In the gas-coal integrated mining field,the conventional design method of pipeline coal pillars leads to a large amount of coal pillars being unrecovered and overlooks the pipeline's safety requirements.Considerin...In the gas-coal integrated mining field,the conventional design method of pipeline coal pillars leads to a large amount of coal pillars being unrecovered and overlooks the pipeline's safety requirements.Considering the coal pillar recovery rate and pipeline's safety requirements,two new shaped coal pillar design approaches for subsurface pipelines were developed.Firstly,the deformation limitations for measuring pipeline safety are categorized into two:no deformation is permitted,and deformation is acceptable within elastic limits.Subsequently,integrating the key stratum theory(KST)and cave angle,a fishbone-shaped coal pillar design approach that does not permit pipeline deformation is established.Meanwhile,combined with the ground subsidence and the pipeline's elastic deformation limit,a grille-shaped coal pillar design approach that accepts deformation pipelines within elastic limits is established.Those two new approaches clarify parameters including mined width,coal pillar width and mined length.Finally,the case study shows that the designed mined width,coal pillar width and mined length of the fishbone-shaped coal pillar are 90,80,and 130 m,while those of the grille-shaped are 320,370,and640 m.Compared with the conventional method,the fishbone-shaped and grille-shaped coal pillar design approaches recovered coal pillar resources of 2.65×10~6and 5.81×10~6t on the premise of meeting the pipeline safety requirements,and the recovery rates increased by 20.5%and 45.0%,with expenditures representing only 56.46%and 20.02%of the respective benefits.These new approaches provide managers with diverse options for protecting pipeline safety while promoting coal pillar recovery,which is conducive to the harmonic mining of gas-coal resources.展开更多
Pump chambers, normally used as dominant structures in mining engineering to insure the safety and production of un-derground coal mines, become generally deformed under conditions of deep mining. Given the geology an...Pump chambers, normally used as dominant structures in mining engineering to insure the safety and production of un-derground coal mines, become generally deformed under conditions of deep mining. Given the geology and engineering condition of Qishan Coal Mine in Xuzhou, the failure characteristics of pump chambers at the –1000 m level show that the main cause can be attributed to the spatial effect induced by intersectional chambers, where one pump is constructed per well. We developed an opti-mized design of the pump room, in which the pump wells in the traditional design are integrated into one compounding well. We suggest that the new design can limit the spatial effect of intersectional chambers during construction given our relevant numerical simulation. The new design is able to simplify the structure of the pump chamber and reduce the amount of excavation required. Based on a bolt-mesh-anchor with a rigid gap coupling supporting technology, the stability of pump chamber can be improved greatly.展开更多
Non-pillar mining,top-coal caving and protected coal seam mining are the most popular mining methods in coal exploitation,and the different mining layouts will change the stress state and failure mechanism of coal in ...Non-pillar mining,top-coal caving and protected coal seam mining are the most popular mining methods in coal exploitation,and the different mining layouts will change the stress state and failure mechanism of coal in front of the working face.In this paper,mining-induced mechanical behaviors under three mining layouts have been simulated in the laboratory to investigate the effects of mining layouts on the deformation and strength of coal.Furthermore,the coal failure mechanism under different mining layouts is analyzed microscopically.The experimental results indicate that the stage characteristics of the coal deformation are obvious.Under the serial action of non-pillar mining,top-coal caving and protected coal seam mining layouts,the values of radial deformation,volume strain and Poisson's ratio increase,while the peak strength and deformation modulus decrease at the same buried depth,and the peak strength under non-pillar mining,top-coal caving and protected coal seam mining is about 3.0,2.5 and 2.0 times of the initial confining pressure,respectively.The results also indicate that the trend of the coal deformation decreases with the increase of the buried depth under the same mining layout,while the strength and deformation modulus increase,and the failure mechanism under three mining layouts is dominated with shear/tensile failure.展开更多
This paper attempts to quantify the effect of backfilling on pillar strength in highwall mining using numerical modelling. Calibration against the new empirical strength formula for highwall mining was conducted to ob...This paper attempts to quantify the effect of backfilling on pillar strength in highwall mining using numerical modelling. Calibration against the new empirical strength formula for highwall mining was conducted to obtain the material parameters used in the numerical modelling. With the obtained coal strength parameters, three sets of backfill properties were investigated. The results reveal that the behavior of pillars varies with the type and amount of backfill as well as the pillar width to mining height ratio(w/h). In case of cohesive backfill, generally 75% backfill shows a significant increase in peak strength, and the increase in peak strength is more pronounced for the pillars having lower w/h ratios. In case of noncohesive backfill, the changes in both the peak and residual strengths with up to 92% backfill are negligible while the residual strength constantly increases after reaching the peak strength only when 100%backfill is placed. Based on the modelling results, different backfilling strategies should be considered on a case by case basis depending on the type of backfill available and desired pillar dimension.展开更多
