The relationship between support and surrounding rock is of great significance to the control of surrounding rock in mining process.In view of the fact that most of the existing numerical simulation methods construct ...The relationship between support and surrounding rock is of great significance to the control of surrounding rock in mining process.In view of the fact that most of the existing numerical simulation methods construct virtual elements and stress servo control to approximately replace the hydraulic support problem,this paper establishes a new numerical model of hydraulic support with the same working characteristics as the actual hydraulic support by integrating numerical simulation software Rhino,Griddle and FLAC3D,which can realize the simulation of different working conditions.Based on this model,the influence mechanism of the supporting strength of hydraulic support on surrounding rock stress regulation and coal stability in front of the top coal caving face in extra thick coal seam were researched.Firstly,under different support intensity,the abutment pressure of the bearing coal and the coal in front of it presents the “three-stage”evolution characteristics.The influence range of support intensity is 15%–30%.Secondly,1.5 MPa is the upper limit of impact that the support strength can have on the front coal failure area.Thirdly,within a displacement range of 2.76 m from the coal wall,a support strength of1.5 MPa provides optimal control of the horizontal displacement of the coal.展开更多
Based on the engineering background of gob-side entry retaining in fully-mechanized longwall with top coal caving(GER-FLTC) on N2105 working face of Yuwu coal mine, by adopting the methods of theoretical analysis and ...Based on the engineering background of gob-side entry retaining in fully-mechanized longwall with top coal caving(GER-FLTC) on N2105 working face of Yuwu coal mine, by adopting the methods of theoretical analysis and numerical calculation, the control techniques of surrounding rocks in GER-FLTC working face are studied in this paper. The two main difficulties of stability of surrounding rocks at gob-side retained entry in fully-mechanized longwall working face are the stability control of top coal and control of large deformation of GER-FLTC working face. Interaction mechanical model between roofing and roadside backfilling in GER-FLTC is established and the equations for the calculation of roof-cutting resistance of roadside backfilling are derived. Results of numerical calculation show that the damage zones of top coal can be categorized into the delaminating zone of top coal above the backfilling, tensile damage zone of top coal above the retained roadway and shear damage zone of the upper rib of the solid coal. Stability control of top coal is the critical part to success of GER-FLTC. With consideration of large deformation of surrounding rocks of gob-side retained entry in fully-mechanized longwall, the support technique of‘‘roofing control and wall strengthening'' is proposed where high strength and highly prestressed anchor rods and diagonal tensile anchor cables support are used for top coal, high strength and highly prestressed yielding anchor rod support is used for solid coal and roadside prestressed load-carrying backfilling is constructed by high-water material, in order to maintain the integrity of the top coal, transfer load, high resistance yielding load-carrying of solid coal, roof-cutting of roadside backfilling and support,and to achieve GER-FLTC. Results from this study are successfully applied in engineering practice.展开更多
The thick-san top-ctal catrig technology has been in use in China for over a decade,and has given rise to siguscant economic efficiendes. Eftorts in reeent years to extend its applica tion to more complex mining condi...The thick-san top-ctal catrig technology has been in use in China for over a decade,and has given rise to siguscant economic efficiendes. Eftorts in reeent years to extend its applica tion to more complex mining conditions, mostly high-gas seams , with or without proneness ofspontaneous combustion. have brought about new safety problems This paper will highlight thefcatures and problems retared with thick-seam top-coal caving systems, compared with conventionai, fully-mecbanized longwall systems , particularly issues retated to methane, spontaneous combustion and dust,and disam the methods and measures to ded with them.展开更多
Based on break characteristics of roofs in fully mechanized top-coal mining of thick shallow coal seams, a fracture mechanics model was built, and the criterion of crack propagation in the main roof was derived using ...Based on break characteristics of roofs in fully mechanized top-coal mining of thick shallow coal seams, a fracture mechanics model was built, and the criterion of crack propagation in the main roof was derived using the fracture mechanics theory. The relationships between the fracture length of the roof and the working resistance of the supports were discovered, and the correlations between the load on the overlying strata and the ratio of the crack's length to the thickness of the roof were obtained. Using a working face of Jindi Coal Mine, Xing county Shanxi province as an example, the relationships between the fracture length of the roof and the working resistance of the supports were analysed in detail. The results give a design basis in hydraulic top coal caving supports, which could provide useful references in the practical application. On-site experiment proves that the periodic weighting step interval of the caving face is 15–16 m, which is basically consistent with the theoretical analysis results, and indicates that the mechanized caving hydraulic support is capable of meeting the support requirements in the mining of a super-thick but shallowly buried coal seam.展开更多
