An improved model to predict the water-inrush risk from an Ordovician limestone aquifer under coal seams: a case study o
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ORIGINAL ARTICLE
An improved model to predict the water‑inrush risk from an Ordovician limestone aquifer under coal seams: a case study of the Longgu coal mine in China Huigong Niu1 · Jiuchuan Wei1 · Huiyong Yin1 · Daolei Xie1 · Weijie Zhang1 Accepted: 30 April 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The mining of stratigraphically low coal seams in North China-type coalfields is subject to water inrush from the underlying Ordovician limestone aquifer. The water-inrush coefficient method that is currently used for the evaluation of the water-inrush risk has inherent shortcomings, because it takes into account only the aquifer head pressure and the aquiclude thickness. Therefore, an improved water-inrush coefficient (IWIC) model is proposed. Based on the normalized water-inrush parameter, water-resisting parameter and structural parameter, the IWIC model is established using a linear weighting method. The first-order weights of each parameter are determined by the analytic hierarchy process, and the second-order weights are determined by the trapezoidal fuzzy number technique. Contour maps of the water-inrush risk calculated with the IWIC model are then obtained. The water-inrush risk grades are classified by thresholds derived via the Jenks natural breaks technique. The IWIC model is applied to the Longgu coal mine, as a typical coal mine in China, to evaluate the water-inrush risk of the lower four coal seams (L4CS). The evaluation results show that the risk of water inrush in the L4CS can be divided into five grades: safe, slightly safe, slightly dangerous, dangerous, and extremely dangerous. Overall, the L4CS mining in the Longgu coal mine is seriously threatened by the underlying Ordovician limestone aquifer. As the depth increases, the risk of water inrush increases from the No. 151 to No. 182 coal seams. Among the L4CS, No. 17 and No. 182 have the highest grade of water-inrush risk, and it is proposed that these two coal seams should not be mined to prevent water-inrush accidents. Keywords Water inrush · Risk evaluation · Improved water-inrush coefficient model · Ordovician limestone aquifer · Longgu coal mine
Introduction China is not only the largest coal producer (Zhao et al. 2012) but also one of the countries with the most serious miningrelated water disasters (Yin et al. 2018). Water disasters have become the second largest disaster in China’s coal mines (Wang and Meng 2018). The coal reserves threatened by water disasters account for 27% of the proven reserves, which total approximately 30 billion tons of reserves (Wu * Jiuchuan Wei [email protected] * Huiyong Yin [email protected] 1
Shandong Provincial Key Laboratory of Depositional Mineralization and Sedimentary Minerals, College of Earth Science and Engineering, Shandong University of Science and Technology, Qingdao 266590, Shandong, China
et al. 2013a). From 1950 to 2018, 188 coal mine accidents resulting in 30 or more deaths per accident occurred in China, and water disasters were one of the majo
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