After the mass closures of entire coal mine districts in Europe at the end of the last century, a new phenomenon of surface movement was observed—an upward movement.Although most surface movement(i.e., subsidence) oc...After the mass closures of entire coal mine districts in Europe at the end of the last century, a new phenomenon of surface movement was observed—an upward movement.Although most surface movement(i.e., subsidence) occurs in the months and years after mining by the longwall method, surface movement still occurs many decades after mining is terminated.After the closure and flooding of underground excavations and surrounding rock, this movement was reversed.This paper focuses on quantifying the upward movement in two neighboring coal mines(Winterslag and Zwartberg, Belgium).The study is based on data from a remote sensing technique: interferometry with synthetic aperture radar(INSAR).The results of the study show that the rate of upward movement in the decade after closure is about 10 mm/year on average.The upward movements are not linked directly to the past exploitation directly underneath a location.The amounts of subsidence at specific locations are linked mainly to their positions relative to an inverse trough shape situated over the entire mined-out areas and their immediate surroundings.Local features, such as geological faults, can have a secondary effect on the local variation of the uplift.The processes of subsidence and uplift are based on completely different mechanisms.Subsidence is initiated by a caving process, while the process of uplift is clearly linked to flooding.展开更多
The prediction of gas emissions arising from underground coal mining has been the subject of extensive research for several decades, however calculation techniques remain empirically based and are hence limited to the...The prediction of gas emissions arising from underground coal mining has been the subject of extensive research for several decades, however calculation techniques remain empirically based and are hence limited to the origin of calculation in both application and resolution. Quantification and management of risk associated with sudden gas release during mining(outbursts) and accumulation of noxious or combustible gases within the mining environment is reliant on such predictions, and unexplained variation correctly requires conservative management practices in response to risk. Over 2500 gas core samples from two southern Sydney basin mines producing metallurgical coal from the Bulli seam have been analysed in various geospatial context including relationships to hydrological features and geological structures. The results suggest variability and limitations associated with the present traditional approaches to gas emission prediction and design of gas management practices may be addressed using predictions derived from improved spatial datasets, and analysis techniques incorporating fundamental physical and energy related principles.展开更多
The paper aims to identify a reasonable method for mining ultra-thick coal seams in an end-slope in surface mine, With a case study of Heidaigou surface coal mine(HSCM), the paper conducted a comparative research on t...The paper aims to identify a reasonable method for mining ultra-thick coal seams in an end-slope in surface mine, With a case study of Heidaigou surface coal mine(HSCM), the paper conducted a comparative research on three mining methods, namely Underground Mining Method(UMM), Highwall Mining System(HMS) and Local Steep Slope Mining Method(LSSMM). A model was firstly established to simulate the impact that UMM and HMS exert on monitoring points and surface deformation. The way that stripping and excavation amount varies with different slope angle, and the corresponding end slope stability were analyzed in the mode of LSSMM. Then a TOPSIS model was established by taking into account six indicators such as recovery ratio, technical complexity and adaptability, the impact on surface mining production, production safety and economic benefits. Finally, LSSMM was determined as the best mining method for mining ultra-thick coal seams in end slope in HSCM.展开更多
It is very important to determine the extent of the fractured zone through which water can flow before coal mining under the water bodies.This paper deals with methods to obtain information about overburden rock failu...It is very important to determine the extent of the fractured zone through which water can flow before coal mining under the water bodies.This paper deals with methods to obtain information about overburden rock failure and the development of the fractured zone while coal mining in Xin'an Coal Mine.The risk of water inrush in this mine is great because 40%of the mining area is under the Xiaolangdi reservoir.Numerical simulations combined with geophysical methods were used in this paper to obtain the development law of the fractured zone under different mining conditions.The comprehensive geophysical method described in this paper has been demonstrated to accurately predict the height of the water-flow fractured zone.Results from the new model, which created from the results of numerical simulations and field measurements,were successfully used for making decisions in the Xin'an Coal Mine when mining under the Xiaolangdi Reservoir.Industrial scale experiments at the number 11201,14141 and 14191 working faces were safely carried out.These achievements provide a successful background for the evaluation and application of coal mining under large reservoirs.展开更多
Exploitation technology of pressure relief coalbed methane in vertical surface wells is a new method for exploration of gas and coalbed methane exploitation in mining areas with high concentrations of gas, where tecto...Exploitation technology of pressure relief coalbed methane in vertical surface wells is a new method for exploration of gas and coalbed methane exploitation in mining areas with high concentrations of gas, where tectonic coal developed. Studies on vertical surface well technology in the Huainan Coal Mining area play a role in demonstration in the use of clean, new energy resources, preventing and reducing coal mine gas accidents and protecting the environment. Based on the practice of gas drainage engineering of pressure relief coalbed methane in vertical surface wells and combined with relative geological and exploration en- gineering theories, the design principles of design and structure of wells of pressure relief coalbed methane in vertical surface wells are studied. The effects of extraction and their causes are discussed and the impact of geological conditions on gas production of the vertical surface wells are analyzed. The results indicate that in mining areas with high concentrations of gas, where tectonic coal developed, a success rate of pressure relief coalbed methane in surface vertical well is high and single well production usually great. But deformation due to coal exploitation could damage boreholes and cause breaks in the connection between aquifers and bore-holes, which could induce a decrease, even a complete halt in gas production of a single well. The design of well site location and wellbore configuration are the key for technology. The development of the geological conditions for coalbed methane have a significant effect on gas production of coalbed methane wells.展开更多
