Abstract:With the increase in coal mining depth,influenced by the increase in ground stress and gas,as well as the complex coupling of multiple factors,"low-parameter and low-index"outburst accidents have occurred from time to time in recent years.The traditional"binary classification"method for identifying hazardous and non-hazardous conditions entails certain uncertainties;in particular,outburst risks near critical values are diffi-cult to determine,failing to meet on-site outburst prevention requirements.To address this issue,a"ternary classification"(danger,threat,no risk)intelligent identification method for outburst risk assessment was pro-posed and studied.Characteristics of typical historical deep outburst accidents were analyzed,and a database of 1,378 coal seam outburst risk samples was constructed based on 18 types of identification indices,including coal seam burial depth,gas pressure,and firmness coefficient.Feature information mining(categorical varia-bles,missing values,and index screening)was employed to preprocess the data,aiming to reduce the impact of high dimensionality and small sample sizes on the modeling of identification methods.Various machine learning identification models were established,combined with the optimization algorithm for hyperparameter tuning.The results indicate that the"ternary classification"performance of the ensemble learning BO-LightG-BM model is significantly superior to that of basic machine learning models.Case verification shows that the identification accuracy for"No Outburst Risk-I"is 100％,and the overall accuracy for"Outburst Threat-II"and"Outburst Danger-III"is 88.9％.This achieves reliable and accurate identification of outburst risk data,providing an effective intelligent identification method for outburst risk assessment.

Abstract:Based on a case study of a coal mine in Shandong,this paper investigates the determination of the e-lastic core width in large coal pillars located in strongly bump-prone mines at depths approaching 1,000 me-ters.Through field tests,the following conclusions are drawn:(1)Using high-power auto-rod-add drilling rigs on site,the degree of stress concentration in the coal pillar area as well as the distribution of elastic zone,plastic zone,and fractured zone were determined based on macroscopic manifestations during drilling,including drilling cuttings particle size,quantity and intensity of coal bursts,and drill jamming incidents.These observa-tions provide a basis for selecting the relief depth of large-diameter boreholes.(2)An analysis of the drilling process indicates that the range of 0-15 meters from both sides of the roadway is predominantly composed of fractured and plastic zones,while a 50-meter central section of the coal pillar constitutes the elastic core zone.(3)The 0-15 meter zones on both sides of the coal pillar are characterized as low-stress areas with limited energy accumulation capacity,exhibiting fewer coal bursts of lower intensity;whereas the central 50-meter sec-tion demonstrates high stress concentration,significant energy storage potential,and frequent coal bursts of greater intensity.(4)Pressure relief boreholes must extend beyond 30 meters in depth,with particular empha-sis on implementing intensive cuttings discharge in the section exceeding 15 meters.This process actively transfers stress from the panel-side elastic core toward the goaf area,effectively mitigating rockburst risks dur-ing subsequent mining of adjacent panels.

Abstract:Coal and gas outburst is a major hazard threatening coal mine safety production,and its scientific identification serves as the prerequisite for disaster prevention and control.Based on a literature review meth-odology,this paper systematically traces the evolution of China's legal and standard system for coal and gas outburst identification from the 1950s to the present,dividing it into three developmental stages—"initial exploration,""gradual establishment,"and"mature improvement"—and analyzes representative regulations and standards at each stage along with their contributions to mine safety.The study identifies key deficiencies in the current system,including ambiguous legislative intent,poor coordination among standards,overly simplis-tic identification indicators,inadequate adaptability of methods,insufficient procedural oversight,and lack of forward-looking planning.To address these issues,the paper proposes clarifying the legislative orientation toward"precision prevention and control,"establishing a coordinated and unified standard framework,expanding novel indicators and methods(e.g.,tectonic stress analysis and intelligent prediction models),im-proving qualification review and third-party supervision mechanisms,and developing a dynamic,future-oriented planning system tailored for intelligent mining and deep mining conditions.Findings indicate that op-timizing the regulatory and standard system can significantly enhance the scientific rigor and effectiveness of outburst identification,thereby offering substantial theoretical and practical value for modernizing China's coal mine safety governance and preventing catastrophic accidents.

