Numerical modelling is an effective technique to improve the understanding of outburst initiation mechanisms and to take appropriate measures to address their threats.Based on the existing two-way sequential coupling ...Numerical modelling is an effective technique to improve the understanding of outburst initiation mechanisms and to take appropriate measures to address their threats.Based on the existing two-way sequential coupling method,two typical types of outbursts,i.e.the gas pocket outburst and the dynamic fracturing outburst,have been successfully simulated using field data from a coalfield in central China.The geological structure commonly observed in the coalfield,known as the‘bedding shear zone’,contributes to the gas pocket outbursts in the region.The model for this type of outburst simulates mininginduced stress and gas pressure distributions during the outburst initiation stage and the subsequent development stage.Both coal ejection and gas release are observed in the model,and the simulation results are consistent with mine site observations,i.e.the amount of ejected coal,outburst cavity profile,and gas release rate change prior to an outburst.The second type of outburst is attributed to gas accumulation and elevated gas pressure due to the gassy floor seam and the heterogeneity in the floor strata,which is explained by the dynamic fracturing theory.While the dynamic coal ejection phenomenon is not captured in the simulation,the abrupt release of retained gas from a floor coal seam is successfully replicated.Both outburst models reveal that abnormal gas emission trends can be used as indicators of an upcoming outburst.The results of this study are expected to provide new insights into the outburst initiation mechanisms and outburst prevention measures.展开更多
Coal and gas outbursts constitute a critical hazard in underground mining operations,characterized by rapid transitions from localized instability to catastrophic failure.Understanding the relationship between initial...Coal and gas outbursts constitute a critical hazard in underground mining operations,characterized by rapid transitions from localized instability to catastrophic failure.Understanding the relationship between initial characteristics and final outburst scale remains a fundamental challenge in geomechanics.This study conceptualizes outbursts as deterministic cascade systems through integrated physical simulations combining high-sensitivity infrasound monitoring with energy analysis under controlled gas pressure(0.5–1.0 MPa)and confining stress(5–10 MPa)conditions.Our complementary analytical algorithms—the absolute amplitude integral and predominant period function—revealed characteristic step-wise patterns in outburst development.Quantitative analysis established a robust correlation(R2=0.91)between initial acoustic response and final outburst intensity.Energy analysis demonstrated that gas expansion dominates the outburst process(91.81%–99.09%of total energy),with desorption gas contributing 59.1%–77.7%.Time-frequency analysis showed systematic frequency migration from high(12–15 Hz)to low(4–8 Hz)bands during outburst progression,reflecting hierarchical spatial scale expansion.The concentrated energy release(>20%of total)within initial 0.2 s provides a mechanistic basis for the deterministic nature of outburst evolution.These mechanistic insights establish a quantitative framework for developing physics-based monitoring protocols and risk assessment methodologies applicable to underground coal mining operations.展开更多
To address the issues of single warning indicators,fixed thresholds,and insufficient adaptability in coal and gas outburst early warning models,this study proposes a dynamic early warning model for gas outbursts based...To address the issues of single warning indicators,fixed thresholds,and insufficient adaptability in coal and gas outburst early warning models,this study proposes a dynamic early warning model for gas outbursts based on adaptive fractal dimension characterization.By analyzing the nonlinear characteristics of gas concentration data,an adaptive window fractal analysis method is introduced.Combined with boxcounting dimension and variation of box dimension metrics,a cross-scale dynamic warning model for disaster prevention is established.The implementation involves three key phases:First,wavelet denoising and interpolation methods are employed for raw data preprocessing,followed by validation of fractal characteristics.Second,an adaptive window cross-scale fractal dimension method is proposed to calculate the box-counting dimension of gas concentration,enabling effective capture of multi-scale complex features.Finally,dynamic threshold partitioning is achieved through membership functions and the 3σprinciple,establishing a graded classification standard for the mine gas disaster(MGD)index.Validated through engineering applications at Shoushan#1 Coal Mine in Henan Province,the results demonstrate that the adaptive window fractal dimension curve exhibits significantly enhanced fluctuation characteristics compared to fixed window methods,with local feature detection capability improved and warning accuracy reaching 86.9%.The research reveals that this model effectively resolves the limitations of traditional methods in capturing local features and dependency on subjective thresholds through multiindicator fusion and threshold optimization,providing both theoretical foundation and practical tool for coal mine gas outburst early warning.展开更多
Based on the principle of Bayesian discriminant analysis, we established a model of Bayesian discriminant analysis for predicting coal and gas outbursts. We selected five major indices which affect outbursts, i.e., in...Based on the principle of Bayesian discriminant analysis, we established a model of Bayesian discriminant analysis for predicting coal and gas outbursts. We selected five major indices which affect outbursts, i.e., initial speed of methane diffusion, a consistent coal coefficient, gas pressure, destructive style of coal and mining depth, as discriminating factors of the model. In our model, we divided the type of coal and gas outbursts into four grades regarded as four normal populations. We then obtained the corresponding discriminant functions through training a set of data from engineering examples as learning samples and evaluated their criteria by a back substitution method to verify the optimal properties of the model. Finally, we applied the model to the prediction of coal and gas outbursts in the Yunnan Enhong Mine. Our results coincided completely with the actual situation. These results show that a model of Bayesian discriminant analysis has excellent recognition performance, high prediction accuracy and a low error rate and is an effective method to predict coal and gas outbursts.展开更多
