Fully mechanized mining(FMM)technology has been applied in Chinese coal mines for more than 40 years.At present,the output of a FMM face has reached 10-million tons with Chinese-made equipment.In this study,the new de...Fully mechanized mining(FMM)technology has been applied in Chinese coal mines for more than 40 years.At present,the output of a FMM face has reached 10-million tons with Chinese-made equipment.In this study,the new developments in FMM technology and equipment in Chinese coal mines during past decades are introduced.The automatic FMM technology for thin seams,complete sets of FMM technology with ultra large shear height of 7 m for thick seams,complete sets of fully mechanized top coal caving technology with large shear height for ultra-thick seams of 20 m,complete sets of FMM technology for complex and difficult seams,including steeply inclined seams,soft coal seams with large inclination angle,and the mechanized filling mining technology and equipment are presented.Some typical case studies are also introduced.Finally,the existing problems with the FMM technology are discussed,and prospect of FMM technology and equipment applied in Chinese coal mines is put forward.展开更多
Simultaneous extraction of the coal and gas is an effective method of eliminating coal mine gas disasters while safely exploiting the coal and achieving efficient gas drainage in China, which is widely accepted by the...Simultaneous extraction of the coal and gas is an effective method of eliminating coal mine gas disasters while safely exploiting the coal and achieving efficient gas drainage in China, which is widely accepted by the main coal-producing countries around the world. However, the concrete definition of simultaneous extraction is vague and there is little accurate theoretical support for the simultaneous extraction of coal and gas, which makes it difficult to determine an efficient gas drainage method appropriate to the features of coal seams. Based on theoretical analysis, laboratory tests and field observations, a specific definition of simultaneous extraction of coal and gas is proposed after analyzing the characteristics of coal seam occurrences in China, and we developed the mechanism of mining-enhanced permeability and established the corresponding theoretical model. This comprises a process of fracture network formation, in which the original fractures are opened and new fractures are produced by unloading damage. According to the theoretical model, the engineering approaches and their quantitative parameters of ＇unloading by borehole drilling＇ for single coal seams and ＇unloading by protective seam mining＇ for groups of coal seams are proposed, and the construction principles for coal exploitation and gas-drainage systems for different conditions are given. These methods were applied successfully in the Tunlan Coal Mine in Shanxi Province and the Panyi Coal Mine in Anhui Province and could assure safe and efficient simultaneous extraction of coal and gas in these outburst coal mines.展开更多
In multiple seams mining, the seam with relatively low gas content （protective seam） is often extracted prior to mining its overlying and/or underlying seams of high gas content and low permeability to minimize the ...In multiple seams mining, the seam with relatively low gas content （protective seam） is often extracted prior to mining its overlying and/or underlying seams of high gas content and low permeability to minimize the risk of high gas emission and outbursts of coal and gas. A key to success with this mining sequence is to gain a detailed understanding of the movement and fracture evolution of the overlying and underlying strata after the protective seam in extracted. In Zhuji mine, the No. 11-2 seam is extracted as a protective seam with the pillarless mining method by retaining goal-side roadways prior to its overlying No. 13-1 seam. An investigation has been undertaken in the panel 1111 （1） of Zhuji mine to physically simulate the movement and fracture evolution of the overlying strata alter the No. 1 I-2 seam is extracted. In the physical simulation, the displacement, strain, and deformation and failure process of the model for simulation were acquired with various means such as grating displacement meter, strain gauges, and digital photography. The simulation result shows that： （1） Initial caving interval of the immediate roof was 21.6 m, the first weighting interval was 23.5-37.3 m with the average interval of 33.5 m, and the periodic weighting interval of the main roof was in a range of 8.2-20.55 m and averaged at 15.2 m. （2） The maximum height of the caving zone after the extraction of No. 11-2 seam was 8.0 m, which was 4 times of the seam mining height and the internal strata of the caving zone collapsed irregularly. The mining-induced fractures developed 8-30 m above the mined No. 11-2 seam, which was 7.525 times of the seam mining height, the fracture zone was about 65° upward from the seam open-off cut toward the goaf, the height of longitudinal joint growth was 4-20 times of the mining seam height, and the height of lateral joint growth was 20-25 times of the mining seam height. （3） The ＂arch-in-arch＂ mechanical structure of the internal goaf was bounded by an expansion angle o展开更多
We studied underground pressure and its mechanism during back-gully mining in a shallow coal seam under a bedrock gully slope,by means of physical simulation,numerical modeling and field monitoring.The results show th...We studied underground pressure and its mechanism during back-gully mining in a shallow coal seam under a bedrock gully slope,by means of physical simulation,numerical modeling and field monitoring.The results show that the intensity of underground pressure is related to its relative position at the coalface.The underground pressure is intensive and the support resistance reaches a maximum when the coalface is at the bottom of the gully,whereas the underground pressure is moderate and decreases gradually when the coalface passes the gully.The mechanism of these changes is analyzed when the slope rotated in a reversed direction to the slope dip during back-gully mining and form an unstable,multilateral block hinged structure,due to slipping.The subsidence of multilateral blocks is considerable when the block fragmentation is small,resulting in enormous changes in the underground pressure.With an increase in the mass of the block body,the block displacement will be reduced in conjunction with an increased clamp effect by both the unbroken rocks and broken rocks in the goaf,resulting in a decrease of the underground pressure.展开更多
文摘Fully mechanized mining(FMM)technology has been applied in Chinese coal mines for more than 40 years.At present,the output of a FMM face has reached 10-million tons with Chinese-made equipment.In this study,the new developments in FMM technology and equipment in Chinese coal mines during past decades are introduced.The automatic FMM technology for thin seams,complete sets of FMM technology with ultra large shear height of 7 m for thick seams,complete sets of fully mechanized top coal caving technology with large shear height for ultra-thick seams of 20 m,complete sets of FMM technology for complex and difficult seams,including steeply inclined seams,soft coal seams with large inclination angle,and the mechanized filling mining technology and equipment are presented.Some typical case studies are also introduced.Finally,the existing problems with the FMM technology are discussed,and prospect of FMM technology and equipment applied in Chinese coal mines is put forward.
