The 121 mining method of longwall mining first proposed in England has been widely used around the world.This method requires excavation of two mining roadways and reservation of one coal pillar to mine one working fa...The 121 mining method of longwall mining first proposed in England has been widely used around the world.This method requires excavation of two mining roadways and reservation of one coal pillar to mine one working face.Due to considerable excavation of roadway,the mining roadway is generally destroyed during coal mining.The stress concentration in the coal pillar can cause large deformation of surrounding rocks,rockbursts and other disasters,and subsequently a large volume of coal pillar resources will be wasted.To improve the coal recovery rate and reduce excavation of the mining roadway,the 111 mining method of longwall mining was proposed in the former Soviet Union based on the 121 mining method.The 111 mining method requires excavation of one mining roadway and setting one filling body to replace the coal pillar while maintaining another mining roadway to mine one working face.However,because the stress transfer structure of roadway and working face roof has not changed,the problem of stress concentration in the surrounding rocks of roadway has not been well solved.To solve the above problems,the conventional concept utilizing high-strength support to resist the mining pressure for the 121 and 111 mining methods should be updated.The idea is to utilize mining pressure and expansion characteristics of the collapsed rock mass in the goaf to automatically form roadways,avoiding roadway excavation and waste of coal pillar.Based on the basic principles of mining rock mechanics,the“equilibrium mining”theory and the“short cantilever beam”mechanical model are proposed.Key technologies,such as roof directional presplitting technology,negative Poisson’s ratio(NPR)high-prestress constant-resistance support technology,and gangue blocking support technology,are developed following the“equilibrium mining”theory.Accordingly,the 110 and N00 mining methods of an automatically formed roadway(AFR)by roof cutting and pressure releasing without pillars are proposed.The mining methods have been applied to a large number of coal mines with different overburdens,coal seam thicknesses,roof types and gases in China,realizing the integrated mode of coal mining and roadway retaining.On this basis,in view of the complex geological conditions and intelligent mining demand of coal mines,an intelligent and unmanned development direction of the“equilibrium mining”method is prospected.展开更多
When the mining goaf is close to the cliff,rock slope subsidence induced by underground mining is significantly affected by its boundary conditions.In this study,an analytical method is proposed by considering the key...When the mining goaf is close to the cliff,rock slope subsidence induced by underground mining is significantly affected by its boundary conditions.In this study,an analytical method is proposed by considering the key strata as a semi-infinite Euler-Bernoulli beam rested on a Winkler foundation with a local subsidence area.The analytical solutions of deflection are derived by analyzing the boundary and continuity conditions of the cliff.Then,the analytical solutions are verified by the results from experimental tests,FEM and InSAR,respectively.After that,the influence of changing parameters on deflections is studied with sensitivity analysis.The results show that the distance between goaf and cliff significantly affects the deflection of semi-infinite beam.The response of semi-infinite beam is obviously determined by the length of goaf and the bending stiffness of beam.The comparisons between semi-infinite beam and infinite beam illustrate the ascendancy of the improved model in such problems.展开更多
A numerical model based on a Continuum-based Distinct Element Method(CDEM) was used to carry out a dynamic simulation of the interaction between shield and rock strata movement in longwall mining. In Northern China, t...A numerical model based on a Continuum-based Distinct Element Method(CDEM) was used to carry out a dynamic simulation of the interaction between shield and rock strata movement in longwall mining. In Northern China, the Ordos coal field geological conditions and operational characteristics were used as a case example. The CDEM was constructed on Ordos coal field shield's operation characteristics and geological conditions. Numerical modelling was carried out to investigate the effects of different mining heights on the caving process, movement characteristics, equilibrium and stability conditions of overburden as the interaction between shield and surrounding rocks. With the numerical model, the internal factors for changes in shield resistance under different mining heights was found. The quantitative relationship between mining heights and shield resistance was also obtained by the numerical simulation.展开更多