According to the feature that coal and gas outbursts is controlled by coal structure in Pingdingshan mine area, based on the study of the distribution law of disturbed coal in Mine Area and the macroscopic characteris...According to the feature that coal and gas outbursts is controlled by coal structure in Pingdingshan mine area, based on the study of the distribution law of disturbed coal in Mine Area and the macroscopic characteristics of coal structure, the characteristics and genesis to micro-pore of disturbed coal, the relationship between the type of coal structure and gas parameter, and the structural feature of coal at outbursts sites are mainly explored in this paper. Further, the steps and methods are put forward that coal structure indices applied to forecast coal and gas outbursts.展开更多
Based on the engineering observations of coal and gas outbursts during mining processes and the experimental results,we built a thin plate mechanical model for layered and spalled coal bodies.We studied the mechanical...Based on the engineering observations of coal and gas outbursts during mining processes and the experimental results,we built a thin plate mechanical model for layered and spalled coal bodies.We studied the mechanical mechanism of outbursts,due to instability,of thin plates of coal rocks under the action of in-plane load and normal load,by using the catastrophe theory.The total potential function is derived for the layered rock system,the cusp catastrophe model for the system is established,the bifurcation set that makes the system unstable is given,the process in which gradual change of action forces leads to catastrophic change of state is analyzed,and the effect of movement path of point(P,q) in the control space on the stability of rock plate is analyzed.The study results show that during the process of coal mining,the stability of the layered coal bodies depends not only on its physical properties and dimensions but also on the magnitudes and changing paths of the in-plane load and the normal load.When the gas in the coal bodies ahead of the mining face is pre-drained,the gas pressure can be reduced and the normal load q can be lowered.Consequently,disasters such as coal and gas outbursts can be effectively prevented.展开更多
Based on the study of regional displaying rules of coal and gas outburst controlled by geological structure in Pingdingshan mining area, the geological structure features in outburst sites were investigated emphatical...Based on the study of regional displaying rules of coal and gas outburst controlled by geological structure in Pingdingshan mining area, the geological structure features in outburst sites were investigated emphatically. The combination type, orientation and least seam thickness in outburst sites were put forward. This research provides a geological mark for forecasting gas outbursts in deep mining.展开更多
Abstract During mining or road-way development, the distribution of stress and coal pore pressure in the coal face and rib around the new opening will change, under certain conditions, dynamic failure of coal in the f...Abstract During mining or road-way development, the distribution of stress and coal pore pressure in the coal face and rib around the new opening will change, under certain conditions, dynamic failure of coal in the form of an outburst can occur. In the modeling studies presented in this paper, an outburst was considered to consist of three distinct stages： preinitiation, initiation and post-initiation, which takes into account the major processes and mechanisms that can influence both outburst-proneness and post-initiation outburst behavior. The model has been applied to simulate the effects of mechanisms in the coal matrix, coal strength, coal damage, geological structures on outbursts. The model constructed using the FLAC software, which were undertaken to research the effects on outbursts of coal strength pressure gradient, and other factors.展开更多
The prediction study on coal and gas outbursts is carried out by monitoring some indices which are sensitive to the initiation of coal and gas outbursts. The values and changing roles of the indices are the foundation...The prediction study on coal and gas outbursts is carried out by monitoring some indices which are sensitive to the initiation of coal and gas outbursts. The values and changing roles of the indices are the foundations of coal and gas outbursts prediction. But now, only the data of ere key monitoring station is used in the coal and gas outbursts prediction practice, and the other data are ignored. In order to overcome the human factor and make full use of the monitoring information, the technique of multi-sensor target tracking is proposed to deal with the microseismic informatiion. With the results of microseismic events, the activities of geological structure, fracure-depth of roof and floor, and the location of gas channel are obtained. These studies indicate that it is considerably possible to predict the coal and gas outbursts using microseismic monitoring with its inherent ability to remotely monitor the progressive failure caused by mining.展开更多
An outburst of coal and gas is a major hazard in underground coal mining. It is generally accepted that an outburst occurs when certain conditions of stress, coal gassiness and physical-mechanical properties of coal a...An outburst of coal and gas is a major hazard in underground coal mining. It is generally accepted that an outburst occurs when certain conditions of stress, coal gassiness and physical-mechanical properties of coal are met. Outbursting is recognized as a two-step process, i.e., initiation and development. In this paper, we present a fully-coupled solid and fluid code to model the entire process of an outburst. The deformation, failure and fracture of solid （coal） are modeled with the discrete element method, and the flow of fluid （gas and water） such as free flow and Darcy flow are modeled with the lattice Boltzmann method. These two methods are coupled in a two-way process, i.e., the solid part provides a moving boundary condition and transfers momentum to the fluid, while the fluid exerts a dragging force upon the solid. Gas desorption from coal occurs at the solid-fluid boundary, and gas diffusion is implemented in the solid code where particles are assumed to be porous. A simple 2D example to simulate the process of an outburst with the model is also presented in this paper to demonstrate the capability of the coupled model.展开更多
