Physical model experiment and numerical analysis on innovative gob-side entry retaining with thick and hard roofs
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ORIGINAL PAPER
Physical model experiment and numerical analysis on innovative gob-side entry retaining with thick and hard roofs Xiaoming Sun 1,2 & Chengwei Zhao 1,2 & Gan Li 1,2 & Bo Zhang 1,2 & Junwei Wang 1,2 & Feng Cai 3 Received: 27 August 2019 / Accepted: 1 November 2020 / Published online: 21 November 2020 # Saudi Society for Geosciences 2020
Abstract Gob-side entry retaining is a common method in underground coal mining. Conventional gob-side entry retaining (CGER) always causes stress concentration and large deformation around roadways under the condition of thick and hard sandstone roofs. Thus, an innovative method of no pillar gob-side entry retaining (NPGER) in longwall mining is proposed in this paper. First, a physical model was established to explore the mechanism of the new method. The modeling results indicate that the progressive caving of the strata in the middle of the stope is consistent with CGER. The major difference between NPGER and CGER is that CGER collapsed with a structure of a long arm beam, but NPGER collapsed with a structure of a short arm beam near the roadway. In the end, a new roadway with a gangue rib was formed when the immediate roof and main roof slipped along the precutting plane. Subsequently, the numerical simulation software Universal Distinct Element Code (UDEC) was adopted to establish the numerical model of the 8501 working face in Tangshangou coal mine. The NPGER process is simulated. The evolution of the roof structure and stress characteristics were clearly demonstrated. The results showed that the roof structure noticeably changed from a long beam to a short beam after roof fracturing. The retained roadway was under low stress conditions, and the stress was transferred to the deep rock. In the end, the NPGER method was applied in the field, and the results showed that the retained roadway could meet the requirements of the next working face, which may provide guidance for longwall mining with thick and hard roofs. Keywords Physical model experiment . Numerical simulation . Conventional gob-side entry retaining . No pillar gob-side entry retaining . Roof structure . Short arm beam
Introduction Gob-side entry retaining is a common mining method in coal mining. In the conventional gob-side entry retaining (CGER) method, the entry of the current mining working face will be retained to be reused for the next working face by constructing Responsible Editor: Murat Karakus * Xiaoming Sun [email protected] 1
State Key Laboratory for Geomechanics & Deep Underground Engineering, China University of Mining & Technology, Beijing 100083, China
2
School of Mechanics and Civil Engineering, China University of Mining & Technology, Beijing 100083, China
3
Centre for Technology Management, China National Coal Group CO., Ltd., Beijing 100120, China
an artificial wall along the gob side. This method not only reduces the work of excavating roadways but also increases coal-recovery rates. Therefore, CGER is an efficient technique (Luan et al. 2018; Li et al. 2018; He et al. 20
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