Abstract:Coal and gas outbursts represent a major hazard in coal mining operations.To achieve a more scien-tific and objective assessment of outburst risk,this study developed a comprehensive evaluation model integra-ting the Analytic Hierarchy Process(AHP)with grey correlation analysis.The model first constructs a three- tier hierarchical structure comprising an objective layer,a criterion layer,and an indicator layer.Indicator weights are determined through expert scoring combined with consistency testing.Grey correlation analysis is then applied to quantify the association degree between each factor and the outburst hazard risk.Finally,a comprehensive evaluation model is formed through weighted summation.Using the No.3 coal seam at Xigou Coal Mine in Yangcheng County,Jincheng City,Shanxi Province as an empirical case,the model calculation in-dicates a comprehensive correlation degree of 0.5292 and a hazard risk level classified as"relatively safe,"which aligns with actual production assessment results.The study demonstrates that the combined model of AHP and grey correlation analysis effectively integrates the systematic nature of AHP in weight determination with the objectivity of grey correlation analysis in data evaluation.Through weighted synthesis,it achieves com-plementary advantages between subjective weights and objective correlation.The tiered control strategy based on evaluation results facilitates the optimized allocation of safety resources.This model framework provides a novel methodological reference for evaluating prominent hazards in coal mining enterprises.

Abstract:Coal and gas outbursts are among the most severe dynamic disasters in Chinese coal mining,where the instability and failure of the coal body are induced by the coupled effects of in-situ stress and gas pres-sure.Accurate assessment of outburst hazards is fundamental to ensuring safe mining operations.This paper provides a systematic overview of the historical development of outburst hazard assessment agencies in China,tracing the evolution of their certification and management systems,and profiling the primary qualified institu-tions operating today.It further analyzes the developmental trends in assessment standards and indicator frame-works,clarifying the scientific rationale behind the transition from early methods based on gas-dynamic phe-nomena to modern comprehensive judgments using measured indicators.This evolution signifies a logical pro-gression from focusing on mechanical properties to the material's fundamental basis—namely,gas content and pressure.Leveraging the practical experience of the North China Institute of Science and Technology as a case study,this paper details a complete workflow for outburst hazard assessment,including methodologies for geo-logical unit delineation,optimal placement of measurement points,and advanced techniques for determining key parameters such as gas pressure,gas content,coal firmness coefficient,and initial gas desorption velocity.The accuracy and representativeness of these measurement results are validated through a reliability analysis of field data from regions including Xinjiang,Shanxi,and Henan.The study concludes that China's approach to out-burst hazard assessment is advancing towards greater procedural standardization,more scientific indicator sys-tems,and systematic data verification,thereby providing a robust technical foundation for the prevention and control of gas-related disasters in coal mines.

Abstract:In response to the frequent occurrence of impact-induced ground pressure in the conditions of syn-cline structures and hard roof,the static stress distribution characteristics of the surrounding rock of the roadway in the syncline structure area were studied through theoretical analysis and numerical simulation meth-ods.The influence of mechanical property factors on stress evolution was analyzed,and the formation and dis-aster-causing laws of impact in the roadway of the syncline structure induced by the hard roof were revealed.The research results show that the horizontal stress concentration degree of the surrounding rock in the syncline structure area is high.The dynamic load released by the fracture of the hard roof,when superimposed,exceeds the critical stress and easily leads to the manifestation of the "high static load and weak disturbance" type of rock burst.When mining in the axis of the syncline,the closer to the axis,the higher the stress peak,and the stress concentration degree of the inclined mining near the syncline axis is higher than that of the inclined min-ing away from the syncline axis.The greater the thickness and hardness of the roof and the greater the curva-ture of the syncline,the higher the stress concentration degree of the surrounding rock.The roof properties have a small influence on the change of the location of the advanced peak stress,while the increase of the syn-cline curvature makes the stress peak position closer to the working face and the stress more concentrated.