In order to explain the mechanism for gas outburst, the process of evolving fractures in coal seams is described using system dynamics with variable boundaries. We discuss the failure modes of coal containing gas and ...In order to explain the mechanism for gas outburst, the process of evolving fractures in coal seams is described using system dynamics with variable boundaries. We discuss the failure modes of coal containing gas and then established the flow rules after failure. The condition under which states of deformation convert is presented and the manner in which these convert is proposed. In the end, the process of gas outbursts is explained in detail. It shows that a gas outburst is a process in which the boundaries of coal seams are variable because of coal failure. If the fractures are not connected or even closed owing to coal/rock stress, fractured zones will retain a certain level of carrying capacity because of the self-sealing gas pressure. When the accumulation of gas energy reaches its limit, coal seams will become unstable and gas outbursts take place.展开更多
This paper discribes a one-dimensional flow model to explain the basic mechanism of coal-gas outbursts.A break-start criterion of coal,as the elementary outburst criterion,is given approximately.In this ideal model,th...This paper discribes a one-dimensional flow model to explain the basic mechanism of coal-gas outbursts.A break-start criterion of coal,as the elementary outburst criterion,is given approximately.In this ideal model,the tectonic pressure before excavation,as a load on coal body,affects the break-start and then the flow field.The flow field is decoupled with the stress field,so that the gas seepage through unbroken coal body,break-start and consequent two-phase flow,and pure gas flow can be analysed independently of the stress field. The tunnelling,an external disturbance that makes the seepage intensify relatively,is an essential factor for initiating outburst.Under steady tunnelling,seepage ought to tend to be steadily progressive.From its asymptotic solution initiation criterion is obtained.This is described by three conditions,possibility condi- tion—tectonic pressure condition,incubation condition—tunnelling or gas condition and triggering condi- tion—seepage velocity condition.展开更多
Measured to control serious coal-gas outburst in coal seam were analyzed by theory and experimented in test site.A new technique to distress the coal-bed and drain methane,called hydraulic slotting,was described in de...Measured to control serious coal-gas outburst in coal seam were analyzed by theory and experimented in test site.A new technique to distress the coal-bed and drain methane,called hydraulic slotting,was described in detail,and the mechanism of hydrau- lic slotting was put forward and analyzed.The characteristic parameter of hydraulic slotting was given in Jiaozuo mining area and the characteristic of validity,adaptability and secu- rity was evaluated.The results show that the stress surrounding the strata and the gas in coal seam is released efficiently and thoroughly while new techniques are taken,as slot- ting at heading face by high pressure large diameter jet.The resistance to coal and gas outbursts is increased dramatically once the area of slotting is increased to a certain size. In the process of driving 2 000 m tunnel by hydraulic slotting excavation,coal and gas outburst never occurre.The technique could be used to prevent and control potential coal-gas outburst in the proceeding of tunnel driving,and the speed tunneling could be as high as more than 2 times.展开更多
Estimating the intensity of outbursts of coal and gas is important as the intensity and frequency of outbursts of coal and gas tend to increase in deep mining. Fully understanding the major factors contributing to coa...Estimating the intensity of outbursts of coal and gas is important as the intensity and frequency of outbursts of coal and gas tend to increase in deep mining. Fully understanding the major factors contributing to coal and gas outbursts is significant in the evaluation of the intensity of the outburst. In this paper, we discuss the correlation between these major factors and the intensity of the outburst using Analysis of Variance(ANOVA) and Contingency Table Analysis(CTA). Regression analysis is used to evaluate the impact of these major factors on the intensity of outbursts based on physical experiments. Based on the evaluation, two simple models in terms of multiple linear and nonlinear regression were constructed for the prediction of the intensity of the outburst. The results show that the gas pressure and initial moisture in the coal mass could be the most significant factors compared to the weakest factor-porosity. The P values from Fisher's exact test in CTA are: moisture(0.019), geostress(0.290), porosity(0.650), and gas pressure(0.031). P values from ANOVA are moisture(0.094), geostress(0.077), porosity(0.420), and gas pressure(0.051). Furthermore, the multiple nonlinear regression model(RMSE: 3.870) is more accurate than the linear regression model(RMSE: 4.091).展开更多
Coal and gas outbursts compromise two-phase gas-solid mixtures as they propagate as shock waves and flows from their sources.Propagation is influenced by the form of the outburst,proximity to source,the structure and ...Coal and gas outbursts compromise two-phase gas-solid mixtures as they propagate as shock waves and flows from their sources.Propagation is influenced by the form of the outburst,proximity to source,the structure and form of the transmitting roadways and the influence of obstacles.The following characterizes the propagation of coal and gas outbursts as two-phase gas-solid flows proximal to source where the coupled effects of pulverized coal and gas flows dominate behavior.The characteristics of shock wave propagation and attenuation were systematically examined for varied roadway geometries using experiments and numerical models.The results demonstrate that the geometry of roadway obstructions is significant and may result in partial compression and sometimes secondary overpressurization in blocked and small comer roadways leading to significant attenuation of outburst shock waves.The shock waves attenuate slowly in both straight and abruptly expanding roadways and more significantly in T-shaped roadways.The most significant attenuation appears in small angle comers and bifurcations in roadways with the largest attenuation occurring in blocked roadways.These results provide basic parameters for simplifying transport in complex roadway networks in the far-field,and guidance for the design of coal and gas outburst prevention facilities and emergency rescue.展开更多
