算土壤粒度分布的分形维数,采用实验测定与模型验证相结合的方法对水分特征曲线进行分析.结果表明,土壤颗粒粒度分布在[10μm,50μm]区间内的分段分维值是表征土壤粒度累积分布显著上升段特征的关键参数,与0~80 kPa吸力范围内的土壤水分特征曲线幂函数模型拟合参数(a、b)有极显著相关关系.研究区内土壤水分特征曲线以分形形式表达的幂函数模型为:θ=100.78×(3-D)S^((D-3)/3),利用土壤结构分形特征能够有效指示其水力性质.

In order to understand the indicative effect of soil structure on its hydraulic properties,undisturbed soil samples from the Ziya-River basin in the North China plain were selected as the research objects.The soil water characteristic curve was measured by tension meter method,and the particle size distribution of soil samples was measured by laser particle size analyzer.The fractal dimension of soil particle size distribution was calculated based on fractal theory.Soil water characteristic curve was analyzed by experimental measurement and model verification.The fractal dimension of soil particle size distribution in the range of[10μm,50μm]is the key parameter to characterize the characteristics of the significant rising section of soil particle size distribution,which is significantly correlated with the fitting parameters(a,b)of the power function model of soil water characteristic curve in the suction range of 0-80 kPa.The power function model expressed by the fractal form of soil water characteristic curve in the study area is:θ=100.78×(3-D)S^((D-3)/3),and the fractal characteristics of soil structure can effectively indicate its hydraulic properties.