Multi-fractal Characteristics Of Reconstructed Soil Pore In Opencast Coal Mine Dump In Loess Area

Soil is a complex porous body. The size, number, geometric shape and the distribution relationship in different soil layers of soil pore are extremely complex. The compaction by large machinery in displacement process can have a strong impact on the pore structure of the soil, so the reconstruction of a good soil structure for vegetation is the core work of land reclamation. Currently, it is still a complex problem to quantify the characterization of pore structure in soil. In the previous study, the parameters- soil porosity and connectivity, etc, describing the characteristics of soil pore can only reflect some of the but not a fully characterization of the complex nature of pore. In order to better quantify the reconstructed soil pore structure on the waste dump, and to analyze the impact of dumping and reclamation on soil pore structure, the soil pore distribution from the original landform and platform on Shanxi Pingshuo ATB opencast coal mine dump in different reclamation years(0 year、20 years、23 years) were scanned with CT. The soil multi-fractal theory was used to analyze multi-fractal parameters of soil pore like, dimension spectrum D(q), multi-fractal singularity exponent α(q), multi-fractal spectrum function f(α(q)), etc. Relationships among different fractal parameters were analyzed in this paper.The results indicate the following conclusions:(1) Combination of CT scanning and computer graphics software can analyze to the size, number and distribution of the pores accurately;(2) With the increasing length of reclamation, the quantity of soil pore and porosity of reclamation improved substantially, but it still had not reach the level of original landscape;(3)The pore distribution of reconstructed soil, in opencast coal mine dump in loess area, had significant multi-fractal characteristics capacity dimension D(0), entropy dimension D(1), the difference of capacity dimension and entropy dimension D(0)-D(1), the width of multi-fractal spectrum Δα and Δf can reflect the non-uniform pore distribution characteristics from different perspectives;(4)Revegetation can improve the soil pore obviously. The index of the soil multi-fractal are better in the soil with longer reclamation, such as a larger range of soil pore size distribution, a higher degree of measure concentration, a bigger soil porosity variation, a lesser discretization extent of pore size distribution. While, there was a large difference between original landscape and soil without vegetation restoration;(5)There were good correlations among multi-fractal parameters of reconstructed soil pore distribution. D(0)、D(1) and Δα(or D(0)、ΔD and Δf) can be simplified as three parameters to quantitatively express multi-fractal characterization of reconstructed soil pore distribution in opencast coal mine loess.Results of this study can provides a theoretical basis for land reclamation and quantifying the quality of reconstructed soil in opencast coal mine dump in loess area.