During the excavation of deep coal and rock mass, the radial stress of the free face changes from three-dimensional compression state to two-dimensional stress, bearing the combined action of dynamic disturbance and s...During the excavation of deep coal and rock mass, the radial stress of the free face changes from three-dimensional compression state to two-dimensional stress, bearing the combined action of dynamic disturbance and static load at the same time. With that, many mines suffer from dynamic disasters, such as coal and gas outburst, rock burst and rock caving during deep mining excavation, which is often accompanied by plate crack, spalling and other disasters, seriously affecting the stability of stope and roadway. Taking thin rectangular coal and rock mass as the research object, the dual equation of the free vibration was derived and the exact solution model of the free vibration was established with the use of Hamilton dual system. Based on the action characteristics of the uniform impact load, the effective mode of the forced vibration was obtained by using the Duhamel integral principle and the orthogonality of the mode function. Based on the third strength theory and the numerical simulation results, the dynamic damage process and development trend of coal and rock mass were analyzed under uniform impact load. It was concluded that the starting position of dynamic damage can be judged by the first order main mode, and the development direction and trend of the damage can be judged by the fifth and sixth order main modes. It was concluded that the vibration mode functions of coal and rock mass with four side fixed (C-C-C-C), the two sides fixed and simply supported on the other (S-C-S-C) are mainly composed of three modes that are the first order (dominant frequency), the fifth order and the sixth order, from which the dynamic damage mechanism is preliminarily studied.展开更多
The rock mass rating(RMR)has been used across the geotechnical industry for half a century.In contrast,the coal mine roof rating(CMRR)was specifically introduced to underground coal mines two decades ago to link geolo...The rock mass rating(RMR)has been used across the geotechnical industry for half a century.In contrast,the coal mine roof rating(CMRR)was specifically introduced to underground coal mines two decades ago to link geological characterization with geotechnical risk mitigation.The premise of CMRR is that strength properties of mine roof rock are influenced by defects typical of coal measures stratigraphy.The CMRR has been used in longwall pillar design,roof support methods,and evaluation of extended cuts,but is rarely evaluated.Here,the RMR and CMRR are applied to a longwall coal mine.Roof rock mass classifications were undertaken at 67 locations across the mine.Both classifications showed marked spatial variability in terms of roof conditions.Normal and reverse faulting occur across the mine,and while no clear relationships exist between rock mass character and faulting,a central graben zone showed heterogeneous rock mass properties,and divergence between CMRR and RMR.Overall,the CMRR data fell within the broad envelope of results reported for extended cuts at Australian and U.S.coal mines.The corollary is that the CMRR is useful,and should not be used in isolation,but rather as a component of a strata control programme.展开更多
Coal-rock as a typical sedimentary rock has obvious stratification,namely it has transversely isotropic feature.Meanwhile,deformation leads to coal-rock mass having the characteristics of different porous and crack st...Coal-rock as a typical sedimentary rock has obvious stratification,namely it has transversely isotropic feature.Meanwhile,deformation leads to coal-rock mass having the characteristics of different porous and crack structures as well as local anisotropy.Equivalent axial and circumferential strain' formulas of the pure coal-rock mass specimen with a single crack were derived through the establishment of equivalent mechanical model of standard cylindrical coal-rock specimen,and have been widely used to a variety of media combined different structures containing multiple cracks.The complete stress strain curve of a real coal-rock specimen was obtained by the CTC test.Additionally,according to the comparison with the theoretical value,the theoretical mechanical model could well explain the deformation characteristics of coal-rock mass and verify its validity.Further,following features were analyzed:strain normalized coefficient and elastic modulus(Poisson's ratio) in vertical and parallel direction to the stratification,stratification angle,porosity,pore radius,normal and tangential stiffness of crack,and the relationship of different crack width with different tangential stiffness of crack.Through the analysis above,it substantiate this claim that the theoretical model with better reliability reflects the transversely isotropic nature of the coal-rock and the local anisotropy caused by the porous and cracks.展开更多