In this study,analyses are conducted on the information features of a construction site,a cornfield and subsidence seeper land in a coal mining area with a synthetic aperture radar (SAR) image of medium resolution. Ba...In this study,analyses are conducted on the information features of a construction site,a cornfield and subsidence seeper land in a coal mining area with a synthetic aperture radar (SAR) image of medium resolution. Based on features of land cover of the coal mining area,on texture feature extraction and a selection method of a gray-level co-occurrence matrix (GLCM) of the SAR image,we propose in this study that the optimum window size for computing the GLCM is an appropriate sized window that can effectively distinguish different types of land cover. Next,a band combination was carried out over the text feature images and the band-filtered SAR image to secure a new multi-band image. After the transformation of the new image with principal component analysis,a classification is conducted selectively on three principal component bands with the most information. Finally,through training and experimenting with the samples,a better three-layered BP neural network was established to classify the SAR image. The results show that,assisted by texture information,the neural network classification improved the accuracy of SAR image classification by 14.6%,compared with a classification by maximum likelihood estimation without texture information.展开更多
A complex substrate consisting of fly ash, coal gangue and excess sludge was used as an experimental soil in pot culture experiments. Different soil compositions were tested by observing the growth of arbuscular mycor...A complex substrate consisting of fly ash, coal gangue and excess sludge was used as an experimental soil in pot culture experiments. Different soil compositions were tested by observing the growth of arbuscular mycorrhizal （AM） fungi inoculated white clover, rye grass or com. The biomass of the host plants, the mycorrhizal colonization （MC） rate and the mycorrhizal depen- dency （MD） were measured. The research addresses the preferable AMF-plant-substrate combination appropriate for restoration of coal mines. We used two inoculation methods： single-inoculation with Glomus versiforme or Glomus mosseae and a dual inocula- tion with both Ctv and Gm. The results show that G^m is the preferable fungi and that dual inoculation does not show advantages for the restoration of coal mines. White clover inoculated with AM fungi is the most suitable condition for restoration of coal mines. The best weight ratio of fly ash, coal gangue and excess sludge was found to be 20：60：20. The optimum treatment conditions of AMF-plant-activated-substrate are described.展开更多
In order to solve the problems of top-coal inadequate destruction and large amounts of gas emission in mining extra thick and hard coal seam,this study investigated the pre-splitting for deep borehole blasting and gas...In order to solve the problems of top-coal inadequate destruction and large amounts of gas emission in mining extra thick and hard coal seam,this study investigated the pre-splitting for deep borehole blasting and gas pre-draining technologies on top coal.The mechanism of the technologies was systematically expounded based on hard top-coal cracks development obtained by numerical simulation and theoretical analysis.The results show that explosive blasting in the hard rock results in a large number of cracks and large displacement in the rock mass due to the effect of explosion stress.Meanwhile,the thick top-coal caves,and desorbing gas flows along the cracks improve gas extraction.Finally,the pre-splitting for deep borehole blasting and gas pre-draining technologies was applied in No.3802 working face of Shui Liandong Coal Mine,which increases monthly output in the face to 67.34 kt and the drained gas concentration to 86.2%.The drained gas average concentration from each borehole reaches 40%,and the effect is remarkable.展开更多
With the increasing depth of coal mining,the requirements for coring devices that maintain pressure are increasing.To adapt to the special environment in deep coal seams and improve the accuracy of testing gas content...With the increasing depth of coal mining,the requirements for coring devices that maintain pressure are increasing.To adapt to the special environment in deep coal seams and improve the accuracy of testing gas content,a low-disturbance pressure-preserving corer was developed.The measurement of gas content using this corer was analyzed.The coring test platform was used to complete a coring function test.A pressurized core with a diameter of 50 mm was obtained.The pressure was 0.15 MPa,which was equal to the pressure of the liquid column of the cored layer,indicating that the corer can be successfully used in a mud environment.Next,a pressure test of the corer was conducted.The results showed that under conditions of low pressure(8 MPa)and high pressure(25 MPa),the internal pressure of the corer remained stable for more than 1 h,indicating that the corer has good ability to maintain pressure.Therefore,the corer can be applied at deep coal mine sites.The results of this research can be used to promote the safe exploitation of deep coal mines and the exploitation of methane resources in coalbeds.展开更多
In this article an attempt to determine the influence of mining factors on the seismic activity during the longwall mining of the upper layer of coal seam no.405/2 in one of the Polish hard coal mines in the Upper Sil...In this article an attempt to determine the influence of mining factors on the seismic activity during the longwall mining of the upper layer of coal seam no.405/2 in one of the Polish hard coal mines in the Upper Silesian Coal Basin was conducted.Two longwall panels were mined in analogous geological conditions and based on the same mining system and technology.However,there was significant difference with regards to the mining factors,which was reflected in the observed seismic activity.Some tools used in mining seismology were applied to illustrate the aforementioned influence of mining factors,e.g.the frequency-energy distribution,the frequency-magnitude distribution,the 2 D distribution of released seismic energy,the relationship between released seismic energy and the volume of mined coal,the Benioff strain release,and the Gutenberg-Richter(GR)b coefficient distribution(b is the proportion between high and low energy tremors).Concerning the Benioff strain release,a new solution,based on the slope of a fitted line in a moving time window,is proposed.展开更多