Based on the evolution of geological dynamics and spatial chaos theory, we proposed the advanced prediction an advanced prediction method of a gas desorption index of drill cuttings to predict coal and gas outbursts. ...Based on the evolution of geological dynamics and spatial chaos theory, we proposed the advanced prediction an advanced prediction method of a gas desorption index of drill cuttings to predict coal and gas outbursts. We investigated and verified the prediction method by a spatial series data of a gas desorption index of drill cuttings obtained from the 113112 coal roadway at the Shitai Mine. Our experimental results show that the spatial distribution of the gas desorption index of drill cuttings has some chaotic charac- teristics, which implies that the risk of coal and gas outbursts can be predicted by spatial chaos theory. We also found that a proper amount of sample data needs to be chosen in order to ensure the accuracy and practical maneuverability of prediction. The relative prediction error is small when the prediction pace is chosen carefully. In our experiments, it turned out that the optimum number of sample points is 80 and the optimum prediction pace 30. The corresponding advanced prediction pace basically meets the requirements of engineering applications.展开更多
The multi-frequency light curves of BL Lacertae during 1997.5 - 1999.5 have been modeled by four outbursts, each having a 3-stage evolution in the （Sm, vm） plane with distinct rising-plateau-decaying phases. It is s...The multi-frequency light curves of BL Lacertae during 1997.5 - 1999.5 have been modeled by four outbursts, each having a 3-stage evolution in the （Sm, vm） plane with distinct rising-plateau-decaying phases. It is shown that the observed light curves can be well fitted for the eight frequencies from 350 GHz to 4.8 GHz. The main characteristics of the model-fitting are; （1） the outbursts are found to have very flat spectra with an optically thin spectral index α （defined as Sv α u^-α） of about 0.15. This is consistent with the results previously obtained by Valtaoja et al. （1992）; （2） it is found that there is no spectral flattening between the rising-plateau phase and the decay phase. In other words, the optically thin spectral index does not change from the rising-plateau phase to the decay phase. These features are in contrast to the 3-stage shocked-in-jet model proposed by Marscher ＆ Gear （1985） for submm- IR-optical flares, in which a spectral flattening of △α = 0.5 is predicted when a transition occurs from the Compton/synchrotron phase （or rising-plateau phase） to the adiabatic phase （or decay phase） with α≥ 0.5 for the shock being non-radiative. We propose a new model to interpret the fitting results, suggesting that the 3-stage evolution of the mm-cm outbursts in BL Lacertae may be related to the process of shock formation and propagation in a highly collimated jet （for example, a ＇parabolic＇ jet）. In particular, during the rising phase, the thickness of the synchrotron-radiating region created by the shock may rapidly increase with time （relative to the jet width） due to the rapid injection of relativistic electrons and a magnetic field, and this leads to the observed behavior that the turnover flux density Sm rapidly increases while the turnover frequency um decreases. In the decay phase, the emitting plasma enters into a free expansion regime without further injection of relativistic electrons and a magnetic field （for example, when a transition from a collimated regime into a conical regime occurs）. The plateau phase is a short period between the two regimes with no distinct features determined.展开更多
Based on the theories of the gas seepage in coal seams and the deformation of the coal-rock medium,the gas seepage field in coal-rock mass is coupled with the deformation field of the coal-rock mass to establish a flu...Based on the theories of the gas seepage in coal seams and the deformation of the coal-rock medium,the gas seepage field in coal-rock mass is coupled with the deformation field of the coal-rock mass to establish a fluidstructure interaction model for the interaction between coal gas and coal-rock masses.The outburst process in coal-rock masses under the joint action of gas pressure and crustal stress is simulated using the material point method.The simulation results show the changes in gas pressure,velocity distribution,maximum principal stress distribution,and damage distribution during the process of the coal and gas outburst,as well as themovement and accumulation of coal-rock masses after the occurrence of the outburst.It was found that the gas pressure gradient was greatest at theworking face after the occurrence of the outburst,the gas pressures and pressure gradients at each location within the coal seamgradually decreased with time,and the damage distribution was essentially the same as the minimum principal stress distribution.The simulation further revealed that the outburst first occurred in themiddle of the tunnel excavation face and that the speed at which particles of coal mass were ejected was highest at the center and decreased toward the upper and lower sides.The study provides a scientific basis for enhancing our understanding of the mechanism behind coal and gas outbursts,as well as their prevention and control.展开更多
The paper presents some information about gas and coal outbursts threat in Polish coal mines.It shows the methodology for threat identification and monitoring for gas and coal outbursts in the Polish coal mines.One of...The paper presents some information about gas and coal outbursts threat in Polish coal mines.It shows the methodology for threat identification and monitoring for gas and coal outbursts in the Polish coal mines.One of the main methods of assessing threats in the mining industry in Poland and China is desorbometric method.The paper presents some results of estimation of uncertainties of the desorption rate Δp,determined in situ,by use of liquid manometric desorbometer gauge.It was observed that,if there are coal subgrains in desorbometer contaminator,the results of desorption rate may be even up to 60% higher than results obtained for the normative sample.Possibly method of the uncertainty reduction are presented in the paper as well.展开更多
In this paper, we present the observations of Comet Hale-Bopp by means of photoelectric and photographic photometry during the period from September to November of 1996. It is shown that there appears to have been 3 o...In this paper, we present the observations of Comet Hale-Bopp by means of photoelectric and photographic photometry during the period from September to November of 1996. It is shown that there appears to have been 3 outbursts around 24 Sept., 26 Oct. and 13 Nov.; and it is also possible that an event of outburst has taken place around 9 Oct.展开更多
基金the National Natural Science Foundation of China(52304105)National Natural Science Foundation of China-National major scientific research instrument development project(52227901)Jiangsu Province International Collaboration Program-Key national industrial technology research and development cooperation projects(BZ2023050).