When mining the fully-mechanized longwall caving face along strike, the unstable equipment, the low top-coal recovery ratio and the difficulty in controlling surrounding rock may occur due to large dip angle. Consider...When mining the fully-mechanized longwall caving face along strike, the unstable equipment, the low top-coal recovery ratio and the difficulty in controlling surrounding rock may occur due to large dip angle. Considering the effects of strike angle on support stability, the ‘‘support-surrounding rock"mechanical models of support topple and support slip were established in this paper. On the basis, the influencing factors of support stability were analyzed and the technical measures of controlling support and surrounding rock stability were put forward. Then the loose particles simulation experiment was conducted to analyze the impacts of caving directions and methods on the top-coal recovery in large dip angle fully-mechanized caving face. Finally, the ‘‘upward sequence and double-openings doublerounds" caving technology was determined. The research results are of great scientific significance and practical values to improve large dip thick seam mining technology.展开更多
The variation of the stress in the bolted surrounding rocks structure of the roadway driven along goaf in a fully mechanized top coal caving face with moderate stable conditions are studied by using numerical calculat...The variation of the stress in the bolted surrounding rocks structure of the roadway driven along goaf in a fully mechanized top coal caving face with moderate stable conditions are studied by using numerical calculation. The essential deformation characteristics of the surrounding rocks in this kind of roadway are obtained and the key technology of bolting support used under these conditions is put forward.展开更多
Based on the deformation characteristics of the roadways driven along goaf in fully mechanized top coal caving faces, the author considers that it is the key to ensure the stability of surrounding rocks of roadway dri...Based on the deformation characteristics of the roadways driven along goaf in fully mechanized top coal caving faces, the author considers that it is the key to ensure the stability of surrounding rocks of roadway driven along goaf to control the deformation during the period affected by mining. Considering the characteristics of the roadway layout in fully mechanized top coal caving faces, a technical scheme of destressing is put forward and the destressing effect is analyzed by using the software of Universal Distinct Element Code 3 0(UDEC 3 0).展开更多
Characteristics of gas emission at the K8206 working face in the Third mine of the Yangquan Coal Group were investigated. The effects of strata movement,advancing velocity of working face,production capacity of workin...Characteristics of gas emission at the K8206 working face in the Third mine of the Yangquan Coal Group were investigated. The effects of strata movement,advancing velocity of working face,production capacity of working face and gas extraction capability of strike high-level entry on gas emission at K8206 working face were analyzed. A regression equation,reflecting the relationship between relative gas emission rate and the production capacity of work-ing faces,was established. Another regression equation showing the relationship between the gas emission rate from adjacent layers when the working face was advancing for one metre and advancing velocity was derived. It can be con-cluded that,1) the amount of gas emitted at the K8206 working face is far greater than that of ordinary top coal caving faces with a dip length of 180-190 m; 2) the dynamic process of gas emission from adjacent layers during the initial mining stage is controlled by the movement of key strata; 3) the amount of gas emitted that needs to be forced out by air is greatly affected by the capability of gas extraction; 4) when the advancing velocity is between 3.5-5.5 m/d or when the output is up to 8-12 kt/d,the gas emission from adjacent layers is almost constant.展开更多
Under the action of abutment pressure in front of fully mechanized coal face with sublevel caving(CFSC),top-coal over CFSC deformed.In the process of whole de- formation of top-coal,it changed from continuum elastic m...Under the action of abutment pressure in front of fully mechanized coal face with sublevel caving(CFSC),top-coal over CFSC deformed.In the process of whole de- formation of top-coal,it changed from continuum elastic mass to non-continuum plastic mass contained fissures,become a loose body.According to its bearing characteristics and mechanical properties,top-coal mass can be divided into four deformation zones along the winning direction of CFSC,i.e.initial stress zone,elastic zone,plastic zone and loose zone.Top-coal in plastic zone located in the post-peak zone of the stress-strain curve for top-coal.With equivalent strain principle of damage mechanics and mathemati- cal theory of statistic,combining the movement law of top-coal,set up a constitutive equa- tion with damage statistics for top-coal in different position in CFSC.The equation illus- trated the mathematical relationship among top-coal bearing capacity,horizontal confining pressure along the winning direction of CFSC and mechanical properties of top-coal mate- rial.The conclusions not only provide a basis for numerical computer simulations on damage deformation and failure mechanism for top-coal,but also further promote the ap- plication of damage mechanics in CFSC.展开更多