For a low permeability single coal seam prone to gas outbursts, pre-drainage of gas is difficult and inefficient, seriously restricting the safety and efficiency of production. Radical measures of increasing gas extra...For a low permeability single coal seam prone to gas outbursts, pre-drainage of gas is difficult and inefficient, seriously restricting the safety and efficiency of production. Radical measures of increasing gas extraction efficiency are pressure relief and infrared antireflection. We have analyzed the effect of mining conditions and the regularity of mine pressure distribution in front of the working face of a major coal mine of the Jiaozuo Industrial （Group） Co. as our test area, studied the width of the depressurization zone in slice mining and analyzed gas efficiency and fast drainage in the advanced stress relaxation zone. On that basis, we further investigated and practiced the exploitation technology of shallow drilling, fan dril- ling and grid shape drilling at the working face. Practice and our results show that the stress relaxation zone is the ideal region for quick and efficient extraction of gas. By means of an integrated extraction technology, the amount of gas emitted into the zone was greatly reduced, while the risk of dangerous outbursts of coal and gas was lowered markedly. This exploration provides a new way to control for gas in working faces of coal mines with low permeability and risk of gas outbursts of single coal seams in the Jiaozuo mining area.展开更多
The development and achievements of modern coal mining with stowing are discussed in this paper. The necessity of developing coal mining with stowing is briefly summarized and internal damage within the strata and ext...The development and achievements of modern coal mining with stowing are discussed in this paper. The necessity of developing coal mining with stowing is briefly summarized and internal damage within the strata and external damage on surface induced by longwall working with caving are discussed. Technological features of coal mining with pneumatic stowing in Germany, and fully mechanised coal mining with solid dense stowing in China, are discussed. In German hard coal mining stowing technologies are for technical, infrastructural and economical reasons not applicable. The discussion includes the stowing material transportation system, the stowing machine, and processes at the face. Progressiveness and application universality of China's fully mechanised coal mining with solid dense stowing are illustrated through practical examples with different conditions. Obviously, the fully mechanised coal mine with solid dense stowing can be improved by automaion systems. This paper discusses further developmental potential of the technology.展开更多
The coal industry in China has been moving from the semiarid eastern to the drier western regions since the beginning of this century.Water protection is of the utmost concern for coal mining in these regions.Lu'a...The coal industry in China has been moving from the semiarid eastern to the drier western regions since the beginning of this century.Water protection is of the utmost concern for coal mining in these regions.Lu'an,as one of the state coal mining bases in China,has been seeing increasingly heavier pressure for the protection of water resources.This article considers Lu'an as an example and describes the ways these concerns may be alleviated.High mine-water utilization rates have effectively reduced wasting of water and,consequently,have reduced water demand.Using the top layers of the Ordavician as aquifuge barriers can prevent floor karst water inrush into the longwall face and can protect the regional Ordovician karst water resources at the same time.The strength of the overlying Quaternary clay can protect against roof collapse and has successfully preserved the Quaternary porous water resource.展开更多
The"three shells"cooperative support technology was proposed herein according to both the large deformation of the rock surrounding large-section chambers in deep mines and the precarious stability of the su...The"three shells"cooperative support technology was proposed herein according to both the large deformation of the rock surrounding large-section chambers in deep mines and the precarious stability of the support structures therein.The development range of the plastic zone in the surrounding rock was controlled by a stress shell to reduce the difficulty of controlling the surrounding rock.Additionally,the residual strength of the rock mass in the plastic zone and the self-bearing capacity of the surrounding rock were improved by a reinforced load-bearing shell.Furthermore,a passive load-bearing shell could restore the triaxial stress state of the surrounding rock on the free surface,reduce the influence of the external environment on the surrounding rock,and reinforce the surrounding rock with the strength of the shell.Reasonable layouts of large-section chambers were determined by analyzing the control effect of the stress shell on the surrounding rock under three kinds of in situ stress fields.The orthogonal test method was applied to reveal the influences of different support parameters in the reinforced loadbearing shell and passive load-bearing shell on the surrounding rock stability.The surrounding rock control effect of the"three shells"collaborative support technology was analyzed through numerical simulation and field monitoring.The results show that the maximum displacement between the roof and floor of the coal preparation chamber in the Xinjulong coal mine was approximately 48 mm,and the maximum displacement between its two sides was approximately 65 mm,indicating that the technology proposed herein could meet the long-term control requirements of the surrounding rock stability for large-section chambers in deep mines.展开更多
Based on data from through-hole and logging,we studied the failure characteristics of surface drainage wells for relieved coal gas in Huainan mining area and its influencing factors.The results show that the damaged p...Based on data from through-hole and logging,we studied the failure characteristics of surface drainage wells for relieved coal gas in Huainan mining area and its influencing factors.The results show that the damaged positions of drainage wells are mainly located at the thick clay layer in the low alluvium and the lithological interface in the upper section of bedrock in west mining area.The failure depth of casing is 244-670 m and concentrates at about 270-460 m deep.These damaged positions are mainly located in the bending zone according to three zones of rock layers in the vertical section above the roof divided. Generally,the casing begins to deform or damage before the face line about 30-150 m.Special formation structure and rock mass properties are the direct causes of the casing failure,high mining height and fast advancing speed are fundamental reasons for rock mass damage.However,the borehole configuration and spacing to the casing failure are not very clear.展开更多
