Using computed tomography (CT) images and multi-fractal theory to quantify the pore distribution of reconstructed soils during ecological restoration in opencast coal-mine

• Using CT images to study the pore distribution of reconstructed soils.
• Using multi-fractal theory to quantify pore distribution of reconstructed soils.
• Mining activities significantly affected soil pore distribution.
• Land reclamation can be used to develop the soil pore distribution.

Opencast coal mining is an anthropogenic activity that changes the antecedent soil profile, including its physical, chemical and biological properties. The compaction resulting from large machinery can have a substantial effect on the reconstructed soil pore structure in opencast coal-mine dumps, thus it was important to reconstruct a suitable soil pore structure for vegetation growth during land reclamation endeavours. To better quantify the characterization of reconstructed soils in opencast coal-mine dumps, high-resolution and lossless computed tomography (CT) images were used to study the effect of dumping and land reclamation on the soil pore structure by scanning soils from the Antaibao Opencast Coal-mine in the Pingshuo mining area. The soils were taken from an undisturbed area and the dump platform using a loess parent material covering with different reclamation time. Photoshop and ArcGIS software were used to process the scanned images and conduct statistical analysis, and multi-fractal theory was used to analyse the distribution characteristics of soil pores. The multi-fractal method can quantify the distribution characterization of the reconstructed soils based on CT images, and multi-fractal parameters, e.g., D(0), D(1), D(0)–D(1), Δα and Δf, can reflect the heterogeneity of different aspects of the soil pore distribution. Mining and dumping activities significantly affected the pore distribution of reconstructed soils; however land reclamation can be used to develop the soil pore distribution of reconstructed soils.