Analyzed the support instable mode of sliding,tripping,and so on,and believed the key point of the support stability control of fully mechanized coal caving face with steep coal seams was to maintain that the seam tru...Analyzed the support instable mode of sliding,tripping,and so on,and believed the key point of the support stability control of fully mechanized coal caving face with steep coal seams was to maintain that the seam true angle was less than the hydraulic support instability critical angle.Through the layout of oblique face,the improvement of support setting load,the control of mining height and nonskid platform,the group support system of end face,the advance optimization of conveyor and support,and the other control tech- nical measures,the true angle of the seam is reduced and the instable critical angle of the support is increased,the hydraulic support stability of fully mechanized coal caving face with steep coal seams is effectively controlled.展开更多
The matching relationship between coal cutting and caving in fully mechanized top-coal caving face is analyzed in detail from the angle of reliability. The coupling equation of reliability is established corresponding...The matching relationship between coal cutting and caving in fully mechanized top-coal caving face is analyzed in detail from the angle of reliability. The coupling equation of reliability is established correspondingly, and the mathematical equation of the coefficient of velocity matching of coal cutting and caving is obtained, which meets a certain reliability demand for making the working procedure of coal caving not influence coal cutting of coal-cutter. The results show that the relationship between the coefficient of the velocity matching and the reliability of coal cutting and caving system is linear on the whole when R <0.9. It is pointed out that different numerical value should be selected for different coal face according to different demand for reliability.展开更多
Longwall Top Coal Caving has been considered as one of the most effective technologies for the extraction of underground thick coal seams. A large number of studies on the applicability of Longwall Top Coal Caving int...Longwall Top Coal Caving has been considered as one of the most effective technologies for the extraction of underground thick coal seams. A large number of studies on the applicability of Longwall Top Coal Caving into new mine sites have linked the success of its application to the geo mechanical understanding of the cavability of the top coal. The paper aims to improve the knowledge of the top coal cavability evaluation. A range of parameters that affect the top coal cavability were first identified. Afterward, a number of cavability assessment methods and classifications were reviewed. The result is important in that it assists researchers in developing an advanced and reliable tool for the top coal cavability evaluation.展开更多
For studying the strata behavior due to multi-slicing top coal caving longwall mining along-the-strike direction in steeply dipping extra thick coal seams,the shield support pressures of the upper and lower slices of ...For studying the strata behavior due to multi-slicing top coal caving longwall mining along-the-strike direction in steeply dipping extra thick coal seams,the shield support pressures of the upper and lower slices of panel 37220 in Dongxia Coal Mine were monitored using the KJ513 dynamic monitoring system.The set up rooms adopted the "horizontal line-arc segment-inclined line" form and used different types of shield supports.The results show that the strata pressure of upper slice panel 37220-1 changed slightly along the strike direction,while along the dip direction it exhibited strong to weak pressure from bottom to top.The first weighting interval of lower slice panel 37220-2 was about 60.8 m,and the average periodic weighting interval were about 22.6 m.The strata behavior of panel 37220-2 exhibited a spatiotemporal characteristic in that periodic weighting occurred first in the middle-upper part,followed by the middle and upper parts,arc segment,and finally the lower part.During the periodic weighting,the weighting interval and intensity also exhibited strong space characteristics.The average dynamic load coefficient was 1.48 and the maximum lateral load of the side shield was 20-25 MPa.展开更多
