Characteristics of macropores in different reconstructed matrix layers in the coal gangue reclamation area of Panyi Mine, Huainan

The coal mine reclamation area is affected by mechanical compaction and disturbance during the construction process, the original structure and sectional hierarchy of the soil have been destroyed, reconstructing soil productivity is difficult to restore to the original soil level, and there is often a problem of good vegetation restoration in the early stage but degradation in the later stage. Macropores are important channels for soil moisture and air circulation, and have a significant impact on the physical, chemical, and biological processes of soil. By combining qualitative and quantitative methods to analyze the characteristics of macropores at different reconstruction matrix levels in reclamation areas, it is helpful to identify key layers of reconstructed soil and optimize the design of reclamation processes. This study uses industrial computed tomography （CT） scanning to create three-dimensional images of soil samples from various reconstructed layers in the Panyi Mine. The original soil is used as a control and digital image quantitative analysis is carried out using VG Studio Max software. The research results show the main distribution range of macropores in different reconstruction layers is relatively consistent, but within the bore range of Ø＞10 mm, the pore contribution rates of the overlying soil and coal gangue layer reach 90.83% and 97.80%, respectively, which are significantly higher than those of the original soil and the mixed soil of mud and gangue. The original soil layer forms a pore fissure network under the influence of vegetation roots and external environment, with enhanced connectivity and reduced specific surface area. It has good infiltration capacity and ecological suitability, and is a key infiltration and plant planting layer in the reclamation profile. The pore structure of the mixed soil layer of mud and gangue is evenly distributed, with a moderate specific surface area and good water storage capacity, making it a typical water storage functional layer in the reclamation profile. The coal gangue layer contains a large amount of fragmented material, with concentrated pores and strong connectivity, but with a small specific surface area, resulting in poor overall water storage performance. It is recommends that coal gangue be fully crushed before filling to improve the uniformity of pore structure; prioritize planting shallow rooted herbaceous plants on the surface to enhance stability, and avoid planting operations during flood season to reduce the risk of water erosion. The research results can provide technical support for optimizing soil structure and improving construction technology in coal gangue reclamation areas.