Abstract:This paper is grounded in the context of the new national energy security strategy and the moderniza-tion of coal mine safety governance system.It is based on the measured data from Guizhou Province in the past five years,then systematically analyzes the core geological control mechanisms and spatiotemporal distribution patterns of gas occurrence,and elaborate on the current situation of prominent identification work in Guizhou.The research indicates that Guizhou's tectonic stress field is complex,with large-scale fold and fault systems exerting a dominant control over gas enrichment and accumulation.A high degree of coupling exists between zones of tectonic stress concentration and anomalous zones of gas pressure and content.The central high-meta-morphic anthracite region,due to its superior hydrocarbon generation and reservoir-cap rock assemblages,re-presents the province's peak gas content zone and a key focus for disaster management.Statistical data show that the number of mines(or instances)identified with outburst risks in Guizhou accounts for 31.7％of the national total,highlighting the arduous nature of outburst prevention tasks.The current prominent identification work faces three major contradictions:the conflict between universal national standards and strong regional geo-logical heterogeneity;the conflict between a static,discrete identification model and the dynamic,continuous evolution of disaster risk;and the conflict between the lag in identification work and the need for synchronous,high-efficiency mine construction.Finally,from the perspectives of top-level design,technological innovation,and regulatory model,this paper proposes the construction of an elastic technical standard system based on risk assessment,establishing a dynamic risk assessment mechanism that spans the entire mine life cycle,and the in-troduction of a blockchain-based regulatory mechanism for the first time.

Abstract:High stress concentration is a prerequisite for the occurrence of dynamic disasters.Understanding the overall distribution of the regional in-situ stress field provides essential guidance for the prevention and control of coal mine dynamic disasters.Taking the coal pillar area of the Tangshan Mine main roadway as the research background,a three - dimensional stress field inversion is conducted using the multiple linear regression method.Based on the least-squares multiple regression analysis,five regression coefficients are ob-tained for the analytical equation:L1= 1.1511,L2= 2.2414,L3= 2.3617,L4= 3.5288,and L5= 2.5271,with a multiple correlation coefficient of r = 0.8961.The inversion results are used to analyze the initial stress field in the coal pillar area and the dynamic evolution characteristics of the coal-rock stress field during the working face extraction.The results indicate that the vertical stress in the No.8 and No.9 coal seams of the roadway coal pillar area ranges from 11.5 to 16.9 MPa,and the maximum principal stress also ranges from 11.5 to 16.9 MPa.The influence of horizontal tectonic movement on the stress field in the coal pillar area is relatively minor.During the extraction of working face T2391,a high degree of stress concentration occurs near the haulage roadway,with a maximum stress of 45 MPa—significantly higher than that near the return airway—indicating that monitoring and control efforts should focus on the haulage roadway side.Conversely,during the extraction of working face T2491,stress concentration is more pronounced near the return airway,with a peak value of 48 MPa,considerably exceeding that on the haulage side;thus,control measures during extraction should primarily focus on the return airway side.

Abstract:Gas content is a crucial indicator for assessing the risk of coal seam outbursts.However,under com-plex geological conditions,significant discrepancies often arise in the determination results.To investigate the applicability of the gas content indicator under such conditions,this study analyzes actual gas parameters from the No.14 coal seam in Dafang County,Guizhou Province.The research reveals that under complex geological environments,the critical value of gas content exhibits a noticeable "drift" phenomenon,making traditional static critical indicators inadequate for accurately reflecting actual outburst risks.To address this issue,this study introduces a resistance strength coefficient X through multi-parameter coupling analysis.Based on re-gression analysis,a dynamic prediction model for the minimum outburst gas content is established.Validation shows that the model's error range is controlled between 2％and 13％,significantly outperforming traditional static indicators in determination accuracy.The study demonstrates that the assessment of gas outburst risk should transition from static indicators to dynamic models.By developing dynamic models that reflect changes in geological conditions,outburst risks can be identified more precisely,thereby enhancing the accuracy of dis-aster prevention and control.

