摘要：The paper contains the results of investigation of interconnections between coals' vitrinite structural features,mode of its crushing under the cyclic nanoindentation with increasing peak load and coals' proneness to formation of airborne respirable dust(ARD)with particles sized＜10 μm(PM10).A specific value of PM10 contents in coals normalized on a fines fraction(with particles sizes of less than 200 μm)was used as a measure of proneness to ARD formation.It has been shown that the aforementioned parameter is predefined by the ratio of amorphous and crystalline carbon compounds in vitrinite and the mode of its crushing.Some preliminary investigation have been done in order to characterize the involvement of inertinite in ARD formation.It was proposed that the inertinite is not as actively involved in the processes of ARD formation of coals as vitrinite,having a more diverse structural features in terms of amorphous to crystalline carbon compounds ratio.

摘要：To enhance the efficiency and cost-effectiveness of coal seam gas extraction in coal mines,this study introduces an inte-grated approach combining drilling,hydraulic punching,and fracturing technologies.This method optimizes drilling media tailored to specific coal seams and fine-tunes technical parameters during drilling and permeability improvement processes.Furthermore,it clarifies the relationships among the coal breaking rate,discharge of drill cuttings,jet velocity,rotation speed,and displacement.This ensures precise and effective permeability improvement in both soft and hard coal formations.To implement this technology,a set of high-performance drilling tool with a large inner diameter,high pressure resistance,and superior sealing capabilities has been developed.Consisting of a water braid,drill pipe and hydraulic ejector,this tool meets the requirements of substantial displacement and high pump pressure.Field test results demonstrate remarkable enhancements in borehole formation,coal breaking and slagging efficiency.Specifically,the operation time is reduced by 60％-80％,the coal output is increased by 1-1.5 times,the pure coal seam gas extraction yield is increased by 1-2 times,and the extraction radius expands by more than 100％.These results highlight significant advancements in operational efficiency and perme-ability improvement effects,paving the way for efficient and economical coal seam gas extraction practices.

摘要：Calorific value is one of the most important properties of coal.Machine learning(ML)can be used in the prediction of calorific value to reduce experimental costs.China is one of the world's largest coal production countries and coal occupies an important position in its national energy structure.However,ML models with a large database for the overall regions of China are still missing.Based on the extensive coal gasification practices in East China University of Science and Technology,we have built ML models with a large database for overall regions of China.An AutoML model was proposed and achieved a minimum MSE of 1.021.SHAP method was used to increase the model interpretability,and model validity was proved with literature data and additional in-house experiments.The model adaptability was discussed based on the databases of China and USA,showing that geography-specific ML models are essential.This study integrated a large coal database and AutoML method for accurate calorific value prediction and could offer key tools for Chinese coal industry.

摘要：Dust pollution in industrial environments should be closely monitored for health and process control.Traditional mea-surement methods often require intrusive sensors and lack continuous real-time capability.A novel non-intrusive,image-based method was proposed for real-time dust concentration estimation.Using a controlled experimental setup with a high-concentration dust generator,images of dust-laden air across a wide concentration range(10-1000 mg/m3)were captured.For each image,the color and texture features were extracted as predictors of dust concentration.Then the poly-nomial regression was used to correlate these image-derived features with actual dust concentrations measured by standard instrumentation.The analysis revealed strong nonlinear relationships:the grayscale mean intensity correlates with dust concentration(R2=0.79),and selected texture features yield even higher correlation(R2＞0.82).These image-derived metrics effectively capture the scattering and attenuation of light caused by suspended dust,serving as reliable proxies for particulate mass.Combining multiple image features into a composite regression model further improved estimation accu-racy.These findings demonstrate that camera-based image analysis can reliably estimate dust concentration in real time,offering a low-cost,non-intrusive alternative to conventional sensors.The approach could facilitate automated calibration of dust-generation systems and enable continuous air quality monitoring in industrial settings.

摘要：Liquid nitrogen(LN2)fracturing has been studied widely in coal-bed methane(CBM)stimulation.Nevertheless,the thawing effect on the frozen coal has been rarely considered.The thawing behaviors of the frozen coal by microwave were researched using nuclear magnetic resonance(NMR),ultrasonic wave,and infrared thermal imaging.The evolution of the pore structure,temperature,water content,and surface cracks of the coal samples treated by freezing and thawing is discussed.NMR results illustrate that microwave thawing not only improves coal's permeability by increasing seepage pores but also removes the water from the coal.On the contrary,air thawing treatment increases the moisture of the coal sample.The losing-water rate of the samples thawed at high power is smaller than that of samples thawed at low power.The microwave thawing treatments generate cracks and reduce the wave velocity of the coal samples,and higher thawing power on the frozen is in more favor of forming macro-cracks under the same input energy.Therefore,microwave thawing on frozen coal can eliminate water blocking damage and provide the flow space for the gas.The study analyzed the feasibility of microwave thawing on the frozen coal and provided a reference method for CBM production.

