Abstract:During coal seam mining,pore gas pressure and in-situ stress exhibit dynamic coupling characteristics in-volving multi-cycle synchronous loading and unloading.Coal deformation and gas migration are jointly driven by these two factors,triggering coal-rock gas dynamic disasters in mines.To further reveal the mechanical-seepage response char-acteristics of coal and their dominant controlling mechanisms under multi-cycle coupling of in-situ stress and gas pressure,triaxial seepage tests are conducted under three cyclic loading-unloading paths:stress-only(OS)cycling with fixed pore pressure,pore pressure-only(OPP)cycling with fixed stress,and stress-pore pressure coupled(SPPC)cycling.A damage constitutive model for coal under SPPC conditions is developed based on statistical damage theory.The results indicate that stress and pore pressure both promote axial compression and radial expansion of coal,while exerting an opposite com-petitive relationship on volumetric strain.This leads to their differentiated effects on seepage channels:stress facilitates volumetric compression,thereby inhibiting gas seepage,whereas pore pressure induces volumetric expansion,thus enhan-cing gas seepage.With an increasing number of cycles,axial strain of coal under all three cyclic paths exhibits a fluctuat-ing increase,whereas radial strain shows a fluctuating decrease.Under the coupled effect of stress and seepage fields,coal subjected to SPPC cycling demonstrates a more sensitive deformation response and greater susceptibility to damage accu-mulation.By the end of the tests,its cumulative residual strain is the largest(axial 0.203× 10-2 and radial-0.059× 10-2)Additionally,permeability of coal under all three cyclic paths at the end of loading exhibits exponential decay with an in-creasing number of cycles,indicating that accumulated cyclic damage hinders the recovery of pore-fractures apertures to their initial state,resulting in diminished seepage capacity.Permeability of coal under OS and SPPC cycling at the end of unloading gradually decreases with more cycles,whereas the opposite is observed under OPP cycling.High-velocity gas repeatedly scours loose coal particles or clay minerals adhering to fracture surfaces,facilitating the expansion of fracture channels.Contribution rate analyses reveal that coal strain evolution is dominantly controlled by stress,with average con-tribution rates of 97.5％,64.9％,and 79.7％to axial,radial,and volumetric strains,respectively.Permeability evolution is absolutely dominated by pore pressure,with a contribution rate exceeding 97.6％.Finally,based on the characteristic that coal element strength follows a Weibull distribution,and considering the strength degradation effect of pore pressure on coal,a coupled damage variable is proposed,and a damage constitutive model based on the D-P(Drucker-Prager)cri-terion under SPPC conditions is developed.This model effectively describes the deformation response characteristics of coal under SPPC during loading-unloading stages.The results provide theoretical support for further elucidating the mech-anical mechanism of coal-rock gas dynamic disasters in mines.

Abstract:In the process of CO2 sequestration in deep coal seams,CO2 usually exists in a supercritical state(ScCO2)and undergoes complex physicochemical reactions with water and coal,resulting in changes of coal chemical composition and structure and thus affecting the CO2 sequestration efficiency.To study the influence laws of ScCO2 on coal chemical com-position and structures under different water contents,ScCO2-coal reaction experiments were conducted using coking coal samples.Then,the differences in coal composition and structure before and after the reaction were discussed.Finally,the influencing mechanism of water contents on the ScCO2-coal reaction was revealed.The results show that:ScCO2 dis-solves carbonate minerals in coal more effectively than clay minerals,and the mass fraction of carbonate minerals in the residual coal increases and then decreases with the increase of water content;at higher water content,the reaction between ScCO2 and carbonate minerals in coal is stronger than that of clay minerals,thus causing a more significant depletion of carbonate minerals.ScCO2 and H2O exert a significant influence on the oxygen-containing functional groups,but they give a weak impact on aromatic and aliphatic hydrocarbons;specifically,ScCO2 reduces the content of oxygen-containing functional groups in coal.Furthermore,as the water content increases,the oxygen-rich index(I2)increases significantly,while the hydrogen-rich index(I1),aromaticity(I3),and condensation degree(I4)exhibit minimal variations.Under the swelling effect of ScCO2,the aromatic layer spacing(d002)shows an increase characteristic,while the ductility(La),the number of aromatic layers(Nc),aromatic carbon rate(fa'),and aliphatic carbon rate(fal)decrease.Furthermore,with in-creasing water content,d002,La,and fa' firstly increase and then decrease,while Lc,Nc and fal exhibit an opposite pattern.Therefore,water can enhance the ScCO2 extraction efficiency of low molecular weight compounds from coal,promoting the disordering of aromatic structure in coal.However,as the water content further increases,it will impede the per-meation of CO2 into the coal matrix.The carbonate minerals in the coal react with ScCO2 preferentially,thereby weaken-ing the extraction effect of ScCO2 on the organic matter in coal.Consequently,ScCO2 has more apparent effect on the dis-solution of organic matter and the destruction of chemical structure in coal on air-dried basis,and more significant dissolu-tion of minerals in coal on saturated basis.