Mineral consumption is increasing rapidly as more consumers enter the market for minerals and as the global standard of living increases. As a result, underground mining continues to progress to deeper levels in order...Mineral consumption is increasing rapidly as more consumers enter the market for minerals and as the global standard of living increases. As a result, underground mining continues to progress to deeper levels in order to tackle the mineral supply crisis in the 21 st century. However, deep mining occurs in a very technical and challenging environment, in which significant innovative solutions and best practice are required and additional safety standards must be implemented in order to overcome the challenges and reap huge eco- nomic gains. These challenges include the catastrophic events that are often met in deep mining engineering： rockbursts, gas outbursts, high in situ and redistributed stresses, large deformation, squeezing and creeping rocks, and high temperature. This review paper presents the current global status of deep mining and high-lights some of the newest technological achievements and opportunities associated with rock mechanics and geotechnical engineering in deep mining. Of the various technical achievements, unmanned workingfaces and unmanned mines based on fully automated mining and mineral extraction processes have become important fields in the 21 st century.展开更多
An increased global supply of minerals is essential to meet the needs and expectations of a rapidly rising world population. This implies extraction from greater depths. Autonomous mining systems, developed through su...An increased global supply of minerals is essential to meet the needs and expectations of a rapidly rising world population. This implies extraction from greater depths. Autonomous mining systems, developed through sustained R＆D by equipment suppliers, reduce miner exposure to hostile work environments and increase safety. This places increased focus on ＂ground control＂ and on rock mechanics to define the depth to which minerals may be extracted economically. Although significant efforts have been made since the end of World War II to apply mechanics to mine design, there have been both technological and organizational obstacles. Rock in situ is a more complex engineering material than is typically encountered in most other engineering disciplines. Mining engineering has relied heavily on empirical procedures in design for thousands of years. These are no longer adequate to address the challenges of the 21st century, as mines venture to increasingly greater depths. The development of the synthetic rock mass （SRM） in 2008 provides researchers with the ability to analyze the deformational behavior of rock masses that are anisotropic and discontinuous-attributes that were described as the defining characteristics of in situ rock by Leopold Mfiller, the president and founder of the International Society for Rock Mechanics （ISRM）, in 1966. Recent developments in the numerical modeling of large-scale mining operations （e.g., caving） using the SRM reveal unanticipated deformational behavior of the rock. The application of massive parallelization and cloud computational techniques offers major opportunities： for example, to assess uncertainties in numerical predictions： to establish the mechanics basis for the empirical rules now used in rock engineering and their validity for the prediction of rock mass behavior beyond current experience： and to use the discrete element method （DEM） in the optimization of deep mine design. For the first time, mining-and rock engineering-will have its own mechanics-based Ulaboratory.＂ This promises to be a major tool in future planning for effective mining at depth. The paper concludes with a discussion of an opportunity to demonstrate the application of DEM and SRM procedures as a laboratory, by back-analysis of mining methods used over the 80-year history of the Mount Lvell Copper Mine in Tasmania.展开更多
Reduction of energy consumption in comminution is of significant importance in mining industry. To reduce such energy consumption the energy efficiency in an individual operation such as blasting must be increased. By...Reduction of energy consumption in comminution is of significant importance in mining industry. To reduce such energy consumption the energy efficiency in an individual operation such as blasting must be increased. By using both new investigations and previous experimental results, this paper demonstrates that (1) kinetic energy carried by moving fragments in rock fracture is notable and it increases with an increasing loading rate;(2) this kinetic energy can be well used in secondary fragmentation in crushing and blasting. Accordingly, part of the muck pile from previous blast should be left in front of new(bench) face in either open pit or underground blasting. If so, when new blast occurs, the fragments from the new blast will collide with the muck pile left from the previous blast, and the kinetic energy carried by the moving fragments will be partly used in their secondary fragmentation.展开更多