For a study of the movement and deformation of coal-rock mass and low protected seams below a stope,as well as for fracture developments and rules of evolution of permeability,we designed a plane strain model test sta...For a study of the movement and deformation of coal-rock mass and low protected seams below a stope,as well as for fracture developments and rules of evolution of permeability,we designed a plane strain model test stand to carry out model tests of similar materials in order to improve the effect of gas drainage from low protected seams and to measure the movement and deformation of coal-rock mass using a method of non-contact close-range photogrammetry.Our results show that 1) using paraffin melting to take the place of coal seam mining can satisfy the mining conditions of a protective seam;2) coal-rock mass under goafs has an upward movement after the protective seam has been mined,causing floor heaving;3) low protected seams become swollen and deformed,providing a good pressure-relief effect and causing the coal-rock mass under both sides of coal pillars to become deformed by compression and 4) the evolution of permeability of low protected seams follows the way of initial values→a slight decrease→a great increase→stability→final decrease.Simultaneously,the coefficient of air permeability increased at a decreasing rate with an increase in interlayer spacing.展开更多
The interaction mechanism between coal and rock masses with supporting materials is significant in roadway control, especially in deep underground mining situations where dynamic hazards frequently happened due to hig...The interaction mechanism between coal and rock masses with supporting materials is significant in roadway control, especially in deep underground mining situations where dynamic hazards frequently happened due to high geo-stress and strong disturbed effects. This paper is to investigate the strain energy evolution in the interaction between coal and rock masses with self-designed energy-absorbing props and rock bolts by numerical modeling with the finite difference method. The interaction between rock and rock bolt/prop is accomplished by the cables element and the interface between the inner and outer props. Roadway excavation and coal extraction conditions in deep mining are numerically employed to investigate deformation, plastic zone ranges, strain energy input, accumulation, dissipation,and release. The effect on strain energy input, accumulation, dissipation, and release with rock deformation, and the plastic zone is addressed. A ratio of strain energy accumulation, dissipation, and release with energy input a, β, γ is to assess the dynamic hazards. The effects on roadway excavation and coal extraction steps of a, β, γ are discussed. The results show that:(1) In deep high geo-stress roadways, the energyabsorbing support system plays a dual role in resisting deformation and reducing the scope of plastic zones in surrounding rock, as well as absorbing energy release in the surrounding rock, especially in the coal extraction state to mitigate disturbed effects.(2) The strain energy input, accumulation is dependent on roadway deformation, the strain energy dissipation is relied on plastic zone area and disturbed effects, and strain energy release density is the difference among the three. The function of energyabsorbing rock bolts and props play a key role to mitigate strain energy release density and amount, especially in coal extraction condition, with a peak density value from 4×10^(4) to 1×10^(4)J/m^(3), and amount value from 3.57×10^(8) to 1.90×10^(6)J.(3) When mining is advanced in small steps, the strain energy accumulation is dominated. While in a large step, the released energy is dominant, thus a more dynamic hazards proneness. The energy-absorbing rock bolt and prop can reduce three times strain energy release amount, thus reducing the dynamic hazards. The results suggest that energy-absorbing props and rock bolts can effectively reduce the strain energy in the coal and rock masses, and prevent rock bursts and other hazards.The numerical model developed in this study can also be used to optimize the design of energyabsorbing props and rock bolts for specific mining conditions.展开更多
In order to evaluate the feasibility of safe mining close to the contact zone under reduced security coal pillar conditions at a coal mine in eastern China, the interaction mechanism of the interface between deep buri...In order to evaluate the feasibility of safe mining close to the contact zone under reduced security coal pillar conditions at a coal mine in eastern China, the interaction mechanism of the interface between deep buried sand and a paleo-weathered rock mass was investigated in the laboratory by direct shear testing. A DRS-1 high pressure soil shear testing machine and orthogonal design method were used in the direct shear tests. Variance and range methods were applied to analyze the sensitivity of each factor that has an influence on the mechanical characters of the interface. The test results show that the normal pressure is the main influencing factor for mechanical characteristics of the interface, while the lithological characters and roughness are minor factors; the shear stress against shear displacement curve for the interface shows an overall hyperbola relationship, no obvious peak stress and dilatancy was observed.When the normal pressure is 6 MPa, the shear strengths of interfaces with different roughness are basically the same, and when the normal pressure is more than 8 MPa, the larger the roughness of the interface, the larger will be the shear strength; the shear strength has a better linear relationship with the normal pressure, which can be described by a linear Mohr–Coulomb criterion.展开更多
