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Purpose: The underground mining of coal leads to land subsidence and changes agricultural land into a water-logged area. This study aims to examine the relationship between coal mining subsidence and crop failure in plains with a high underground water table. Methods: The Dongtan Coal Mine in Jining City of Shandong Province in China was selected as an example. Samples were gathered at gradient intervals based on the strike, dip, and angular bisector directions. The spatial variability and spatial correlation were analyzed by combining classical statistics and geostatistics. Results: The order of the coefficient of variation in each parameter was as follows: the available phosphorus > available potassium > leaf area index (LAI) > biomass > soil moisture content > chlorophyll content (SPAD) > soil organic matter (SOM) > alkaline nitrogen (AN) > bulk density > elevation. Except the biomass had moderately spatially dependent, the other parameters all exhibited a strongly spatially dependent. At the level of 0.01, the correlation coefficient between SOM and AN was 0.67. The correlation coefficients relating biomass with SPAD and LAI were 0.70 and 0.69, respectively, and between SPAD and LAI was 0.68. The correlation coefficients between distance and altitude, distance and biomass, and altitude and biomass are 0.95, 0.67, and 0.65, respectively. Conclusion: Coal mining leads to stretching and deformation of the ground, land subsidence, and changes in the physicochemical properties of the soil. In this case, the yield of aboveground crops is poor, but under the influence of external factors such as irrigation and breeding, the threat of coal mining to crop growth has been reduced. [ABSTRACT FROM AUTHOR]

In eastern China, coal mining has damaged a large amount of farmland, posing a great threat to food security. Backfilling with coal waste, fly ash, and sediments from rivers is an effective method to restore farmland. This study was conducted at the reclaimed area (RA) and the undisturbed area (UA) in Shandong Province, China. Soil and plant analyzer development (SPAD) of corn was selected as an indicator of crop growth. Multi-spectral data was obtained by the unmanned aerial vehicle equipped with a camera. By analyzing the correlation between SPAD and spectral bands, the common vegetation index is improved. Different regression methods were used to construct the SPAD inversion model. The distribution of corn SPAD was monitored to objectively evaluate reclamation technology. The results are as follows: (1) the vegetation index improved using the red-edge band has a higher correlation with SPAD, and the largest coefficient of determination (R2) value is 0.779; (2) the optimum inversion model for both jointing stage (R2 = 0.676) and milky stage (R2 = 0.661) is the linear regression model; the optimum model for both tasseling stage (R2 = 0.809) and filling stage (R2 = 0.830) is the partial least squares regression model; (3) the SPAD inversion map of RA and UA obtained by the optimum model shows that the corn grown in RA is slightly better than in UA. This study realized the rapid and efficient monitoring of the reclamation effects based on multi-spectral imagery and verified the feasibility of backfilling reclamation with Yellow River sediment in coal mining subsidence areas. [ABSTRACT FROM AUTHOR]

Coal mining in high groundwater table areas causes many environmental issues. In China, such regions have three unique and significant characteristics, (1) multiple coal seams; (2) thick coal seams and (3) high groundwater, which lead to mine subsidence ponds. In the past, reclamation of disturbed land was carried out after subsidence stabilised. Such reclamation is a low-percentage of reclaimed farmland, and has high reclamation cost, difficult construction conditions, because of relatively flat terrain and the shortage of backfilling materials in flat topography. Therefore, salvaging the topsoil before it is submerged in water and reusing it while subsidence becomes stable would be a good way to improve the reclamation efficiency. This paper considers a longwall panel in Shandong province as a case study. Dynamic mining subsidence was simulated using mining subsidence prediction software. To illustrate subsidence development and its effects on farmland, the ground was first divided into cell size of 40 m along with pre-mining topography. The mining subsidence and water logging time for each cell were then calculated. Based on the simulations, the topsoil removal time, scope and depth of topsoil was determined. The salvaged topsoil could be reused subsequently, which would provide enough filling material to raise the percentage of reclaimed farmland, and reduce reclamation costs. The research benefits the development of concurrent mining and reclamation technology in underground mining sites, and promotes the synchronisation of exploitations and treatments. [ABSTRACT FROM AUTHOR]