文摘Numerical modelling is an effective technique to improve the understanding of outburst initiation mechanisms and to take appropriate measures to address their threats.Based on the existing two-way sequential coupling method,two typical types of outbursts,i.e.the gas pocket outburst and the dynamic fracturing outburst,have been successfully simulated using field data from a coalfield in central China.The geological structure commonly observed in the coalfield,known as the‘bedding shear zone’,contributes to the gas pocket outbursts in the region.The model for this type of outburst simulates mininginduced stress and gas pressure distributions during the outburst initiation stage and the subsequent development stage.Both coal ejection and gas release are observed in the model,and the simulation results are consistent with mine site observations,i.e.the amount of ejected coal,outburst cavity profile,and gas release rate change prior to an outburst.The second type of outburst is attributed to gas accumulation and elevated gas pressure due to the gassy floor seam and the heterogeneity in the floor strata,which is explained by the dynamic fracturing theory.While the dynamic coal ejection phenomenon is not captured in the simulation,the abrupt release of retained gas from a floor coal seam is successfully replicated.Both outburst models reveal that abnormal gas emission trends can be used as indicators of an upcoming outburst.The results of this study are expected to provide new insights into the outburst initiation mechanisms and outburst prevention measures.
基金funded by the National Natural Science Foundation of China(No.52464016)the Guizhou Provincial Foundation Research Project(No.QKHJC-[2024]Youth 141)+1 种基金the Guizhou Provincial Basic Research Program(No.MS[2025]632)the Young Researcher Growth Project of Guizhou Provincial Department of Education(No.QJJ-[2024]25).
文摘Coal and gas outbursts constitute a critical hazard in underground mining operations,characterized by rapid transitions from localized instability to catastrophic failure.Understanding the relationship between initial characteristics and final outburst scale remains a fundamental challenge in geomechanics.This study conceptualizes outbursts as deterministic cascade systems through integrated physical simulations combining high-sensitivity infrasound monitoring with energy analysis under controlled gas pressure(0.5–1.0 MPa)and confining stress(5–10 MPa)conditions.Our complementary analytical algorithms—the absolute amplitude integral and predominant period function—revealed characteristic step-wise patterns in outburst development.Quantitative analysis established a robust correlation(R2=0.91)between initial acoustic response and final outburst intensity.Energy analysis demonstrated that gas expansion dominates the outburst process(91.81%–99.09%of total energy),with desorption gas contributing 59.1%–77.7%.Time-frequency analysis showed systematic frequency migration from high(12–15 Hz)to low(4–8 Hz)bands during outburst progression,reflecting hierarchical spatial scale expansion.The concentrated energy release(>20%of total)within initial 0.2 s provides a mechanistic basis for the deterministic nature of outburst evolution.These mechanistic insights establish a quantitative framework for developing physics-based monitoring protocols and risk assessment methodologies applicable to underground coal mining operations.
基金funded by the National Key Research and Development ProgramFund for Young Scientists(No.2021YFC2900400)+5 种基金the National Natural Science Foundation of China(No.52304123)Fundamental Research Funds for the Central Universities(No.2024CDJXY025)Sichuan-Chongqing Science and Technology Innovation Cooperation Program Project(No.CSTB2024TIAD-CYKJCXX0016)Postdoctoral Research Foundation of China(No.2023M730412)Postdoctoral Fellowship Program of China Postdoctoral Science Foundation(No.GZB20230914)Chongqing Outstanding Youth Science Foundation Program(No.CSTB2023NSCQ-JQX0027)。
文摘To address the issues of single warning indicators,fixed thresholds,and insufficient adaptability in coal and gas outburst early warning models,this study proposes a dynamic early warning model for gas outbursts based on adaptive fractal dimension characterization.By analyzing the nonlinear characteristics of gas concentration data,an adaptive window fractal analysis method is introduced.Combined with boxcounting dimension and variation of box dimension metrics,a cross-scale dynamic warning model for disaster prevention is established.The implementation involves three key phases:First,wavelet denoising and interpolation methods are employed for raw data preprocessing,followed by validation of fractal characteristics.Second,an adaptive window cross-scale fractal dimension method is proposed to calculate the box-counting dimension of gas concentration,enabling effective capture of multi-scale complex features.Finally,dynamic threshold partitioning is achieved through membership functions and the 3σprinciple,establishing a graded classification standard for the mine gas disaster(MGD)index.Validated through engineering applications at Shoushan#1 Coal Mine in Henan Province,the results demonstrate that the adaptive window fractal dimension curve exhibits significantly enhanced fluctuation characteristics compared to fixed window methods,with local feature detection capability improved and warning accuracy reaching 86.9%.The research reveals that this model effectively resolves the limitations of traditional methods in capturing local features and dependency on subjective thresholds through multiindicator fusion and threshold optimization,providing both theoretical foundation and practical tool for coal mine gas outburst early warning.
基金supported by the National Hi-tech Research and Development Program of China (No.2006BAK03B02-04) the New Century Excellent Talent Support Plan of Ministry of Education of China (No.NCET-06-0477)
文摘Based on the principle of Bayesian discriminant analysis, we established a model of Bayesian discriminant analysis for predicting coal and gas outbursts. We selected five major indices which affect outbursts, i.e., initial speed of methane diffusion, a consistent coal coefficient, gas pressure, destructive style of coal and mining depth, as discriminating factors of the model. In our model, we divided the type of coal and gas outbursts into four grades regarded as four normal populations. We then obtained the corresponding discriminant functions through training a set of data from engineering examples as learning samples and evaluated their criteria by a back substitution method to verify the optimal properties of the model. Finally, we applied the model to the prediction of coal and gas outbursts in the Yunnan Enhong Mine. Our results coincided completely with the actual situation. These results show that a model of Bayesian discriminant analysis has excellent recognition performance, high prediction accuracy and a low error rate and is an effective method to predict coal and gas outbursts.
