Abstract:To improve gas management in small coal pillars,comprehensive gas drainage was implemented in the extra-thick coal seams of the 8204 working face at Tashan Coal Mine.Numerical simulations,combined with field measurements and quantitative gas source analysis,were used to examine the distribution and behaviour of gas in the working face.The study introduced ground vertical well extraction as a control method and identified the best times for gas extraction.Results showed that fractures within the small coal pillar formed channels for gas flow,causing convection between the 8206 goaf and the 8204 working face.This process made the 8206 goaf the primary gas source for the 8204 working face,contributing 62.0%of the total gas.The best gas extraction effect was achieved within the range of 20 meters ahead of the working face to 120 meters behind the working face.The use of ground vertical shaft extraction effectively maintained gas concentrations well below the critical threshold of 0.8%.This approach significantly reduced gas levels and offers practical guidance for managing gas in similar mining conditions.

Abstract:In order to study the evolution law of shock bump induced by over-fault mining in deep mining face and the measures to prevent and control rock burst,the energy and frequency of shock bump in the fault area were first analyzed and studied during the mining process of the 11301 working face of Zhaolou Coal Mine.The evolution law of shock bump was analyzed from the perspective of strata movement.Then,after conducting CT back analysis in the working face,the pressure relief measures were taken,and the effect of the pressure relief measures was tested by using the existing impact risk early warning model and early warning criteria.The results show that when the 11301 working face is close to the fault area,the large energy event and frequency are significantly higher than the normal area;during the mining period of the working face,high-energy shock bump occurs in the roof near the two faults.The CT inversion results show the distribution of impact risk areas in the 11301 working face.In the impact risk area,the pressure relief measures of the combination of two large-diameter boreholes,floor loose blasting and roof forced roof breaking were carried out.The anomaly index of the impact risk early warning model was used to evaluate the effect of pressure relief and energy reduction.It was found that the anti-impact effect of pressure relief measures was significant.The research results can provide reference for preventing rock burst accidents in deep mining fault areas.

Abstract:To enhance the accuracy and applicability of optical interference methane concentration analyzers,particularly in the low-oxygen environments of underground coal mines,this study addresses the common issues of unstable readings and large measurement deviations.Building on the traditional optical interference methane concentration model,we incorporated the effects of environmental temperature,air pressure,and the varying concentrations of O2 and N2 in methane-containing gas mixtures.Based on these considerations,we developed and constructed an optimized measurement model in which the refractive index was treated as a variable rather than a fixed parameter.To validate the improved model,we conducted comparative laboratory experiments using standard gas mixtures.We prepared nine different mixtures containing O2,CH4,CO2,and N2,varying O2 concentrations at 18.00%,19.00%,and 20.00%,and CH4 concentrations at 0.50%,1.00%,and 1.50%.The results showed that the methane concentrations calculated by the optimized model closely matched the laboratory standard values and were unaffected by changes in O2 concentration.The maximum error did not exceed 0.03%,demonstrating significantly higher accuracy than traditional optical interference analyzers.In summary,the optimized optical interference methane concentration measurement model not only improves accuracy but also overcomes the limitations of traditional analyzers,which are sensitive to environmental O2 levels.This makes the new model more suitable for accurately measuring methane concentrations in the complex environments of underground coal mines.

Abstract:In order to solve the problem of job type adaptation of production technologist of emergency rescue team for gas explosion accident in coal mine,guided by the thought of"enterprise emergency,social rescue",scenario analysis and Bayesian network were combined to deduce the emergency rescue process of gas explosion accident.Firstly,the characteristics of the current situation of emergency rescue in coal mine accidents were analyzed,and five situational elements were determined,including scenario state,disaster environment,emergency response,response target and self-evolution law.Then the Bayesian network was introduced to determine the relationship between the elements of the scene,and the fuzzy theory was used to deal with the optimization.The scenario deduction model for gas explosion accidents was built.Finally,a coal mine gas explosion accident case was selected,and a posterior probability and sensitivity analysis was carried out by Netica software to find the key emergency response actions,which were matched with the tasks of various types of coal mine jobs.The job type adaptation scheme of production technologist of part-time emergency rescue team for gas explosion accident in coal mine was obtained,and the rationality of the model was verified.The research can provide certain references for the adaptation of emergency rescue job types in coal mines.