Abstract:Against the backdrop of China's current management goal of"zero outburst"for coal seams and the new situation where regulatory authorities are placing greater emphasis on in-process and post-event su-pervision of outburst identification work,identification institutions have become increasingly rigorous and pru-dent in both the control of identification processes and the issuance of conclusions.This paper employs litera-ture review,case analysis,and on-site investigations to analyze the limitations of existing identification indica-tors and methods.It dissects critical issues such as the heightened risk of sudden changes in identification in-dicators due to dynamic mining activities,disputes regarding the delineation of identification scopes,challenges in accurate determining gas grades in adjacent outburst-prone coal mines,and shortcomings in the initiation procedures for outburst identification.To mitigate the potential risks these problems pose to coal mine safety and to enhance the reliability of identification conclusions,this paper proposes several countermeasures:strengthening the general survey of hidden gas-geological disaster-causing factors,closely monitoring and cap-turing outburst precursor information during the production process,implementing the"one working face,one strategy"prevention and control measures for transitional non-outburst coal seams,and adopting risk control measures for coal seam outbursts in deep mining.The above strategies can provide a reference for standardizing and scientizing the coal and gas outburst identification work,and are of great significance for im-proving coal mine safety production and promoting the revision and enhancement of national and industrial standards.

Abstract:To overcome the limitations of traditional methods in analyzing the multi-factor coupling disaster of rock burst,accurately decipher the causal logic of this hazard,and achieve proactive risk management,this study utilizes 56 authoritative accident investigation reports from 2001 to 2024 as samples.The FP-growth al-gorithm is employed to mine unstructured text,extracting high-frequency co-occurrence causes through a three-dimensional filtering mechanism based on support,confidence,and lift.Subsequently,the mining results are integrated with domain knowledge to construct a Bayesian network topology with prior-posterior dynamic updating capability,enabling probabilistic reasoning of the causal chain and risk inversion.The study reveals the nonlinear disaster patterns arising from the coupling of "geology-mining-management" factors,quantita-tively identifies the dominant role of geological factors such as coal-rock impact propensity,geological struc-tures,and mining depth,as well as the key triggering effects of mining factors like excavation disturbances and coal pillars.It also clarifies the risk amplification effect of management factors,such as insufficient safety awareness.Based on the quantitative analysis results,targeted proactive control measures for rock burst risk are proposed,providing a scientific basis for coal mining enterprises to optimize mining plans and precisely deploy pressure relief monitoring projects.This approach can facilitate the transition of rock burst prevention and con-trol from experience-driven to data-knowledge collaborative driven.

Abstract:In response to the frequent seismic events in the triangular coal pillar area,influenced by the out-board layout of longwall LW7618,significant faults,and the nearby goaf,this study employed numerical model-ing,analytical analysis,and field testing to examine the stress distribution characteristics of the surrounding rock during mining.A reinforcement and pressure-relief scheme was developed to prevent coal bursts in this area.The results show that the stress distribution of the surrounding rock in the triangular coal pillar area was analyzed during the"square" period of the longwall and the entry phase of the adjacent goaf,revealing that the maximum advanced abutment pressure increased by 28.3％and 37.3％,respectively.Seismic wave CT inver-sion results indicated that as the scale of mining expanded,the"island effect" in the triangular coal pillar area intensified,with the maximum velocity anomaly(An)increasing by 52％,and the extent of burst-risk regions in the longwall expanding by 53.3％.A reinforcement and pressure-relief scheme,including controlled roof- cutting blasting and coal blasting pressure relief,was implemented to reduce the stress levels of the coal-rock mass in the triangular coal pillar area,thereby effectively preventing coal bursts during mining in this zone.