Abstract:China is rich in deep coal resources.With the continuous depletion of shallow coal resources,deep coal mining is imperative.Currently,over 40 coal mines in China have reached or exceeded a mining depth of 1 000 meters,with the deepest reaching 1510 meters,mainly distributed in the central and eastern regions and the northeastern mining areas.Ad-ditionally,some mining areas in the west,such as the Ordos,Longdong,and Binchang mining areas,have also entered deep mining.Compared with medium and shallow mines,deep mines are characterized by high ground stress,strong min-ing-induced disturbance,large deformation(in soft rock)and strong impact(in hard rock).The deformation of the sur-rounding rock in deep mine roadways is marked by strong dilatancy,strong rheology and severely impact damage.The stress environment and geomechanical properties of the surrounding rock in deep roadways were deeply analyzed,and the deformation and failure characteristics of the surrounding rock in deep soft rock roadways were studied.It was found that the large deformation in deep soft rock roadways was mainly caused by three types of deformation:dilatancy,rheology of coal and rock mass,and structural rheology.The mechanism of large deformation and instability of the surrounding rock in deep soft rock,high stress and strong mining-induced disturbance roadways was revealed.The concept of coordinated control of surrounding rock support,modification and pressure relief in deep roadways was proposed.The fundamental principle of this coordinated control was expounded.The spatio-temporal coordinated action of various surrounding rock control methods was analyzed.The principle of"three active"coordinated control of surrounding rock support,modifica-tion and pressure relief in deep roadways was clarified.Different coordinated control methods of surrounding rock in deep roadways were proposed.The"three-in-one"coordinated control technology of surrounding rock support,modification and pressure relief was developed,including high prestressed bolts and cables and thin spray active support,high-pressure splitting grouting active modification,and hydraulic fracturing active pressure relief technology.The grouting bolting with high pretension and pressure in synergy control technology was developed for the advanced section of the working face to strengthen support,forming a complete surrounding rock control technology for deep working face roadways(including gateway,open-off cut and advanced area).New materials for bolting,such as a 700 MPa ultra-high-strength,ultra-high elongation(30％post-fracture),and high-impact toughness bolt,was developed.Three types of high injectability,high ad-hesion and high strength grouting materials,including nano-modified coal and rock-friendly single-liquid inorganic-organ-ic composite grouting materials and micro-nano double-liquid inorganic-organic composite grouting materials,and high strength and high toughness roadway surface spraying protective materials were developed.Other innovations include the development of high prestressed grouting bolts and cables with high pressure,as well as 35 MPa pneumatic and 45 MPa hydraulic high-pressure grouting pumps,plus a pressure-flow-density multi-parameter grouting monitoring system have been developed.Underground local hydraulic fracturing equipment and underground directional long horizontal borehole large-flow hydraulic fracturing equipment with high-pressure were developed.The complete set of coordinated control technology for deep roadway surrounding rock was systematically integrated and successfully applied in complex and dif-ficult roadways in deep mining areas such as Xinji,Xinwen,Huaibei,Wanbei and Binchang,including deep soft rock roadways,ultra-deep high stress roadways,deep strong mining-induced disturbance roadways,deep soft and broken sur-rounding rock roadways and deep thick hard roof strong impact roadways.The deformation of the surrounding rock in roadways was significantly reduced,and the stability of the surrounding rock was significantly improved,which strongly support the safety and efficient production of deep coal mines.Finally,the development directions of the theory,techno-logy,materials and equipment for the control of deep roadway surrounding rock in the future were prospected.

Abstract:Shearer working conditions have strong stochastic complex and variable factors,its whole life cycle course of stochastic load spectrum acquisition and discrete sequence processing,as well as the whole domain load spectrum synthes-is and digitization is the key basic engineering technology common problems of high-end equipment reliability design ana-lysis and its fatigue life prediction.Constructing the correlation matrix of shearer sensors and detection quantities,detec-tion quantities and feature quantities,adopting the superposition processing of row and column coefficients of the compre-hensive correlation matrix to give the comprehensive correlation and importance of sensors and feature quantities,and pro-posing the quantitative evaluation method of feature quantity correlation in the process of multi-sensor information detec-tion.Considering drum parameters,working parameters of shearer,nature and distribution parameters of coal rock,pro-posed a longitudinal amplitude and transverse time-range cumulative normalization algorithm for the load spectrum,as well as a proportional synthesis method for the segmental load spectrum and whole domain load spectrum of the drum cut-ting coal rock.Giving fusion algorithms for cutting motor current,rocker arm vibration and heightened hydraulic cylinder pressure information,approximate estimation of scale factor algorithms,etc.Establish the instantaneous load model and the load spectrum random distribution superposition algorithm of the drum cutting coal rock,combine the experimental load spectrum of the single pick cutting coal rock with the theoretical model,and obtain the segmented theoretical load spectrum of the drum cutting coal rock.The numerical simulation and experimental load spectrum containing noise in-formation are processed by the adaptive weight EMD-IECM load spectrum optimal noise reduction smoothing algorithm,which gives a graded cumulative time-range ratio statistical algorithm of the drum cutting coal rock segmented load spec-trum,and puts forward the synthesis and digitization method of the whole domain load spectrum.The results show that the correlation between the cutting load and coal rock strength and the detection information of each sensor is more signific-ant,and the detection information of vibration sensors,current sensors and pressure sensors can better reflect the cutting characteristic quantity and cutting state.Adaptive weighting EMD-IECM load spectrum optimal noise reduction and smoothing algorithm,which can automatically adjust the weights of the indicators according to the data itself,and obtain the reconstructed load spectrum with balanced similarity and smoothness.Through the application of examples,it is known that the amplitude graded cumulative time-range ratio of the whole domain load spectrum shows a normal distribu-tion law,which is in line with the actual situation of the project,and verifies the validity and completeness of the synthesis and digitization method of the whole domain load spectrum of the drum cutting coal rock.

