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
By turning to the theory of elastic thin plates, a mechanical model of the main roof breaking for severely inclined seam under long wall working was esbalished, in which formulaes were deduced for the calculation of t...By turning to the theory of elastic thin plates, a mechanical model of the main roof breaking for severely inclined seam under long wall working was esbalished, in which formulaes were deduced for the calculation of the stress distribution. When the main roof stress distribution was characterized, the failure form of the roof in the long wall coal seam under work was given with the failure criterion deduced. The deduced failure criterion was then applied to the No.3232（3） face of the Li- zuizi Coal Mine; the first pressure for the working face was accurately predicted. Results of the field application show that the main roof of the severely inclined coal seam under long wall working breaks in the O-X pattern, which is basically in accor- dance with the reality.展开更多
In order to enter effective parameters of rock mass in a numerical model,the relationships between mechanical parameters of rock and rock mass were obtained by an inversion method and an orthogonal test,given our meas...In order to enter effective parameters of rock mass in a numerical model,the relationships between mechanical parameters of rock and rock mass were obtained by an inversion method and an orthogonal test,given our measurements of the maximum heights of two failure zones in the Longdong coal mine. Using the maximum heights of the caving zone and the water-conducting fractured zone as test indices the modulus of elasticity,the Poisson ratio,cohesion and tension strength as test factors and different values of reduction enhancement factors as test levels,an orthogonal test was designed to obtain an optimum simulation scheme.From the analysis of different values of reduction enhancement factors which affect the test indices,an optimum factor combination for modification of parameters could be inferred.By using modified parameters in our numerical simulation,the maximum heights of the caving zone and the water-conducting fractured zone in the extensive Xiyi area were determined as 15.06 m and 36.92 m.These values were almost the same as those obtained by similar material simulation（8.5 m and 37.0 m）and empirical prediction（8.4 m and 34.4 m）.These results indicate that the modification of parameters is a rational method.展开更多
Based on the mechanical experiment of brittle coal-rock and the damage mechanical theory, a damage model was established. Coal-Rock damage mechanical characteristic was researched. Furthermore, interior energy transfo...Based on the mechanical experiment of brittle coal-rock and the damage mechanical theory, a damage model was established. Coal-Rock damage mechanical characteristic was researched. Furthermore, interior energy transformation mechanism of rock was analyzed from the point of view of damage mechanics and damage energy release rate of brittle coal rock was derived. By analyzing the energy transformation of rock burst, a new conception, damage energy index of rock burst, was put forward. The condition of rock burst was also established.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Supported by the National Natural Science Foundation of China （51074005, 51004004, 51074003）
文摘By turning to the theory of elastic thin plates, a mechanical model of the main roof breaking for severely inclined seam under long wall working was esbalished, in which formulaes were deduced for the calculation of the stress distribution. When the main roof stress distribution was characterized, the failure form of the roof in the long wall coal seam under work was given with the failure criterion deduced. The deduced failure criterion was then applied to the No.3232（3） face of the Li- zuizi Coal Mine; the first pressure for the working face was accurately predicted. Results of the field application show that the main roof of the severely inclined coal seam under long wall working breaks in the O-X pattern, which is basically in accor- dance with the reality.
文摘In order to enter effective parameters of rock mass in a numerical model,the relationships between mechanical parameters of rock and rock mass were obtained by an inversion method and an orthogonal test,given our measurements of the maximum heights of two failure zones in the Longdong coal mine. Using the maximum heights of the caving zone and the water-conducting fractured zone as test indices the modulus of elasticity,the Poisson ratio,cohesion and tension strength as test factors and different values of reduction enhancement factors as test levels,an orthogonal test was designed to obtain an optimum simulation scheme.From the analysis of different values of reduction enhancement factors which affect the test indices,an optimum factor combination for modification of parameters could be inferred.By using modified parameters in our numerical simulation,the maximum heights of the caving zone and the water-conducting fractured zone in the extensive Xiyi area were determined as 15.06 m and 36.92 m.These values were almost the same as those obtained by similar material simulation（8.5 m and 37.0 m）and empirical prediction（8.4 m and 34.4 m）.These results indicate that the modification of parameters is a rational method.
基金Doctoral fund of ministry of education,China(2 0 0 0 0 61115 ) the teaching and research award program for outstandingyoung teachers in higher education institutions of MOE,P.R.C.,(TRAPOYT)
文摘Based on the mechanical experiment of brittle coal-rock and the damage mechanical theory, a damage model was established. Coal-Rock damage mechanical characteristic was researched. Furthermore, interior energy transformation mechanism of rock was analyzed from the point of view of damage mechanics and damage energy release rate of brittle coal rock was derived. By analyzing the energy transformation of rock burst, a new conception, damage energy index of rock burst, was put forward. The condition of rock burst was also established.