文摘According to the feature that coal and gas outbursts is controlled by coal structure in Pingdingshan mine area, based on the study of the distribution law of disturbed coal in Mine Area and the macroscopic characteristics of coal structure, the characteristics and genesis to micro-pore of disturbed coal, the relationship between the type of coal structure and gas parameter, and the structural feature of coal at outbursts sites are mainly explored in this paper. Further, the steps and methods are put forward that coal structure indices applied to forecast coal and gas outbursts.
基金provided by the National Natural Science Foundation of China (Nos.50574072, 50874089 and 50534049)the Special Scientific Foundation of the Shaanxi Department of Education (No.08JK366) is gratefully acknowledged
文摘Based on the engineering observations of coal and gas outbursts during mining processes and the experimental results,we built a thin plate mechanical model for layered and spalled coal bodies.We studied the mechanical mechanism of outbursts,due to instability,of thin plates of coal rocks under the action of in-plane load and normal load,by using the catastrophe theory.The total potential function is derived for the layered rock system,the cusp catastrophe model for the system is established,the bifurcation set that makes the system unstable is given,the process in which gradual change of action forces leads to catastrophic change of state is analyzed,and the effect of movement path of point(P,q) in the control space on the stability of rock plate is analyzed.The study results show that during the process of coal mining,the stability of the layered coal bodies depends not only on its physical properties and dimensions but also on the magnitudes and changing paths of the in-plane load and the normal load.When the gas in the coal bodies ahead of the mining face is pre-drained,the gas pressure can be reduced and the normal load q can be lowered.Consequently,disasters such as coal and gas outbursts can be effectively prevented.
基金National Natural Science Foundation of China(4 0 0 0 2 0 10 ) and Research Fund for Doctoral Program of Higher Edu-cation (92 2 90 0 8)
文摘Based on the study of regional displaying rules of coal and gas outburst controlled by geological structure in Pingdingshan mining area, the geological structure features in outburst sites were investigated emphatically. The combination type, orientation and least seam thickness in outburst sites were put forward. This research provides a geological mark for forecasting gas outbursts in deep mining.
基金Supported by the National Natural Science Foundation of China （50474010） China Postdoctoral Science Foundation（2005038319）+1 种基金 Natural Science Foundation of Liaoning （20061075） Educational Science Foundation of Liaoning （05L177）
文摘Abstract During mining or road-way development, the distribution of stress and coal pore pressure in the coal face and rib around the new opening will change, under certain conditions, dynamic failure of coal in the form of an outburst can occur. In the modeling studies presented in this paper, an outburst was considered to consist of three distinct stages： preinitiation, initiation and post-initiation, which takes into account the major processes and mechanisms that can influence both outburst-proneness and post-initiation outburst behavior. The model has been applied to simulate the effects of mechanisms in the coal matrix, coal strength, coal damage, geological structures on outbursts. The model constructed using the FLAC software, which were undertaken to research the effects on outbursts of coal strength pressure gradient, and other factors.
基金supported by National Basic Research Programof China(973Program,2010CB226805)Shandong Province Natural Science Fund(Z2008F01)Key Laboratory of Mine Disaster Prevention and Control of Education Ministry(MDPC0809,MDPC0811)
文摘The prediction study on coal and gas outbursts is carried out by monitoring some indices which are sensitive to the initiation of coal and gas outbursts. The values and changing roles of the indices are the foundations of coal and gas outbursts prediction. But now, only the data of ere key monitoring station is used in the coal and gas outbursts prediction practice, and the other data are ignored. In order to overcome the human factor and make full use of the monitoring information, the technique of multi-sensor target tracking is proposed to deal with the microseismic informatiion. With the results of microseismic events, the activities of geological structure, fracure-depth of roof and floor, and the location of gas channel are obtained. These studies indicate that it is considerably possible to predict the coal and gas outbursts using microseismic monitoring with its inherent ability to remotely monitor the progressive failure caused by mining.
文摘An outburst of coal and gas is a major hazard in underground coal mining. It is generally accepted that an outburst occurs when certain conditions of stress, coal gassiness and physical-mechanical properties of coal are met. Outbursting is recognized as a two-step process, i.e., initiation and development. In this paper, we present a fully-coupled solid and fluid code to model the entire process of an outburst. The deformation, failure and fracture of solid （coal） are modeled with the discrete element method, and the flow of fluid （gas and water） such as free flow and Darcy flow are modeled with the lattice Boltzmann method. These two methods are coupled in a two-way process, i.e., the solid part provides a moving boundary condition and transfers momentum to the fluid, while the fluid exerts a dragging force upon the solid. Gas desorption from coal occurs at the solid-fluid boundary, and gas diffusion is implemented in the solid code where particles are assumed to be porous. A simple 2D example to simulate the process of an outburst with the model is also presented in this paper to demonstrate the capability of the coupled model.