Abstract:To explore the evolution characteristics of the pore structure of bituminous coal and the mechanism of methane promotion under the combined action of static magnetic field and microorganisms,this research,based on the convention-al anaerobic culture system,added high and low intensity magnetic field treatment groups(0,20,40 mT),and systematic-ally carried out laboratory methane production rate experiments,16S rRNA high-throughput sequencing,Fourier trans-form infrared spectroscopy(FTIR),scanning electron microscopy(SEM)and low-temperature liquid nitrogen adsorption-desorption experiments(BET).The results show that:During the 20-day culture period,the methane production rate of the low magnetic field anaerobic culture group(20 mT)was the highest,reaching 4.61 μmol/(g·h),which was 2.73 times higher than that of the control group.At the genus level,the low magnetic field treatment significantly enriched the Clostridium-sensu-stricto-1 species,with an abundance increase of 15％compared to the control group,and the proportion of acetate-nutrient methane-producing archaea Methanosarecina reached 76％.Functional gene annotation indicated that the expression of fatty acid metabolism,methane metabolism and benzoic acid metabolism pathways in the low magnetic field group was significantly enhanced.Infrared spectroscopy data showed that the addition of static magnetic field in-creased the proportion of fatty acid functional groups-CH,—CH2,—CH3 in coal,increased the microbial action sites,and thus increased the rate of in-situ microbial decomposition of each organic matter in coal.The liquid nitrogen adsorp-tion data of coal indicated that the nitrogen adsorption capacity of the low magnetic field group was 2.25 times and 1.48 times that of raw coal and the control group,respectively,and the proportion of micropore volume reached 76.68％,and the fractal dimension also significantly increased,indicating a more complex pore structure.The SEM observations of the coal samples' surfaces in the low magnetic field group showed more obvious coal body folds,and bacteria were visible at the same magnification.Compared with other groups of coal samples,the coal sample fissures were more developed.The research results reveal the evolution patterns of microbial communities and changes in pore structure under the influence of different static magnetic field intensities in coal samples,aiming to provide a theoretical basis for the efficient extrac-tion of coalbed methane.

Abstract:The moon harbors exceptionally abundant and strategically valuable spatial and material resources.As human lunar exploration gradually enters a new phase of development and utilization,lunar mining is transitioning from a stra-tegic concept to tangible possibility.However,the unique properties of lunar regolith and the extreme complexity of the deep-space environment pose significant challenges to lunar mining.It has become imperative to explore and establish fundamental theories and key technologies for lunar mining that are applicable to the in-situ lunar environmental condi-tions.From the perspective of mining engineering,this paper systematically reviews the types and distribution character-istics of lunar mineral resources and compares the complexity and particularity of the lunar mining environment with ter-restrial mining.Focusing on the key technical processes of"exploration-mining-utilization"involved in lunar mining,it elaborates on the main technical approaches and their current development status across five critical areas:in-situ lunar re-source exploration and identification,mining and processing,conversion and utilization,lunar base construction,and in-situ energy support.The core mechanisms and adaptive challenges are also discussed.Based on this,addressing the key theoretical and future technological demands of lunar mining,the paper proposes a new paradigm for theoretical research in deep-space geomechanics,spanning from micro to macro scales,and identifies research directions for remote sensing prediction theories of lunar geomechanical properties at a global scale.Furthermore,it refines the conceptual framework and research directions for key technologies that require breakthroughs,such as deep in-situ coring technology with in-situ environmental conditions preservation for lunar prospecting,in-situ thermoelectric power generation technology on the moon,and lunar subsurface tunneling technology.Suggestions for theoretical construction and technical implementation are provided,which are expected to offer theoretical and technical guidance for future lunar mining engineering,in-situ re-source development and utilization,lunar surface base construction,and underground space development.

Abstract:In order to realize the whole life cycle of the same surface well in the process of pre-mining,in-mine cooperat-ive drainage and residual coalbed methane recovery in the goaf,and improve the service life and gas drainage efficiency of the wellbore of the coalbed methane surface well.Relying on the stratified mining project of high gas thick coal seam in Yuecheng Mine of Jinneng Holding Group,the surface pre-pumping well of the 2301 working face of the mine was selec-ted as the object,and the collaborative research on overlying strata movement and wellbore response was carried out,and the structural stress and drainage channel evolution characteristics of the surface well under the condition of"one surface well used in three field"were analyzed.Based on the migration theory of"horizontal three zones and vertical three belts"in the goaf,the stress section and potential failure site of the surface well at different mining stages are revealed,and the combination technology of local protection of the wellbore and the protection of the screen pipe section is proposed to form a wellbore anti-deformation system composed of safety protection screen pipe and cut seam casing.Combined with the characteristics of overlying strata movement and fracture evolution after upper stratified mining,the transformation and reuse process of surface pre-pumping wells is constructed.The engineering application results show that:The surface well is arranged at the inflection point of surface subsidence and appropriately biased to the center of the stope,which can effectively avoid the influence area of the mining core and ensure the stability of the wellbore.By hanging at the wellhead and laying the cutting casing in the fractured zone,a four-in-one efficient gas migration channel of"wellbore-cutting cas-ing-perforating casing-overlay fracture"is constructed.After the upper layered mining,the pre-pumping well located in the"O"circle,at the anticline structure and within the oblique length of 0.2-0.4 times the working face from the return air lane can achieve"one surface well used in three field".Applying this technology,the surface wells of Yuecheng Mine have extracted a total of 5 856.5× 104 m3 of coalbed methane,with an average methane concentration of 51.1％,which real-izes the extension of the function of pre-mining pre-extraction wells to in-mining and post-mining extraction.Through"one well and three uses",the maximum gas concentration in the upper corner of the 2301 working face was reduced from 0.77％to 0.45％,the minimum value was reduced from 0.22％to 0.06％,and the average concentration was reduced from 0.34％to 0.25％.The integrated technology of"one surface well used in three field"gas drainage mode and wellbore pro-tection and channel construction has been researched and formed,which provides a technical idea for the multi-stage con-tinuous utilization of surface wells and the coordinated development of coal-gas in high-gas mining areas.

