Abstract
Some of the coal deposits in the northwest region of China are at relatively shallow depths, covered by a thin layer of bedrock and a thick layer of wind-blown sand. We studied the mechanics and permeability of a clay aquiclude by X-ray diffraction and triaxial loading tests and the fracturing of the overlying bedrock and aquiclude in physical simulation tests. The results indicate that if the bedrock thickness is 90 m or more, the height, distribution pattern, and damage to the water-conducting fractured and caving zones (“belts”) are normal. If the bedrock thickness is 30 m or less, the “three belts make one” phenomenon occurs, and caving extends into the soil layer; the overlying rock is completely perforated by vertical fractures and the collapse spreads to the surface. When the bedrock thickness is between 30 and 90 m, the height of the water-conducting fractured zone is inhibited by the weathered rock and cohesive soil layers, and the height of the “two belts” is significantly decreased. This can be used to prevent and control coal mine water hazard.
Zusammenfassung
Einige der Steinkohlenlagerstätten Nordwest-Chinas liegen relativ tagesnah und sind überlagert von geringmächtigem Festgestein und einer mächtigen Serie äolischer Sande. Untersucht wurden die Geomechanik und Durchlässigkeit des tonigen Grundwasserstauers mittels Röntgenphasenanalyse und Triaxialkompressionsversuchen sowie das Bruchverhalten des hangenden Festgesteins und Grundwasserstauers anhand physikalischer Simulationstests. Die Ergebnisse zeigen, dass wenn die Festgesteinsüberlagerungsmächtigkeit 90 m beträgt, beide Deformationszonen voll ausgebildet sind und dass sich Höhe, Verteilungsmuster und Schadensbild der wasserführenden Kluft- und Bruchzonen normal darstellen. Beträgt die Festgesteinsmächtigkeit 30 m, tritt das Phänomen des Zusammenfallens der drei Zonen auf, und die Bruchzone erstreckt sich bis in die Lockergesteinsschicht; die Deckschichten werden vollkommen perforiert und es kommt zur Ausbildung von Tagesbrüchen. Liegt die Deckgebirgsmächtigkeit zwischen 30 m und 90 m, so wird die Mächtigkeit der wasserführenden Kluftzone durch Felsverwitterungszone und bindige Gesteinsschichten begrenzt, und die Mächtigkeit der beiden Zonen ist erheblich geringer. Dies kann zur Vermeidung und Beherrschung von Wassereinbrüchen in Kohlegruben genutzt werden.
Resumen
Algunos de los depósitos de carbón en la región noroeste de China se encuentran a profundidades relativamente poco profundas, cubiertos por una delgada capa de roca madre y una gruesa capa de arena arrastrada por el viento. Estudiamos la mecánica y la permeabilidad de un acuicludo de arcilla mediante difracción de rayos X y pruebas de carga triaxial y la fractura del lecho de roca suprayacente y el acuicludo en pruebas de simulación física. Los resultados indican que si el grosor del lecho de roca es de 90 m, los “dos cinturones” están completamente desarrollados, y la altura, el patrón de distribución y el daño de las zonas fracturadas y espeleológicas que conducen el agua son normales. Si el grosor del lecho de roca es de 30 m, se produce el fenómeno de “tres cinturones hacen uno” y la espeleología se extiende hacia la capa del suelo; la roca suprayacente está completamente perforada por fracturas verticales y el colapso se extiende a la superficie. Cuando el espesor del lecho de roca es superior a 30 m e inferior a 90 m, la altura de la zona fracturada conductora de agua es inhibida por las capas de roca meteorizada y de suelo cohesivo y la altura de los “dos cinturones” se reduce significativamente. Esto puede usarse para prevenir y controlar el riesgo en las minas de carbón.