The authors applied the Secondary Ion Mass Spectrometry (SIMS) technique to the analysis of compositions and structures of vitrinites fusinites, fusinites bitumens and graptolites in the hydrocarbon source rocks with ...The authors applied the Secondary Ion Mass Spectrometry (SIMS) technique to the analysis of compositions and structures of vitrinites fusinites, fusinites bitumens and graptolites in the hydrocarbon source rocks with different maturities dscribed their SIMS spectral characteristics and found that different macerals have differnt spectra which, reflected the compositional and structural differences of macerals. Moreover, the change bod of parameter CH2+/CH3+ can be used for the evaluation of thermal evolution regularity of macerals in the hydrocarbon source rocks The study results show that the SIMS technique is a powerful means for microara analysis of macerals in coals and source rocks. It is certain that the study level of macerals can be raised by detailed study of SIMS results of SIMS results of macerals.展开更多
According to the rock burst features occurred in the coal mass of roadway rib in one mine,the mechanics model of coal mass and roof structure system along the edge of goaf was founded to analyze the stress of roof roc...According to the rock burst features occurred in the coal mass of roadway rib in one mine,the mechanics model of coal mass and roof structure system along the edge of goaf was founded to analyze the stress of roof rock layer,so the subside curve of roof rock layer was deduced.Furthermore,the stability of coal and rock system were analyzed,the critical load and critical resistance zone were used to judge the danger degree of rock burst occurrence.The influence of coal mass strength,brittleness degree,coal seam thickness,roof thickness,suspending length,equivalent shear module on the critical load, critical resistance zone was confirmed.So the rock burst occurrence conditions of coal mass in roadway rib mainly depend on mining depth,coal seam thickness and hard roof and floor,which are decided by the above studies,and successfully applied in prediction and prevention of rock burst in this mine.展开更多
In accordance with the confusion on classification of source rocks, the authors raised a source rock classification for its enriched and dispersed organic matter types based on both Alpern’s idea and maceral genesis/...In accordance with the confusion on classification of source rocks, the authors raised a source rock classification for its enriched and dispersed organic matter types based on both Alpern’s idea and maceral genesis/composition. The determined rock type is roughly similar to palynofacies of Combaz , whereas it is "rock maceral facies (for coal viz. coal facies)" in strictly speaking. Therefore, it is necessary to use the organic ingredients classification proposed by the authors so that it can be used for both maceral analysis and environment research . This source rock classification not only shows sedimentology and diagenetic changes but also acquires organic matter type even if hydrocarbon potential derived from maceral’s geochemical parameters. So, it is considered as genetic classification. The "rock maceral facies" may be transformed to sedimentary organic facies , which is used as quantitative evaluation means if research being perfect.Now, there are many models in terms of structure either for coal or for kerogen. In our opinion, whatever coal or kerogen ought be polymer, then we follow Combaz’s thought and study structure of amorphous kerogens which are accordance with genetic mechanism showing biochemical and geochemical process perfectly. Here, we use the time of flight secondary ion mass spectrometry (TOFSIMS) to expand Combaz’s models from three to five. They are also models for coal.展开更多
The purpose of this study was to develop a physico-mathematical model and technique for estimation of chemical bond stability depending on electric field intensity of an external point charge.A hypothesis for a possib...The purpose of this study was to develop a physico-mathematical model and technique for estimation of chemical bond stability depending on electric field intensity of an external point charge.A hypothesis for a possible physico-chemical mechanism of the formation of additional harmful gases in the rock destruction by blasting was proposed.The theoretical basis of the hypothesis is the method of theretical evaluation of bond energy depending on the distance to a point charge,the third Coulomb centre.The quantum-mechanical model for calculating the electronic terms of molecules makes it possible to solve problems associated with the determination of parameters of molecules under the action of various physical fields on the system under consideration.The model was approved for some diatomic molecules.The discrepancy between the experimental data and calculated data did not exceed 14%,which proves accuracy of the obtained results.The model can be used in the field of research into the causes of gas-dynamic phenomena in underground coal mines,in studies of the degree of stability of nanostructured components of coal under physical influences,and in the theoretical design of new compounds and structures in the field of nanomaterial science and nanotechnology.展开更多