Abstract:To mitigate the thickness effect of the Dual Energy X-Ray Transmission(DE-XRT)system and achieve accur-ate identification and density prediction of coal and gangue within a wide thickness range,this study thoroughly summar-izes the imaging principle of DE-XRT and fuses depth cameras with DE-XRT at the data level.Based on the size of coal gangue and regional similarity,the DE-XRT images and thickness images were partitioned.By expanding single pixels in-to multi-pixel sets,the two types of information were utilized more accurately and efficiently.Furthermore,using the X-ray and thickness information of each partition as the basis,fused information is calculated via the X-ray energy attenu-ation formula,and then aggregated into block matrices.Multidimensional heterogeneous features were extracted from these block matrices and the DE-XRT images.A robust pre-identification model was then constructed by combining the Relief feature selection algorithm with a Support Vector Machine(SVM)classifier optimized by a GA(Genetic Al-gorithm).Additionally,via transformation calculations of block matrices and statistical analysis of large-scale samples,the fuzzy intervals of coal at various density levels were determined,and a density prediction model based on these intervals was developed.This model considers the impact of using a single formula to calculate coals of different density grades.By establishing fuzzy intervals,the problem of coal density prediction is decomposed into multiple density-grade prediction problems.Meanwhile,the degree of deviation between the target to be predicted and the interval lower limit is used to characterize its proximity to the lower-limit density grade.Experimental results demonstrated that,on a dataset with coal densities ranging from 1.30 to 1.80 g/cm3,gangue densities greater than 1.80 g/cm3,and average thicknesses spanning 5 to 100 mm,the pre-identification model achieved an Pre of 97.522％and an F1 of 0.962.Compared with existing X-ray al-gorithms,grayscale texture methods,and deep learning algorithms,the Pre and F1 were improved by at least 6.433％and 2.888％,respectively.The density prediction model exhibited a mean error not exceeding 5.882％.Specifically,46.993％of targets had prediction errors below 4％,and 93.233％had errors below 10％.The proposed models effectively reduce the impact of the thickness effect on the sorting system,enhance the accuracy of coal-gangue identification and density prediction across a broad thickness range,and provide a theoretical foundation for developing intelligent photoelectric coal-gangue sorting technologies.

Abstract:Flexible cutting tools reaming is a new method of coal seam unloading pressure and enhancing permeability,in order to resolve the problem of insufficient ability of flexible cutting tools breaking coal at the present period,improve the performance of coal breaking by optimizing the structural parameters of flexible cutting tools under certain kinetic energy.Therefore,2D numerical model of coal breaking by flexible cutting tools is established to clarify the evolution of coal stress field and crack extension characteristics within the process of coal breaking,investigate the effects of different in-stallation angles,number of cutting teeth and cutting tooth distance on the stress evolution and crack formation of coal body from the mesoscopic scale.Clearly defined the effect of the number of cutting teeth on the energy evolution law of the coal breaking process in kinetic-energy unity condition,and reveal the mechanism of influence between installation angle and cutting tooth distance on the crack extension of the coal body.Results show that the coal body stress wave is af-fected by the installation angle of cutting tooth as abnormal propagation,the installation angle of 0°-20° is impact break-ing coal,the middle cracks and side cracks radiate around by the impact point,and crack quantity is distributed uniformly.At 25°-40° is the impact-abrasive coal breaking,the impact effect is dominated,side cracks are developed,and double peaks of cutting tooth loads occurred,maximum crushing area at 35° installation angle.Under certain kinetic energy,with increase the number of cutting teeth,the energy conversion time is decreased,and the area of coal breaking is increased.The strain energy peak and strain energy concentration of the double cutting teeth become better,improved rapid develop-ment and connectivity of fractures.Double cutting tooth impact forms a connecting curved compression stress area inside the coal body.Force chains connect between the two impact points and provide preconditions for the formation of frac-tures between particles,thus improving the damage effect of coal break.There exists the optimal cutting tooth installation angle to improve the force transmission effect so that the coal body breaking area is maximized,and there exists the ideal cutting tooth spacing to connect the breaking area with each other,fully utilizing the cooperative coal breaking effect of the double cutting teeth.

Abstract:In order to reduce CO2 emissions and water consumption in coal-fired power generation,improve the effi-ciency of waste-to-energy incineration,and enhance the speed and efficiency of biological wastewater treatment,a coupled system integrating waste and sewage treatment with circulating fluidized bed power units is proposed.Specifically,anaer-obic fermentation,domestic and industrial wastewater treatment systems are constructed alongside the circulating fluid-ized bed boiler units.The anaerobic fermentation system is designed to handle waste from the food industry,agriculture,and livestock sectors,while the domestic and industrial wastewater treatment systems treat sewage and industrial wastewa-ter respectively.The heat required for fermentation and wastewater treatment is sourced from low-pressure steam extrac-tion or exhaust waste heat from turbines.The biogas produced from fermentation is coupled with coal-fired power genera-tion,while the sludge is used to produce organic fertilizers.Domestic sludge can be co-fired with coal in the fluidized bed boiler,and industrial sludge can be either co-fired or treated for harmlessness based on its composition.Combustible waste unsuitable for fermentation is preprocessed and directly fed into the fluidized bed boiler for co-firing with coal.A case study was conducted on a 2×350 MW supercritical circulating fluidized bed unit coupled with waste incineration and wastewater treatment systems.Energy efficiency calculations,application scenarios,and benefit analyses were performed.The results indicate that for a city with a population of 1 million,annual waste-to-energy incineration can reduce standard coal consumption by 115 900-193 200 t and CO2 emissions by 308 300-513 900 t.In terms of biogas utilization,it can be directly co-fired with coal in the furnace for power generation,or coupled with gas turbines and coal-fired units through flue gas or steam integration.As the gas turbine capacity increases,the power generation efficiency of the coupled system continues to improve.Under the same conditions,flue gas coupling yields higher efficiency than steam coupling.The coupled system also offers additional benefits such as water conservation,reduced construction costs for fermentation fa-cilities,land and total investment savings,and eligibility for financial subsidies.In summary,the integration of circulating fluidized bed units with waste incineration and wastewater treatment systems delivers significant environmental and social benefits.Although this approach may face practical challenges such as cross-industry and cross-departmental coordination,it remains worthy of further research,particularly in the planning and development of new urban areas,where it holds greater implementation potential.

