Abstract
The focus of China’s coal mining in recent years has shifted to western China, which has a fragile ecological environment. The Jurassic coal in this area is buried at shallow depths and is very thick. Currently, the two main issues are the inrush of underground water and the disruption to shallow surface water supplies brought on by mining. Accurately predicting the height of the water-conducting fractured zone (WCFZ) is the key to preventing roof water damage and attaining water conservation in this mining area. A nearest neighbor bootstrap regression (NNBR) model was established to predict the height of the WCFZ for working face 117 of the Jinjitan coal mine in western China, which uses fully mechanized top coal caving longwall mining. The model was verified based on the measured heights of the WCFZ (30 groups of measured data) using the actual mining thickness (> 8 m) and working face width as predictive factors. The mean error of the model’s prediction was 1.5 m and the mean absolute percentage error was 13.6%, which was better than the result predicted using the established conventional empirical formula. The model was improved by applying a safety factor of 1.3, which met the 96.7% reliability requirements. The height of the WCFZ of working face 117 was predicted using this model, and the predicted value was compared with values measured by optical fiber monitoring and simple hydrological observations. The height of the WCFZ measured by optical fiber was 184.8 m, the predicted value was 196.0 m, and the relative error of that prediction was 6.0%. The hydrologically observed value was 221.0 m, the predicted value for that location was 225.7 m, and the relative error was 2.1%. Thus, the NNBR model is capable of reliably predicting the height of the WCFZ and it appears that it can be used to compute the safe water control height above mechanized top coal caving mines in western China’s very thick Jurassic coal seams.
摘 要
摘 要:近年来,中国煤炭开采的重心已经转移到生态环境脆弱的西部地区。该地区侏罗系煤层埋藏浅,厚度大。目前,影响着西部地区的煤矿开采的两个主要问题分别为顶板水害和浅层地表水补给的破坏,而准确预测导水裂隙带高度是防止顶板水害、实现矿区节水的关键。本研究建立了最近邻抽样回归模型,对西部金鸡滩煤矿117工作面综采放顶煤长壁开采导水裂隙带高度进行了研究。以采厚(> 8 m)和工作面宽度为预测因子,以导水裂隙带( 30组实测数据)的实测高度为基础对模型进行验证。模型预测的平均误差为1.5 m,平均绝对百分比误差为13.6 %,优于既定的传统经验公式的预测结果。研究对模型进行了优化,应用1.3的安全系数,使其满足96.7%的可靠性要求。本研究利用该模型对117工作面导水裂隙带高度进行了预测,并将预测值与光纤监测和简单水文观测进行了对比:通过光纤测量的导水裂隙带高度为184.8 m,模型预测值为196.0 m,相对误差为6.0%;水文观测值为221.0 m,模型预测值为225.7 m,相对误差为2.1 %。因此,应用最近邻抽样回归模型能够可靠地预测导水裂隙带高度,适用于中国西部巨厚侏罗系煤层综放开采的两带高度预计。
Zusammenfassung
Der Schwerpunkt des chinesischen Kohlebergbaus hat sich in den letzten Jahren nach Westchina verlagert, wo die Umweltbedingungen ökologisch sehr vulnerabel sind. Die Kohleschichten aus dem Jura lagern in diesem Gebiet in geringer Tiefe und sind sehr mächtig. Als Hauptschwierigkeiten stellen sich derzeit das mögliche Eindringen von Grundwasser in den Untertagebergbau und eine potentielle Unterbrechung der oberflächennahen Wasserversorgung durch den Bergbau dar. Die genaue Vorhersage der Höhe der wasserführenden Bruchzone (WCFZ) ist als Schlüssel zur Verhinderung von Wassereinbrüchen aus dem Hangenden sowie für den Grundwasserschutz im Bergbaugebiet identifiziert worden. Zur Vorhersage der Höhe der WCFZ für die Ortsbrust 117 des Jinjitan-Kohlebergwerks im Westen Chinas, in dem eine vollmechanisierter Strebbau betrieben wird, wurde ein Nearest-Neighbour-Bootstrap-Regressionsmodell (NNBR) entwickelt. Das Modell ist anhand der gemessenen Höhen der WCFZ (30 Gruppen von Messdaten) verifiziert worden, wobei die tatsächliche Abbaumächtigkeit (> 8 m) und die Strebbreite als Vorhersagefaktoren verwendet wird. Der mittlere Vorhersagefehler des Modells betrug 1.5 m, der mittlere absolute prozentuale Fehler 13.6 %. Der Fehler war damit geringer als bei Methoden, welche auf herkömmlichen empirischen Formeln beruhen. Das Modell wurde durch Anwendung eines Sicherheitsfaktors von 1,3 verbessert, wodurch die Anforderungen an die Zuverlässigkeit auf bis zu 96.7 % erhöht worden sind. Die Höhe der WCFZ an der Ortsbrust 117 konnte mit Hilfe dieses Modells prognostiziert und die Ergebnisse anschließend mit Werten aus der Überwachung mit Lichtwellenleitern und einfache hydrogeologischen Beobachtungen verglichen werden. Die mittels Lichtwellenleiter gemessene Höhe der WCFZ betrug 184.8 m, der vorhergesagte Wert lag bei 196.0 m. Der relative Fehler der Vorhersage betrug somit 6.0 %. Die hydrogeologisch beobachtete Höhe der WCFZ lag bei 221.0 m, der vorhergesagte Wert lag lokal bei 225.7 m. Der relative Fehler betrug somit 2.1 %. Es wird geschlussfolgert, dass das NNBR-Modell in der Lage ist, die Höhe der WCFZ zuverlässig vorherzusagen. Es scheint, dass diese Methode für die Berechnung einer sicheren Wasserkontrollhöhe über mechanisierten Kohlebergwerken in den sehr mächtigen Jura-Kohleflözen Westchinas verwendet werden kann.
Resumen
En los últimos años, la minería del carbón en China se ha centrado en el oeste del país, que tiene un entorno ecológico frágil. El carbón jurásico de esta zona está enterrado a poca profundidad y en capas muy gruesas. En la actualidad, los dos problemas principales son la irrupción de las aguas subterráneas y la alteración de los suministros de aguas superficiales poco profundas provocada por la minería. La predicción con exactitud de la altura de la zona fracturada conductora de agua (WCFZ) es la clave para prevenir los daños del agua en el techo y lograr la conservación del agua en esta zona minera. Se estableció un modelo de regresión de vecinos más cercanos (NNBR) para predecir la altura de la WCFZ para la cara de trabajo 117 de la mina de carbón de Jinjitan, en el oeste de China, que utiliza minería de tajo largo de espeleología de carbón superior totalmente mecanizada. El modelo se verificó a partir de las alturas medidas de la WCFZ (30 grupos de datos medidos) utilizando el espesor real de la mina (> 8 m) y la anchura del frente de trabajo como factores de predicción. El error medio de la predicción del modelo fue de 1,5 m y el porcentaje medio de error absoluto fue del 13,6%, lo cual fue mejor que el resultado predicho utilizando la fórmula empírica convencional establecida. El modelo se mejoró aplicando un factor de seguridad de 1,3, que cumplía los requisitos de fiabilidad del 96,7%. La altura de la WCFZ de la cara de trabajo 117 se predijo utilizando este modelo y el valor predicho se comparó con los valores medidos por la monitorización de la fibra óptica y las simples observaciones hidrológicas. La altura de la WCFZ medida por fibra óptica fue de 184,8 m mientras que el valor predicho fue de 196,0 m; el error relativo de esa predicción fue del 6,0%. El valor observado hidrológicamente fue de 221,0 m mientras que el valor predicho para ese lugar fue de 225,7 m; el error relativo fue del 2,1%. Por lo tanto, el modelo NNBR es capaz de predecir de forma fiable la altura de la WCFZ y parece que puede utilizarse para calcular la altura de control de agua segura por encima de las minas de carbón mecanizadas en la parte superior de los filones de carbón jurásicos del oeste de China.