Numerical simulation-FLAC^(3D) and equivalent material simulation were carried out to analyze the damaged patterns and lows, distribution of plastic width of face, and surrounding rock of FMTC during the advance of wo...Numerical simulation-FLAC^(3D) and equivalent material simulation were carried out to analyze the damaged patterns and lows, distribution of plastic width of face, and surrounding rock of FMTC during the advance of work face with different thick coal seams based on engineering geology and exploitation technology of 1151(3) fully mechanized top-coal caving (FMTC) face in Xieqiao Colliery.The results show that there is damage,and the destruction characteristics of surrounding rock and coal mass are different obviously in asymmetric exploitation layout.The damaged zone in surrounding rock and the coal of the return airway is larger than that of the intake airway.Moreover, the retained coal pillars are all damaged by tension and shear fracture, and plastic zone in coal mass in the dip direction ahead of Face is nonuniform.There are large damage zones in roof and floor strata, surrounding rock, and coal of return and intake airways near work face.The damaged zone in the upper part of Face is larger than that in middle and lower parts.The fruits of this paper are of guiding significance for engineering practices, such as support design and choice, roadway supporting and maintaining, rock pressure control of FMTC face, etc.展开更多
The article focuses on a theoretical and experimental framework for the quantification of interaction between nonlinear geomechnical and physicochemical processes in high-stress coal-bearing rock mass during mining un...The article focuses on a theoretical and experimental framework for the quantification of interaction between nonlinear geomechnical and physicochemical processes in high-stress coal-bearing rock mass during mining under high seismic risk due to large-scale blasting and earthquakes,as well as because of structural and temperature effects.The tests were aimed to examine and study comprehensively the piston mechanism of gas exchange and mass transfer processes,revealed recently at the Institute of Mining,SB RAS,as well as to explain the fact that the earthquake-induced low-velocity(quasi-meter range)pendulum waves(velocity to 1 m/s and frequency of 0.5–5 Hz)could stimulate an increase in the gas content in coal mines.In order to perform laboratory investigation at the Institute of Mining SB RAS,special-purpose stand for analyzing gas exchange and mass transfer processes in coal-bearing geomaterials under various thermodynamic conditions(P,V,T)and gas composition was constructed in cooperation with the Institute of Semiconductors Physics SB RAS.Matching of air flow rate with compression pressures allowed to obtain relations showing that air flow rate increases at the uncertain time interval under the increasing of the compression pressure.The same measurements was carried out with another gases such as Hydrogen H_(2),Helium He,methane CH_(4),carbon dioxide CO_(2) and carbon oxide CO.The laboratory tests aimed to detailed investigation of the previously revealed“piston mechanism”of gas exchange and mass transfer processes in the coal specimens and their quantitative description in terms of theory of the pendulum waves were carried in the first time.Consequently,there are some arguments for the testing of the opportunity of quantitative description of the“piston mechanism”related to gas exchange and mass transfer processes in the scale of coal mines.It is relevant when pendulum waves induced by powerful earthquakes and technical blasting reaches the mine.展开更多
Aiming at the rock burst prevention in coal mines,this study argue that a rock burst is the instability of the coal mass deformation system with the infinite deformation response subjected to a small disturbance,and t...Aiming at the rock burst prevention in coal mines,this study argue that a rock burst is the instability of the coal mass deformation system with the infinite deformation response subjected to a small disturbance,and the concepts of control,disturbance and response variables of the coal mass deformation system are proposed.The analytical solution of rock bursts of circular roadways is derived,using a mechanical model of the coal mass deformation system of circular roadways,and the stress and energy conditions of the disturbance response instability of a rock burst are also presented.Based on the disturbance response instability theory,this study identifies the factors controlling the occurrence of rock bursts,involving the coal uniaxial compressive strength,coal bursting liability and roadway support stress.The relationship between the critical stress and the critical resistance zone of surrounding rock in roadways,the coal uniaxial compressive strength,roadway support stress,roadway geometric parameters and coal burst liability is revealed,and the critical stress index evaluation method of rock burst risk is proposed.Considering the disturbance and response variables of rockburst occurrence,a monitoring system of rock burst based on stress and energy monitoring is established.Considering managing the disturbance and control variables,regional and local prevention measures of rock burst are proposed from four aspects:destressing in coal mass,avoiding the mutual disturbance between multi-group mining or excavation,reducing the dynamic load disturbance and weakening of the physical properties of the coal mass.Based on the enhancement principle of the roadway support stress on the critical load of rockburst occurrence and the energy absorption effect of the support,an energy absorption and anti-bursting support technology for roadways are proposed.The disturbance response instability theory of rock bursts has formed a technical system from the aspects of mechanism,prediction and prevention to guide the engineering practice for rock burst mitigation.展开更多