Abstract:Based on the overburden conditions of Shendong and Northern Shaanxi coal bases,through the statistical ana-lysis of the measured roof weighting characteristics and overburden caving height in large mining height working faces,combined with physical simulation tests,the overburden caving characteristics of large mining height working faces were studied,and the definition of the equivalent immediate roof for large mining height working faces was proposed.Accord-ing to the filling degree of the equivalent immediate roof to the goaf,the roof structure was divided into fully filled type and non-fully filled type,and the static load of the short cantilever beam structure of the equivalent immediate roof on the working face support was analyzed.The study shows that the single key stratum of the overburden in large mining height working faces generally forms a"high position oblique step voussior beam"structure,and the sliding instability of this structure is the main cause of strong weighting in the working face.After the failure of the lower key stratum in the double key strata of the overburden in large mining height working faces,a stable"voussior beam"structure or an"oblique step voussior beam"structure prone to sliding instability can be formed,while the upper key stratum generally forms a"voussi-or beam"structure.That is,the double key strata of the overburden forms a"double voussior beam"structure or an"ob-lique step voussior beam-voussior beam"structure,with the more common"oblique step voussior beam-voussior beam"structure causing intense pressure.The synchronous and asynchronous instability of the key blocks in the upper and lower key strata are the causes of large and small periodic weighting in the working face.Based on the"oblique step voussior beam-voussior beam"roof structure model for large mining height working faces,a theoretical calculation method for the working resistance of the working face support was proposed and verified by engineering cases,which can provide a the-oretical basis for roof control and support selection in large mining height working faces.

Abstract:In order to investigate the effects of the composition,structure,and occurrence modes of small molecules in coal on their dissolution behavior,as well as the changes in the pore structure of coal after their dissolution,Shendong coal is sequentially extracted by petroleum ether and carbon disulfide(CS2)using Soxhlet extraction method.The extracts and the residues are characterized by FTIR and N2 adsorption,respectively.The results show that the curves of cumulative ex-traction rate versus extraction time can clearly reflect the sequential dissolution stages of small molecules with three occur-rence forms(free state,micropore-embedded state,and network-embedded state)in different solvents.CS2 is effective for both aliphatic and aromatic substances in coal due to its strong permeability and high solubility,while petroleum ether mainly acts on aliphatic substances.For the dissolution of network-embedded small molecules,CS2 is more effective than petroleum ether.For free state small molecules,those aliphatic hydrocarbons with long side-chain or long-chain structures are preferentially dissolved by petroleum ether,followed by the dissolution of short side-chain small molecules with CS2.For micropore-embedded state small molecules,CS2 preferentially dissolves polycyclic aromatic hydrocarbons,followed by the co-dissolution of small molecules with polycyclic,bicyclic,and monocyclic structures.For network-embedded state small molecules,petroleum ether cannot effectively dissolve them due to the difficulty in penetration,whereas CS2 firstly dissolves short side-chain structures,and then the dissolution of long side-chain or long-chain aliphatic hydrocarbons oc-curs after a long extraction time.There is basically no co-dissolution relationship between hydrogen-bonded-OH(—NH)and phenolic structures and aliphatic structures.Hydrogen-bonded—OH(—NH)and phenolic structures can be dissolved only after a large amount of aliphatic structures are dissolved.Due to the existence of multiple effects during the solvent extraction process,the pore size evolution process becomes very complex,but the total pore volume of the resid-ual coal generally increases as the dissolution amount of aliphatic small molecules decreases(the dissolution amount of aromatic small molecules increases).

Abstract:Our country has abundant coal rock gas resources.Hydraulic fracturing is a key technology for effectively de-veloping coal rock gas reservoirs.Due to the differences in the mechanical properties,microstructure,gas occurrence states,and productivity-controlling factors of deep coal rock compared with shallow and medium-depth coal reservoirs,as well as the significant property variation in reservoirs between blocks,the adaptability of current fracturing technologies still faces challenges.Innovation in reservoir stimulation technologies is essential for the efficient development of coal rock gas.The difficulties in reservoir stimulation brought by the geological characteristics of coal rock gas reservoirs are discussed first.To deal with the geological features and the challenges of fracturing technology,an efficient development concept of matrix pore-cleat/fracture simultaneous stimulation,summarized as"point desorption,line dredging,fracture geometry improvement,and propped bulk fracture network",is proposed,and the following key issues are figured out based on its connotation:① fracturing-induced matrix pore structure and pore surface property modification,enhanced gas desorption,imbibition displacement,and adsorbed-phase and free-phase methane collaborative and efficient gas supply;② activate cleats/fractures,shorten gas diffusion distances,and facilitate matrix reserves releasing;③ promote uniform fracture propagation,enhance fracture complexity,and precisely control fracture morphology;④ full-scale proppant sup-port for coal rock reservoirs that"precisely matches proppant particle size with multi-level fracture widths,supports bed-ding-plane fractures,and provides three-dimensional support for cleat and main fractures".Results indicate that it is neces-sary to further study the relationship between fracture parameters and production dynamics based on the gas storage and production characteristics of deep coal rocks,in order to identify fracture parameters that can realize the adsorbed and free gas"continuous-cooperative"supply,and to provide support for fracture property control and treating design optimization.Conduct in-depth research on hydraulic fracture network propagation rules in coal rock reservoirs and fracture propaga-tion numerical simulation technologies,and combine the net pressure log-log diagram during fracturing to effectively con-trol the fracture network propagation behavior in coal rock gas reservoirs.Use high-viscosity and leakage-weakening fluid first to create the main fractures,then use low-viscosity fluid to create complex fractures,achieving"controlled near-well-bore fracture complexity and sufficiently extended fractures"to form a"long fracture network".To deal with the require-ment of high conductivity and larger volume for fracture networks in deep coal rock formations,maximizing fracture volume and optimizing flow capacity with limited proppant and fluid is an effective way to reduce costs and increase effi-ciency.Propose the full-scale proppant-support fracturing technology for deep coal rock reservoirs to achieve long-term connectivity of"main fractures+bedding planes+cleats"and increase the effective support volume of fractures.Optim-ize different proppants and fiber combinations through long-term fracture conductivity tests for multi-size fractures with different proppant placement patterns.Improve existing fracturing fluid systems,explore water-reducing,high-sand-ratio,low-cost fracturing fluids,and clean desorption-promoting agents.