Behavior choice, coal mine monitoring, and control intensity are combined in a general mathematical model established from the perspective of a behavioral game. A case study is provided with effective conditions of mo...Behavior choice, coal mine monitoring, and control intensity are combined in a general mathematical model established from the perspective of a behavioral game. A case study is provided with effective conditions of monitoring provided. This paper defines the expected value difference of control return and behavior cost difference and discusses the measurement and optimization of variable indexes, including the monitoring intensity and costs of control. The results imply that the control of unsafe behavior can be more effective when monitoring and control of coal mines are both improved. Monitoring will be useful when the rewards for displaying safe behavior, and the monitoring of unsafe behavior, are improved to a high level.展开更多
基金funded by the National Natural Science Foundation of China (No.52225402)Inner Mongolia Research Institute,China University of Mining and Technology-Beijing (IMRI23003)。
文摘In the gas-coal integrated mining field,the conventional design method of pipeline coal pillars leads to a large amount of coal pillars being unrecovered and overlooks the pipeline's safety requirements.Considering the coal pillar recovery rate and pipeline's safety requirements,two new shaped coal pillar design approaches for subsurface pipelines were developed.Firstly,the deformation limitations for measuring pipeline safety are categorized into two:no deformation is permitted,and deformation is acceptable within elastic limits.Subsequently,integrating the key stratum theory(KST)and cave angle,a fishbone-shaped coal pillar design approach that does not permit pipeline deformation is established.Meanwhile,combined with the ground subsidence and the pipeline's elastic deformation limit,a grille-shaped coal pillar design approach that accepts deformation pipelines within elastic limits is established.Those two new approaches clarify parameters including mined width,coal pillar width and mined length.Finally,the case study shows that the designed mined width,coal pillar width and mined length of the fishbone-shaped coal pillar are 90,80,and 130 m,while those of the grille-shaped are 320,370,and640 m.Compared with the conventional method,the fishbone-shaped and grille-shaped coal pillar design approaches recovered coal pillar resources of 2.65×10~6and 5.81×10~6t on the premise of meeting the pipeline safety requirements,and the recovery rates increased by 20.5%and 45.0%,with expenditures representing only 56.46%and 20.02%of the respective benefits.These new approaches provide managers with diverse options for protecting pipeline safety while promoting coal pillar recovery,which is conducive to the harmonic mining of gas-coal resources.
基金supported by the Major Project of the National Basic Research Program of China (No2006CB202200)the Program for New Century Excellent Talents in Uni-versity (NoNCET07-0800)the Special Fund for Basic Research and Operating Expenses of the China University of Mining & Technology, Beijing and the Academician workstation in enterprise of Jiangsu Province (No.BM2009563)
文摘Pump chambers, normally used as dominant structures in mining engineering to insure the safety and production of un-derground coal mines, become generally deformed under conditions of deep mining. Given the geology and engineering condition of Qishan Coal Mine in Xuzhou, the failure characteristics of pump chambers at the –1000 m level show that the main cause can be attributed to the spatial effect induced by intersectional chambers, where one pump is constructed per well. We developed an opti-mized design of the pump room, in which the pump wells in the traditional design are integrated into one compounding well. We suggest that the new design can limit the spatial effect of intersectional chambers during construction given our relevant numerical simulation. The new design is able to simplify the structure of the pump chamber and reduce the amount of excavation required. Based on a bolt-mesh-anchor with a rigid gap coupling supporting technology, the stability of pump chamber can be improved greatly.
基金funded by the State Key Basic Research Program of China(No.2011CB201201)the National Key TechnologyR&D Program(No.2008BAB36B07)the National Natural Science Foundation of China(Nos.51134018 and 50674092)
文摘Non-pillar mining,top-coal caving and protected coal seam mining are the most popular mining methods in coal exploitation,and the different mining layouts will change the stress state and failure mechanism of coal in front of the working face.In this paper,mining-induced mechanical behaviors under three mining layouts have been simulated in the laboratory to investigate the effects of mining layouts on the deformation and strength of coal.Furthermore,the coal failure mechanism under different mining layouts is analyzed microscopically.The experimental results indicate that the stage characteristics of the coal deformation are obvious.Under the serial action of non-pillar mining,top-coal caving and protected coal seam mining layouts,the values of radial deformation,volume strain and Poisson's ratio increase,while the peak strength and deformation modulus decrease at the same buried depth,and the peak strength under non-pillar mining,top-coal caving and protected coal seam mining is about 3.0,2.5 and 2.0 times of the initial confining pressure,respectively.The results also indicate that the trend of the coal deformation decreases with the increase of the buried depth under the same mining layout,while the strength and deformation modulus increase,and the failure mechanism under three mining layouts is dominated with shear/tensile failure.
文摘This paper attempts to quantify the effect of backfilling on pillar strength in highwall mining using numerical modelling. Calibration against the new empirical strength formula for highwall mining was conducted to obtain the material parameters used in the numerical modelling. With the obtained coal strength parameters, three sets of backfill properties were investigated. The results reveal that the behavior of pillars varies with the type and amount of backfill as well as the pillar width to mining height ratio(w/h). In case of cohesive backfill, generally 75% backfill shows a significant increase in peak strength, and the increase in peak strength is more pronounced for the pillars having lower w/h ratios. In case of noncohesive backfill, the changes in both the peak and residual strengths with up to 92% backfill are negligible while the residual strength constantly increases after reaching the peak strength only when 100%backfill is placed. Based on the modelling results, different backfilling strategies should be considered on a case by case basis depending on the type of backfill available and desired pillar dimension.