文摘During the excavation of deep coal and rock mass, the radial stress of the free face changes from three-dimensional compression state to two-dimensional stress, bearing the combined action of dynamic disturbance and static load at the same time. With that, many mines suffer from dynamic disasters, such as coal and gas outburst, rock burst and rock caving during deep mining excavation, which is often accompanied by plate crack, spalling and other disasters, seriously affecting the stability of stope and roadway. Taking thin rectangular coal and rock mass as the research object, the dual equation of the free vibration was derived and the exact solution model of the free vibration was established with the use of Hamilton dual system. Based on the action characteristics of the uniform impact load, the effective mode of the forced vibration was obtained by using the Duhamel integral principle and the orthogonality of the mode function. Based on the third strength theory and the numerical simulation results, the dynamic damage process and development trend of coal and rock mass were analyzed under uniform impact load. It was concluded that the starting position of dynamic damage can be judged by the first order main mode, and the development direction and trend of the damage can be judged by the fifth and sixth order main modes. It was concluded that the vibration mode functions of coal and rock mass with four side fixed (C-C-C-C), the two sides fixed and simply supported on the other (S-C-S-C) are mainly composed of three modes that are the first order (dominant frequency), the fifth order and the sixth order, from which the dynamic damage mechanism is preliminarily studied.
基金Staff at Vale Australia,in particular Lachlan Cunningham and Priscilla Page,are thanked for facilitating underground access to the Carborough Downs Mine.The research was kindly supported by Moultrie Group and Golder Associates.
文摘The rock mass rating(RMR)has been used across the geotechnical industry for half a century.In contrast,the coal mine roof rating(CMRR)was specifically introduced to underground coal mines two decades ago to link geological characterization with geotechnical risk mitigation.The premise of CMRR is that strength properties of mine roof rock are influenced by defects typical of coal measures stratigraphy.The CMRR has been used in longwall pillar design,roof support methods,and evaluation of extended cuts,but is rarely evaluated.Here,the RMR and CMRR are applied to a longwall coal mine.Roof rock mass classifications were undertaken at 67 locations across the mine.Both classifications showed marked spatial variability in terms of roof conditions.Normal and reverse faulting occur across the mine,and while no clear relationships exist between rock mass character and faulting,a central graben zone showed heterogeneous rock mass properties,and divergence between CMRR and RMR.Overall,the CMRR data fell within the broad envelope of results reported for extended cuts at Australian and U.S.coal mines.The corollary is that the CMRR is useful,and should not be used in isolation,but rather as a component of a strata control programme.
基金supported by the State Key Basic Research Project of China(No.2011CB201201)the National Natural Science Foundation of China(Nos.51134018 and 11172318)the Key Technologies R&D Program of China(No.2008BAB36B07)
文摘Coal-rock as a typical sedimentary rock has obvious stratification,namely it has transversely isotropic feature.Meanwhile,deformation leads to coal-rock mass having the characteristics of different porous and crack structures as well as local anisotropy.Equivalent axial and circumferential strain' formulas of the pure coal-rock mass specimen with a single crack were derived through the establishment of equivalent mechanical model of standard cylindrical coal-rock specimen,and have been widely used to a variety of media combined different structures containing multiple cracks.The complete stress strain curve of a real coal-rock specimen was obtained by the CTC test.Additionally,according to the comparison with the theoretical value,the theoretical mechanical model could well explain the deformation characteristics of coal-rock mass and verify its validity.Further,following features were analyzed:strain normalized coefficient and elastic modulus(Poisson's ratio) in vertical and parallel direction to the stratification,stratification angle,porosity,pore radius,normal and tangential stiffness of crack,and the relationship of different crack width with different tangential stiffness of crack.Through the analysis above,it substantiate this claim that the theoretical model with better reliability reflects the transversely isotropic nature of the coal-rock and the local anisotropy caused by the porous and cracks.