Abstract:Based on the intelligent coal mine construction task of CHN ENERGY Shendong Baode Coal Mine,this paper proposes a general construction scheme for an intelligent mine based on"5G+Industrial Internet"under the principle of"Unified Data,Unified Model,Unified Platform,and Unified Solution",and constructs a"Four Layers+Two Wings"un-derground 5G integrated bearing network architecture:the Perception and Control Layer deploys various sensors to col-lect production and safety data,the Infrastructure Layer takes the 5G+N× 100G FlexE Hard Slicing Network as the core to achieve efficient transmission,the Smart Platform Layer undertakes data storage and in-depth analysis,the Decision and Application Layer supports multi-scenario intelligent applications,and the"Two Wings"refer to the unified data stand-ards and industrial security protection system that ensure data interconnection and network security;medium frequency is adopted to meet the large bandwidth demand of the working face,while low frequency is used to achieve long-distance coverage of roadways,and the uplink transmission is enhanced through TDD(Time Division Duplex)time slot reversal and SUL(Supplemental Uplink)technology,and relying on FlexE slicing technology,5 types of slices are divided to meet the latency and bandwidth requirements of different services,effectively supporting various intelligent scenarios such as fully mechanized mining inspection and remote driving of shuttle cars.Four core technologies were developed:① Multi-behavior Time-series Planning Rapid Tunneling Technology:It innovates the"Roadheader-Bolter Integrator+Shuttle Car+Self-moving Conveyor Tail"equipment,integrates GA-BP(Genetic Algorithm-Back Propagation)neural network-based adaptive cutting,LiDAR obstacle perception,and power line carrier communication,solves the"last 100 meters"transportation bottleneck,and increases tunneling efficiency and advance rate by 10％and 15％respectively;② 5G+Di-gital Twin-based Long-distance Directional Drilling Technology:It improves drilling accuracy by combining dynamic azi-muth gamma geological steering;③"Automatic+Memory+Intelligent"Three-level Coal Caving System for extra-thick coal seams:It balances coal quality and resource recovery rate through asynchronous progressive scheduling,PID(Propor-tional-Integral-Derivative)closed-loop control,and AI(Video+Acoustic)coal-gangue identification;④ Regional Multi-hazard Integrated Early Warning Technology:It integrates multi-source safety hazard monitoring data,adopts the CNN-LSTM(Convolutional Neural Network-Long Short-Term Memory)architecture to build a model,and achieves an early warning consistency rate of over 95％.Field application shows that this study has realized full-scenario 5G coverage in Baode Coal Mine,successfully warned of incidents such as water hazards and methane over-limit,shortened the disaster response time,and improved the mine safety management level.By deeply integrating 5G+Industrial Internet technology with the core business of coal mines,this study enables the mine to leap from single monitoring to"intelligent identifica-tion,accurate early warning,and linked disposal",providing a technical paradigm and practical case for the high-quality development of coal mine intellectualization.

Abstract:Coal and co-associated energy minerals are strategic resources essential for national energy security and exhibit widespread characteristics of co-occurrence and spatial superposition.Achieving green,safe,efficient,and intelligent col-laborative development is vital for ensuring long-term resource stability and supply security.This study analyzes the ma-jor challenges in engineering geological assurance,mineral rights delineation,geological responses during co-mining,and the development of digital-intelligent mining technologies and equipment.Key technical difficulties are identified,includ-ing sensing multiphase-multifield strata responses,coordinating multi-stage mining processes,characterizing groundwa-ter disturbance and flow redistribution,controlling pollutant migration,and managing disaster prevention and emergency response.The results indicate that the"AI+"paradigm will serve as an important pathway for future resource develop-ment.An unmanned intelligent co-mining model is proposed to address the distinctive reservoir responses under high tem-perature,high hydraulic pressure,high geostress,low permeability,and strong disturbance feedback.By integrating intelli-gent sensing,data fusion,and intelligent decision-making technologies,multimodal paradigm models and multi-scenario disaster prediction and emergency control models are constructed to reveal the mechanisms of disaster initiation and evol-ution under coupled multiphysics conditions.An embodied-robot and edge-computing cluster is further developed to es-tablish a bidirectional data network,and a resilient,self-healing heterogeneous data system combining distributed and centralized structures is formed through multi-source machine learning,enabling precise human-machine collaborative and autonomous decision-making and supporting the development of a"mine heart-mine brain-mine body"digital-intelli-gent paradigm.Focusing on four key scientific problems-multiphysics coupling and disaster mechanisms,integrated pro-cess technologies for collaborative mining,ecological restoration and chain-type emergency response,and digital-intelli-gent network and equipment architecture-six major research directions are outlined,including efficient resource extrac-tion and safety assurance,disturbance mitigation technologies,groundwater regulation and pollutant migration control,mine-water pollution prevention and utilization,unmanned intelligent mining construction,and three-dimensional func-tional development of underground spaces.These efforts provide technical support for pilot demonstration projects and promote the large-scale,high-quality development of collaborative mining of coal and co-associated energy minerals.