Abstract:Rockburst is a typical dynamic disaster of coal and rock in the coal mining process,posing a serious threat to the safety production of coal mines in China.To address the common issues in existing rockburst risk assessment methods,such as the singularity of indicators and insufficient analysis of the coupling mechanism between dynamic and static stress,this study proposes a comprehensive evaluation method based on multi- source stress concentration indices.This method constructs four types of stress concentration indices—static load,geological,mining-induced,and roof dynamic load disturbance—to quantitatively characterize the degree of stress concentration at the working face during different mining stages,and then integrates them into a com-prehensive stress concentration index K,which is used to classify rockburst risk levels.Using a practical exam-ple from the 1200 isolated working face of a mine in Shanxi,the stress evolution patterns were analyzed through FLAC3D numerical simulation,and the evaluation results were verified using field monitoring data.The results show that the method can effectively identify rockburst risk areas during the mining of the working face,demon-strating the feasibility of stress index-based rockburst risk assessment and providing new ideas for safe coal mining and rockburst risk evaluation analysis.

Abstract:In deep coal mining,multiple mining disturbances(MMI)from the upper protective layer and adja-cent goaf lead to a complex reconstruction of the coal seam stress field,significantly affecting gas occurrence and desorption behavior.Traditional single-disturbance theory is inadequate for accurately guiding gas disaster prevention and control under such conditions.Therefore,clarifying the spatial response relationship between stress distribution and gas parameters under multiple mining disturbances has become a theoretical bottleneck and an urgent practical need for achieving precise early warning of gas disasters.This study focuses on the 11063(lower)return air roadway in Majiatian Coal Mine as the engineering background.Utilizing field meas-urement methods,it quantitatively analyzes the evolution of key indicators—such as drilling cuttings quantity(S),gas desorption index(K1),and residual gas content(W)—with spatial position(ranging from 6.9m to 27.4m from the goaf).The experimental results show that:(1)The distribution of drilling cuttings exhibits a"double-peak" stress characteristic under multiple mining disturbances,with a pronounced pressure-relief stress elevation zone located near the goaf(Zone B2)and a closed stress elevation zone approximately 21.4m from the goaf(Zone B1).(2)The peak values of the gas desorption index K1 and residual gas content are both observed in Zone B1 rather than in Zone B2 where the absolute stress is higher.This indicates that gas pa-rameters are closely associated with related to the"closure" of stress rather than its absolute magnitude,revea-ling a non-monotonic response mechanism.(3)By integrating the three indicators—S,K1,and W—Zone B1 can be accurately identified as a "three-high" hazard zone characterized by high ground stress,high gas con-tent,and high desorption potential.Theoretically,this study elucidates the response mechanism of "multiple mining disturbances-stress field evolution - gas desorption and migration," correcting the traditional that focu-ses solely on absolute stress values.In practice,it clarifies that the second stress concentration zone(Zone B1)is the key target for gas disaster prevention and control.The findings provide critical theoretical support and data for establishing a multi-parameter coupling-based precise early warning method and formulating targeted control measures under similar mining conditions.

Abstract:A yield-support composite coal pillar system integrates both narrow and wide pillars.It functions by combining mechanisms of yieldable ground release and stable support to prevent impact-induced instability(Coal burst)in coal pillars.This study is based on the boundary coal pillars of a 290 m wide extraction area located in an outburst-prone mine in Ordos.It designs a"yield-support" combined scheme based on limit e-quilibrium theory and employs the finite element method to simulate the stress evolution and failure process un-der the mining-induced activities of the adjacent longwall face,clarifying the typical stress concentration areas during mining.The results indicate significant high-stress concentrations throughout the entire yield pillar and within a 20-meter zone of the adjacent supporting pillar,as well as in a 50-meter zone on the side of the sup-porting pillar farthest from the yield pillar.In contrast,an approximately 136m-wide area inside the supporting pillar constitutes a low-stress zone.At a mining depth of 750m,the critical width for the yield pillar is deter-mined to be 33.7 m;the currently designed yield pillar satisfies this stability requirement.Dynamic simulation further elucidates the mechanical behavior of the composite structure:a 40 m wide yield coal pillar effectively dissipates the deformation energy of the overlying strata through extensive plastic deformation,redirecting stress toward the two adjacent bearing coal pillars.This ultimately results in an asymmetric stress field,where the stress peak and plastic zone depth on the goaf side of the bearing coal pillars are significantly greater than those on the solid coal side.The core engineering value of this study lies in replacing traditional single coal pillar designs with yield-bearing composite coal pillars in deep rock burst-prone mines to more effectively mitigate rock burst impacts.Based on the stress distribution results,key anti-rock burst prevention zones are clearly delineated.In practical engineering applications,targeted reinforcement support or pressure relief measures can be implemented in these areas,thereby achieving scientific and precise prevention and control.The research findings provide valuable insights for the design of"yield-bearing" composite coal pillars in deep rock burst- prone mines in China.

