Given the difficulties encountered in roadway support under coal pillars,we studied the characteristics of stress distribution and their effect on roadway stability,using theoretical analysis and numerical simulation....Given the difficulties encountered in roadway support under coal pillars,we studied the characteristics of stress distribution and their effect on roadway stability,using theoretical analysis and numerical simulation.The results show that,under a coal pillar,vertical stress in a floor stratum increases while horizontal stress decreases.We conclude that the increased difference between vertical and horizontal stress is an important reason for deformation of the surrounding rock and failures of roadways under coal pillars.Based on this,we propose control technologies of the surrounding rock of a roadway under a coal pillar,such as high strength and high pre-stressed bolt support,cable reinforcement support single hydraulic prop with beam support and reinforcement by grouting of the surrounding rock,which have been successfully applied in a stability control project of a roadway under a coal pillar.展开更多
Exploitation of coal seams in the Upper Silesian Coal Basin is conducted in complex and difficult conditions. These difficulties are connected with the occurrence of many natural mining hazards and limitations resulti...Exploitation of coal seams in the Upper Silesian Coal Basin is conducted in complex and difficult conditions. These difficulties are connected with the occurrence of many natural mining hazards and limitations resulting from the existing in this area surface infrastructure. One of the most important problems of Polish mining is the rock burst hazard and reliable evaluation of its condition. During long-years’ mining practice in Poland a comprehensive system of evaluation and control of this hazard was developed. In the paper the main aspects of rock burst hazard state evaluation will be presented, comprising: 1) rock mass inclination for rock bursts, i.e., rock strength properties investigation, comprehensive parametric evaluation of rock mass inclination for rock bursts, prognosis of seismic events induced by mining operations, methods of computer-aided modelling of stress and rock mass deformation parameters distribution, strategic rock mass classification under rock burst degrees; 2) immediate seismic and rock burst hazard state evaluation, i.e., low diameter test drilling method, seismologic and seismoacoustic method, comprehensive method of rock burst hazard state evaluation, non-standard methods of evaluation; 3) legal aspects of rock burst hazard state evaluation. Selected elements of the hazard state evaluation system are illustrated with specific practical examples of their application.展开更多
Hard roof is the main factor that induces rock-burst.In view of the present obvious weakness of control measures for hard roof rockburst in domestic collieries,the mechanism and field application of directional hydrau...Hard roof is the main factor that induces rock-burst.In view of the present obvious weakness of control measures for hard roof rockburst in domestic collieries,the mechanism and field application of directional hydraulic fracturing technology for rock-burst prevention have been investigated in this paper using theoretical analysis and numerical simulation.The results show that the weighting span of the main roof and the released kinetic energy as well as the total elastic energy decreased greatly after the directional fracturing of hard roof with the mining progression,thereby reducing the rockburst hazard degree to coal body.The directional hydraulic fracturing technology was carried out in 6305 working face of Jisan Coal Mine to prevent rockburst.Field practices have proved that this technology is much simpler and safer to operate with better prevention effect compared with blasting.By optimizing the operation procedures and developing a new technology of automated high-pressure delivery pipe,the maximum fracturing radius now reaches more than 9 m and the borehole depth exceeds 20 m.Additionally,drilling cutting method was applied to monitor the stress of the coal mass before and after the fracturing,and the drill cuttings dropped significantly which indicates that the burst prevention effect of directional hydraulic fracturing technology is very remarkable.The research results of this paper have laid a theoretical and practical foundation for the widespread application of the directional hydraulic fracturing technology in China.展开更多
In order to effectively control the deformation and failure of surrounding rocks in a coal roadway in a deep tectonic region, the deformation and failure mechanism and stability control mechanism were studied. With su...In order to effectively control the deformation and failure of surrounding rocks in a coal roadway in a deep tectonic region, the deformation and failure mechanism and stability control mechanism were studied. With such methods as numerical simulation and field testing, the distribution law of the displacement, stress and plastic zone in the surrounding rocks was analyzed. The deformation and failure mechanisms of coal roadways in deep tectonic areas were revealed: under high tectonic stress, two sides will slide along the roof or floor; while the plastic zone of the two sides will extend along the roof or floor,leading to more serious deformation and failure in the corner of two sides and the bolt supporting the corners is readily cut off by the shear force or tension force. Aimed at controlling the large slippage deformation of the two sides, serious deformation and failure in the corners of the two sides and massive bolt breakage, a ‘‘controlling and yielding coupling support'' control technology is proposed. Firstly, bolts which do not pass through the bedding plane should be used in the corners of the roadway, allowing the two sides to have some degree of sliding to achieve the purpose of ‘‘yielding'' support, and which avoid breakage of the bolts in the corner. After yielding support, bolts in the corner of the roadway and which pass through the bedding plane should be used to control the deformation and failure of the coal in the corner. ‘‘Controlling and yielding coupling support'' technology has been successfully applied in engineering practice, and the stability of deep coal roadway has been greatly improved.展开更多