Against the background of analyzing coal wall stability in 14101 fully mechanized longwall top coal caving face in Majialiang coal mine,based on the torque equilibrium of the coal wall,shield support and the roof stra...Against the background of analyzing coal wall stability in 14101 fully mechanized longwall top coal caving face in Majialiang coal mine,based on the torque equilibrium of the coal wall,shield support and the roof strata,an elastic mechanics model was established to calculate the stress applied on the coal wall.The displacement method was used to obtain the stress and deformation distributions of the coal wall.This study also researched the influence of support resistance,protective pressure to the coal wall,fracture position of the main roof and mining height on the coal wall deformation.The following conclusions are drawn:(1) The shorter the distance from the longwall face,the greater the vertical compressive stress and horizontal tensile stress borne by the coal wall.The coal wall is prone to failure in the form of compressive-shear and tension;(2) With increasing support resistance,the revolution angle of the main roof decreases linearly.As the support resistance and protective force supplied by the face guard increases,the maximum deformation of the coal wall decreases linearly;(3) As the face approaches the fracture position of the main roof,coal wall horizontal deformation increases significantly,and the coal wall is prone to instability;and(4) The best mining height of 14101 longwall face is 3.0 m.展开更多
In order to prevent spontaneous coal combustion occurring at a fully mechanized caving face with large obliquity in deep mines in China,we have analyzed the characteristics of spontaneous coal combustion and explain t...In order to prevent spontaneous coal combustion occurring at a fully mechanized caving face with large obliquity in deep mines in China,we have analyzed the characteristics of spontaneous coal combustion and explain theoretically the factors affecting spontaneous coal combustion,such as rock bursts,high temperatures,high ventilation resistance,slow advancing speed and large obliquity mining.Key technologies to prevent spontaneous combustion occurring in sharply inclined seams in deep mines are proposed;these include pouring water,stopping leakage in upper and lower corners of the working face,choking off the goaf and covering the coal.CO concentrations were controlled within two years to less than 15×10-6 at the upper corner by applying these technologies at the 1410 working face of the Huafeng coal mine.Our method has significant theoretical value and is of practical importance in controlling spontaneous coal combustion occurring at a fully mechanized caving face with large obliquity in deep mines.展开更多
A mechanical model to control the top-coal deformation is established in accordance with the structural characters of the gob-side entry surrounding rock for the fully-mechanic top-coal caving; the analytical solution...A mechanical model to control the top-coal deformation is established in accordance with the structural characters of the gob-side entry surrounding rock for the fully-mechanic top-coal caving; the analytical solution of top coal roof-sag curve is deduced with Winkler elastic foundation beam model. By means of a calculating and analytic program, the top coal roof-sag values are calculated under the conditions of different supporting intensities, widths of narrow pillars and stiffness of top coal; meanwhile, the relationship between the roof-sag values and supporting intensity, width of narrow pillars and stiffness of top coal is analyzed as well. With the actual situation of the gob-side entry taken into consideration, the parameters of top-coal control are determined and a supporting plan is proposed for the top-coal control,which is proved to be reliable and effective by on-site verification. Some theoretical guidance and advice are put forward for the top-coal deformation control in gob-side entry for fully mechanized top-coal caving face.展开更多
基金supported by Distinguished Youth Funds of National Natural Science Foundation of China (No.51925402)National Natural Science Foundation of China (Nos.51904203 and 52174125)+4 种基金the China Postdoctoral Science Foundation (No.2021M702049)the Tencent Foundation or XPLORER PRIZEShanxi Science and Technology Major Project Funds (No.20201102004)Shanxi-Zheda Institute of Advanced Materials and Chemical Engineering (No.2021SX-TD001)Open Fund Research Project Supported by State Key Laboratory of Strata Intelligent Control and Green Mining Co-founded by Shandong Province and the Ministry of Science and Technology (No.SICGM202209)。
文摘The relationship between support and surrounding rock is of great significance to the control of surrounding rock in mining process.In view of the fact that most of the existing numerical simulation methods construct virtual elements and stress servo control to approximately replace the hydraulic support problem,this paper establishes a new numerical model of hydraulic support with the same working characteristics as the actual hydraulic support by integrating numerical simulation software Rhino,Griddle and FLAC3D,which can realize the simulation of different working conditions.Based on this model,the influence mechanism of the supporting strength of hydraulic support on surrounding rock stress regulation and coal stability in front of the top coal caving face in extra thick coal seam were researched.Firstly,under different support intensity,the abutment pressure of the bearing coal and the coal in front of it presents the “three-stage”evolution characteristics.The influence range of support intensity is 15%–30%.Secondly,1.5 MPa is the upper limit of impact that the support strength can have on the front coal failure area.Thirdly,within a displacement range of 2.76 m from the coal wall,a support strength of1.5 MPa provides optimal control of the horizontal displacement of the coal.