Abstract:To address the comprehensive management and development needs of large,complex,and aging mining areas,this study proposes a multi-objective,multi-level collaborative modeling method.By integrating diverse information sources,such as mining geology and engineering data,a comprehensive database was established to support the construction of geological and engineering models which is applied to the Fushun coalfield.These models are dynamically integrated to form collaborative models that can be tailored to varying objectives and levels of detail based on actual requirements.The modeling process emphasizes a multi-objective approach encompassing management,simulation,integration,and development,while supporting multi-level representations for different applications.Results demonstrate that the collaborative model accurately reflects the characteristics of the mining area and provides a scientific foundation for effective management and future development.This modeling method offers robust technical support and valuable guidance for managing and developing large,complex,and older mining areas.

Abstract:In view of the technical problems such as low efficiency and poor effect of gas control in 21210 working face of Chensilou Coal Mine,fine gas geological analysis was conducted to study the gas occurrence law of the working face.The main controlling geological factors affecting gas occurrence were determined,and five gas-abnormal areas were delineated.A multi-measure collaborative gas control technology was adopted,including regional outburst prevention measures such as"cross-seam boreholes+hydraulic flushing"combined with"advance treatment of borehole drilling along seam+treatment in the advance mining pressure-relief area",gas control measures for the upper corner like"directional long high-level borehole+common short high-level borehole",and outburst prevention measures for the working face such as"gas extraction/venting+coal seam water injection".The application results show that the original gas content of the 21210 working face ranges from 3.07 m3/t to 11.79 m3/t,and the direct measurement method of underground coal seam gas pressure(passive pressure measurement method)is adopted to measure the gas pressure from 0 MPa to 0.65 MPa.After the evaluation of extraction reaching the standard,the measured residual gas content in the coal seam is 2.30 m3/t to 5.61 m3/t,and the residual gas pressure is all 0 MPa.The extracted gas volume is 3.629 million m3,and the pre-extraction rate is 47%.The desorbable gas content is 3.50 m3/t.The gas extraction effect within the evaluation scope meets the standard,achieving efficient gas extraction and safe mining in the working face.

Abstract:Real-time monitoring of vibration of horizontal directional drilling bottom hole drilling tools is of great significance for ensuring drilling safety and improving drilling efficiency.Traditional vibration sensors have limitations in power supply,while self-powered vibration sensors are more suitable for actual working conditions.Based on the principle of triboelectric nanogenerator,this study proposes a novel self-powered vibration sensor that can fully utilize the induced electricity generation during the drilling process and simultaneously measure the vibration frequency.Experimental results show that the sensor can work normally in a temperature range of 0℃to 105℃and a relative humidity range of 0 to 90%,with a vibration frequency measurement range of 0 Hz to 13 Hz and a measurement error of less than±3%.Additionally,the sensor can be installed on a plane with a tilt angle of less than 45°.Furthermore,the power output of the sensor can reach a maximum of 0.61 μW,and when used in parallel with multiple sensors for power storage,it can supply power to other underground measuring instruments.The research findings can provide valuable reference for developers of underground measurement and sensor equipment.

Abstract:During the coal mining process in the Hujirt mining area of the Ordos Basin,significant impacts are observed from the aquifers of the Jurassic Zhiluo Formation and the Cretaceous Zhidan Group,with average thicknesses of 153 m and 350 m,respectively.Situated between these aquifers is a relatively impermeable layer from the Anding Formation,averaging about 94 m in thickness.These layers together constitute a thick composite confined aquifer system atop the mining area.This study,taking the Shilawusu Coal Mine as the research object,aims to clarify the previously ambiguous water-inrush mechanism from the thick composite aquifer in the roof of the coal seam mining in the Hujirt mining area.Analyzing the water yield in the goaf of the working face and the response characteristics of the water level of the thick composite aquifer on the roof,combined with the development law of the water conducted zone,three modes of roof water-inrush and filling were identified:lateral replenishment from the lower aquifer,comprehensive replenishment from the composite aquifer,and lateral replenishment mainly from the upper aquifer.This delineates a"stepwise progression"in the mechanism of water-inrush at the identified working face.Through numerical simulation,the contribution of each aquifer to the underground water-inrush across five stages of working face retreat was calculated.The findings indicate that in the first stage,the Zhiluo Formation aquifer is the primary contributor to water-inrush,accounting for about 87.3%of the total.In the second stage,the contribution of the Zhidan Group aquifer surpasses 70.0%.In the third stage,replenishment from the Zhidan Group aquifer decreases gradually,while the contribution of the Zhiluo Formation aquifer increases slowly to 34.0%.The fourth stage witnesses a sharp increase in groundwater replenishment from the Zhidan Group,constituting 75.0%of the total water-inrush volume.In the final stage,groundwater replenishment from the Zhidan Group diminishes gradually,with the contribution from the Zhiluo Formation increasing slightly to 29.3%.The simulation results align closely with empirical observations,affirming the"stepwise progression"water inrush mechanism.