In this paper, the law of roof-coal movement has been investigated through the field measurement, theoretical analysis and numerical calculation. Several results, which are of important values for caving process, desi...In this paper, the law of roof-coal movement has been investigated through the field measurement, theoretical analysis and numerical calculation. Several results, which are of important values for caving process, design of the supports, controlling end-face stability, raising recovery rate, realizing working face high output and other related aspects in practice, have been obtained. These results mainly include the following: roof-coal breaking curve of soft-coal seam, roof-coal movement curve of soft-coal and medium-hard coal seam, and roof-coal movement equation. The roof-coal caveability has been analyzed.展开更多
By analyzing the characteristics and the production mechanism of rock burstthat goes with abnormal gas emission in deep coal seams,the essential method of eliminatingabnormal gas emission by eliminating the occurrence...By analyzing the characteristics and the production mechanism of rock burstthat goes with abnormal gas emission in deep coal seams,the essential method of eliminatingabnormal gas emission by eliminating the occurrence of rock burst or depressingthe magnitude of rock burst was considered.The No.237 working face was selected asthe typical working face contacting gas in deep mining;aimed at this working face,a systemof rock burst prediction and control for coal seam contacting gas in deep mining wasestablished.This system includes three parts:① regional prediction of rock burst hazardbefore mining,② local prediction of rock burst hazard during mining,and ③ rock burstcontrol.展开更多
Surrounding rock control in the overlying protective coal seam is a challenging topic for de-stressed mining of multi-seamed coal.Current research findings on roadway control were used in the design of a physical mode...Surrounding rock control in the overlying protective coal seam is a challenging topic for de-stressed mining of multi-seamed coal.Current research findings on roadway control were used in the design of a physical model of a complex textured roof having a varying thickness.The model was used to study roadway instability and collapse caused by dynamic pressure.The results show that when the thickness of the roof exceeds the bolted depth the roadway security is least and the roof has the greatest possibility for collapse.Numerical simulations were also carried out to study stress redistribution before and after roadway excavation during underlying protective seam mining.The evolution of roadway displacement and fracture,as affected by support methods,has been well studied.A series of support principles and technologies for mining affected roadways has been proposed after demonstration of successful practical application in the Huainan Mines.These principles and technologies are of extended value to deep coal mining support in China.展开更多
Based on theoretical analysis, similarity simulation tests, numerical simulation analysis and field observations, we analyzed rock collapse and rules of fraction evolution of overlying rocks and studied the rules in c...Based on theoretical analysis, similarity simulation tests, numerical simulation analysis and field observations, we analyzed rock collapse and rules of fraction evolution of overlying rocks and studied the rules in controlling the effect of an extremely thick igneous rock, found above a main mining coal seam in an area prone to coal mine disasters in the Haizi Coal Mine. The results show that this igneous rock, called a "main key stratum", will not subside nor break for a long time, causing lower fractures and bed separations not to close. The presence of igneous rock plays an important role in rock bursts, mine floods, gas outburst and surface subsidence in coal mines. By analyzing the rules in controlling the effect of this igneous rock, we provide useful references for safety and high efficiency mining in coal mines under special geological conditions.展开更多
The mechanical principle and surrounding rock deformation feature of highstress coal roadway was analyzed.The condition of stress balance of the kind of theroadway was put forward.The surrounding rock control principl...The mechanical principle and surrounding rock deformation feature of highstress coal roadway was analyzed.The condition of stress balance of the kind of theroadway was put forward.The surrounding rock control principle and supporting techniqueof high stress coal roadway were discussed.It was very important to control early daysdeformation of coal sides.The supporting strength is should increased,so the strengthloss of coal sides is decreased.The range of plastic fluid zone is reduced.The abovemention-ned principle is applied in industrial test,and the new supporting technique is ap-plied successfully.展开更多
Randomness and fuzziness involved in rock failure analysis are discussed in the present paper.Fuzzy stochastic process is introduced to simulate pillar/strata deformation process.Study shows that the evolution from da...Randomness and fuzziness involved in rock failure analysis are discussed in the present paper.Fuzzy stochastic process is introduced to simulate pillar/strata deformation process.Study shows that the evolution from damage to failure of the rock materials under complex stress environments conforms to diffusion process.Coal pillar strength is analyzed using fuzzy failure analysis in two coal mines.展开更多
基金the National Natural Science Foundation of China(No.50774077)the State Key Laboratory of Coal Resources and Safe Mining Autonomous Study Subject Foundation of China(No.SKLCRSM08X04)+2 种基金the National Basic Research Program of China,the National Excellence Doctor Degree Dissertation Special Foundation of China(No.200760)the New Century Talent Support Program of the Ministry of Education of China(No.NCET-06-0475)the Youth Scientific Research Foundation of China University of Mining & Technology(No. 2008A002)
文摘Given the difficulties encountered in roadway support under coal pillars,we studied the characteristics of stress distribution and their effect on roadway stability,using theoretical analysis and numerical simulation.The results show that,under a coal pillar,vertical stress in a floor stratum increases while horizontal stress decreases.We conclude that the increased difference between vertical and horizontal stress is an important reason for deformation of the surrounding rock and failures of roadways under coal pillars.Based on this,we propose control technologies of the surrounding rock of a roadway under a coal pillar,such as high strength and high pre-stressed bolt support,cable reinforcement support single hydraulic prop with beam support and reinforcement by grouting of the surrounding rock,which have been successfully applied in a stability control project of a roadway under a coal pillar.
