黄土区露天煤矿排土场重构土壤颗粒组成的多重分形特征

Multi-fractal characteristics of reconstructed soil particle in opencas coal mine dump in loess area

排土场复垦土壤是由人为方式通过不同重构工艺构成的复杂整体,其由不同颗粒组成、具有不规则形状的特性,其核心工作是重构一个适合植被生长的土壤结构。为了更好地对排土场重构土壤结构进行定量表征,该文通过引入土壤多重分形理论,对山西平朔矿区安太堡露天煤矿排土场4种重构土壤方案(含砾石黄土母质覆盖、含煤矸石黄土覆盖、全黄土母质覆盖、含料姜土黄土覆盖)的2 mm以下土壤粒径分布进行了多重分形参数计算,计算参数包括广义维数谱D(q)、多重分形奇异性指数α(q)以及多重分形谱函数f(α(q))等,并对不同分形参数之间的关系进行了计算。通过研究发现:该研究区大型露天煤矿排土场重构土壤颗粒组成具有明显的多重分形特征,D(0)、D(1)、D(1)/D(0)、Δα和Δf反映了土壤颗粒分布的非均匀质特征;该研究区黄土重构剖面的土壤粒径分布范围较小、测度集中程度较高、离散程度较小,土壤粒径组成非均匀性低;多重分形参数之间具有较好的相关性,可以简化选择D(0)、D(1)/D(0)和Δα或D(0)、D(1)和Δf 3个参数实现对黄土区重构土壤颗粒组成分布的定量表征;黄土重构剖面0～90 cm内土壤多重分形参数变化明显,黄土区表层土壤覆盖厚度应在90 cm以上,煤矸石和砾石对重构土壤颗粒的离散程度有一定的影响,应排弃在90 cm以下土层。该研究可为黄土区露天煤矿排土场土地复垦以及重构土壤质量的量化提供理论依据。

Reconstructed soil from an opencast mine dump in a loess area was a complex unity that was made up by humans using different reconstruction technology. It is composed by different soil particles with irregular shapes, and has a self-similar structure. The good soil structure for vegetation growth as reconstructed is the core work of land reclamation. In order to better quantify the soil structure reconstructed in a dump, the soil particle size distribution from four kinds of soil reconstruction modes in the Shanxi Pingshuo ATB Opencast Coal Mine dump was analyzed using the soil multi-fractal theory. Soil reconstruction modes included soil ccovered using loess with gravel, soil covered using loess with coal gangue, covering the whole soil with loess material, and soil covered using loess with Liao Jiangtu. Generalized dimension spectrum D（q）, multi-fractal singularity exponent a（q）, multi-fractal spectrum function f（a（q）） and other multi-fractal parameters were calculated, and the relationships among the different fractal parameters were analyzed in this paper. The results indicated the following conclusions. （1） The particle distribution of reconstructed soil had significant multi-fractal characteristics in an opencast coal mine dump in the study area. D（0）, D（1）, D（1）/D（O）, Aa and Af can reflect the non-uniform particle size distribution characteristics from different perspectives. （2） There was a smaller range of soil particle size distribution, a higher degree of measurement concentration, discrete to a lesser discretization extent, a lower non-uniformity of soil particle size distribution in the soil reconstruction mode of covering the whole loess material, and the function of the mode in changing soil particle size distribution was superior to the modes containing gangue and gravel. （3） The small probability subset of soil particles composition predominated and the soil contained more large particles in the reconstructed soil in the opencast coal mine dump of the loess area. （4） There were good correlations among the multi-fractal parameters of the reconstructed soil particles distribution. D（0）, D（1）/D（O） and Aa（or D（0）, D（1） and Af） can be simplified as three parameters to quantitatively express multi-fractal characterization of the reconstructed soil particle distribution in the study area. （5） The soil multi-fractal parameters in the reconstruction loess section 0-90 cm changed significantly, and the soil thickness covering loess should be more than 90 cm. Gangue and gravel have a certain impact on the dispersion degree of reconstruction soil particles distribution, and should be abandoned in the soil layers below 90cm to reduce its effect on soil particles composition and to improve vegetation restoration .This study can provides a theoretical basis for land reclamation and a quantitative expression of reconstruction soil quality in an opencast coal mine dump of a loess area.