Abstract
Barrier pillars are an effective and fundamental measure to prevent water inrush when mining shallow coal seams under an unconsolidated, confined aquifer. Based on the complex geological and hydrogeological conditions in the southern area of the Qidong coal mine, the no. 61 coal seam there was selected for a research demonstration. A fluid–solid coupled numerical simulation was carried out using the universal distinct element code. The hydraulic pressures and seepage rates in overlying strata were analyzed for two mining cases, near the aquifer and near the fault. The results showed that the degree of interconnection between the bed-separated and vertical fractures, and increases in hydraulic pressures and seepage rates in overlying strata were key factors in predicting potential water inrush when mining shallow coal seams under an unconsolidated, confined aquifer. Combining the numerical simulation results with China’s coal mining requirements, the no. 61 coal seam can be mined up to 90 m beneath the unconsolidated, confined aquifer, which limits mining to an altitude of −509.36 m. The width of the barrier pillar should be 30.7 m near the fault.
Zusammenfassung
Bergfesten als Barrieren sind eine effiziente und grundsätzliche Maßnahme, um Wassereinbrüchen beim Abbau von oberflächennahen Kohleflözen unter einem unverfestigten, gespannten Aquifer vorzukehren. Auf der Basis komplexer geologischer und hydrogeologischer Verhältnisse im südlichen Teil der Qidong Kohlenmine wurde das 61. Kohlenflöz für eine Forschungsdemonstration ausgewählt. Eine Fluid-Feststoff gekoppelte numerische Simulation wurde unter Nutzung des Universal Distinct Element Code (UDEC) ausgeführt. Hydraulische Drücke und Sickerraten in den überlagernden Schichten wurden für zwei Abbauvarianten untersucht, nahe am Aquifer und nahe an der Störung. Die Ergebnisse zeigten, daß der Verbindungsgrad zwischen Trennflächen parallel zur Schichtung und vertikalen Trennflächen, sowie der Anstieg hydraulischer Drücke und der Sickerraten in den Hangendschichten Schlüsselfaktoren für die Vorhersage potentieller Wassereinbrüche sind, wenn oberflächennahe Kohleflöze unter einem unverfestigten, gespannten Aquifer abgebaut werden. Die Zusammenführung der Resultate der numerische Simulation mit Chinas Anforderungen an den Kohlenbergbau zeigt, daß das 61. Kohlenflöz bis 90 m unter den unverfestigten, gespannten Aquifer abgebaut werden kann, das heißt bis zu einer Höhe von −509,36 m. Nahe an der Störung sollte die Bergfeste als Barriere eine Breite von 30.7 m aufweisen.
Resumen
Los pilares barrera son una medida fundamental y efectiva para prevenir las irrupciones de agua para la minería de vetas de carbón de poca profundidad bajo un acuífero confinado y no consolidado. Basados en las complejas condiciones geológicas e hidrogeológicas en el área sur de la mina de carbón Qidong, la veta de carbón no. 61 fue seleccionada para una demostración. Se realizó una simulación numérica de acoplamiento sólido-fluído usando el código universal de elementos distintos (UDEC). Las presiones hidráulicas y los índices de filtración en estratos superpuestos fueron analizadas para dos casos de minería cerca del acuífero y cerca de la falla. Los resultados mostraron que el grado de interconexión entre el lecho separado y las fracturas verticales, y el incremento de las presiones hidráulicas y los índices de filtración en estratos superpuestos, fueron factores clave en la predicción de la potencial irrupción de agua en la minería de vetas de carbón debajo de un acuífero confinado y no consolidado. Combinando los resultados de la simulación numérica con los requerimientos de la minería de carbón en China, la veta de carbón no. 61 debería ser explotada hasta 90 m debajo del acuífero confinado, no consolidado, que limita la minería a una altitud de −509,36 m. El ancho del pilar barrera debería ser 30,7 m cerca de la falla.
摘要
防水煤岩柱的留设能够有效预防松散承压含水层下浅部煤层开采时顶板突水事故的发生。根据祁东煤矿南部采区复杂地质及水文地质条件,选取61煤层为研究对象,利用通用离散元软件UDEC进行流固耦合数值模拟,分析了近松散承压含水层与近断层两种开采方案中的覆岩水压与渗流速率。结果表明:离层裂隙与垂向裂隙彼此的连通程度和覆岩水压与渗流速率的增大是识别松散承压含水层下开采潜在突水的关键因素。结合数值模拟结果与中国煤炭开采规程,确定了61煤层能够被开采至松散承压含水层以下90 m(上限标高为−509.36 m);断层防水煤岩柱宽度为30.7 m。
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Acknowledgments
This work was financially supported by the National Natural Science Foundation of China (Grants 41372244, 41172216, and 41373095) and the Anhui Natural Science Foundation of China (1308085ME61). The authors sincerely thank the reviewers for their thorough reviews and useful suggestions.
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Chen, L., Feng, X., Xie, W. et al. Using a Fluid–Solid Coupled Numerical Simulation to Determine a Suitable Size for Barrier Pillars When Mining Shallow Coal Seams Beneath an Unconsolidated, Confined Aquifer. Mine Water Environ 36, 67–77 (2017). https://doi.org/10.1007/s10230-016-0404-6
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DOI: https://doi.org/10.1007/s10230-016-0404-6