基金the Major Programs of the National Basic Research Program of China (No.2005CB221503)the National Natural Science Foundation of China (Nos. 70533050 and 50674089) for their support of this project
文摘For a study of the movement and deformation of coal-rock mass and low protected seams below a stope,as well as for fracture developments and rules of evolution of permeability,we designed a plane strain model test stand to carry out model tests of similar materials in order to improve the effect of gas drainage from low protected seams and to measure the movement and deformation of coal-rock mass using a method of non-contact close-range photogrammetry.Our results show that 1) using paraffin melting to take the place of coal seam mining can satisfy the mining conditions of a protective seam;2) coal-rock mass under goafs has an upward movement after the protective seam has been mined,causing floor heaving;3) low protected seams become swollen and deformed,providing a good pressure-relief effect and causing the coal-rock mass under both sides of coal pillars to become deformed by compression and 4) the evolution of permeability of low protected seams follows the way of initial values→a slight decrease→a great increase→stability→final decrease.Simultaneously,the coefficient of air permeability increased at a decreasing rate with an increase in interlayer spacing.
基金the National Natural Science Foundation of China(Nos.52204114,52274145,U22A20165,and 52174089)the Natural Science Foundation of Jiangsu Province(No.BK20210522)+2 种基金the National Key Research and Development Program of China(No.2022YFE0128300)the China Postdoctoral Science Foundation(No.2023M733758)the Shandong Postdoctoral Science Foundation(No.SDCX-ZG-202302037).
文摘The interaction mechanism between coal and rock masses with supporting materials is significant in roadway control, especially in deep underground mining situations where dynamic hazards frequently happened due to high geo-stress and strong disturbed effects. This paper is to investigate the strain energy evolution in the interaction between coal and rock masses with self-designed energy-absorbing props and rock bolts by numerical modeling with the finite difference method. The interaction between rock and rock bolt/prop is accomplished by the cables element and the interface between the inner and outer props. Roadway excavation and coal extraction conditions in deep mining are numerically employed to investigate deformation, plastic zone ranges, strain energy input, accumulation, dissipation,and release. The effect on strain energy input, accumulation, dissipation, and release with rock deformation, and the plastic zone is addressed. A ratio of strain energy accumulation, dissipation, and release with energy input a, β, γ is to assess the dynamic hazards. The effects on roadway excavation and coal extraction steps of a, β, γ are discussed. The results show that:(1) In deep high geo-stress roadways, the energyabsorbing support system plays a dual role in resisting deformation and reducing the scope of plastic zones in surrounding rock, as well as absorbing energy release in the surrounding rock, especially in the coal extraction state to mitigate disturbed effects.(2) The strain energy input, accumulation is dependent on roadway deformation, the strain energy dissipation is relied on plastic zone area and disturbed effects, and strain energy release density is the difference among the three. The function of energyabsorbing rock bolts and props play a key role to mitigate strain energy release density and amount, especially in coal extraction condition, with a peak density value from 4×10^(4) to 1×10^(4)J/m^(3), and amount value from 3.57×10^(8) to 1.90×10^(6)J.(3) When mining is advanced in small steps, the strain energy accumulation is dominated. While in a large step, the released energy is dominant, thus a more dynamic hazards proneness. The energy-absorbing rock bolt and prop can reduce three times strain energy release amount, thus reducing the dynamic hazards. The results suggest that energy-absorbing props and rock bolts can effectively reduce the strain energy in the coal and rock masses, and prevent rock bursts and other hazards.The numerical model developed in this study can also be used to optimize the design of energyabsorbing props and rock bolts for specific mining conditions.
基金the National Natural Science Foundation of China(Nos.41172290 and40572160)
文摘In order to evaluate the feasibility of safe mining close to the contact zone under reduced security coal pillar conditions at a coal mine in eastern China, the interaction mechanism of the interface between deep buried sand and a paleo-weathered rock mass was investigated in the laboratory by direct shear testing. A DRS-1 high pressure soil shear testing machine and orthogonal design method were used in the direct shear tests. Variance and range methods were applied to analyze the sensitivity of each factor that has an influence on the mechanical characters of the interface. The test results show that the normal pressure is the main influencing factor for mechanical characteristics of the interface, while the lithological characters and roughness are minor factors; the shear stress against shear displacement curve for the interface shows an overall hyperbola relationship, no obvious peak stress and dilatancy was observed.When the normal pressure is 6 MPa, the shear strengths of interfaces with different roughness are basically the same, and when the normal pressure is more than 8 MPa, the larger the roughness of the interface, the larger will be the shear strength; the shear strength has a better linear relationship with the normal pressure, which can be described by a linear Mohr–Coulomb criterion.