文摘After the mass closures of entire coal mine districts in Europe at the end of the last century, a new phenomenon of surface movement was observed—an upward movement.Although most surface movement(i.e., subsidence) occurs in the months and years after mining by the longwall method, surface movement still occurs many decades after mining is terminated.After the closure and flooding of underground excavations and surrounding rock, this movement was reversed.This paper focuses on quantifying the upward movement in two neighboring coal mines(Winterslag and Zwartberg, Belgium).The study is based on data from a remote sensing technique: interferometry with synthetic aperture radar(INSAR).The results of the study show that the rate of upward movement in the decade after closure is about 10 mm/year on average.The upward movements are not linked directly to the past exploitation directly underneath a location.The amounts of subsidence at specific locations are linked mainly to their positions relative to an inverse trough shape situated over the entire mined-out areas and their immediate surroundings.Local features, such as geological faults, can have a secondary effect on the local variation of the uplift.The processes of subsidence and uplift are based on completely different mechanisms.Subsidence is initiated by a caving process, while the process of uplift is clearly linked to flooding.
基金support of the Australian Government Research Training Program Scholarshipgratefully acknowledge the direct financial support of Me Cee Solutions Pty Ltd
文摘The prediction of gas emissions arising from underground coal mining has been the subject of extensive research for several decades, however calculation techniques remain empirically based and are hence limited to the origin of calculation in both application and resolution. Quantification and management of risk associated with sudden gas release during mining(outbursts) and accumulation of noxious or combustible gases within the mining environment is reliant on such predictions, and unexplained variation correctly requires conservative management practices in response to risk. Over 2500 gas core samples from two southern Sydney basin mines producing metallurgical coal from the Bulli seam have been analysed in various geospatial context including relationships to hydrological features and geological structures. The results suggest variability and limitations associated with the present traditional approaches to gas emission prediction and design of gas management practices may be addressed using predictions derived from improved spatial datasets, and analysis techniques incorporating fundamental physical and energy related principles.
基金provided by the National Natural Science Foundation of China(No.90510002)the Science and Technology Research of the Ministry of Education of China(No.306008)
文摘The paper aims to identify a reasonable method for mining ultra-thick coal seams in an end-slope in surface mine, With a case study of Heidaigou surface coal mine(HSCM), the paper conducted a comparative research on three mining methods, namely Underground Mining Method(UMM), Highwall Mining System(HMS) and Local Steep Slope Mining Method(LSSMM). A model was firstly established to simulate the impact that UMM and HMS exert on monitoring points and surface deformation. The way that stripping and excavation amount varies with different slope angle, and the corresponding end slope stability were analyzed in the mode of LSSMM. Then a TOPSIS model was established by taking into account six indicators such as recovery ratio, technical complexity and adaptability, the impact on surface mining production, production safety and economic benefits. Finally, LSSMM was determined as the best mining method for mining ultra-thick coal seams in end slope in HSCM.
基金the National Basic Research Program of China(No.2007CB209401) for its financial support
文摘It is very important to determine the extent of the fractured zone through which water can flow before coal mining under the water bodies.This paper deals with methods to obtain information about overburden rock failure and the development of the fractured zone while coal mining in Xin'an Coal Mine.The risk of water inrush in this mine is great because 40%of the mining area is under the Xiaolangdi reservoir.Numerical simulations combined with geophysical methods were used in this paper to obtain the development law of the fractured zone under different mining conditions.The comprehensive geophysical method described in this paper has been demonstrated to accurately predict the height of the water-flow fractured zone.Results from the new model, which created from the results of numerical simulations and field measurements,were successfully used for making decisions in the Xin'an Coal Mine when mining under the Xiaolangdi Reservoir.Industrial scale experiments at the number 11201,14141 and 14191 working faces were safely carried out.These achievements provide a successful background for the evaluation and application of coal mining under large reservoirs.
基金Projects 2007AA06Z220 supported by the Hi-tech Research and Development Program of China307014 by the Key Science and Technology Program of the Ministry of Education
文摘Exploitation technology of pressure relief coalbed methane in vertical surface wells is a new method for exploration of gas and coalbed methane exploitation in mining areas with high concentrations of gas, where tectonic coal developed. Studies on vertical surface well technology in the Huainan Coal Mining area play a role in demonstration in the use of clean, new energy resources, preventing and reducing coal mine gas accidents and protecting the environment. Based on the practice of gas drainage engineering of pressure relief coalbed methane in vertical surface wells and combined with relative geological and exploration en- gineering theories, the design principles of design and structure of wells of pressure relief coalbed methane in vertical surface wells are studied. The effects of extraction and their causes are discussed and the impact of geological conditions on gas production of the vertical surface wells are analyzed. The results indicate that in mining areas with high concentrations of gas, where tectonic coal developed, a success rate of pressure relief coalbed methane in surface vertical well is high and single well production usually great. But deformation due to coal exploitation could damage boreholes and cause breaks in the connection between aquifers and bore-holes, which could induce a decrease, even a complete halt in gas production of a single well. The design of well site location and wellbore configuration are the key for technology. The development of the geological conditions for coalbed methane have a significant effect on gas production of coalbed methane wells.