基金supported by Chinese National Programs for Fundamental Research and Development(973 Program)(2013CB227905)Natural Science Foundation of Jiangsu Province of China(BK20140210)
文摘Based on the engineering background of gob-side entry retaining in fully-mechanized longwall with top coal caving(GER-FLTC) on N2105 working face of Yuwu coal mine, by adopting the methods of theoretical analysis and numerical calculation, the control techniques of surrounding rocks in GER-FLTC working face are studied in this paper. The two main difficulties of stability of surrounding rocks at gob-side retained entry in fully-mechanized longwall working face are the stability control of top coal and control of large deformation of GER-FLTC working face. Interaction mechanical model between roofing and roadside backfilling in GER-FLTC is established and the equations for the calculation of roof-cutting resistance of roadside backfilling are derived. Results of numerical calculation show that the damage zones of top coal can be categorized into the delaminating zone of top coal above the backfilling, tensile damage zone of top coal above the retained roadway and shear damage zone of the upper rib of the solid coal. Stability control of top coal is the critical part to success of GER-FLTC. With consideration of large deformation of surrounding rocks of gob-side retained entry in fully-mechanized longwall, the support technique of‘‘roofing control and wall strengthening'' is proposed where high strength and highly prestressed anchor rods and diagonal tensile anchor cables support are used for top coal, high strength and highly prestressed yielding anchor rod support is used for solid coal and roadside prestressed load-carrying backfilling is constructed by high-water material, in order to maintain the integrity of the top coal, transfer load, high resistance yielding load-carrying of solid coal, roof-cutting of roadside backfilling and support,and to achieve GER-FLTC. Results from this study are successfully applied in engineering practice.
文摘The thick-san top-ctal catrig technology has been in use in China for over a decade,and has given rise to siguscant economic efficiendes. Eftorts in reeent years to extend its applica tion to more complex mining conditions, mostly high-gas seams , with or without proneness ofspontaneous combustion. have brought about new safety problems This paper will highlight thefcatures and problems retared with thick-seam top-coal caving systems, compared with conventionai, fully-mecbanized longwall systems , particularly issues retated to methane, spontaneous combustion and dust,and disam the methods and measures to ded with them.
文摘Based on break characteristics of roofs in fully mechanized top-coal mining of thick shallow coal seams, a fracture mechanics model was built, and the criterion of crack propagation in the main roof was derived using the fracture mechanics theory. The relationships between the fracture length of the roof and the working resistance of the supports were discovered, and the correlations between the load on the overlying strata and the ratio of the crack's length to the thickness of the roof were obtained. Using a working face of Jindi Coal Mine, Xing county Shanxi province as an example, the relationships between the fracture length of the roof and the working resistance of the supports were analysed in detail. The results give a design basis in hydraulic top coal caving supports, which could provide useful references in the practical application. On-site experiment proves that the periodic weighting step interval of the caving face is 15–16 m, which is basically consistent with the theoretical analysis results, and indicates that the mechanized caving hydraulic support is capable of meeting the support requirements in the mining of a super-thick but shallowly buried coal seam.
基金provided by the National Key Basic Research Program of China (973 Program) (No. 2015CB251600)the Qing Lan Projectthe Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD)
文摘When mining the fully-mechanized longwall caving face along strike, the unstable equipment, the low top-coal recovery ratio and the difficulty in controlling surrounding rock may occur due to large dip angle. Considering the effects of strike angle on support stability, the ‘‘support-surrounding rock"mechanical models of support topple and support slip were established in this paper. On the basis, the influencing factors of support stability were analyzed and the technical measures of controlling support and surrounding rock stability were put forward. Then the loose particles simulation experiment was conducted to analyze the impacts of caving directions and methods on the top-coal recovery in large dip angle fully-mechanized caving face. Finally, the ‘‘upward sequence and double-openings doublerounds" caving technology was determined. The research results are of great scientific significance and practical values to improve large dip thick seam mining technology.
文摘The variation of the stress in the bolted surrounding rocks structure of the roadway driven along goaf in a fully mechanized top coal caving face with moderate stable conditions are studied by using numerical calculation. The essential deformation characteristics of the surrounding rocks in this kind of roadway are obtained and the key technology of bolting support used under these conditions is put forward.
文摘Based on the deformation characteristics of the roadways driven along goaf in fully mechanized top coal caving faces, the author considers that it is the key to ensure the stability of surrounding rocks of roadway driven along goaf to control the deformation during the period affected by mining. Considering the characteristics of the roadway layout in fully mechanized top coal caving faces, a technical scheme of destressing is put forward and the destressing effect is analyzed by using the software of Universal Distinct Element Code 3 0(UDEC 3 0).
