Abstract
Taking the Suiqi coalfield located in North China as the object, where the coal seam burial depth is more than 1100 m, the water abundance of the roof pore thermal storage aquifer is better than average, the ground temperature is abnormally high, and hydrogeological data are relatively lacking, this paper selects and determines eight index factors that influence the mining of the coalfield. Based on the analytic hierarchy process (AHP), the index factor weight is defined, and then, the threat degree of the roof thermal storage aquifer to the coal mining is quantitatively evaluated and divided by using the fuzzy variable set theory. The evaluation results show that the threat degree of the roof in the eastern region is generally greater than that in the western region and that the closer it is to the coal seam outcrop line, the higher the threat degree is; near the boreholes, in the areas Qs1,Qs5, Qs8, Sx1, Tk5, Zc4, and Zc7, which are close to the hidden outcrop line of the coal seam, the classification characteristic value of the threat degree is greater than 3.5, which is in the high-threat zone for disasters caused by roof thermal storage aquifers during coal seam mining. The area above the medium-threat zone accounts for 71.82% of the total study area, indicating that deep coal mining is affected by multiple factors and that roof water and heat disasters are more likely to occur.
Highlights
In North China coalfields and southern Ordos Basin coalfields, minable coal seams are directly or indirectly covered by thermal storage aquifers of different thicknesses and coal seam mining operations face the serious threats of double roof water inrush and geothermal disasters
To ensure the safety of underground mining engineering, the threat degree of the roof thermal storage aquifer has become an urgent problem that needs to be solved in coal mine production through scientific evaluation
Yang and Sun determined the height of the water flowing through the fractured zone by using a field measurement, numerical simulation, and empirical formulas in the “upper three zones” theory to reasonably determine the size of a waterproof safety coal pillar [14]
Summary
In North China coalfields and southern Ordos Basin coalfields, minable coal seams are directly or indirectly covered by thermal storage aquifers of different thicknesses and coal seam mining operations face the serious threats of double roof water inrush and geothermal disasters. Yang and Sun determined the height of the water flowing through the fractured zone by using a field measurement, numerical simulation, and empirical formulas in the “upper three zones” theory to reasonably determine the size of a waterproof safety coal pillar [14]. Based on the gray correlation analytic hierarchy process, Zhang and Yang proposed a prediction model for the roof water inrush when mining a shallow coal seam, and the model was verified with engineering examples [16]. Ren and Wu revised the “three figure double prediction method” and evaluated the risk of water inrush in the area where the height of the caving zone formed by coal mining is lower than the elevation of the roof aquifer [19]. The results can provide technical support for the layout of mining engineering and safety production under the cover of a thermal storage aquifer and can provide a reference for the identification of roof water and heat disasters in other mining areas in the North China coalfield
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