基于分形维数的斜坡非饱和带土体大孔隙分布研究

Macropores Study on Vadose Zones of Hillslope Based on Fractal Dimension

对取自于云南省昭通市头寨滑坡滑源区附近的两个大尺度(25cm×25cm×50cm)土柱样品进行CT扫描,选取典型剖面切片,通过CT值范围将大孔隙分离从而研究土体中的大孔隙分布;计算大孔隙分布分维数(盒维数),研究其大孔隙的不规则特征,结果表明:土体中大孔隙的盒维数随深度增加呈单调递减规律,且与大孔隙度具有显著正相关关系;但大孔隙度只能表征在某一深度上大孔隙的分布多少,而大孔隙的不规则特征则需盒维数表征;最后得到大孔隙的累积大孔隙度与大孔隙孔径(在盒维数为常数时)符合幂函数规律,研究结果有利于利用分形理论建立大孔隙模型,从而研究水分在大孔隙中运动过程。

In this study,two soil cores of 25 cm in width,25 cm in length,and 50 cm in height from vegetated slope in Panhe,Yunnan Province,China were collected as research objects.Base on X-ray computed tomography,a series of slice images were collected.According to CT value,the macropores can be separated from soil matrix for typical slices.Abnormity characteristics were also studied by means of fractal dimension（box-counting method）analysis.Results show that there is a positive correlation between macroporosity and their box-counting dimension which decreases with soil depth,but macroporosity only characterize the proportion of macropores;the abnormity could be represented by box-counting dimension.In addition,cumulative macroporosity increases in power function along with the pore diameter when dimension is constant.