Abstract:Although dust monitoring and control have been achieved in the coal mine belt transfer point through the installation of sensors and dust reduction equipment,when the concentration of dust in the area is abnormal,the investigation of the abnormal causes still highly relies on manual experience,and there is a problem of response lag.In order to remotely,quickly,and accurately locate the cause of abnormal causes,a dust concentration anomaly tracing algorithm integrating the ordered constraint Apriori algorithm and the traceability tree mechanism is proposed.Based on the status of regional device deployment,the Apriori algorithm with ordered constraints is used to mine abnormal association rules and generate a table of abnormal causes with priorities.By combining the dynamic threshold and instantaneous threshold of dust concentration to set the traceability trigger conditions,a multi-level traceability tree integrating backtracking markers and node weights is constructed.When the trigger conditions are met,a depth-first search algorithm based on backtracking markers and node priorities is adopted to quickly locate the cause of the anomaly.Experiment results show that in the scenario of mine belt transfer point,this algorithm can effectively identify the high-frequency causes of abnormal dust concentration(such as spray device failure),and the traceability accuracy rate is 96.96%.

Abstract:Multiple faults occur in the WII02040501 working face of Tunbao Coal Mine and run through the whole working face,and one side is mined out.In view of the abnormal microseismic and mine pressure behavior in the triangular coal pillar area during the mining period of the working face,the mechanism of stress anomaly in the triangular coal pillar area under the mining disturbance was revealed through theoretical analysis,and the variation laws of the stress field and energy field of the triangular coal pillar under the influence of faults were studied through numerical simulation.The results show that the fault-type triangular coal pillar area is affected by the mutual superposition of the advance abutment pressure,the abutment pressure of the fault and the hanging roof pressure of the adjacent goaf,resulting in a high degree of stress concentration in the fault-type triangular coal pillar area.Under the action of fault barrier,the static load stress and accumulated elastic energy in the triangular coal pillar area increase with the decrease of the distance between the working face and the fault.When the working face is 150 m away from the fault,the static load stress and elastic energy in the triangular coal pillar area begin to rise,and reach the peak when it is 50 m away from the fault.The measures of blasting pressure relief and energy release of roof and coal in triangular coal pillar area are put forward,and the effect of pressure relief project is verified.

Abstract:In order to investigate the impact of adsorption-desorption behavior of coal seam gas on the effectiveness of nitrogen injection and displacement,experiments were conducted using N2-CH4 gas mixtures with varying ratios.The performance of adsorption-desorption was analysed through the coal strain,adsorption-desorption rates,and changes in pore pressure.The results show that during the adsorption stage,the gas enters the pore space of coal seam quickly at the beginning.CH4 rapidly occupies the adsorption site,followed by gradually reduction in the adsorption rate.Enhancing the volume fraction of N2 can improve the diffusion and adsorption of gas,thereby increasing the adsorption rate and gradually reducing the pore pressure.The coal is compressed and contracted throughout this process.However,it expands due to adsorption after continuous gas injection,and the strain value here is reduced with the increasing volume ratio of N2.During the desorption stage,gas is swiftly expelled under the effect of pressure gradients,causing a sharp decline in pore pressure.The desorption rate first decreases and then tends to stabilize.The coal first expands axially and then continuously contracts.The strain variation is inversely related to the volume fraction of N2.