Abstract:Compared to single-seam mining,the close-distance coal seam group is strongly influenced by the movement of overburden structure resulting from upper seam mining.The mining of the lower seam will trigger a"repetitive"move-ment of the overburden structure,resulting in more complex ground pressure behavior and introducing substantial uncer-tainty to the control of surrounding rock in lower seams.Based on the occurrence characteristics of interlayer hard strata and the evolution of bearing structures under close-distance coal seam group mining conditions,four types of overburden structural models were proposed:fully bearing-type,partially degraded bearing-type,partially failed bearing-type,and de-graded-failed combined bearing-type.The dynamic evolution of these four structures during the initial and periodic weighting stages was analyzed,and the influence mechanisms of different mining stages on working face support and roadway stability were clarified.The evolution law of the fracture arch extension angle and its influencing factors were further analyzed.By comprehensively considering horizontal thrust between key blocks,mining height,interlayer spacing,and the bulking characteristics of the overburden,the mechanical and engineering transformation conditions for these four structure types were proposed.Taking the close-distance coal seam group in the Shuangma No.1 Mine as a case study,the overburden structure type was identified by similar material tests and numerical simulation.The deformation and failure of the surrounding rock in the lower coal seam,as well as the associated energy evolution,were further analyzed.Based on the relationship between the total energy absorbed by the surrounding rock and its peak energy threshold,the instability mechanism of the surrounding rock in the lower coal seam was revealed.Moreover,considering the additional stresses in the lower seam induced by different overburden structural movements,a method for calculating the instability identifica-tion coefficient was provided,and an energy criterion for surrounding rock instability was proposed.Results shown that the instability identification coefficient for the roof of the roadway at the Ⅰ 0104205 working face is 0.246,while the value for the sides is 0.962,indicating that an instability risk exists.On this basis,a progressive control technology system of"far-field pressure relief-near-field reinforcement"suitable for different overburden structure types was proposed.After application in the haulage roadway of the Ⅰ 0104205 working face,the force on the anchor cables was reduced by 17.3％,and the convergence of the roof-to-floor and both sides decreased by 60.5％and 61.9％,respectively,indicating signific-ant control effects on the surrounding rock.Finally,the relationship between various influencing factors and the overbur-den structure types in close-distance coal seam group was discussed.

Abstract:The ecological protection and high-quality development of Yellow River Basin constitute a major national strategy,however,water scarcity has become the greatest constraint to its development.As an important unconventional water resource,mine water possesses significant strategic potential to alleviate regional water shortages by fully exploit-ing its resource attributes.In addition,by reducing the direct discharge of mine water,it mitigates pollution risks to sur-face water environments.Nonetheless,the overall utilization level of mine water remains low and unevenly distributed across regions.Based on a systematic analysis of the characteristics and utilization status of mine water resources in Yel-low River Basin,a strategic framework for their protection and use is explored.The findings reveal notable regional dis-parities:the mine water inflow intensity exhibits a gradient increase from west to east along the basin;the total inflow volume shows a spatial pattern of higher values in the central region and lower values at both ends;water quality displays a gradient with a high degree of mineralization upstream,complex types midstream,and relatively better quality down-stream.Based on the relative relationship between coal production and mine water inflow,four typical patterns have been identified:"high production-low discharge","low production-high discharge","balanced production and discharge",and"low production-low discharge."Mine water utilization rates vary widely,ranging from less than 30％to over 90％,with industrial use dominating the utilization structure,while ecological and agricultural uses remain underdeveloped.Drawing on advanced international experiences,a four-dimensional coordinated strategic framework—"spatial,functional,tempor-al,and institutional"—is established,forming a full-chain layered governance system characterized by"source reduction,harmless treatment during processes,resource recovery at the tail end,and terminal recharge."Key projects are deployed,including precise emission reduction and pollution control engineering,intelligent mine water monitoring networks,qual-ity-based hierarchical treatment systems,innovative utilization models,and regional recharge storage with groundwater re-mediation,alongside safeguard measures such as policies and regulations,collaborative governance,and technological in-novation.Ultimately,the transition of mine water in Yellow River Basin from an"environmental burden"to a"strategic resource"is promoted,providing solid water resource security for regional ecological protection and high-quality develop-ment.

Abstract:Deep coal resources with abundant reserves and considerable thermal potential are receiving increased attention in mining engineering,given the accelerating transformation of the global energy structure and the growing demand for clean energy.To address extraction challenges and environmental pressures while ensuring economic feasibility and sus-tainable development,efforts are made to enable carbon reduction and green transformation under high-efficiency utiliza-tion of deep coal resources.A systematic review of"deep coal resource fluidized mining","coal chemical mining",and"coal-based power"informs the introduction of a detonation-generation mining approach and its technical framework.The approach places coal-powder detonation combustion technology at its core and integrates advanced detonation combustion-mechanical/magnetohydrodynamic power generation,forming a detonation-turbine/MHD hybrid power system that sup-ports efficient conversion and clean utilization of coal resources.Four fundamental theories are presented,including the Coal-powder Detonation Energy Release mechanism,the Coupled Coal-powder Detonation-generation Power Scheme,a Full Life Cycle Detonation-power Generation Dynamic Management Mechanism,and the Blasting-electric Power Deep coal mining theory and method.Discussion centers on four key technologies:Stable coal/gas two-phase detonation,deton-ation model construction and dynamic process optimization,detonation-based power generation efficiency assessment,and comprehensive design for detonation-based coal mining,demonstrating their role in upgrading deep coal mining practices.On this foundation,a systematic engineering strategy is proposed to clarify the synergy between mining processes and the detonation-based power generation mode,highlight safety management and process optimization priorities at each critical stage,and refine the overall detonation-generation pathway for deep coal resource development.This pathway offers valu-able insights for establishing a coal-based power system and promoting the clean and efficient utilization of deep coal re-sources in China.