Voids, which have not been liquidated and associated with shallow mining excavations, pose a serious threat of potential formation of sinkholes. This threat is connected with the loss of stability of voids that had be...Voids, which have not been liquidated and associated with shallow mining excavations, pose a serious threat of potential formation of sinkholes. This threat is connected with the loss of stability of voids that had been formed as a result of mining operations in the deeper strata. Taking into account the impact of lower coal seams mining on shallow excavations and based on the example of a region that had been intensely exploited, this paper proposes a methodology for analysing the stability of shallow mine voids in the rock mass. Deformations in the excavation region were calculated by using FLAC2D computer pro- gram and assigning the Coulomb-Mohr model to the rock mass. Based on the numerical analysis, this paper evaluated the stability of the void in the event of a roof support fall. The results indicate the like- lihood of void formation. Based on the Budryk-Knotbe theory, the deformations of rock mass and sand- stone strata in the roof of the void, which had been caused by mining exploitation in consecutive years, were calculated. The results of numerical calculations and analyses were compared with the limit defor- mations values of sandstone in tension. It is concluded that the exploitations cause the void to break down. The proposed method can forecast the discontinuous deformations threats in the areas that have undergone shallow undermining exploitation and the areas of underground urban.展开更多
The woody vegetation is an important plant community constituent of tropical inselbergs,yet it remains largely overlooked.These environments of high socio-cultural and ecological value face pressures in many places,ma...The woody vegetation is an important plant community constituent of tropical inselbergs,yet it remains largely overlooked.These environments of high socio-cultural and ecological value face pressures in many places,mainly related to mining exploitation and fires.This study provides the first systematic overview of inselberg woody vegetation in the Brazilian Atlantic Forest.We used four inselbergs as models to characterize the composition and structure of the woody vegetation.In addition,the biomass and carbon storage were estimated using the general equations for tropical regions and carbon concentration values.Ten transects(50 m×2 m)were systematically installed on each inselberg,and all woody plants with a diameter at breast height≥5 cm were measured,registered,and identified.A total of 312 individuals belonging to 26 species,23 genera,and 14 families were found.The Fabaceae family and the genus Eugenia(Myrtaceae)exhibited a higher richness.The woody community's diameters ranged from 5.0 to 116.9 cm(with a mean of 23.9 cm),and heights ranged from 1.7 to 16.0 m(with a mean of 6.2 m).All specialist lithophyte woody species found on inselbergs are wind-dispersed.Among the endemic species of the Atlantic Forest,four were endemic to inselbergs,with Pseudobombax petropolitanum and Wunderlichia azulensis being threatened.A few species dominated the communities:P.petropolitanum,Guapira opposita,Amburana cearensis,and Tabebuia reticulata.Carbon accumulated in aboveground biomass ranged from 14 to 48 Mg ha-1,indicating variability in woody vegetation structure and growing conditions among inselbergs.Lastly,we highlight target species for potential use for inselberg vegetation restoration in stone mining areas in Atlantic Forest.展开更多
The fault is potentially vulnerability's geological structure in the working face and its vicinity,and it is also a crucial geological factor affecting coal mine safety exploitation.To investigate the unstable fai...The fault is potentially vulnerability's geological structure in the working face and its vicinity,and it is also a crucial geological factor affecting coal mine safety exploitation.To investigate the unstable failure of surrounding rock induced by fault activation under the influence of adoption,which was studied utilizing field case and numerical analysis for the deformation and failure process of surrounding rock near the fault-affected zone.Combined with field cases,this paper analyzes disturbance stress and roof abscission layer monitoring in effecting zones of fault activation.Using the discrete element 3DEC numerical analysis method,the model of surrounding rock unstable fracture induced by fault activation under adoption is established.The unstable fracture and stress variation characteristics of surrounding rock induced by fault activation during the excavation of the upper side wall and lower side wall of the faults are simulated and analyzed.Field analysis shows that as the coal working face continues to advance,the mining stress gradually increases.There is a zigzag wave on the relationship curve between coal mining and roof displacement near the fault,which reveals that the surrounding rock of the fault activation affected zone is in the superposition state of static load and dynamic load.Furthermore,the simulation results show that the stress and displacement of surrounding rock near the fault increase with the advance of coal mining face.The closer to the fault plane,the displacement gradually returns to zero,and the stress is also in a lower state.展开更多
Minerals are the material foundation for advancing human civilization,the starting point of the manufacturing supply chain,and strategic resources essential for national security and economic progress.In recent years,...Minerals are the material foundation for advancing human civilization,the starting point of the manufacturing supply chain,and strategic resources essential for national security and economic progress.In recent years,deep learning and big data have strongly supported improving mining efficiency and safety in underground hard rock mines.Against this backdrop,this paper focuses on the production processes and vital auxiliary aspects of underground mining in hard rock mines.It delves into six aspects:driling,blasting,transportation,hoisting,ventilation,and support and flling.The paper elaborates on the latest advancements in intelligent technology research for each aspect and provides a summary and outlook on the key technologies relevant to these processes.Research results show that the current intelligent technology used in underground mining not only improves production efficiency but also further improves the safety production level of mining enterprises.To achieve intelligent unmanned mining,bottleneck problems in each primary process must be further addressed.展开更多