基金Projects 50374066 supported by the National Natural Science Foundation of ChinaNCET-05-0478 by the Program for New Century Excellent Talents in University
文摘Characteristics of gas emission at the K8206 working face in the Third mine of the Yangquan Coal Group were investigated. The effects of strata movement,advancing velocity of working face,production capacity of working face and gas extraction capability of strike high-level entry on gas emission at K8206 working face were analyzed. A regression equation,reflecting the relationship between relative gas emission rate and the production capacity of work-ing faces,was established. Another regression equation showing the relationship between the gas emission rate from adjacent layers when the working face was advancing for one metre and advancing velocity was derived. It can be con-cluded that,1) the amount of gas emitted at the K8206 working face is far greater than that of ordinary top coal caving faces with a dip length of 180-190 m; 2) the dynamic process of gas emission from adjacent layers during the initial mining stage is controlled by the movement of key strata; 3) the amount of gas emitted that needs to be forced out by air is greatly affected by the capability of gas extraction; 4) when the advancing velocity is between 3.5-5.5 m/d or when the output is up to 8-12 kt/d,the gas emission from adjacent layers is almost constant.
基金Supported by the Scientific Research Business of China University of Mining & Technology (Beijing) (2009QZ04) the National Natural Science Foundation of China (50974123)
基金the National Natural Science Foundation of China(40638040/D0214,50534070/E04)
文摘Under the action of abutment pressure in front of fully mechanized coal face with sublevel caving(CFSC),top-coal over CFSC deformed.In the process of whole de- formation of top-coal,it changed from continuum elastic mass to non-continuum plastic mass contained fissures,become a loose body.According to its bearing characteristics and mechanical properties,top-coal mass can be divided into four deformation zones along the winning direction of CFSC,i.e.initial stress zone,elastic zone,plastic zone and loose zone.Top-coal in plastic zone located in the post-peak zone of the stress-strain curve for top-coal.With equivalent strain principle of damage mechanics and mathemati- cal theory of statistic,combining the movement law of top-coal,set up a constitutive equa- tion with damage statistics for top-coal in different position in CFSC.The equation illus- trated the mathematical relationship among top-coal bearing capacity,horizontal confining pressure along the winning direction of CFSC and mechanical properties of top-coal mate- rial.The conclusions not only provide a basis for numerical computer simulations on damage deformation and failure mechanism for top-coal,but also further promote the ap- plication of damage mechanics in CFSC.
基金the National Natrual Science Foundation of China(50504014)
文摘Analyzed the support instable mode of sliding,tripping,and so on,and believed the key point of the support stability control of fully mechanized coal caving face with steep coal seams was to maintain that the seam true angle was less than the hydraulic support instability critical angle.Through the layout of oblique face,the improvement of support setting load,the control of mining height and nonskid platform,the group support system of end face,the advance optimization of conveyor and support,and the other control tech- nical measures,the true angle of the seam is reduced and the instable critical angle of the support is increased,the hydraulic support stability of fully mechanized coal caving face with steep coal seams is effectively controlled.
文摘The matching relationship between coal cutting and caving in fully mechanized top-coal caving face is analyzed in detail from the angle of reliability. The coupling equation of reliability is established correspondingly, and the mathematical equation of the coefficient of velocity matching of coal cutting and caving is obtained, which meets a certain reliability demand for making the working procedure of coal caving not influence coal cutting of coal-cutter. The results show that the relationship between the coefficient of the velocity matching and the reliability of coal cutting and caving system is linear on the whole when R <0.9. It is pointed out that different numerical value should be selected for different coal face according to different demand for reliability.
基金supported by the UNSW Australia-Vietnam Ministry of Education and Training(MOET)Scholarship Program
文摘Longwall Top Coal Caving has been considered as one of the most effective technologies for the extraction of underground thick coal seams. A large number of studies on the applicability of Longwall Top Coal Caving into new mine sites have linked the success of its application to the geo mechanical understanding of the cavability of the top coal. The paper aims to improve the knowledge of the top coal cavability evaluation. A range of parameters that affect the top coal cavability were first identified. Afterward, a number of cavability assessment methods and classifications were reviewed. The result is important in that it assists researchers in developing an advanced and reliable tool for the top coal cavability evaluation.