基金Supported by the National Natural Science Foundation of China (51004003) the Natural Science Foundation of Ministry of Education of Anhui Province (K J2010A091 )
文摘The authors applied the Secondary Ion Mass Spectrometry (SIMS) technique to the analysis of compositions and structures of vitrinites fusinites, fusinites bitumens and graptolites in the hydrocarbon source rocks with different maturities dscribed their SIMS spectral characteristics and found that different macerals have differnt spectra which, reflected the compositional and structural differences of macerals. Moreover, the change bod of parameter CH2+/CH3+ can be used for the evaluation of thermal evolution regularity of macerals in the hydrocarbon source rocks The study results show that the SIMS technique is a powerful means for microara analysis of macerals in coals and source rocks. It is certain that the study level of macerals can be raised by detailed study of SIMS results of SIMS results of macerals.
基金the Natural Science Fund of Liaoning Province(20042176)
文摘According to the rock burst features occurred in the coal mass of roadway rib in one mine,the mechanics model of coal mass and roof structure system along the edge of goaf was founded to analyze the stress of roof rock layer,so the subside curve of roof rock layer was deduced.Furthermore,the stability of coal and rock system were analyzed,the critical load and critical resistance zone were used to judge the danger degree of rock burst occurrence.The influence of coal mass strength,brittleness degree,coal seam thickness,roof thickness,suspending length,equivalent shear module on the critical load, critical resistance zone was confirmed.So the rock burst occurrence conditions of coal mass in roadway rib mainly depend on mining depth,coal seam thickness and hard roof and floor,which are decided by the above studies,and successfully applied in prediction and prevention of rock burst in this mine.
基金National Natural Science Foundation of China(4 9672 13 1)
文摘In accordance with the confusion on classification of source rocks, the authors raised a source rock classification for its enriched and dispersed organic matter types based on both Alpern’s idea and maceral genesis/composition. The determined rock type is roughly similar to palynofacies of Combaz , whereas it is "rock maceral facies (for coal viz. coal facies)" in strictly speaking. Therefore, it is necessary to use the organic ingredients classification proposed by the authors so that it can be used for both maceral analysis and environment research . This source rock classification not only shows sedimentology and diagenetic changes but also acquires organic matter type even if hydrocarbon potential derived from maceral’s geochemical parameters. So, it is considered as genetic classification. The "rock maceral facies" may be transformed to sedimentary organic facies , which is used as quantitative evaluation means if research being perfect.Now, there are many models in terms of structure either for coal or for kerogen. In our opinion, whatever coal or kerogen ought be polymer, then we follow Combaz’s thought and study structure of amorphous kerogens which are accordance with genetic mechanism showing biochemical and geochemical process perfectly. Here, we use the time of flight secondary ion mass spectrometry (TOFSIMS) to expand Combaz’s models from three to five. They are also models for coal.
基金The studies were accomplished within the framework of the project"Investigation of coal nanostructure as a source of coal mine methane"with a financial support of the Ministry of Education and Science of Ukraine according to the Order No.199 of February 10,2017.
文摘The purpose of this study was to develop a physico-mathematical model and technique for estimation of chemical bond stability depending on electric field intensity of an external point charge.A hypothesis for a possible physico-chemical mechanism of the formation of additional harmful gases in the rock destruction by blasting was proposed.The theoretical basis of the hypothesis is the method of theretical evaluation of bond energy depending on the distance to a point charge,the third Coulomb centre.The quantum-mechanical model for calculating the electronic terms of molecules makes it possible to solve problems associated with the determination of parameters of molecules under the action of various physical fields on the system under consideration.The model was approved for some diatomic molecules.The discrepancy between the experimental data and calculated data did not exceed 14%,which proves accuracy of the obtained results.The model can be used in the field of research into the causes of gas-dynamic phenomena in underground coal mines,in studies of the degree of stability of nanostructured components of coal under physical influences,and in the theoretical design of new compounds and structures in the field of nanomaterial science and nanotechnology.