基金This work was supported by the Natural Science Foundation of China(Grant Nos.52074164 and 42077267)the Major Scientific and Technological Innovation Project of Shandong Province,China(Grant No.2019SDZY04)。
文摘The 121 mining method of longwall mining first proposed in England has been widely used around the world.This method requires excavation of two mining roadways and reservation of one coal pillar to mine one working face.Due to considerable excavation of roadway,the mining roadway is generally destroyed during coal mining.The stress concentration in the coal pillar can cause large deformation of surrounding rocks,rockbursts and other disasters,and subsequently a large volume of coal pillar resources will be wasted.To improve the coal recovery rate and reduce excavation of the mining roadway,the 111 mining method of longwall mining was proposed in the former Soviet Union based on the 121 mining method.The 111 mining method requires excavation of one mining roadway and setting one filling body to replace the coal pillar while maintaining another mining roadway to mine one working face.However,because the stress transfer structure of roadway and working face roof has not changed,the problem of stress concentration in the surrounding rocks of roadway has not been well solved.To solve the above problems,the conventional concept utilizing high-strength support to resist the mining pressure for the 121 and 111 mining methods should be updated.The idea is to utilize mining pressure and expansion characteristics of the collapsed rock mass in the goaf to automatically form roadways,avoiding roadway excavation and waste of coal pillar.Based on the basic principles of mining rock mechanics,the“equilibrium mining”theory and the“short cantilever beam”mechanical model are proposed.Key technologies,such as roof directional presplitting technology,negative Poisson’s ratio(NPR)high-prestress constant-resistance support technology,and gangue blocking support technology,are developed following the“equilibrium mining”theory.Accordingly,the 110 and N00 mining methods of an automatically formed roadway(AFR)by roof cutting and pressure releasing without pillars are proposed.The mining methods have been applied to a large number of coal mines with different overburdens,coal seam thicknesses,roof types and gases in China,realizing the integrated mode of coal mining and roadway retaining.On this basis,in view of the complex geological conditions and intelligent mining demand of coal mines,an intelligent and unmanned development direction of the“equilibrium mining”method is prospected.
基金supported by the National Natural Science Foundation of China(No.52074042)National Key R&D Program of China(No.2018YFC1504802).
文摘When the mining goaf is close to the cliff,rock slope subsidence induced by underground mining is significantly affected by its boundary conditions.In this study,an analytical method is proposed by considering the key strata as a semi-infinite Euler-Bernoulli beam rested on a Winkler foundation with a local subsidence area.The analytical solutions of deflection are derived by analyzing the boundary and continuity conditions of the cliff.Then,the analytical solutions are verified by the results from experimental tests,FEM and InSAR,respectively.After that,the influence of changing parameters on deflections is studied with sensitivity analysis.The results show that the distance between goaf and cliff significantly affects the deflection of semi-infinite beam.The response of semi-infinite beam is obviously determined by the length of goaf and the bending stiffness of beam.The comparisons between semi-infinite beam and infinite beam illustrate the ascendancy of the improved model in such problems.
基金funded by the National Natural Science Foundation of China (Nos. U1261207 and 51274086)
文摘A numerical model based on a Continuum-based Distinct Element Method(CDEM) was used to carry out a dynamic simulation of the interaction between shield and rock strata movement in longwall mining. In Northern China, the Ordos coal field geological conditions and operational characteristics were used as a case example. The CDEM was constructed on Ordos coal field shield's operation characteristics and geological conditions. Numerical modelling was carried out to investigate the effects of different mining heights on the caving process, movement characteristics, equilibrium and stability conditions of overburden as the interaction between shield and surrounding rocks. With the numerical model, the internal factors for changes in shield resistance under different mining heights was found. The quantitative relationship between mining heights and shield resistance was also obtained by the numerical simulation.
