This study, which considers coal mining sites, aims to solve problems pertaining to the immense permeability, poor stability, and the environmental pollution of soil. In regard to reconstituted soil, the novel “2+1” layered construction technology entails designing a water-resisting layer, a modified layer, and an evaporation inhibition layer on the surface of the gangue hill. This technology, which entails constructing a novel type of reconstituted soil, considered four mechanical and physical soil properties, namely soil particle size, humidity, unit weight, and soil structure grade. The construction of novel reconstituted soils should consider the influence of biological factors and that of an arid environment, as well as the influence of the soil permeability coefficient, water content, density, temperature, and water-soil interaction; simultaneously, it should consider the chemical composition. With respect to the water-resisting layer, we selected loess and feldspathic sandstone that exhibited high clay content, and we utilized a 20 cm design thickness. The modified layer was composed of sandy loess, weathered coal, and feldspathic sandstone. This layer was exhibited a 60 cm design thickness, and it considered the characteristics pertaining to vegetation, soil compactness, and soil chemical composition. The evaporation inhibition layer was designed using materials such as gravel and straw checkerboard. Regional tests indicated that verified the rational robustness of the novel “2+1” reconstituted soil layered construction. The results provide a reference for ensuring the ecological sustainability of coal mining sites that characterize the arid, desert areas of Northwest China.

Topographic reconstruction is the fundamental task of the ecological rehabilitation in abandoned mines, which affects the results of the whole ecological system rehabilitation. The technology of near-natural topographic reconstruction constructs the terrain by using the adjacent, undisturbed natural terrains as a reference, and it has become a hot research issue for land reclamation and ecological rehabilitation in recent years. But in reconstructing the near-natural terrain, one must first determine what kinds of characteristics of the natural terrain should be referred to, what necessary parameters should be used, and what indexes should be used to evaluate the results of the topographical design. All these issues still have not been investigated systematically. In this study, the arid desert region in Northwest China was taken as the target area and the theoretical analysis tool of the “Grounded Theory” was applied to discuss these issues systematically. Based on a large amount of literature research and the records obtained from the semi-structured interviews of 12 experts, a three-level parameter system for the near-natural topographic reconstruction in the abandoned mines was finally constructed by three-level coding using the method of the “Grounded Theory”. The parameter system contains a total of three main categories, eight sub-categories, and 26 parameters. The parameters developed in the system can support all aspects of the near-natural terrain design processes, and they can cover the parameter needs in multiple aspects of the topographic reconstruction of the mining sites. This work can provide support for further research on the methods of near-natural topographic reconstruction and improve its technical system.

The huge pit formed after open-pit mining can partially change the local water system. Taking a typical open-pit coal mine in Wuhai City as an example, this study used survey data, hydrological analysis technology and a Rainfall-Run model to analyze the changes in the water system and runoff. The results indicate that the water system in the coal mining site has changed in the confluence path because of the mining pits and dumps formed by coal mining operations. Taking the local conditions into account, a water system restoration scheme using the pit for floodwater storage is proposed, that is, using the pit to retain upstream flood on the basis of an unobstructed downstream river flow. This scheme has several benefits. First, it can reduce the pressure of downstream flood control. Second, the sediment brought by the flood will be stored in the pit, which is conducive to reducing soil erosion. Third, it is conducive to the conservation of regional groundwater. Fourth, the retained water can be used for irrigation, which is conducive to the improvement of the surrounding ecology. The results of this study can provide references for the restoration and management of mining areas and ecological restoration in the arid desert area of Northwest China.