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Geomechanics and Engineering
  Volume 22, Number 2, July25 2020, pages 133-142
DOI: http://dx.doi.org/10.12989/gae.2020.22.2.133
 


Case study of the mining-induced stress and fracture network evolution in longwall top coal caving
Cong Li, Jing Xie, Zhiqiang He, Guangdi Deng, Bengao Yang and Mingqing Yang

 
Abstract
    The evolution of the mining-induced fracture network formed during longwall top coal caving (LTCC) has a great influence on the gas drainage, roof control, top coal recovery ratio and engineering safety of aquifers. To reveal the evolution of the mining-induced stress and fracture network formed during LTCC, the fracture network in front of the working face was observed by borehole video experiments. A discrete element model was established by the universal discrete element code (UDEC) to explore the local stress distribution. The regression relationship between the fractal dimension of the fracture network and mining stress was established. The results revealed the following: (1) The mining disturbance had the most severe impact on the borehole depth range between approximately 10 m and 25 m. (2) The distribution of fractures was related to the lithology and its integrity. The coal seam was mainly microfractures, which formed a complex fracture network. The hard rock stratum was mainly included longitudinal cracks and separated fissures. (3) Through a numerical simulation, the stress distribution in front of the mining face and the development of the fracturing of the overlying rock were obtained. There was a quadratic relationship between the fractal dimension of the fractures and the mining stress. The results obtained herein will provide a reference for engineering projects under similar geological conditions.
 
Key Words
    longwall top coal caving; fracture network; mining-induced stress; fractal dimension; fracture connectivity
 
Address
Cong Li, Jing Xie, Zhiqiang He, Guangdi Deng, Bengao Yang and Mingqing Yang: 1.) State Key Laboratory of Hydraulics and Mountain River Engineering,
College of Water Resource and Hydropower, Sichuan University, Chengdu, 610065, China
2.) MOE Key Laboratory of Deep Underground Science and Engineering, Sichuan University, Chengdu 610065, China
 

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