摘要：The rapid growth of offshore wind farm construction requires reliable pile foundation designs that can withstand complex marine loads.However,current design practices for these foundations often neglect the potential threat of submarine debris flows,which can exert highly destructive forces.This study employs a CFD approach to simulate the effects of submarine debris flows on piles in intricate marine environments,with model accuracy validated against a series of laboratory experiments calculating lateral forces from debris flows.We investigate the impact of debris flows on piles across a range of Reynolds numbers,including variations in rheological properties,density,impact velocity,and initial debris flow heights.Our results reveal that the dominant force exerted by submarine debris flows on piles is primarily a horizontal drag force.We identify three distinct stages in the impact process and emphasize the peak drag force as the critical load on the pile.The study provides a comprehensive analysis of the mechanisms driving variations in drag force and highlights the nonuniform distribution of drag forces along the pile's length.The debris flow height significantly influences not only the magnitude of the peak drag force but also the action point location of this force along the pile.Finally,we propose quantifiable methods for evaluating the peak drag force coefficient and its action point,enhancing the design resilience of pile foundations against submarine debris flows.

摘要：As a new type of underground water conservancy project,underground reservoirs in coal mines play a crucial role in pro-tecting and utilizing water resources during mining operations.The safety and reliability of the dam body are key to this technology.Focusing on the basic situation of the Shendong 2-2 coal seam coal mine underground reservoir,this paper uses mechanical analysis,mechanical testing and other methods.From the perspective of the dam body stability under the combined effects of seismic activity and water immersion,this study analyzes the changes in the stability of the dam body during reservoir operation.It focuses on the dynamic impacts of earthquakes and mining-induced tremors,along with the long-term effects of water immersion.By comprehensively analyzing the changes in stress,displacement,and other param-eters when the combined dam body(coal pillar+concrete)fails,the research identifies the locations and causes of damage to the dam body under the impact of earthquakes.It also proposes precursor information and characteristics of dam body instability under long-term water immersion and dynamic load effects.The results indicate that under water storage condi-tions(horizontal stress combined with water immersion),the coal pillar undergoes displacement and eventually becomes unstable,facturing upon reaching its limit strength.Water immersion reduces the mechanical strength of the coal pillar.-For a coal pillar 15 m thick,the maximum water storage height is 50 m.It is recommended that displacement changes be used as precursor information for dam body monitoring and early warning during the actual water storage process.The"coal pillar-concrete"combined dam body can resist earthquakes of magnitude 10 and above(1.2 g).During earthquakes,the bottom and middle parts of the dam are the main locations of stress concentration,with the stress change pattern being bottom＞middle＞top.Due to the difference in material properties between the concrete and coal pillar dam bodies,the difference in acceleration between the two during earthquakes is about 1.14 times,causing the bottom of the coal pillar to be the first to break.Additionally,the stress peak on the submerged side body during an earthquake is about 10％higher than that on the front.This research is important for the stability analysis and monitoring and early warning of underground reservoirs in coal mines and provides a reference for the stability of other underground projects.

摘要：CO2 enhanced oil recovery plays an important role in carbon storage and utilization.However,the incomplete understand-ing of the underlying microscopic convection-diffusion mechanisms in complex pore structures has constrained the broader industrial application of CO2 geo-sequestration.This work develops a pore-scale numerical model considering molecular convection-diffusion to investigate CO2-oil miscible displacement in two-and three-dimensional porous structures of con-glomerate rocks.The effects of CO2 injection rates and pore structure properties on convection-diffusion are analyzed.By reconstructing the distribution of unexploited pores,the CO2 sweep efficiency is quantitatively evaluated.Furthermore,a sequestration factor is proposed to evaluate the CC2 storage capacity during miscible displacement.Convection significantly enhances the CC2 mass fraction in fractures with high flow rates.Subsequently,CO2 gradually diffuses into matrix pores without velocity distribution.Both convection and diffusion contribute to improving CO2 displacement efficiency.Diffusion facilitates the dissolution of CO2 into oil within small-diameter pores,and convection effectively mobilizes oil in large pore bodies.Developed and homogeneous pore structures enhance CO2 displacement efficiency,whereas CO2 flows along the main flow channels in heterogeneous pore structures,resulting in lower displacement efficiency.Diffusion plays a crucial role in CC2 storage within porous media.At low injection rates,dissolved CO2 is trapped in poorly connected and blind-end pores.The injection rate is negatively correlated with the sequestration factor.