基金Projects 40771143 supported by the National Natural Science Foundation of China2007AA12Z162 by the Hi-tech Research and Development Program of China
文摘In this study,analyses are conducted on the information features of a construction site,a cornfield and subsidence seeper land in a coal mining area with a synthetic aperture radar (SAR) image of medium resolution. Based on features of land cover of the coal mining area,on texture feature extraction and a selection method of a gray-level co-occurrence matrix (GLCM) of the SAR image,we propose in this study that the optimum window size for computing the GLCM is an appropriate sized window that can effectively distinguish different types of land cover. Next,a band combination was carried out over the text feature images and the band-filtered SAR image to secure a new multi-band image. After the transformation of the new image with principal component analysis,a classification is conducted selectively on three principal component bands with the most information. Finally,through training and experimenting with the samples,a better three-layered BP neural network was established to classify the SAR image. The results show that,assisted by texture information,the neural network classification improved the accuracy of SAR image classification by 14.6%,compared with a classification by maximum likelihood estimation without texture information.
基金Project 2007024 supported by the Environmental Science and Technology Fund of the Environmental Protection Department of Jiangsu Province
文摘A complex substrate consisting of fly ash, coal gangue and excess sludge was used as an experimental soil in pot culture experiments. Different soil compositions were tested by observing the growth of arbuscular mycorrhizal （AM） fungi inoculated white clover, rye grass or com. The biomass of the host plants, the mycorrhizal colonization （MC） rate and the mycorrhizal depen- dency （MD） were measured. The research addresses the preferable AMF-plant-substrate combination appropriate for restoration of coal mines. We used two inoculation methods： single-inoculation with Glomus versiforme or Glomus mosseae and a dual inocula- tion with both Ctv and Gm. The results show that G^m is the preferable fungi and that dual inoculation does not show advantages for the restoration of coal mines. White clover inoculated with AM fungi is the most suitable condition for restoration of coal mines. The best weight ratio of fly ash, coal gangue and excess sludge was found to be 20：60：20. The optimum treatment conditions of AMF-plant-activated-substrate are described.
基金financially supported by the National Natural Science Fund of China(Nos.51004003 and 51474009)Anhui Province Education Department Natural Science Fund Key Project of China(No.KJ2010A091)
文摘In order to solve the problems of top-coal inadequate destruction and large amounts of gas emission in mining extra thick and hard coal seam,this study investigated the pre-splitting for deep borehole blasting and gas pre-draining technologies on top coal.The mechanism of the technologies was systematically expounded based on hard top-coal cracks development obtained by numerical simulation and theoretical analysis.The results show that explosive blasting in the hard rock results in a large number of cracks and large displacement in the rock mass due to the effect of explosion stress.Meanwhile,the thick top-coal caves,and desorbing gas flows along the cracks improve gas extraction.Finally,the pre-splitting for deep borehole blasting and gas pre-draining technologies was applied in No.3802 working face of Shui Liandong Coal Mine,which increases monthly output in the face to 67.34 kt and the drained gas concentration to 86.2%.The drained gas average concentration from each borehole reaches 40%,and the effect is remarkable.
基金supported by the National Natural Science Foundation of China(No.51827901)the National Natural Science Foundation of China(No.52225403)+1 种基金the Program for Guangdong Introducing Innovative and Entrepreneurial Teams of China(No.2019ZT08G315)the Sichuan Science and Technology Program of China(No.2023NSFSC0780).
文摘With the increasing depth of coal mining,the requirements for coring devices that maintain pressure are increasing.To adapt to the special environment in deep coal seams and improve the accuracy of testing gas content,a low-disturbance pressure-preserving corer was developed.The measurement of gas content using this corer was analyzed.The coring test platform was used to complete a coring function test.A pressurized core with a diameter of 50 mm was obtained.The pressure was 0.15 MPa,which was equal to the pressure of the liquid column of the cored layer,indicating that the corer can be successfully used in a mud environment.Next,a pressure test of the corer was conducted.The results showed that under conditions of low pressure(8 MPa)and high pressure(25 MPa),the internal pressure of the corer remained stable for more than 1 h,indicating that the corer has good ability to maintain pressure.Therefore,the corer can be applied at deep coal mine sites.The results of this research can be used to promote the safe exploitation of deep coal mines and the exploitation of methane resources in coalbeds.
文摘In this article an attempt to determine the influence of mining factors on the seismic activity during the longwall mining of the upper layer of coal seam no.405/2 in one of the Polish hard coal mines in the Upper Silesian Coal Basin was conducted.Two longwall panels were mined in analogous geological conditions and based on the same mining system and technology.However,there was significant difference with regards to the mining factors,which was reflected in the observed seismic activity.Some tools used in mining seismology were applied to illustrate the aforementioned influence of mining factors,e.g.the frequency-energy distribution,the frequency-magnitude distribution,the 2 D distribution of released seismic energy,the relationship between released seismic energy and the volume of mined coal,the Benioff strain release,and the Gutenberg-Richter(GR)b coefficient distribution(b is the proportion between high and low energy tremors).Concerning the Benioff strain release,a new solution,based on the slope of a fitted line in a moving time window,is proposed.