Abstract:In response to the prominent problem of insufficient transmission distance faced by the wireless radio wave perspective technology in the fully mechanized coal mining wide working face,the influence posture of the transceiver coil on the perspective ability was analyzed in depth.Based on the magnetic dipole theory and stratiform medium model,the expressions for the magnetic components in horizontal and vertical orientations were derived.A detection method combining vertical coil launch with improved Hankel integral adaptive computation was proposed and implemented.The results show that under the condition of a double-layer medium similar to a coal seam,when using the vertical coil launch method,the propagation distance of electromagnetic waves in the coal seam is farther,and the received signal strength is significantly higher than that of the horizontal coil method.On site comparative testing confirmed that this method effectively increased the strength of electromagnetic wave received signals by about 25%,resulting in more stable signals and enhanced anti-interference capabilities.The tomographic imaging results successfully delineated the geological anomaly area(collapse column)within the working face,and the detection effect was verified by later mining.

Abstract:Aiming at the problem of rock burst prevention and control in isolated working faces under deep mining conditions,the 003 deep well isolated working face in the central mining area of Qujiang Coal Mine in Fengcheng,Jiangxi Province was taken as the research object.By combining laboratory tests,theoretical analysis and numerical simulation,a systematic study was conducted on the coal-rock impact tendency of isolated working faces,the structural characteristics of overlying rocks in isolated working faces,and the stress evolution features during the mining period.The test results indicate that the coal seam and floor of the 003 isolated island working face exhibit no burst tendency,while the coal seam roof shows a strong burst tendency.FLAC3D numerical simulation shows that with the coal face advancing,the stress concentration coefficient of the coal pillar in the front gradually increases from 1.05 to 1.24.Especially during the"square"mining period of mining,the concentration coefficient is relatively high.On-site roof pre-cracking blasting pressure relief was carried out and tested by the drill stress cuttings method.This pressure relief method effectively weakened the static load level and had a good anti-impact control effect.

Abstract:The complex conditions within closed fire zones make gas monitoring challenging,resulting in varied sampling results.To address this,our study evaluates the reliability and priority of different monitoring indicators.We used temperature-programmed experiments to optimize early warning indicators and developed a hierarchical early warning model.The grey correlation method was applied to assess the relationship between selected indicators and parameters within the closed area,ensuring their suitability.The model was then validated using field data.Results identified four key characteristic temperatures for Tingnan coal:30℃,70℃,100℃,and 200℃.The volume fraction of CO,as well as the initial detection temperatures of C2H4 and C2H2,were chosen as primary early warning indicators.Additionally,the commonly used composite index RC,O was confirmed as an effective warning indicator.Strong correlations were found between the CO volume fraction,RC,O,O2 volume fraction,and the pressure difference(ΔH)between the inside and outside of the closed area.The correlation was highest with O2 volume fraction(0.801 3 for CO and 0.785 8 for RC,O),followed by ΔH(0.696 8 for CO and 0.672 1 for RC,O).Continuous monitoring showed that RC,O exceeded the minimum threshold for a blue warning on the second day and continued to rise,successfully triggering the model's blue warning alert.These findings demonstrate that the hierarchical early warning model is effective and can be reliably applied in practice.

Abstract:In view of the dust pollution problem from blasting muckpile,as well as mining and loading operation at the Heidaigou Open-Pit Coal Mine,a dust suppression with rapid penetration effect was formulated.The formula was optimized through orthogonal tests and permeability performance tests,and the mass fractions of the optimal components were determined as follows:waterborne polyurethane 0.10%,xanthan gum 0.02%,polyethylene glycol(PEG-1500)0.06%,and fast penetration T 0.50%.Field applications of the dust suppression were conducted,accompanied by assessments of moisture content,monitoring of dust concentration,and scanning electron microscopy(SEM)analysis.The results indicated that the dust suppression exhibited excellent moisture retention and effective dust suppression capabilities.Specifically,when compared to the application of pure water at equivalent rates,moisture loss was reduced by 26.7%,while dust suppression efficiency increased by 14.5%.Additionally,it was observed that dust emissions decreased progressively with increasing application rates of the dust suppression solution.A comprehensive cost analysis determined that applying 15 tons of the dust suppression solution per 10-meter area of the blasting muckpile provided the best cost-performance ratio.