Abstract:To address the challenge of integrated prevention and control of coal mine rock burst and water in-rush,taking the 207 working face of Tinnan coal mine in Shaanxi province as the engineering background,a"layer-differentiated regulation" technical approach was proposed.This technology combines the pre-splitting and pressure relief of upper rock strata(for rock burst prevention)with the fragmentation and crushing of low-er rock masses(for water inrush prevention),thus achieving integrated disaster prevention and control.Utili-zing 3DEC discrete element numerical simulation,the response characteristics of rock strata under natural con-ditions and three scenarios involving the weakening of upper,middle,and lower rock strata were systematically compared and analyzed.The effectiveness of the integrated prevention and control strategy was further validated through on-site data analysis.The research shows that the weakening of different layers significantly impacts disaster control.The middle layer weakening can simultaneously weaken the key layer,significantly in-crease the expansion coefficient,reduce the height of the water-conducting fracture zone to 130m,and only re-quires a supplementary pre-splitting of 30m to reduce the risk of rock burst,making it the most effective strate-gy.The upper layer weakening results in a height of 140m(requiring a supplementary pre-splitting of 30m),and the lower layer weakening results in a height of 140m(requiring a supplementary pre-splitting of 35m).A comprehensive comparison reveals that middle layer weakening>upper layer weakening>lower layer weake-ning,which is the optimal strategy for the integrated prevention and control of rock burst and water inrush.On- site application shows that after pre-splitting and weakening,the number of high-energy microseismic events in the 207 working face has significantly decreased,and the energy distribution is controllable,verifying the ef-fective suppression of rock burst.At the same time,the pre-drainage of the roof has reduced the extent of the water-conducting fracture zone's impact on the aquifer,eliminating the risk of water inrush.This study pro-vides a theoretical basis and key technical approach for mines with complex disasters.

Abstract:To investigate the synergistic response mechanism between single - column energy - absorbing supports and the surrounding rock of tunnels under dynamic impact loads,ABAQUS numerical simulation was employed.By analyzing mechanical parameters such as surrounding rock stress,deformation,plastic strain,and support deformation,this study examines the dynamic response characteristics of energy-absorbing tunnel sup-ports under both vertical and lateral impacts.The results indicate that under vertical impact,as impact energy increases,indicators such as tunnel rock stress,roof settlement,floor heave,and lateral contraction all exhibit an upward trend.This increase readily triggers destructive phenomena including floor heave,sidewall deforma-tion,and pillar drilling through the base.Compared to single-pillar support,energy-absorbing roadway supports exhibit similar peak rock mass stresses but reduced stress concentration zones.Roof settlement,floor heave,and lateral contraction all decrease to varying degrees.Additionally,the supports and roadway demon-strate synergistic effects in both lateral and vertical displacement.The plastic deformation of the tunnel rock mass follows an"A"distribution,primarily concentrated at the junction between the tunnel sidewall and roof,as well as within the sidewall itself.Under lateral impact,individual pillars shift leftward,undergoing lateral ben-ding deformation that significantly reduces their load-bearing capacity.The energy-absorbing support effec-tively restricts lateral tunnel displacement,significantly constraining roof-floor displacement and sidewall com-pression.The synergistic interaction between the lateral support of the energy-absorbing tunnel support and the energy-absorbing impact absorber markedly improves the uneven loading issue of individual pillars.These findings provide a reference for controlling the tunnel rock mass under dynamic loading conditions.