基金financial support from the National Basic Research Program of China (No.2005CB221500)the National Natural Science Foundation of China (Nos.50534049,50674087 and 50974107)the Natural Science Foundation of Jiangsu Province (No.BK2007029)
文摘In order to explain the mechanism for gas outburst, the process of evolving fractures in coal seams is described using system dynamics with variable boundaries. We discuss the failure modes of coal containing gas and then established the flow rules after failure. The condition under which states of deformation convert is presented and the manner in which these convert is proposed. In the end, the process of gas outbursts is explained in detail. It shows that a gas outburst is a process in which the boundaries of coal seams are variable because of coal failure. If the fractures are not connected or even closed owing to coal/rock stress, fractured zones will retain a certain level of carrying capacity because of the self-sealing gas pressure. When the accumulation of gas energy reaches its limit, coal seams will become unstable and gas outbursts take place.
基金The project supported by the National Natural Science Foundation of China
文摘This paper discribes a one-dimensional flow model to explain the basic mechanism of coal-gas outbursts.A break-start criterion of coal,as the elementary outburst criterion,is given approximately.In this ideal model,the tectonic pressure before excavation,as a load on coal body,affects the break-start and then the flow field.The flow field is decoupled with the stress field,so that the gas seepage through unbroken coal body,break-start and consequent two-phase flow,and pure gas flow can be analysed independently of the stress field. The tunnelling,an external disturbance that makes the seepage intensify relatively,is an essential factor for initiating outburst.Under steady tunnelling,seepage ought to tend to be steadily progressive.From its asymptotic solution initiation criterion is obtained.This is described by three conditions,possibility condi- tion—tectonic pressure condition,incubation condition—tunnelling or gas condition and triggering condi- tion—seepage velocity condition.
基金National Nature Science Foundation of China(50534070)International Science and Technology Cooperation and Communion Key Project of Ministry Science and Technology of China(2005DFA61030)+1 种基金Natural Science Foundation of Henan Province(200510460014)Coal Mine Gas and Fire Prevention and Control Key Laboratory Foundation of Henan Province(HKLGF200708)
文摘Measured to control serious coal-gas outburst in coal seam were analyzed by theory and experimented in test site.A new technique to distress the coal-bed and drain methane,called hydraulic slotting,was described in detail,and the mechanism of hydrau- lic slotting was put forward and analyzed.The characteristic parameter of hydraulic slotting was given in Jiaozuo mining area and the characteristic of validity,adaptability and secu- rity was evaluated.The results show that the stress surrounding the strata and the gas in coal seam is released efficiently and thoroughly while new techniques are taken,as slot- ting at heading face by high pressure large diameter jet.The resistance to coal and gas outbursts is increased dramatically once the area of slotting is increased to a certain size. In the process of driving 2 000 m tunnel by hydraulic slotting excavation,coal and gas outburst never occurre.The technique could be used to prevent and control potential coal-gas outburst in the proceeding of tunnel driving,and the speed tunneling could be as high as more than 2 times.
基金provided by the Natural Science Foundation Project(Key)of Chongqing(No.cstc2013jjB0012)the National Natural Science Foundation of China(No.51434003)the National Natural Science Foundation of China(No.51474040)
文摘Estimating the intensity of outbursts of coal and gas is important as the intensity and frequency of outbursts of coal and gas tend to increase in deep mining. Fully understanding the major factors contributing to coal and gas outbursts is significant in the evaluation of the intensity of the outburst. In this paper, we discuss the correlation between these major factors and the intensity of the outburst using Analysis of Variance(ANOVA) and Contingency Table Analysis(CTA). Regression analysis is used to evaluate the impact of these major factors on the intensity of outbursts based on physical experiments. Based on the evaluation, two simple models in terms of multiple linear and nonlinear regression were constructed for the prediction of the intensity of the outburst. The results show that the gas pressure and initial moisture in the coal mass could be the most significant factors compared to the weakest factor-porosity. The P values from Fisher's exact test in CTA are: moisture(0.019), geostress(0.290), porosity(0.650), and gas pressure(0.031). P values from ANOVA are moisture(0.094), geostress(0.077), porosity(0.420), and gas pressure(0.051). Furthermore, the multiple nonlinear regression model(RMSE: 3.870) is more accurate than the linear regression model(RMSE: 4.091).
基金the State Key Research Development Program of China(Grant No.2018YFC0808101)the National Natural Science Foundation of China(51774292,51874314,51604278,51804312)the Yue Qi Distinguished Scholar Project,China University of Mining&Technology,Beijing,the Yue Qi Young Scholar Project,China University of Mining&Technology,Beijing.
文摘Coal and gas outbursts compromise two-phase gas-solid mixtures as they propagate as shock waves and flows from their sources.Propagation is influenced by the form of the outburst,proximity to source,the structure and form of the transmitting roadways and the influence of obstacles.The following characterizes the propagation of coal and gas outbursts as two-phase gas-solid flows proximal to source where the coupled effects of pulverized coal and gas flows dominate behavior.The characteristics of shock wave propagation and attenuation were systematically examined for varied roadway geometries using experiments and numerical models.The results demonstrate that the geometry of roadway obstructions is significant and may result in partial compression and sometimes secondary overpressurization in blocked and small comer roadways leading to significant attenuation of outburst shock waves.The shock waves attenuate slowly in both straight and abruptly expanding roadways and more significantly in T-shaped roadways.The most significant attenuation appears in small angle comers and bifurcations in roadways with the largest attenuation occurring in blocked roadways.These results provide basic parameters for simplifying transport in complex roadway networks in the far-field,and guidance for the design of coal and gas outburst prevention facilities and emergency rescue.