基金the Major State Basic Research Program of China which provided for our financial support (No. 2005CB221501)
文摘For a low permeability single coal seam prone to gas outbursts, pre-drainage of gas is difficult and inefficient, seriously restricting the safety and efficiency of production. Radical measures of increasing gas extraction efficiency are pressure relief and infrared antireflection. We have analyzed the effect of mining conditions and the regularity of mine pressure distribution in front of the working face of a major coal mine of the Jiaozuo Industrial （Group） Co. as our test area, studied the width of the depressurization zone in slice mining and analyzed gas efficiency and fast drainage in the advanced stress relaxation zone. On that basis, we further investigated and practiced the exploitation technology of shallow drilling, fan dril- ling and grid shape drilling at the working face. Practice and our results show that the stress relaxation zone is the ideal region for quick and efficient extraction of gas. By means of an integrated extraction technology, the amount of gas emitted into the zone was greatly reduced, while the risk of dangerous outbursts of coal and gas was lowered markedly. This exploration provides a new way to control for gas in working faces of coal mines with low permeability and risk of gas outbursts of single coal seams in the Jiaozuo mining area.
文摘The development and achievements of modern coal mining with stowing are discussed in this paper. The necessity of developing coal mining with stowing is briefly summarized and internal damage within the strata and external damage on surface induced by longwall working with caving are discussed. Technological features of coal mining with pneumatic stowing in Germany, and fully mechanised coal mining with solid dense stowing in China, are discussed. In German hard coal mining stowing technologies are for technical, infrastructural and economical reasons not applicable. The discussion includes the stowing material transportation system, the stowing machine, and processes at the face. Progressiveness and application universality of China's fully mechanised coal mining with solid dense stowing are illustrated through practical examples with different conditions. Obviously, the fully mechanised coal mine with solid dense stowing can be improved by automaion systems. This paper discusses further developmental potential of the technology.
基金the sponsor by the National Natural Science Foundation of China (No. 50974115)the Program of Introducing Talents of Discipline to Universities (No.B07028)
文摘The coal industry in China has been moving from the semiarid eastern to the drier western regions since the beginning of this century.Water protection is of the utmost concern for coal mining in these regions.Lu'an,as one of the state coal mining bases in China,has been seeing increasingly heavier pressure for the protection of water resources.This article considers Lu'an as an example and describes the ways these concerns may be alleviated.High mine-water utilization rates have effectively reduced wasting of water and,consequently,have reduced water demand.Using the top layers of the Ordavician as aquifuge barriers can prevent floor karst water inrush into the longwall face and can protect the regional Ordovician karst water resources at the same time.The strength of the overlying Quaternary clay can protect against roof collapse and has successfully preserved the Quaternary porous water resource.
基金This work was supported by the Fundamental Research Funds for the Central Universities(No.2019XKQYMS61).
文摘The"three shells"cooperative support technology was proposed herein according to both the large deformation of the rock surrounding large-section chambers in deep mines and the precarious stability of the support structures therein.The development range of the plastic zone in the surrounding rock was controlled by a stress shell to reduce the difficulty of controlling the surrounding rock.Additionally,the residual strength of the rock mass in the plastic zone and the self-bearing capacity of the surrounding rock were improved by a reinforced load-bearing shell.Furthermore,a passive load-bearing shell could restore the triaxial stress state of the surrounding rock on the free surface,reduce the influence of the external environment on the surrounding rock,and reinforce the surrounding rock with the strength of the shell.Reasonable layouts of large-section chambers were determined by analyzing the control effect of the stress shell on the surrounding rock under three kinds of in situ stress fields.The orthogonal test method was applied to reveal the influences of different support parameters in the reinforced loadbearing shell and passive load-bearing shell on the surrounding rock stability.The surrounding rock control effect of the"three shells"collaborative support technology was analyzed through numerical simulation and field monitoring.The results show that the maximum displacement between the roof and floor of the coal preparation chamber in the Xinjulong coal mine was approximately 48 mm,and the maximum displacement between its two sides was approximately 65 mm,indicating that the technology proposed herein could meet the long-term control requirements of the surrounding rock stability for large-section chambers in deep mines.
基金sponsored by the National High-Tech Research and Development Program of China(No.2007AA06Z220)the Key Science and Technology Program of Ministry of Education(No. 307014)the Research Program of Huainan Mining Group.
文摘Based on data from through-hole and logging,we studied the failure characteristics of surface drainage wells for relieved coal gas in Huainan mining area and its influencing factors.The results show that the damaged positions of drainage wells are mainly located at the thick clay layer in the low alluvium and the lithological interface in the upper section of bedrock in west mining area.The failure depth of casing is 244-670 m and concentrates at about 270-460 m deep.These damaged positions are mainly located in the bending zone according to three zones of rock layers in the vertical section above the roof divided. Generally,the casing begins to deform or damage before the face line about 30-150 m.Special formation structure and rock mass properties are the direct causes of the casing failure,high mining height and fast advancing speed are fundamental reasons for rock mass damage.However,the borehole configuration and spacing to the casing failure are not very clear.
基金Project supports from The Humanistic and Social Scientific Research Planning Program in Ministry of Education of China (No.12YJA630063)The Social Science Foundation of Jiangsu Province of China (No. 10GLB001)the Ph.D. Programs Foundation of Ministry of Education of China (No. 20100095120014) are acknowledged
文摘Behavior choice, coal mine monitoring, and control intensity are combined in a general mathematical model established from the perspective of a behavioral game. A case study is provided with effective conditions of monitoring provided. This paper defines the expected value difference of control return and behavior cost difference and discusses the measurement and optimization of variable indexes, including the monitoring intensity and costs of control. The results imply that the control of unsafe behavior can be more effective when monitoring and control of coal mines are both improved. Monitoring will be useful when the rewards for displaying safe behavior, and the monitoring of unsafe behavior, are improved to a high level.