Abstract:The fissures produced by blasting pressure relief are widely distributed in the rockburst coal seam.To investigate the effect of crack dip angle on the progressive failure characteristic of coal with bursting liability,uniaxial compression test were carried out on coal samples with different crack dip angles.The following results were obtained:① As the crack dip angle increases,there is a rise in peak strength and elastic modulus,the peak strain increases first and then decreases again,and the peak transverse strain increases first and then decreases.② With the increase of crack dip angle,the characteristic stress of coal sample cracking and damage shows a stepwise change.The cracking and damage stresses increase in a"three-stage"manner.The characteristic stresses increase linearly at 0°,15°,30°,and 45°,rise rapidly at 45°,60°,and 75°,and increase slowly at 75° and 90°.③ A method for jointly evaluating the bursting liability by bursting energy index,yield,damage time step,and pre-peak fissure percentage was proposed.It was found that the bursting liability of coal samples with 45° fractures was the weakest.④ A progressive failure model of fractured coal samples was established to analyze its failure mechanism.When the dip is less than 60°,the instability of the coal sample is significantly affected by the prefabricated fractures.The crack initiation position is at the tip or middle of the fissures,and the crack type is mainly a mixture of tensile and shear.When the dip is more than 60°,the influence of fissures on instability behavior is relatively weak.

Abstract:In order to study the fragmentation behavior of particle coal,this study takes coal samples from four mining areas as the research object.By changing the particle size of particle coal,drop hammer test was carried out to study the influence of the change in the initial particle size on parameters such as particle size distribution,newly added surface area and crushing work ratio of particle coal after crushing.The results show that the converted diameter of crushed particle coal increases with the increase of initial particle size,among which greater than or equal to 8 mm and less than 10 mm particle coal in Hongliulin Coal Mine and greater than or equal to 2 mm and less than 4 mm particle coal in Zhaogu Coal Mine are 0.015 0 mm and 0.006 2 mm,respectively.The particle breakage rate decreases with the increase of initial particle size.The volume fraction distribution of pulverized coal less than 0.075 mm after crushing follows the Gauss distribution law.The newly added surface area decreases with the increase of initial particle size,among which,the newly added surface area after crushing of greater than or equal to 2 mm and less than 4 mm particle coal in Zhaogu Coal Mine and greater than or equal to 8 mm and less than 10 mm particle coal in Yuka No.1 Coal Mine in Qinghai Province is 154 261.30 mm2 and 73 048.17 mm2,respectively.The crushing work ratio increases with the increase of particle size,among which greater than or equal to 2 mm and less than 4 mm particle coal in Zhaogu Coal Mine and greater than or equal to 8 mm and less than 10 mm particle coal in Yuka No.1 Coal Mine are 280.04 J/m2 and 591.39 J/m2,respectively.

Abstract:The accumulation of coal gangue not only poses great harm to the environment,but also causes great waste of resources.Adding biomass helps improve the combustion performance of coal gangue,and co-combustion is an efficient method for handling both coal gangue and biomass.Co-pyrolysis experiments of coal gangue and major biomass components(lignin,cellulose,and hemicellulose)were carried out by the combination of thermogravimetric analysis with Fourier transform infrared spectroscopy to investigate the influence of biomass components on coal gangue pyrolysis,along with the interaction in pyrolysis weight loss and gas product characteristics between coal gangue and biomass components.The results show that the blending of lignin,cellulose and hemicellulose in coal gangue can reduce the initial decomposition temperature and peak temperature of the mixture,improve the comprehensive pyrolysis index and promote the pyrolysis of coal gangue.The interaction mechanism between the main components of coal gangue and biomass in terms of thermal weight loss is related to pyrolysis temperature and blending ratio.The blending of a small amount of cellulose and hemicellulose has a great influence on the gas products of coal gangue,and the addition of lignin changes the release law of CO2 from coal gangue.Based on the influence of the main components of biomass on the pyrolysis process of coal gangue and the interaction of pyrolysis weight loss,it is suggested that the blending ratio of lignin should be greater than 50%,while the blending ratio of cellulose and hemicellulose should be controlled within 25%.