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References
Adhikary DP, Guo H (2015) Modelling of longwall mining-induced strata permeability change. Rock Mech Rock Eng 48(1):345–359. https://doi.org/10.1007/s00603-014-0551-7
Bi YS, Wu JW, Zhai XR, Huang K (2022) A prediction model for the height of the water-conducting fractured zone in the roof of coal mines based on factor analysis and RBF neural network. Arab J Geosci 15:241. https://doi.org/10.1007/s12517-022-09523-3
Chen WC, Li WP, Yang Z, Wang QQ (2021) Analysis of mining-induced variation of the water table and potential benefits for ecological vegetation: a case study of Jinjitan coal mine in Yushenfu mining area. China Hydrogeol J 29(4):1629–1645. https://doi.org/10.1007/s10040-021-02325-z
Fan H, Wang LG, Lu YL, Li ZL, Li WS, Wang K (2020) Height of water-conducting fractured zone in a coal seam overlain by thin bedrock and thick clay layer: a case study from the Sanyuan coal mine in north China. Environ Earth Sci. https://doi.org/10.1007/s12665-020-8873-0
Guo CF, Yang Z, Li S, Lou JF (2020) Predicting the water-conducting fracture zone (WCFZ) height using an MPGA-SVR approach. Sustainability 12(5):1809. https://doi.org/10.3390/su12051809
Hu XJ, Li WP, Cao DT, Liu MC (2012) Index of multiple factors and expected height of fully mechanized water flowing fractured zone. J China Coal Soc 37(04):613–620. https://doi.org/10.13225/j.cnki.jccs.2012.04.026. (in Chinese)
Hu YB, Li WP, Wang QQ, Liu SL, Wang ZK (2019) Evolution of floor water inrush from a structural fractured zone with confined water. Mine Water Environ 38(2):252–260. https://doi.org/10.1007/s10230-019-00599-0
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(7):1162–1174. https://doi.org/10.1016/j.ijrmms.2009.02.005
Kersey AD (2018) Leveraging three decades of fiber Bragg grating sensing technology. Laser Focus World 54(8):30–34
Lai XP, Liu BW, Shan PF, Cui F, Zhang Y, Zhang XD, Bai R, Wu X (2021) Study on the predictionof the height of two zones in the overlying strata under a strong shock. Geofluids. https://doi.org/10.1155/2021/4237061
Lei S, Bian Z, Daniels JL, He X (2010) Spatio-temporal variation of vegetation in an arid and vulnerable coal mining region. Min Sci Technol (china) 20(3):485–490. https://doi.org/10.1016/s1674-5264(09)60230-1
Liu Y, Yuan SC, Yang BB, Liu JW, Ye ZY (2019) Predicting the height of the water-conducting fractured zone using multiple regression analysis and GIS. Environ Earth Sci. https://doi.org/10.1007/s12665-019-8429-3
Liu JH, Zhao YL, Tan T, Zhang LY, Zhu ST, Xu FY (2022) Evolution and modeling of mine water inflow and hazard characteristics in southern coalfields of China: a case of Meitanba mine. I Nt J MinSci Technol. https://doi.org/10.1016/j.ijmst.2022.04.001
Lou GZ, Tan Y (2021) Prediction of the height of water flowing fractured zone based on PSO-BP neural network. Coal Geol Explor 49(04):198–204. https://doi.org/10.3969/j.issn.1001-1986.2021.04.024. (in Chinese)
Majdi A, Hassani FP, Nasiri MY (2012) Prediction of the height of destressed zone above the mined panel roof in longwall coal mining. Int J Coal Geol 98:62–72. https://doi.org/10.1016/j.coal.2012.04.005
Miao XX, Cui XM, Wang JA, Xu JL (2011) The height of fractured water-conducting zone in undermined rock strata. Eng Geol 120(1–4):32–39. https://doi.org/10.1016/j.enggeo.2011.03.009
Rana JC, Singh A, Sharma Y, Pradheep K, Mendiratta N (2010) Dynamics of plant bio resources in Western Himalayan region of India - watershed based study. Current Sci 98(2):192–203
Rui G, Hao Y, Feng J, Mei XC, Wang XL (2018) Influential factors and control of water inrush in a coal seam as the main aquifer. Int J Min Sci Technol 28(2):187–193. https://doi.org/10.1016/j.ijmst.2017.12.017
Shi XC, Zhang JX (2021) Characteristics of overburden failure and fracture evolution in shallow buried working face with large mining height. Sustainability 13(24):13775. https://doi.org/10.3390/su132413775
