Coal (Rock) pillar retaining in the mining of protective layer would cause gas dynamic disaster in the protected layer. Based on the gas geological conditions of the two-layer coal seam in Jinhe Coal Mine of Yaojie Mining District, the stress evolution law of coal seam in the rock pillar affected area was studied by theoretical analysis and numerical simulation, and the crack development law of coal seam in different loading stages under conventional triaxial loading was studied by CT scanning technology. With the analysis of the stress evolution and crack development of coal in rock pillar affected area, the gas extraction effect under different stress states and the gas desorption law after pressure relief antireflection were studied on site. The results showed that the stress of coal in the rock pillar affected area is in the approximate elastic stage of the conventional triaxial stress-strain curve, and the cracks of coal are mainly closed at this stage. Meanwhile, the increase of stress leaded to the decrease of coal permeability and the poor gas extraction effect. CT scanning tests under conventional triaxial loading were carried out in the laboratory, and three-dimensional visual models of coal sample cracks were constructed at different loading stages. When loading to the linear elastic stage, the crack volume and surface area were reduced by 74% and 71% compared with the ones in initial state. At the same time, the expression between stress σ and crack density T was further established. After comprehensive control measures such as intensive drilling discharge, presplitting blasting and coal water injection were taken to the coal in rock pillar affected area, the crack density T could reach the crack development level of the conventional triaxial loading softening stage, realizing the crack development of the coal under low stress. The enclosed gas in front of the coal could desorption flow during the roadway driving. And the predict index value K also decreased from 0.57 mL/(g·min) to 0.17 mL/(g·min) continuously. The safety of coal roadway in rock pillar affected area was realized, and the accuracy of numerical simulation and laboratory test results was verified, which had certain reference significance for coal roadway excavation under this similar conditions.
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http://dx.doi.org/10.1038/s41598-024-76612-6 | DOI Listing |
Sci Rep
January 2025
School of Mines, Jiangsu Engineering Laboratory of Mine Earthquake Monitoring and Prevention, China University of Mining and Technology, Xuzhou, 221116, China.
Aiming at the problems of complex stress and large deformations in the surrounding rocks of the roadway driven under the goafs of small collieries and heading for adjacent advancing coal face, by numerical modeling and field practice, the failure characteristics of the overlying coal and rocks were investigated, and the stopping and resuming times of the roadway excavation were identified. A zoning-based reinforcement technique was put forward and applied in engineering practice. The results showed that (1) The roadway roof was divided into four zones: "Rolid coal zone", "Residual pillar zone", "Roof caved zone", and "Roof un-caved zone".
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December 2024
College of Energy Engineering, Xi'an University of Science and Technology, Xi'an, 710054, China.
Affected by weakening effect of water in the goaf, the bearing capacity of coal pillar reduced, and coal pillar rock burst is prone to occur, which is a serious threat to mine safety in production. In order to study the equivalent width and stability of coal pillar in water-rich coal seam, taking the section coal pillar of a working face as the research object, combined with laboratory test, theoretical analysis, simulation and engineering practice, the stress, elastic core area width, damage degree and energy accumulation of 36 m water-immersed coal pillar and 26 m, 28 m, 30 m, 32 m, 36 m unimmersed coal pillars are analyzed. The research results show that: (1) The reasonable width of coal pillar under flooded and unflooded conditions is 36.
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December 2024
School of Environmental Science, Liaoning University, Shenyang, 110036, China.
In response to the frequent occurrence of high-energy microseismic events in coal mines in China, a back propagation neural network (BPNN) prediction model based on surface subsidence data has been proposed to provide a basis for safely and efficiently predicting coal mine disasters. Theoretical research on the relationship between surface displacement, mining disturbance, and high-energy microseismic event levels has demonstrated a significant correlation among these factors. When there is a sudden increase or decrease in surface displacement or mining disturbance, the advancing working face typically exhibits dynamic characteristics.
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November 2024
College of Emergency Management, Nanjing Tech University, Nanjing, 211816, China.
Sci Rep
November 2024
School of Resource and Environment and Safety Engineering, Hunan University of Science and Technology, Xiangtan, 411201, Hunan, China.
Deep close distance coal seam mining is affected by the goaf of upper coal and remaining coal pillar, and the roadway of lower coal is difficult to maintain stability. By means of theoretical analysis, physical simulation test and numerical simulation, this paper analyzes the failure characteristics of roadway in deep close distance coal seam and the evolution law of stress field, and optimizes the reasonable layout of lower coal roadway. The results show that: (1) The analytical formula of the evolution of the floor principal stress difference with depth is derived theoretically, and the distribution law of the shear stress of the rock mass in the floor of the coal seam is obtained.
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