摘要
中国西北某些地区的煤层沉积较浅,为薄层基岩和厚层风积沙覆盖。利用X衍射和三轴载荷试验分析了泥质隔水层的力学特性和渗透性,采用物理模拟方法研究上覆基岩和隔水层的裂隙特性。结果表明:如果基岩厚度为90 m,“两带”充分发育,导水裂隙带和冒落带的高度、分布和破坏规律正常;如果基岩厚30 m,则发生“三带合一”现象,冒落延伸到土壤层,采动垂向裂隙贯穿上覆岩层,垮落至地表;当基岩厚度为30~90 m时,导水裂隙带高度受风化岩石和粘结性土壤抑制,两带高度大幅减小。研究成果用于煤矿突水灾害防治。
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References
Chen K, Wang X (2015) Analysis of the factors causing roof water inrush in coal seam mining with thin bedrock. Chem Eng Trans 46:679–684
Christopher N, Zacharias A, Gabriel B (2017) Assessment of potential impacts to surface and subsurface water bodies due to longwall mining. Int J Min Sci Technol 27:57–64
Fan L (2005) Discussing on coal mining under water-containing condition. Coal Geol Explor 33:50–53 (in Chinese)
Fan L, Jiang Z (2003) Research on coal mining under competent loose aquifer and properties of aquiclude in Yushen mining area. Coal Geol China 15:52–53 (in Chinese)
Fan L, Jiang Z (2004) Engineering geologic background of coal mining under water-containing condition in Yushen coal mining area. Coal Geol Explor 32:32–35 (in Chinese)
Gu D (2016) Technology development and engineering practice for protection and utilization of water resources in coal mining in Western China. Front Eng Manag. https://doi.org/10.15302/J-FEM-2016010
Hu Q, Tian C, Tan Y, Sun H, Dai L, Cao J (2018) Study of the hard roof mechanical properties in the process of repeated coal mining. J Chin Univ Min Technol 47:68–73 (in Chinese)
Huang Q (2000) Study on roof structure and rock strata control of shallow coal seam in longwall mining. China Univ of Mining and Technology Press, Beijing (in Chinese)
Huang Q (2005) Studies on load-transmitting factor of thick sandy soil layer on key roof stratum in shallow seam mining. Chin J Geotech Eng 27:672–676 (in Chinese)
Huang Q (2009) Simulation of clay aquifuge stability of water conservation mining in shallow-buried coal seam. Chin J Rock Mech Eng 28:988–992 (in Chinese)
Huang Q, Liu T (2006) Simulating test on the subsidence law of subsurface water resisting layer upon shallow coalbed mining. Coal Geol Explor 34:34–37 (in Chinese)
Huang Q, Qian M, Shi P (1999) Structural analysis of main roof stability during periodic weighting in longwall face. J Chin Coal Soc 24:581–585 (in Chinese)
Huang Q, Wei B, Zhang W (2010a) Study of downward crack closing of clay aquiclude in shallow-buried coal seam. J Min Saf Eng 27:35–39 (in Chinese)
Huang Q, Zhang W, Hou Z (2010b) Study of simulation materials of aquifuge for solid–liquid coupling. Chin J Rock Mech Eng 29:2813–2818 (in Chinese)
Karacan CO, Goodman G (2009) Hydraulic conductivity changes and influencing factors in longwall overburden determined by slug tests in gob gas ventholes. Int J Rock Mech Min Sci 46:1162–1174
Li W, Ye G (2000) Study on the engineering geological conditions of protected water resources during coal mining action in Yu-Shen-Fu Mine area in the North Shanxi Province. J Chin Coal Soc 25:449–454 (in Chinese)
Li S, Fan C, Luo M, Yang Z, Lan T, Zhang H (2017) Structure and deformation measurements of shallow overburden during top coal caving longwall mining. Int J Min Sci Technol 27:1081–1085
Liu X, Tan Y, Ning J, Tian C, Wang J (2015) The height of water-conducting fractured zones in longwall mining of shallow coal seams. Geotech Geol Eng 33:693–700
Liu J, Sui W, Zhao Q (2017) Environmentally sustainable mining: a case study of intermittent cut-and-fill mining under sand aquiclude. Environ Earth Sci 562
Ma L, Zhang D, Qiao J (2008) Physical simulation of water crack distribution characteristics in overlying strata under coal mining conditions. J Liaoning Tech Univ (Nat Sci) 27:649–652 (in Chinese)