基金Financial support for this work, provided by the National Basic Research Program of China (No.2011CB201204)the National Youth Science Foundation Program (No.50904068)+1 种基金the Heilongjiang Science & Technology Scientific Research Foundation Program for the Eighth Introduction of Talent (No.06-26)the National Engineering Research Center for Coal Gas Control
文摘Based on the evolution of geological dynamics and spatial chaos theory, we proposed the advanced prediction an advanced prediction method of a gas desorption index of drill cuttings to predict coal and gas outbursts. We investigated and verified the prediction method by a spatial series data of a gas desorption index of drill cuttings obtained from the 113112 coal roadway at the Shitai Mine. Our experimental results show that the spatial distribution of the gas desorption index of drill cuttings has some chaotic charac- teristics, which implies that the risk of coal and gas outbursts can be predicted by spatial chaos theory. We also found that a proper amount of sample data needs to be chosen in order to ensure the accuracy and practical maneuverability of prediction. The relative prediction error is small when the prediction pace is chosen carefully. In our experiments, it turned out that the optimum number of sample points is 80 and the optimum prediction pace 30. The corresponding advanced prediction pace basically meets the requirements of engineering applications.
基金This research has made use of data from the University of Michigan Radio Astronomy Observatory which is supported by funds from the University of Michigan and by a series of grants from the NSF.This paper is partly based on observations carried out at the 30 m telescope of IRAM,which is supported by INSU/CNRS (France),MPG (Germany) and IGN (Spain)
文摘The multi-frequency light curves of BL Lacertae during 1997.5 - 1999.5 have been modeled by four outbursts, each having a 3-stage evolution in the （Sm, vm） plane with distinct rising-plateau-decaying phases. It is shown that the observed light curves can be well fitted for the eight frequencies from 350 GHz to 4.8 GHz. The main characteristics of the model-fitting are; （1） the outbursts are found to have very flat spectra with an optically thin spectral index α （defined as Sv α u^-α） of about 0.15. This is consistent with the results previously obtained by Valtaoja et al. （1992）; （2） it is found that there is no spectral flattening between the rising-plateau phase and the decay phase. In other words, the optically thin spectral index does not change from the rising-plateau phase to the decay phase. These features are in contrast to the 3-stage shocked-in-jet model proposed by Marscher ＆ Gear （1985） for submm- IR-optical flares, in which a spectral flattening of △α = 0.5 is predicted when a transition occurs from the Compton/synchrotron phase （or rising-plateau phase） to the adiabatic phase （or decay phase） with α≥ 0.5 for the shock being non-radiative. We propose a new model to interpret the fitting results, suggesting that the 3-stage evolution of the mm-cm outbursts in BL Lacertae may be related to the process of shock formation and propagation in a highly collimated jet （for example, a ＇parabolic＇ jet）. In particular, during the rising phase, the thickness of the synchrotron-radiating region created by the shock may rapidly increase with time （relative to the jet width） due to the rapid injection of relativistic electrons and a magnetic field, and this leads to the observed behavior that the turnover flux density Sm rapidly increases while the turnover frequency um decreases. In the decay phase, the emitting plasma enters into a free expansion regime without further injection of relativistic electrons and a magnetic field （for example, when a transition from a collimated regime into a conical regime occurs）. The plateau phase is a short period between the two regimes with no distinct features determined.
基金The article received China National Natural Science Found(41601574).
文摘Based on the theories of the gas seepage in coal seams and the deformation of the coal-rock medium,the gas seepage field in coal-rock mass is coupled with the deformation field of the coal-rock mass to establish a fluidstructure interaction model for the interaction between coal gas and coal-rock masses.The outburst process in coal-rock masses under the joint action of gas pressure and crustal stress is simulated using the material point method.The simulation results show the changes in gas pressure,velocity distribution,maximum principal stress distribution,and damage distribution during the process of the coal and gas outburst,as well as themovement and accumulation of coal-rock masses after the occurrence of the outburst.It was found that the gas pressure gradient was greatest at theworking face after the occurrence of the outburst,the gas pressures and pressure gradients at each location within the coal seamgradually decreased with time,and the damage distribution was essentially the same as the minimum principal stress distribution.The simulation further revealed that the outburst first occurred in themiddle of the tunnel excavation face and that the speed at which particles of coal mass were ejected was highest at the center and decreased toward the upper and lower sides.The study provides a scientific basis for enhancing our understanding of the mechanism behind coal and gas outbursts,as well as their prevention and control.
基金supported by a Grant from the Ministry of Science and Higher Education of Poland(NR09-0038-06,Poland)
文摘The paper presents some information about gas and coal outbursts threat in Polish coal mines.It shows the methodology for threat identification and monitoring for gas and coal outbursts in the Polish coal mines.One of the main methods of assessing threats in the mining industry in Poland and China is desorbometric method.The paper presents some results of estimation of uncertainties of the desorption rate Δp,determined in situ,by use of liquid manometric desorbometer gauge.It was observed that,if there are coal subgrains in desorbometer contaminator,the results of desorption rate may be even up to 60% higher than results obtained for the normative sample.Possibly method of the uncertainty reduction are presented in the paper as well.
基金NationalNaturalScienceFoundationofChina (No .195 730 19No .196 5 30 0 1)andbyNaturalScienceFoundationofJiansuProvince
文摘In this paper, we present the observations of Comet Hale-Bopp by means of photoelectric and photographic photometry during the period from September to November of 1996. It is shown that there appears to have been 3 outbursts around 24 Sept., 26 Oct. and 13 Nov.; and it is also possible that an event of outburst has taken place around 9 Oct.
