According to geological conditions of No. 3 and No. 4 coal seams （namely A3 and B4） of the Pan＇er coal mine and the parameters of panels 11223, 11224, and 11124 with fully-mechanical coal mining, we built 2D simila...According to geological conditions of No. 3 and No. 4 coal seams （namely A3 and B4） of the Pan＇er coal mine and the parameters of panels 11223, 11224, and 11124 with fully-mechanical coal mining, we built 2D similar material simulation and FLAC3D numerical simulation models to investigate the development of mining-induced stress and the extraction effect of pressure-relief gas with large height and upward mining. Based on a comprehensive analysis of experimental data and observations, we obtained the deformation and breakage characteristics of strata overlying the coal seam, the development patterns of the mining-induced stress and fracture, and the size of the stress-relief area. The stress-relief effect was investigated and analyzed in consideration with mining height and three thick hard strata. Because of the group of three hard thick strata located in the main roof and the residual stress of mined panel 11124, the deformation, breakage, mining-induced stress and fracture development, and the stress-relief coefficient were discontinuous and asymmetrical. The breakage angle of the overlying strata, and the compressive and expansive zones of coal deformation were mainly controlled by the number, thickness, and strength of the hard stratum. Compared with the value of breakage angle derived by the traditional empirical method, the experimental value was lower than the traditional results by 3°-4°below the hard thick strata group, and by 13°-19° above the hard thick strata group. The amount of gas extracted from floor drainage roadway of B4 over 17 months was variable and the amount of gas per month differed considerably, being much smaller when panel 11223 influenced the area of the three hard thick strata. Generally, the stress-relief zone of No. 4 coal seam was small under the influence of the hard thick strata located in the main roof, which played an important role in delaying the breakage time and increasing the breakage space. In this study we gained understanding of the stress-relief mechanism influenced by the hard thick roof. The research results and engineering practice show that the main roof of the multiple hard thick strata is a critical factor in the design of panel layout and roadways for integrated coal exploitation and gas extraction, provides a theoretical basis for safe and high-efficient mining of coal resources.展开更多
Based on the boundary support conditions of overlying high-position,hard and thick strata,a Winkler foundation beam mechanical model was built.Computational expressions for the characteristics and position of the bend...Based on the boundary support conditions of overlying high-position,hard and thick strata,a Winkler foundation beam mechanical model was built.Computational expressions for the characteristics and position of the bending moment for high-position,hard and thick strata were constructed by theoretical analysis,and the initial breaking position of high-position,hard and thick strata was also analyzed.The breaking process and evolution law of mining stress in high-position,hard and thick strata were studied by similar material simulation tests.Studies show that:due to the foundation deformation effect of the lower strata,the initial break position in high-position,hard thick layers is in the middle of goaf;vertical tension fractures first occur under the middle surface,then tilt tension fractures form at both sides and a non-uniform thickness of the fracture structure forms and produces subsidence deformation;behind the coal wall tilt fractures extend and eventually complete the migration.Mining stress produces obvious changes before and after the breakage of the high,hard and thick stratum;high stress concentration forms in front of the coal wall before breakage and fracture stress concentration significantly reduces after migration.Coal seam mining under high-position,hard thick strata can easily induce dynamic phenomena.展开更多
基金Acknowledgments This work is supported by the National Nature Science Foundation of China （51374011）.
文摘According to geological conditions of No. 3 and No. 4 coal seams （namely A3 and B4） of the Pan＇er coal mine and the parameters of panels 11223, 11224, and 11124 with fully-mechanical coal mining, we built 2D similar material simulation and FLAC3D numerical simulation models to investigate the development of mining-induced stress and the extraction effect of pressure-relief gas with large height and upward mining. Based on a comprehensive analysis of experimental data and observations, we obtained the deformation and breakage characteristics of strata overlying the coal seam, the development patterns of the mining-induced stress and fracture, and the size of the stress-relief area. The stress-relief effect was investigated and analyzed in consideration with mining height and three thick hard strata. Because of the group of three hard thick strata located in the main roof and the residual stress of mined panel 11124, the deformation, breakage, mining-induced stress and fracture development, and the stress-relief coefficient were discontinuous and asymmetrical. The breakage angle of the overlying strata, and the compressive and expansive zones of coal deformation were mainly controlled by the number, thickness, and strength of the hard stratum. Compared with the value of breakage angle derived by the traditional empirical method, the experimental value was lower than the traditional results by 3°-4°below the hard thick strata group, and by 13°-19° above the hard thick strata group. The amount of gas extracted from floor drainage roadway of B4 over 17 months was variable and the amount of gas per month differed considerably, being much smaller when panel 11223 influenced the area of the three hard thick strata. Generally, the stress-relief zone of No. 4 coal seam was small under the influence of the hard thick strata located in the main roof, which played an important role in delaying the breakage time and increasing the breakage space. In this study we gained understanding of the stress-relief mechanism influenced by the hard thick roof. The research results and engineering practice show that the main roof of the multiple hard thick strata is a critical factor in the design of panel layout and roadways for integrated coal exploitation and gas extraction, provides a theoretical basis for safe and high-efficient mining of coal resources.
基金financially supported by the National Natural Science Foundation of China (No.51374139)the Natural Science Foundation of Shandong Province (No.ZR2013EEM018)the Scientific Research Innovation Team Support Plan of Shandong University of Science and Technology
文摘Based on the boundary support conditions of overlying high-position,hard and thick strata,a Winkler foundation beam mechanical model was built.Computational expressions for the characteristics and position of the bending moment for high-position,hard and thick strata were constructed by theoretical analysis,and the initial breaking position of high-position,hard and thick strata was also analyzed.The breaking process and evolution law of mining stress in high-position,hard and thick strata were studied by similar material simulation tests.Studies show that:due to the foundation deformation effect of the lower strata,the initial break position in high-position,hard thick layers is in the middle of goaf;vertical tension fractures first occur under the middle surface,then tilt tension fractures form at both sides and a non-uniform thickness of the fracture structure forms and produces subsidence deformation;behind the coal wall tilt fractures extend and eventually complete the migration.Mining stress produces obvious changes before and after the breakage of the high,hard and thick stratum;high stress concentration forms in front of the coal wall before breakage and fracture stress concentration significantly reduces after migration.Coal seam mining under high-position,hard thick strata can easily induce dynamic phenomena.