基金Supported by the National Basic Research Program (2010CB226806)the National Science and Technology Supporting Program Key Item(2008BAB36B01)the Funded Project of Anhui University of Science and Technology Academic Outstanding Innovation Team
文摘Numerical simulation-FLAC^(3D) and equivalent material simulation were carried out to analyze the damaged patterns and lows, distribution of plastic width of face, and surrounding rock of FMTC during the advance of work face with different thick coal seams based on engineering geology and exploitation technology of 1151(3) fully mechanized top-coal caving (FMTC) face in Xieqiao Colliery.The results show that there is damage,and the destruction characteristics of surrounding rock and coal mass are different obviously in asymmetric exploitation layout.The damaged zone in surrounding rock and the coal of the return airway is larger than that of the intake airway.Moreover, the retained coal pillars are all damaged by tension and shear fracture, and plastic zone in coal mass in the dip direction ahead of Face is nonuniform.There are large damage zones in roof and floor strata, surrounding rock, and coal of return and intake airways near work face.The damaged zone in the upper part of Face is larger than that in middle and lower parts.The fruits of this paper are of guiding significance for engineering practices, such as support design and choice, roadway supporting and maintaining, rock pressure control of FMTC face, etc.
基金support of Russian Science Foundation (Project No.23-17-00148)as a part of R&D project (State registry No.121062200075-4).
文摘The article focuses on a theoretical and experimental framework for the quantification of interaction between nonlinear geomechnical and physicochemical processes in high-stress coal-bearing rock mass during mining under high seismic risk due to large-scale blasting and earthquakes,as well as because of structural and temperature effects.The tests were aimed to examine and study comprehensively the piston mechanism of gas exchange and mass transfer processes,revealed recently at the Institute of Mining,SB RAS,as well as to explain the fact that the earthquake-induced low-velocity(quasi-meter range)pendulum waves(velocity to 1 m/s and frequency of 0.5–5 Hz)could stimulate an increase in the gas content in coal mines.In order to perform laboratory investigation at the Institute of Mining SB RAS,special-purpose stand for analyzing gas exchange and mass transfer processes in coal-bearing geomaterials under various thermodynamic conditions(P,V,T)and gas composition was constructed in cooperation with the Institute of Semiconductors Physics SB RAS.Matching of air flow rate with compression pressures allowed to obtain relations showing that air flow rate increases at the uncertain time interval under the increasing of the compression pressure.The same measurements was carried out with another gases such as Hydrogen H_(2),Helium He,methane CH_(4),carbon dioxide CO_(2) and carbon oxide CO.The laboratory tests aimed to detailed investigation of the previously revealed“piston mechanism”of gas exchange and mass transfer processes in the coal specimens and their quantitative description in terms of theory of the pendulum waves were carried in the first time.Consequently,there are some arguments for the testing of the opportunity of quantitative description of the“piston mechanism”related to gas exchange and mass transfer processes in the scale of coal mines.It is relevant when pendulum waves induced by powerful earthquakes and technical blasting reaches the mine.
基金supported by the National Natural Science Foundation of China(51974150 and U1908222)National key research and development program(2022YFC3004605).
文摘Aiming at the rock burst prevention in coal mines,this study argue that a rock burst is the instability of the coal mass deformation system with the infinite deformation response subjected to a small disturbance,and the concepts of control,disturbance and response variables of the coal mass deformation system are proposed.The analytical solution of rock bursts of circular roadways is derived,using a mechanical model of the coal mass deformation system of circular roadways,and the stress and energy conditions of the disturbance response instability of a rock burst are also presented.Based on the disturbance response instability theory,this study identifies the factors controlling the occurrence of rock bursts,involving the coal uniaxial compressive strength,coal bursting liability and roadway support stress.The relationship between the critical stress and the critical resistance zone of surrounding rock in roadways,the coal uniaxial compressive strength,roadway support stress,roadway geometric parameters and coal burst liability is revealed,and the critical stress index evaluation method of rock burst risk is proposed.Considering the disturbance and response variables of rockburst occurrence,a monitoring system of rock burst based on stress and energy monitoring is established.Considering managing the disturbance and control variables,regional and local prevention measures of rock burst are proposed from four aspects:destressing in coal mass,avoiding the mutual disturbance between multi-group mining or excavation,reducing the dynamic load disturbance and weakening of the physical properties of the coal mass.Based on the enhancement principle of the roadway support stress on the critical load of rockburst occurrence and the energy absorption effect of the support,an energy absorption and anti-bursting support technology for roadways are proposed.The disturbance response instability theory of rock bursts has formed a technical system from the aspects of mechanism,prediction and prevention to guide the engineering practice for rock burst mitigation.