基金Acknowledgments This research was supported by the National Program on Key Basic Research Project of China （973 Program） （2011CB201204）, the Visitor Foundation of the State Key Laboratory of Coal Mine Disaster Dynamics and Control （Chongqing University） （2011DA105287-FW201405）, the National Natural Science Foundation of China （51374204 and 51304204）, and a project funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions.
文摘Simultaneous extraction of the coal and gas is an effective method of eliminating coal mine gas disasters while safely exploiting the coal and achieving efficient gas drainage in China, which is widely accepted by the main coal-producing countries around the world. However, the concrete definition of simultaneous extraction is vague and there is little accurate theoretical support for the simultaneous extraction of coal and gas, which makes it difficult to determine an efficient gas drainage method appropriate to the features of coal seams. Based on theoretical analysis, laboratory tests and field observations, a specific definition of simultaneous extraction of coal and gas is proposed after analyzing the characteristics of coal seam occurrences in China, and we developed the mechanism of mining-enhanced permeability and established the corresponding theoretical model. This comprises a process of fracture network formation, in which the original fractures are opened and new fractures are produced by unloading damage. According to the theoretical model, the engineering approaches and their quantitative parameters of ＇unloading by borehole drilling＇ for single coal seams and ＇unloading by protective seam mining＇ for groups of coal seams are proposed, and the construction principles for coal exploitation and gas-drainage systems for different conditions are given. These methods were applied successfully in the Tunlan Coal Mine in Shanxi Province and the Panyi Coal Mine in Anhui Province and could assure safe and efficient simultaneous extraction of coal and gas in these outburst coal mines.
基金Acknowledgments The program was supported by the National Natural Science Foundation of China （51427804） and the Open Found of State Key Laboratory of Deep Coal Mining ＆ Environment Protection.
文摘In multiple seams mining, the seam with relatively low gas content （protective seam） is often extracted prior to mining its overlying and/or underlying seams of high gas content and low permeability to minimize the risk of high gas emission and outbursts of coal and gas. A key to success with this mining sequence is to gain a detailed understanding of the movement and fracture evolution of the overlying and underlying strata after the protective seam in extracted. In Zhuji mine, the No. 11-2 seam is extracted as a protective seam with the pillarless mining method by retaining goal-side roadways prior to its overlying No. 13-1 seam. An investigation has been undertaken in the panel 1111 （1） of Zhuji mine to physically simulate the movement and fracture evolution of the overlying strata alter the No. 1 I-2 seam is extracted. In the physical simulation, the displacement, strain, and deformation and failure process of the model for simulation were acquired with various means such as grating displacement meter, strain gauges, and digital photography. The simulation result shows that： （1） Initial caving interval of the immediate roof was 21.6 m, the first weighting interval was 23.5-37.3 m with the average interval of 33.5 m, and the periodic weighting interval of the main roof was in a range of 8.2-20.55 m and averaged at 15.2 m. （2） The maximum height of the caving zone after the extraction of No. 11-2 seam was 8.0 m, which was 4 times of the seam mining height and the internal strata of the caving zone collapsed irregularly. The mining-induced fractures developed 8-30 m above the mined No. 11-2 seam, which was 7.525 times of the seam mining height, the fracture zone was about 65° upward from the seam open-off cut toward the goaf, the height of longitudinal joint growth was 4-20 times of the mining seam height, and the height of lateral joint growth was 20-25 times of the mining seam height. （3） The ＂arch-in-arch＂ mechanical structure of the internal goaf was bounded by an expansion angle o
基金financial support for this work,provided by the National Natural Science Foundation of China(Nos.51004101 and 50904063)the Science Foundation for Young Scholars of China University of Mining & Technology(Nos.2008A003 and 2009A001 )the Graduate Student Scientific Research Innovation in the University of Jiangsu Province(No.CX07B_149z).
文摘We studied underground pressure and its mechanism during back-gully mining in a shallow coal seam under a bedrock gully slope,by means of physical simulation,numerical modeling and field monitoring.The results show that the intensity of underground pressure is related to its relative position at the coalface.The underground pressure is intensive and the support resistance reaches a maximum when the coalface is at the bottom of the gully,whereas the underground pressure is moderate and decreases gradually when the coalface passes the gully.The mechanism of these changes is analyzed when the slope rotated in a reversed direction to the slope dip during back-gully mining and form an unstable,multilateral block hinged structure,due to slipping.The subsidence of multilateral blocks is considerable when the block fragmentation is small,resulting in enormous changes in the underground pressure.With an increase in the mass of the block body,the block displacement will be reduced in conjunction with an increased clamp effect by both the unbroken rocks and broken rocks in the goaf,resulting in a decrease of the underground pressure.