Abstract:The mining of coal under buildings has always been a major technical challenge for coal mines.To address this issue in China,the bedding separation grouting subsidence reduction experiments were carried out from the 1980s in about 10 coal mines,achieving certain results.However,since the actual subsidence reduction rate did not meet the require-ments for building protection,the technical feasibility of mining coal under buildings through bedding separation grouting was questioned and gradually abandoned.Based on the key stratum theory of strata control and the full-stratigraphy aca-demic thought,the overburden isolated grouting technology was developed.It was first successfully applied in Huaibei mining area in 2009,solving the problem of mining coal under buildings.Its application scope,scale,and fields have been continuously expanding.Currently,the enthusiasm for overburden isolated grouting is on the rise.To promote the healthy development of the industry's technology,it is necessary to scientifically review and comprehensively examine the devel-opment process,and clearly define the differences at the theoretical and technical levels.This innovations of overburden isolated grouting in theory,technology,and practice are systematically discussed.At the principle level,it clearly shifts the technical essence from the"searching for bedding separation"of bedding separation grouting to the"compaction grouting"of isolated grouting,firmly establishing the correct guiding ideology and theoretical direction.From the perspective of the cumulative effect of unloading and expansion of the overburden due to mining,it is found that the bedding separation is suppressed,and the maximum amount is usually less than 10％of the mining height.In some conditions,there is even no bedding separation.Bedding separation grouting focuses on the"bedding separation space"and fills it,which has been proven to have a small filling volume and a low grouting-to-mining ratio,and is difficult to prevent the key stratum from breaking and sinking.This is the fundamental reason why the subsidence reduction effect of bedding separation grouting is not as expected.The compaction grouting method of overburden isolated grouting changes the passive"searching for bed-ding separation"to the active"creating space".Through the"lifting up and pressing down"effect of grouting pressure,the unloading and expansion strata below the key stratum are re-pressed before its breakage and sinking,thereby generating a grouting space,significantly increasing the grouting-to-mining ratio,and forming a compacted support structure in the middle of the goaf,which provides support to the key stratum structure and maintains long-term stability.Based on the principle innovation,the technical level has overcome three major problems:where to grout,how much to grout,and how to grout,transforming the abstract theory of compaction grouting into a process method.In terms of grouting layers,the concept of the main layer position was innovatively proposed,fundamentally ensuring the subsidence control effect of grouting.Through the application of theoretical methods such as the prediction of the height of the fracture zone based on the position of the key stratum,the isolated layer and safety of grouting were ensured.Especially under the guidance of the full-stratigraphy academic thought,in the condition of thin bedrock and thick unconsolidated layer,the overburden struc-ture shifts from the key stratum of the bedrock to the arch structure of the unconsolidated layer,the grouting layer of over-burden isolated grouting has evolved from the bedrock to the bottom boundary of the unconsolidated layer,and practical innovations have been achieved.Focusing on the key technical issues of filling volume and grouting-to-mining ratio,the theory clarifies the process from solid slurry to liquid slurry and then to compacted consolidation of filling materials,and determines the spatial trapezoidal state of the filling body based on the movement law of strata.A formula for calculating the grouting-to-mining ratio considering rock mass expansion and surface subsidence is proposed,fundamentally answer-ing the questions of how much can be grouted and how much needs to be grouted,and completely overturning the cogni-tion of estimating the filling volume based on the bedding separation volume.Furthermore,a grouting control technology centered on grouting-to-mining matching is proposed,transforming compaction grouting into controllable guided grouting,ensuring the subsidence reduction effect from the source.Coupled with a series of design methods for grouting borehole layout and the application of monitoring and regulation of parameters such as grouting pressure,density,and flow rate,the long-term healthy operation of grouting through boreholes in the mining-induced black box strata and the stability of sur-face subsidence control effects have been achieved.Supported by a series of theories and key technologies,overburden isolated grouting has increased the grouting-to-mining ratio to over 50％,and controlled the surface subsidence coefficient below 0.1,meeting the requirements for buildings protection.It has achieved the mining without relocation of villages(subsidence reduction),the comprehensive utilization of millions of tons of coal-based solid waste(emission reduction),the protection of aquifers(leakage reduction),and the prevention of mine earthquakes(vibration reduction).The develop-ment direction is to address the shortage of solid waste filling materials in coal mines and the"dual carbon"goals by us-ing CO2 as grouting material to achieve the"one injection,five reductions"effect of subsidence reduction,emission reduc-tion,leakage reduction,vibration reduction,and carbon reduction,and realize green mining and low-carbon utilization of coal resources.

Abstract:Heat release from surrounding rock is the dominant heat source in deep high-temperature mines,and its key parameter-the unsteady heat-transfer dimensionless number Kuτ-directly determines the accuracy of air-temperature prediction.Existing methods for obtaining Kuτ(analytical series,charts,tables,piecewise regressions,or case-by-case nu-merical simulations)are either computationally cumbersome,suffer from large interpolation errors,or cannot be imple-mented in batches,thus failing to meet engineering demands for rapid,accurate and unified calculations.To address the above issues,a study on the calculation method of the unsteady heat-transfer dimensionless number between roadway sur-rounding rock and airflow has been carried out.Taking a circular roadway as the research object,a dimensionless transi-ent heat-conduction equation in polar coordinates is established and expresses Kuτ as a function of the Biot number Bi and the Fourier number Fo.The finite-volume method is employed for discretisation;the nodal radii and time steps are ar-ranged in geometric progressions to guarantee accuracy during the violent unsteady stage while maintaining computation-al efficiency at later times.An in-house solver developed in Visual Studio is used to obtain high-precision discrete solu-tions over the ranges of different Bi and 0.01≤Fo ≤ 1 000.Through a variable transformation,a highly linear relation-ship between(Bi-Kuτ)-1 and Fo-0.5 is discovered,on the basis of which a unified quadratic-polynomial regression formula is constructed.The numerical results agree well with classical analytical solutions,validating the model and the code.The regression formula is concise and free of piecewise definitions;its average relative error is 1.8％and its maximum relative error is 4.2％,outperforming existing piecewise regressions.A case study shows that the unsteady heat-transfer dimension-less number drops to 29.0％,7.7％and 5.0％of its initial value after 5 days,1 year and 10 years of ventilation,respect-ively,consistent with field observations.A unified explicit expression of Kuτ valid over the entire continuous ranges of Bi and Fo is presented,eliminating the limitations of piece-wise fitting.Owing to its compact form,the formula can be dir-ectly embedded in mine air-temperature prediction software to achieve second-level accurate calculation of heat dissipa-tion from surrounding rock for hundreds of roadways,offering a reliable and efficient tool for rapid thermal-hazard assess-ment and cooling design in deep mines.The method is readily extendable to non-circular cross-sections and heterogen-eous rock,and future work will couple air temperature-humidity processes to enable dynamic prediction of the thermal en-vironment of entire mines.