文摘Mineral consumption is increasing rapidly as more consumers enter the market for minerals and as the global standard of living increases. As a result, underground mining continues to progress to deeper levels in order to tackle the mineral supply crisis in the 21 st century. However, deep mining occurs in a very technical and challenging environment, in which significant innovative solutions and best practice are required and additional safety standards must be implemented in order to overcome the challenges and reap huge eco- nomic gains. These challenges include the catastrophic events that are often met in deep mining engineering： rockbursts, gas outbursts, high in situ and redistributed stresses, large deformation, squeezing and creeping rocks, and high temperature. This review paper presents the current global status of deep mining and high-lights some of the newest technological achievements and opportunities associated with rock mechanics and geotechnical engineering in deep mining. Of the various technical achievements, unmanned workingfaces and unmanned mines based on fully automated mining and mineral extraction processes have become important fields in the 21 st century.
文摘An increased global supply of minerals is essential to meet the needs and expectations of a rapidly rising world population. This implies extraction from greater depths. Autonomous mining systems, developed through sustained R＆D by equipment suppliers, reduce miner exposure to hostile work environments and increase safety. This places increased focus on ＂ground control＂ and on rock mechanics to define the depth to which minerals may be extracted economically. Although significant efforts have been made since the end of World War II to apply mechanics to mine design, there have been both technological and organizational obstacles. Rock in situ is a more complex engineering material than is typically encountered in most other engineering disciplines. Mining engineering has relied heavily on empirical procedures in design for thousands of years. These are no longer adequate to address the challenges of the 21st century, as mines venture to increasingly greater depths. The development of the synthetic rock mass （SRM） in 2008 provides researchers with the ability to analyze the deformational behavior of rock masses that are anisotropic and discontinuous-attributes that were described as the defining characteristics of in situ rock by Leopold Mfiller, the president and founder of the International Society for Rock Mechanics （ISRM）, in 1966. Recent developments in the numerical modeling of large-scale mining operations （e.g., caving） using the SRM reveal unanticipated deformational behavior of the rock. The application of massive parallelization and cloud computational techniques offers major opportunities： for example, to assess uncertainties in numerical predictions： to establish the mechanics basis for the empirical rules now used in rock engineering and their validity for the prediction of rock mass behavior beyond current experience： and to use the discrete element method （DEM） in the optimization of deep mine design. For the first time, mining-and rock engineering-will have its own mechanics-based Ulaboratory.＂ This promises to be a major tool in future planning for effective mining at depth. The paper concludes with a discussion of an opportunity to demonstrate the application of DEM and SRM procedures as a laboratory, by back-analysis of mining methods used over the 80-year history of the Mount Lvell Copper Mine in Tasmania.
文摘Reduction of energy consumption in comminution is of significant importance in mining industry. To reduce such energy consumption the energy efficiency in an individual operation such as blasting must be increased. By using both new investigations and previous experimental results, this paper demonstrates that (1) kinetic energy carried by moving fragments in rock fracture is notable and it increases with an increasing loading rate;(2) this kinetic energy can be well used in secondary fragmentation in crushing and blasting. Accordingly, part of the muck pile from previous blast should be left in front of new(bench) face in either open pit or underground blasting. If so, when new blast occurs, the fragments from the new blast will collide with the muck pile left from the previous blast, and the kinetic energy carried by the moving fragments will be partly used in their secondary fragmentation.
文摘Voids, which have not been liquidated and associated with shallow mining excavations, pose a serious threat of potential formation of sinkholes. This threat is connected with the loss of stability of voids that had been formed as a result of mining operations in the deeper strata. Taking into account the impact of lower coal seams mining on shallow excavations and based on the example of a region that had been intensely exploited, this paper proposes a methodology for analysing the stability of shallow mine voids in the rock mass. Deformations in the excavation region were calculated by using FLAC2D computer pro- gram and assigning the Coulomb-Mohr model to the rock mass. Based on the numerical analysis, this paper evaluated the stability of the void in the event of a roof support fall. The results indicate the like- lihood of void formation. Based on the Budryk-Knotbe theory, the deformations of rock mass and sand- stone strata in the roof of the void, which had been caused by mining exploitation in consecutive years, were calculated. The results of numerical calculations and analyses were compared with the limit defor- mations values of sandstone in tension. It is concluded that the exploitations cause the void to break down. The proposed method can forecast the discontinuous deformations threats in the areas that have undergone shallow undermining exploitation and the areas of underground urban.