基金funds supported by the Key Program of National Natural Science Foundation of China(No.51634007)
文摘For studying the strata behavior due to multi-slicing top coal caving longwall mining along-the-strike direction in steeply dipping extra thick coal seams,the shield support pressures of the upper and lower slices of panel 37220 in Dongxia Coal Mine were monitored using the KJ513 dynamic monitoring system.The set up rooms adopted the "horizontal line-arc segment-inclined line" form and used different types of shield supports.The results show that the strata pressure of upper slice panel 37220-1 changed slightly along the strike direction,while along the dip direction it exhibited strong to weak pressure from bottom to top.The first weighting interval of lower slice panel 37220-2 was about 60.8 m,and the average periodic weighting interval were about 22.6 m.The strata behavior of panel 37220-2 exhibited a spatiotemporal characteristic in that periodic weighting occurred first in the middle-upper part,followed by the middle and upper parts,arc segment,and finally the lower part.During the periodic weighting,the weighting interval and intensity also exhibited strong space characteristics.The average dynamic load coefficient was 1.48 and the maximum lateral load of the side shield was 20-25 MPa.
基金provided by the Priority Academic Program Development of Jiangsu Higher Education Institutions,the Graduate Students of Jiangsu Province Innovation Program (No.CXZZ13_0948)the National Natural Science Foundation of China (No.51304202)the Natural Science Foundation of Jiangsu Province (No.BK20130190)
文摘Against the background of analyzing coal wall stability in 14101 fully mechanized longwall top coal caving face in Majialiang coal mine,based on the torque equilibrium of the coal wall,shield support and the roof strata,an elastic mechanics model was established to calculate the stress applied on the coal wall.The displacement method was used to obtain the stress and deformation distributions of the coal wall.This study also researched the influence of support resistance,protective pressure to the coal wall,fracture position of the main roof and mining height on the coal wall deformation.The following conclusions are drawn:(1) The shorter the distance from the longwall face,the greater the vertical compressive stress and horizontal tensile stress borne by the coal wall.The coal wall is prone to failure in the form of compressive-shear and tension;(2) With increasing support resistance,the revolution angle of the main roof decreases linearly.As the support resistance and protective force supplied by the face guard increases,the maximum deformation of the coal wall decreases linearly;(3) As the face approaches the fracture position of the main roof,coal wall horizontal deformation increases significantly,and the coal wall is prone to instability;and(4) The best mining height of 14101 longwall face is 3.0 m.
基金Projects 2007B53 supported by the Foundation for National Excellent Doctoral Dissertation of ChinaBK2008123 by the Natural Science Foundation of Jiangsu Province
文摘In order to prevent spontaneous coal combustion occurring at a fully mechanized caving face with large obliquity in deep mines in China,we have analyzed the characteristics of spontaneous coal combustion and explain theoretically the factors affecting spontaneous coal combustion,such as rock bursts,high temperatures,high ventilation resistance,slow advancing speed and large obliquity mining.Key technologies to prevent spontaneous combustion occurring in sharply inclined seams in deep mines are proposed;these include pouring water,stopping leakage in upper and lower corners of the working face,choking off the goaf and covering the coal.CO concentrations were controlled within two years to less than 15×10-6 at the upper corner by applying these technologies at the 1410 working face of the Huafeng coal mine.Our method has significant theoretical value and is of practical importance in controlling spontaneous coal combustion occurring at a fully mechanized caving face with large obliquity in deep mines.
基金funded by the National Natural Science Foundation of China(No.51374201,51323004)the State Key Development Program for Basic Research of China(No.2013CB227900)the College Student’s Program for Innovation of China University of Mining and Technology of China(No.201507)
文摘A mechanical model to control the top-coal deformation is established in accordance with the structural characters of the gob-side entry surrounding rock for the fully-mechanic top-coal caving; the analytical solution of top coal roof-sag curve is deduced with Winkler elastic foundation beam model. By means of a calculating and analytic program, the top coal roof-sag values are calculated under the conditions of different supporting intensities, widths of narrow pillars and stiffness of top coal; meanwhile, the relationship between the roof-sag values and supporting intensity, width of narrow pillars and stiffness of top coal is analyzed as well. With the actual situation of the gob-side entry taken into consideration, the parameters of top-coal control are determined and a supporting plan is proposed for the top-coal control,which is proved to be reliable and effective by on-site verification. Some theoretical guidance and advice are put forward for the top-coal deformation control in gob-side entry for fully mechanized top-coal caving face.