基金Project R0903003 supported by the Research-Development Project of Poland
文摘Exploitation of coal seams in the Upper Silesian Coal Basin is conducted in complex and difficult conditions. These difficulties are connected with the occurrence of many natural mining hazards and limitations resulting from the existing in this area surface infrastructure. One of the most important problems of Polish mining is the rock burst hazard and reliable evaluation of its condition. During long-years’ mining practice in Poland a comprehensive system of evaluation and control of this hazard was developed. In the paper the main aspects of rock burst hazard state evaluation will be presented, comprising: 1) rock mass inclination for rock bursts, i.e., rock strength properties investigation, comprehensive parametric evaluation of rock mass inclination for rock bursts, prognosis of seismic events induced by mining operations, methods of computer-aided modelling of stress and rock mass deformation parameters distribution, strategic rock mass classification under rock burst degrees; 2) immediate seismic and rock burst hazard state evaluation, i.e., low diameter test drilling method, seismologic and seismoacoustic method, comprehensive method of rock burst hazard state evaluation, non-standard methods of evaluation; 3) legal aspects of rock burst hazard state evaluation. Selected elements of the hazard state evaluation system are illustrated with specific practical examples of their application.
基金supported by the Fundamental Research Funds for the Central Universities (No. 2010QNB24)the National Basic Research Program of China (No. 2010CB226805)the Independent Foundation of State Key Laboratory of Coal Resources and Safe Mining (No. SKLCRSM10X05)
文摘Hard roof is the main factor that induces rock-burst.In view of the present obvious weakness of control measures for hard roof rockburst in domestic collieries,the mechanism and field application of directional hydraulic fracturing technology for rock-burst prevention have been investigated in this paper using theoretical analysis and numerical simulation.The results show that the weighting span of the main roof and the released kinetic energy as well as the total elastic energy decreased greatly after the directional fracturing of hard roof with the mining progression,thereby reducing the rockburst hazard degree to coal body.The directional hydraulic fracturing technology was carried out in 6305 working face of Jisan Coal Mine to prevent rockburst.Field practices have proved that this technology is much simpler and safer to operate with better prevention effect compared with blasting.By optimizing the operation procedures and developing a new technology of automated high-pressure delivery pipe,the maximum fracturing radius now reaches more than 9 m and the borehole depth exceeds 20 m.Additionally,drilling cutting method was applied to monitor the stress of the coal mass before and after the fracturing,and the drill cuttings dropped significantly which indicates that the burst prevention effect of directional hydraulic fracturing technology is very remarkable.The research results of this paper have laid a theoretical and practical foundation for the widespread application of the directional hydraulic fracturing technology in China.
基金Financial support for this work, provided by the National Natural Science Foundation of China (No. 51204166)the Henan Polytechnic University Doctor Foundation (No. B2012-081)
文摘In order to effectively control the deformation and failure of surrounding rocks in a coal roadway in a deep tectonic region, the deformation and failure mechanism and stability control mechanism were studied. With such methods as numerical simulation and field testing, the distribution law of the displacement, stress and plastic zone in the surrounding rocks was analyzed. The deformation and failure mechanisms of coal roadways in deep tectonic areas were revealed: under high tectonic stress, two sides will slide along the roof or floor; while the plastic zone of the two sides will extend along the roof or floor,leading to more serious deformation and failure in the corner of two sides and the bolt supporting the corners is readily cut off by the shear force or tension force. Aimed at controlling the large slippage deformation of the two sides, serious deformation and failure in the corners of the two sides and massive bolt breakage, a ‘‘controlling and yielding coupling support'' control technology is proposed. Firstly, bolts which do not pass through the bedding plane should be used in the corners of the roadway, allowing the two sides to have some degree of sliding to achieve the purpose of ‘‘yielding'' support, and which avoid breakage of the bolts in the corner. After yielding support, bolts in the corner of the roadway and which pass through the bedding plane should be used to control the deformation and failure of the coal in the corner. ‘‘Controlling and yielding coupling support'' technology has been successfully applied in engineering practice, and the stability of deep coal roadway has been greatly improved.