Abstract:To mitigate rock burst hazards in kilometer-deep coal mines,a comparative analysis was conducted between the conventional coal pillar method and the Gob-side Entry Retaining by Roof Cutting(GERRC)technique.The rock burst prevention mechanism of GERRC was elucidated,which operates through three pri-mary aspects:reduction of static load,attenuation of dynamic load,and elimination of potential shock-prone rock masses.Taking the No.103 workface of the 3#lower coal seam at a burial depth of 1,000-1,063m in a representative mine as the engineering background,key technical parameters were systematically designed and optimized.These parameters included pre-splitting blasting of the immediate roof,reinforced support for the roof and ribs,temporary roadway support,and specifications for the gangue-retention and sealing system.The design was implemented on siteand field monitoring demonstrated that the optimized GERRC method effectively controlled strata movement,minimized roof separation,and maintained the integrity of deep roof strata.In com-parison with the conventional gob-side entry driving approach that utilizes 5-m protective coal pillars,the GERRC technique significantly reduced both the risk level and spatial extent of rock burst-prone zones.The results confirm the feasibility of applying the roof cutting and pressure relief method for rock burst prevention in deep coal mines.

Abstract:With the increasing depth of coal mining,the prevalence of coal and gas outburst-prone mines has risen,accompanied by significant challenges such as high gas content and difficulties in gas drainage.This pa-per proposes a three-stage pre-drainage method aimed at mitigating outbursts.By employing an integrated model of "surface wells+directional long boreholes+conventional boreholes",this approach effectively re-duces the gas content within coal seams.Engineering tests conducted at the Jinsheng Yong'an Hongtai Coal Mine demonstrate that the system significantly enhances drainage efficiency:surface wells achieved a cumula-tive gas extraction volume of 70,205,192 m3,while directional long boreholes further improved pre-drainage effectiveness,and conventional boreholes served as a supplementary means,effectively covering local areas not reached by directional drilling and eliminating extraction blind zones.The gas pre-drainage rate exceeded 50％,with residual gas content and pressure reduced to 5.7223 m3/t and 0.178 MPa,respectively.Compared to pre-drainage conditions,these values represent decreases of 54％and 44％,respectively.This method has proven effective in controlling coal and gas outburst hazards,thereby ensuring safe production in outburst- prone mines.

Abstract:Gas pressure measurement is a critical technical means for the prevention and control of gas disas-ters in coal mines.When cross-layer drilling conditions are unavailable,gas pressure must be determined through in-seam drilling,wherein grouting pressure significantly influences sealing quality and consequently measurement accuracy.This study therefore investigates reasonable grouting pressure to address the challenge of precise gas pressure measurement in in-seam boreholes.Theoretical analysis reveals that gas leakage chan-nels formed by pressure-relief fractures are the key factor affecting sealing effectiveness.A grouting seepage model is established based on Darcy's law,and COMSOL Multiphysics is employed to simulate slurry diffusion characteristics under grouting pressures ranging from 1.0 MPa to 7.0 MPa.Simulation results indicate that at 5.0 MPa grouting pressure,the slurry diffusion radius reaches approximately 44 cm,while increasing pressure to 7.0MPa yields merely a 1 cm increase(approximately a 2％increment).Based on the fitting curve correla-ting grouting pressure with diffusion radius,5.0MPa is identified as the reasonable grouting pressure.Taking the No.3 coal seam of a mine in Jincheng as the engineering background,six in-seam boreholes were con-structed in the transportation roadway of the 3701 working face to evaluate the pressure measurement perform-ance of the "two plugs and one injection" pressurized sealing under varying pressures.The findings demon-strate that a grouting pressure of 5.0 MPa effectively seals fractures in in-seam boreholes,enhances the accu-racy of gas pressure parameters,and provides significant engineering guidance for the prevention and control of coal mine gas disaster.