基金the project funding from Fundacao de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIGNo: APQ-02049-21)+3 种基金the National Council for Scientific and Technological Development (CNPqgrant 312567/2021-9)the Carlos Chagas Filho Foundation for Research Support of the State of Rio de Janeiro (FAPERJgrant E26/201.007/2022) for funding support
文摘The woody vegetation is an important plant community constituent of tropical inselbergs,yet it remains largely overlooked.These environments of high socio-cultural and ecological value face pressures in many places,mainly related to mining exploitation and fires.This study provides the first systematic overview of inselberg woody vegetation in the Brazilian Atlantic Forest.We used four inselbergs as models to characterize the composition and structure of the woody vegetation.In addition,the biomass and carbon storage were estimated using the general equations for tropical regions and carbon concentration values.Ten transects(50 m×2 m)were systematically installed on each inselberg,and all woody plants with a diameter at breast height≥5 cm were measured,registered,and identified.A total of 312 individuals belonging to 26 species,23 genera,and 14 families were found.The Fabaceae family and the genus Eugenia(Myrtaceae)exhibited a higher richness.The woody community's diameters ranged from 5.0 to 116.9 cm(with a mean of 23.9 cm),and heights ranged from 1.7 to 16.0 m(with a mean of 6.2 m).All specialist lithophyte woody species found on inselbergs are wind-dispersed.Among the endemic species of the Atlantic Forest,four were endemic to inselbergs,with Pseudobombax petropolitanum and Wunderlichia azulensis being threatened.A few species dominated the communities:P.petropolitanum,Guapira opposita,Amburana cearensis,and Tabebuia reticulata.Carbon accumulated in aboveground biomass ranged from 14 to 48 Mg ha-1,indicating variability in woody vegetation structure and growing conditions among inselbergs.Lastly,we highlight target species for potential use for inselberg vegetation restoration in stone mining areas in Atlantic Forest.
基金supported by the National key Research and development program for young scientists(2021YF2900400)Supported by Youth Foundation of National Natural Science Foundation of China(52104077)Major collaborative innovation project of Guizhou's mineral prospecting breakthrough strategic action[2022]ZD001-02-02,which are all gratefully appreciated.
文摘The fault is potentially vulnerability's geological structure in the working face and its vicinity,and it is also a crucial geological factor affecting coal mine safety exploitation.To investigate the unstable failure of surrounding rock induced by fault activation under the influence of adoption,which was studied utilizing field case and numerical analysis for the deformation and failure process of surrounding rock near the fault-affected zone.Combined with field cases,this paper analyzes disturbance stress and roof abscission layer monitoring in effecting zones of fault activation.Using the discrete element 3DEC numerical analysis method,the model of surrounding rock unstable fracture induced by fault activation under adoption is established.The unstable fracture and stress variation characteristics of surrounding rock induced by fault activation during the excavation of the upper side wall and lower side wall of the faults are simulated and analyzed.Field analysis shows that as the coal working face continues to advance,the mining stress gradually increases.There is a zigzag wave on the relationship curve between coal mining and roof displacement near the fault,which reveals that the surrounding rock of the fault activation affected zone is in the superposition state of static load and dynamic load.Furthermore,the simulation results show that the stress and displacement of surrounding rock near the fault increase with the advance of coal mining face.The closer to the fault plane,the displacement gradually returns to zero,and the stress is also in a lower state.
基金supported by the National Natural Science Foundation of China (No.U21A20106)the Chinese Academy of Engineering Project (Nos.2022-33-29 and 2023-XY-44).
文摘Minerals are the material foundation for advancing human civilization,the starting point of the manufacturing supply chain,and strategic resources essential for national security and economic progress.In recent years,deep learning and big data have strongly supported improving mining efficiency and safety in underground hard rock mines.Against this backdrop,this paper focuses on the production processes and vital auxiliary aspects of underground mining in hard rock mines.It delves into six aspects:driling,blasting,transportation,hoisting,ventilation,and support and flling.The paper elaborates on the latest advancements in intelligent technology research for each aspect and provides a summary and outlook on the key technologies relevant to these processes.Research results show that the current intelligent technology used in underground mining not only improves production efficiency but also further improves the safety production level of mining enterprises.To achieve intelligent unmanned mining,bottleneck problems in each primary process must be further addressed.