文摘In this paper, the law of roof-coal movement has been investigated through the field measurement, theoretical analysis and numerical calculation. Several results, which are of important values for caving process, design of the supports, controlling end-face stability, raising recovery rate, realizing working face high output and other related aspects in practice, have been obtained. These results mainly include the following: roof-coal breaking curve of soft-coal seam, roof-coal movement curve of soft-coal and medium-hard coal seam, and roof-coal movement equation. The roof-coal caveability has been analyzed.
基金Supported by the National Natural Science Foundation(Instrument)of China(50427401)the National High Technology Research and Development Program of China(2006AA06Z119)+1 种基金the National Key Technology R&D Program in 11th Five Years Plan of China(2007BA29B01)the New Century Excellent Talents in University(NCET-06-0477)
文摘By analyzing the characteristics and the production mechanism of rock burstthat goes with abnormal gas emission in deep coal seams,the essential method of eliminatingabnormal gas emission by eliminating the occurrence of rock burst or depressingthe magnitude of rock burst was considered.The No.237 working face was selected asthe typical working face contacting gas in deep mining;aimed at this working face,a systemof rock burst prediction and control for coal seam contacting gas in deep mining wasestablished.This system includes three parts:① regional prediction of rock burst hazardbefore mining,② local prediction of rock burst hazard during mining,and ③ rock burstcontrol.
基金Financial support for this work,provided by the National Key Technology R&D Program(No.2007BAK28B00)the National Natural Science Foundation for the Youth of China(No.50904064)+2 种基金the Research Fund for the Youth of China University of Mining & Technology(No.2008A004)the State Key Laboratory of Coal Resources and Safe Mining,CUMT(No.SKLCRSM09X03)the Research Fund of the State Key Laboratory of Coal Resources and Mine Safety,CUMT(No.08KF10)
文摘Surrounding rock control in the overlying protective coal seam is a challenging topic for de-stressed mining of multi-seamed coal.Current research findings on roadway control were used in the design of a physical model of a complex textured roof having a varying thickness.The model was used to study roadway instability and collapse caused by dynamic pressure.The results show that when the thickness of the roof exceeds the bolted depth the roadway security is least and the roof has the greatest possibility for collapse.Numerical simulations were also carried out to study stress redistribution before and after roadway excavation during underlying protective seam mining.The evolution of roadway displacement and fracture,as affected by support methods,has been well studied.A series of support principles and technologies for mining affected roadways has been proposed after demonstration of successful practical application in the Huainan Mines.These principles and technologies are of extended value to deep coal mining support in China.
基金the National Basic Research Program of China (No.2005CB221503)the National Natural Science Foundation of China (Nos.70533050 and 50674089)+1 种基金the National Foundation for the Youth of China (No.50904068)the Research Fund for the Youth of China University of Mining & Technology (No.OY091223)
文摘Based on theoretical analysis, similarity simulation tests, numerical simulation analysis and field observations, we analyzed rock collapse and rules of fraction evolution of overlying rocks and studied the rules in controlling the effect of an extremely thick igneous rock, found above a main mining coal seam in an area prone to coal mine disasters in the Haizi Coal Mine. The results show that this igneous rock, called a "main key stratum", will not subside nor break for a long time, causing lower fractures and bed separations not to close. The presence of igneous rock plays an important role in rock bursts, mine floods, gas outburst and surface subsidence in coal mines. By analyzing the rules in controlling the effect of this igneous rock, we provide useful references for safety and high efficiency mining in coal mines under special geological conditions.
基金National Natural Science Foundation(50674045)Youth Project of Hunan Education Office(04B020)
文摘The mechanical principle and surrounding rock deformation feature of highstress coal roadway was analyzed.The condition of stress balance of the kind of theroadway was put forward.The surrounding rock control principle and supporting techniqueof high stress coal roadway were discussed.It was very important to control early daysdeformation of coal sides.The supporting strength is should increased,so the strengthloss of coal sides is decreased.The range of plastic fluid zone is reduced.The abovemention-ned principle is applied in industrial test,and the new supporting technique is ap-plied successfully.
文摘Randomness and fuzziness involved in rock failure analysis are discussed in the present paper.Fuzzy stochastic process is introduced to simulate pillar/strata deformation process.Study shows that the evolution from damage to failure of the rock materials under complex stress environments conforms to diffusion process.Coal pillar strength is analyzed using fuzzy failure analysis in two coal mines.