Miao X, Pu H, Bai H (2008) Principle of water-resisting key strata and its application in water-preserved mining. J Chin Univ Min Technol 37:1–4 (in Chinese)
Miao X, Cui X, Wang J, Xu J (2011) The height of fissured water-conducting zone in undermined rock strata. Eng Geol 120:32–39
Su B, Yue J (2017) Research of the electrical anisotropic characteristics of water-conducting fissured zones in coal seams. Appl Geophys 14:216–224
Su B, Malekian R, Yu J, Feng X, Liu Z (2016) Electrical anisotropic response of water conducted fissured zone in the mining goaf. IEEE Access 4:6216–6224
Wang F, Duan C, Tu S, Liang N, Bai Q (2017) Hydraulic support crushed mechanism for the shallow seam mining face under the roadway pillars of room mining goaf. Int J Min Sci Technol 27:860–863
Xia B, Jia J, Yu B, Zhang X, Li X (2017) Coupling effects of coal pillars of thick coal seams in large-space stopes and hard stratum on mine pressure. Int J Min Sci Technol 27:965–972
Yuan L, Zhang T, Zhao Y, Ren B, Hao X, Xu C (2017) Precise coordinated mining of coal and associated resources: a case of environmental coordinated mining of coal and associated rare metal in Ordos basin. J Chin Univ Min Technol 46:449–459 (in Chinese)
Yuan L, Zhang N, Kan J, Wang Y (2018) The concept, model and reserve forecast of green coal resources in China. J Chin Univ Min Technol 47:1–8 (in Chinese)
Zhang S, Liu Y (2012) A simple and efficient way to detect the mining induced water-conducting fracturedd zone in overlying strata. Energy Proc 16:70–75
Zhang D, Fan G, Liu Y, Ma L (2010) Field trials of aquifer protection in longwall mining of shallow coal seams in China. Int J Rock Mech Min Sci 47:908–914
Zhang D, Fan G, Ma L, Wang X (2011) Aquifer protection during longwall mining of shallow coal seams: a case study in the Shendong coalfield of China. Int J Coal Geol 86:190–196
Zhang J, Jiang H, Deng X, Ju F (2014) Prediction of the height of the water-conducting zone above the mined panel in solid backfill mining. Mine Water Environ 33:317–326
Zhang J, Zhang Q, Spearing A, Miao X, Guo S, Sun Q (2017a) Green coal mining technique integrating mining-dressing-gas draining-backfilling-mining. Int J Min Sci Technol 27:17–27
Zhang S, Tang S, Zhang D, Fan G, Wang Z (2017b) Determination of the height of the water-conducting fracturedd zone in difficult geological structures: a case study in Zhao Gu No. 1 coal seam. Sustainability 9:1077. https://doi.org/10.3390/su9071077
Zhou D, Wu K, Li L, Yu J (2016) Impact of thick alluvial soil on a fractured water-conducting zone: an example from Huainan coal mine, China. J S Afr Inst Min Metall 431:440. https://doi.org/10.17159/2411-9717/2016/v116n5a9
Zou Q, Lin B (2018) Fluid–solid coupling characteristics of gas-bearing coal subject to hydraulic slotting: an experimental investigation. Energy Fuel 32:1047–1060
Acknowledgements
This work was financially supported by the National Science and Technology Major Project of China (Grants 2016ZX05043005 and 2016ZX05045007) and National Natural Science Foundation of China (Grant 5170041013), which are gratefully acknowledged. We also thank the anonymous reviewers for their comments and suggestions to improve the manuscript.
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Liu, Z., Fan, Z. & Zhang, Y. Fracture Characteristics of Overlying Bedrock and Clay Aquiclude Subjected to Shallow Coal Seam Mining. Mine Water Environ 38, 136–147 (2019). https://doi.org/10.1007/s10230-018-0549-6
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DOI: https://doi.org/10.1007/s10230-018-0549-6