Wang XL, Li H (2022) Failure height and fracture evolution pattern of overburden rock in fully mechanized cave mining. Arabian J Geosci 15:443. https://doi.org/10.1007/s12517-022-09705-z
Wang WS, Xiang HL, Ding J (2001a) Predication of hydrology and water resources with Nearest Neighbor Bootstrapping Regressive Model. Int J Hydroelect Energy 2:8–10 (in Chinese)
Wang WS, Yuan P, Ding J (2001b) Application of nearest neighbor bootstrap regressive model in predication of water environment. China Environ Sci 04:80–83 (in Chinese)
Wang BJ, Li K, Shi B, Wei GQ (2009) Test on application of distributed fiber optic sensing technique into soil slope monitoring. Landslides 6(1):61–68. https://doi.org/10.1007/s10346-008-0139-y
Wang QQ, Li WP, Chen W, Bai HY (2015) GIS-based assessment of landslide susceptibility using certainty factor and index of entropy models for the Qianyang County of Baoji city. China J Earth Syst Sci 124(7):1399–1415. https://doi.org/10.1007/s12040-015-0624-3
Wang QQ, Li WP, Li T, Li XQ, Liu SL (2018) Goaf water storage and utilization in arid regions of northwest China: a case study of Shennan coal mine district. J Clean Prod 202:33–44. https://doi.org/10.1016/j.jclepro.2018.08.123
Wang F, Xu JL, Chen SJ, Ren MZ (2019) Method to predict the height of the water conducting fractured zone based on bearing structures in the overlying strata. Mine Water Environ 38(4):767–779. https://doi.org/10.1007/s10230-019-00638-w
Wang ZK, Li WP, Wang QQ, Hu YB, Du JF (2021) Monitoring the dynamic response of the overlying rock-soil composite structure to underground mining using BOTDR and FBG sensing technologies. Rock Mech Rock Eng 54(9):5095–5116. https://doi.org/10.1007/s00603-021-02530-y
Wu ZS, Xu B, Takahashi T, Harada T (2008) Performance of a BOTDR optical fibre sensing technique for crack detection in concrete structures. Struct Infrastruct Eng 4(4):311–323. https://doi.org/10.1080/15732470600899346
Xu SY, Zhang YB, Shi H (2018) Advances in the height of fractured water-conducting zone of mining overburden. Sci Technol Eng 18(34):139–148 (in Chinese)
Xue JK, Wang H, Zhao CH, Yang J, Zhou ZF, Li DB (2020) Prediction of the height of water-conducting fracture zone and water-filliing model of roof aquifer in Jurassic coalfield in Ordos Basin. J Min Saf Eng 37(06):1222–1230. https://doi.org/10.13545/j.cnki.jmse.2020.06.017. (in Chinese)
Yan HS (1998) Nonlinear statistical forecasting method and its application. Yunnan Science and Technology Press, Kunming (in Chinese)
Yang P, Yang WF, Nie YX, Saleem F, Lu F, Ma RK, Li RP (2021) Predicting the height of the water-conducting fractured zone based on a multiple regression model and information entropy in the northern Ordos Basin, China. Mine Water Environ. https://doi.org/10.1007/s10230-021-00805-y
Zhang J, Wang JP (2014) Similar simulation and practical research on the mining overburden roof strata “three zones” height. J Min Saf Eng 31(02):249–254. https://doi.org/10.13545/j.issn1673-3363.2014.02.014. (in Chinese)
Zhu TG, Li WP, Wang QQ, Hu YB, Fan KF, Du JF (2020) Study on the height of the mining-induced water-conducting fracture zone under the Q(2l) loess cover of the Jurassic coal seam in northern Shaanxi. China Mine Water Environ 39(1):57–67. https://doi.org/10.1007/s10230-020-00656-z
Acknowledgements
The authors express their gratitude to everyone that provided assistance for the present study. The study was jointly supported by the National Natural Science Foundation of China (Grant 42007240) and the Natural Science Foundation of Jiangsu Province (BK20190646).
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Han, Y., Wang, Q., Li, W. et al. Predicting the Height of the Water-Conducting Fractured Zone in Fully Mechanized Top Coal Caving Longwall Mining of Very Thick Jurassic Coal Seams in Western China Based on the NNBR Model. Mine Water Environ 42, 121–133 (2023). https://doi.org/10.1007/s10230-023-00918-6
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DOI: https://doi.org/10.1007/s10230-023-00918-6