Fracture structure of the overburden in the layered mining of extremely thick coal seams: Developmental patterns of caving zones and hydraulically conductive fracture zones and fracture characteristics

Authors

ZHANG Xin, Shandong Energy Group South America Co., Ltd., Qingdao 266000, ChinaFollow
CHEN Youkuo, Shandong Energy Group Construction Group Co., Ltd., Jining 273500, China
MENG Hailun, Shandong Energy Group Construction Group Co., Ltd., Jining 273500, China
QIN Qifa, Shandong Energy Group Construction Group Co., Ltd., Jining 273500, China
CHENG Xianggang, School of Resources and Geosciences, China University of Mining and Technology, Xuzhou 221116, ChinaFollow
HUANG Rongjie, School of Resources and Geosciences, China University of Mining and Technology, Xuzhou 221116, China
DONG Hairui, Shandong Energy Group Construction Group Co., Ltd., Jining 273500, China
SUN Wenbin, School of Resources and Geosciences, China University of Mining and Technology, Xuzhou 221116, China; Beijing Tanchuang Resources Technology Co., Ltd., Jining 272000, China
QIAO Wei, School of Resources and Geosciences, China University of Mining and Technology, Xuzhou 221116, China

Abstract

Objective The Zhunnan Coalfield, a coalfield on the southern margin of the Junggar Basin in Xinjiang, boasts abundant coal resources. However, water hazards in mines severely constrain the safe and efficient coal production in the coalfield. Since hydraulically conductive fractures in roofs serve as primary hydraulically conductive channels formed in the mining of the mining face, it is particularly crucial to investigate the developmental patterns of these fractures during the layered mining of extremely thick coal seams. Methods This study explored the (9-15)08 mining face of the Liuhuanggou Coal Mine in Xinjiang. Using ground exploration holes and borehole televiewers, this study examined the developmental characteristics of the caving zone and hydraulically conductive fracture zones in the overburden under different mining conditions. Through numerical simulations, this study delved into the developmental patterns of hydraulically conductive fracture zones in the descending mining of multiple coal seams, analyzed the migration and fracture characteristics of the overburden in the layered mining of extremely thick coal seams, and explored the patterns of the fracture structural of the overburden. Results and Conclusion The results indicate that the layered mining of extremely thick coal seams somewhat inhibits the development of hydraulically conductive fracture zones. Due to the increase in the number of layers, the degree of overburden damage gradually intensifies, its mechanical properties decrease, and cracks increase. As a result, the overburden exhibits the characteristics of weak layers, thereby inhibiting the upward development of hydraulically conductive fracture zones. Under the layered mining of extremely thick coal seams, the fracture structure of the overburden generally presents a macro-large-small pattern. Macroscopically, the fracture structure displays a pressure arch structure within the mining influence range. Additionally, because of the caving and hinge of rock masses in high- and low-lying strata, the high- lying overburden exhibits a large beam structure. In contrast, the low-lying rock masses are subjected to the superimposed effects of layered mining, and the hinge points of the rock masses within the caving zones are connected to form an overall continuous M-shaped pattern. Consequently, the low-lying rock masses emerge as small M-shaped hinge structures. The findings of this study will provide a theoretical basis and guidance for research into the formation mechanisms of accidents, as well as disaster prevention and control, on the mining sites of extremely thick coal seams.

Keywords

extremely thick coal seam, layered mining, hydraulically conductive fracture zone, fracture structure, Zhunnan Coalfield in Xinjiang

DOI

10.12363/issn.1001-1986.24.05.0290

Recommended Citation

ZHANG Xin, CHEN Youkuo, MENG Hailun, et al. (2024) "Fracture structure of the overburden in the layered mining of extremely thick coal seams: Developmental patterns of caving zones and hydraulically conductive fracture zones and fracture characteristics," Coal Geology & Exploration: Vol. 52: Iss. 12, Article 11.
DOI: 10.12363/issn.1001-1986.24.05.0290
Available at: https://cge.researchcommons.org/journal/vol52/iss12/11

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