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Fracture Characteristics of Overlying Bedrock and Clay Aquiclude Subjected to Shallow Coal Seam Mining

  • Zhiguo Liu
  • Zhenli Fan
  • Yujun Zhang
Technical Article

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.

Keywords

Water hazard Mining disturbance Fracture evolution Water-conducting fractured zone 

Klüftungscharakteristik von Hangendgestein und Tongrundwasserstauer unter dem Einfluss von oberflächennahem Kohlenflözbergbau

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.

Características de la fractura del lecho rocoso suprayacente y del acuicludo de arcilla sometido a la explotación de minas de carbón poco profundas

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.

浅埋煤层开采时上覆基岩和泥质隔水层的裂隙特征

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。

Notes

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.

Supplementary material

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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Coal Mining and Designing BranchChina Coal Research InstituteBeijingChina
  2. 2.Coal Ming and Designing DepartmentTiandi Science & Technology Co., LtdBeijingChina

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