摘要：In recent years,the co-incineration with industrial organic solid waste(IOSW)in municipal solid waste(MSW)incinera-tors has been an effective method for addressing MSW volume deficiencies and expediting IOSW disposal.However,co-incinerating IOSW raises several concerns,particularly regarding the altered characteristics of incineration ash.This study investigated the impact on ash characteristics at co-incineration ratios of 20％,30％,and 40％in a 500 t/d MSW incinerator.IOSW consisted mainly of plastic,fabric,and leather,and it contained relatively high levels of chlorine,sulfur,and heavy metals.The findings indicated that co-incineration marginally affected the crystalline structure of ashes but altered the chemical composition of part ashes.Higher IOSW ratios reduced the Ca content to 5.80％and increased the concentrations of Cl,Na,and K in particulate matter(PM).The use of calcium-based agents to reduce acid gas concentra-tions lowered Cl,Na,and K in baghouse fly ash(BHFA).Heavy metal concentrations in superheater and economizer ash remained relatively stable,whereas the elevated levels of As,Cd,Pb,Zn,and Cu in PM with rising co-incineration ratios were attributed to increased temperatures and HCl concentrations.BHFA displayed reduced heavy metal content,likely due to dilution by deacidification agents.The leaching concentrations of Cr,Pb,Zn,and Cu in BHFA slightly increased,while those of As and Se decreased due to higher pH and reduction reactions.Most heavy metals in the leachate,except Pb,complied with regulatory limits.This investigation provides insights into ash characteristics at IOSW co-incineration ratios of up to 40％and offers guidance for subsequent treatment and disposal of fly ash.

摘要：The mining height of a coal seam is a critical factor influencing the detachment,collapse,and formation of the collapse angle of the strata during strata movement.To clarify the mechanism by which mining height affects strata movement characteris-tics,a physical model experiment was conducted based on the geological conditions of the Panel 122104 in Caojiatan Coal Mine in Shaanxi.The experiment examined strata movement at mining heights of 1 m and 10 m,identifying differences in detachment,collapse behavior,and collapse angles under these two conditions.The results indicate the following:Delami-nation range directly governs collapse patterns,with higher stress concentration accelerating delamination initiation and expanding affected zones.1 m mining height exhibits a"superposed fixed beam"structure with lower strength compared to the"fixed beam+cantilever beam"configuration under 10 m height.A model estimating collapse step shows 9.13％average error.Strata structure dictates collapse angle mechanisms:Pseudo-plastic deformation under 1 m height determines collapse angle through vertical tensile stress boundaries,whereas 10 m height exhibits brittle fracture behavior with collapse angles approximating fracture angles.Periodic collapse volume above working face directly correlates with mine pressure intensity and is positively correlated with the caving step distance,collapse angle,and caving range.These parameters show higher values under 10 m mining height,resulting in more pronounced mine pressure manifestations compared to 1 m conditions.

摘要：Reducing greenhouse gas emissions and improving unconventional gas recovery are pressing challenges worldwide.This study investigates the leading role of coal permeability in CO2-enhanced coalbed methane recovery(CO2-ECBM)using an improved thermo-hydro-mechanical(THM)coupling model.The model is validated and applied to the simulation of CO2-ECBM process under varying permeability.The direct positive relationship between both cumulative CH4 produc-tion and cumulative CO2 injection with coal permeability,and operating duration of CO2-ECBM is negatively correlated with coal permeability.The delay in the injection start time will extend the operating duration of CO2-ECBM and over-come the problem of early CO2 breakthrough.An increase in both delayed start time for injection and coal permeability progressively boosts CH4 production,while diminishing CO2 sequestration.The optimal start timing for CO2 injection is contingent upon primary objectives,such as CO2 sequestration or CH4 production.For the primary constraint of CO2 sequestration,the optimal starting time should be before the peak gas production.For the primary constraint of CH4 production,the optimal starting time should be after the peak gas production.In analyzed instances,the optimal timing for CO2 injection exhibits an inverse correlation with coal permeability.The results provide practical insights for CO2 injection optimization and field applications.

摘要：Hydrogen,a genuinely clean energy,is a promising alternative to fossil fuels.Inspired by underground gas storage of methane,establishing underground hydrogen storage(UHS)in depleted oil and gas reservoirs has emerged as a significant research focus.Carbonate reservoirs,where widely-presented fractures can facilitate the high-speed injection and production of gases,are hence ideal candidates for building underground hydrogen storage facilities.During the cyclic injection and extraction processes of UHS,the formation is subjected to stress disturbances,leading to stress sensitivity.Understanding the stress sensitivity patterns of carbonate rocks is crucial for optimizing injection and production strategies.This study reconstructed three-dimensional digital models of fractured carbonate rocks from the L gas field using micro-CT scanning technology.Utilizing the finite element method,we investigated the microscopic permeability characteristics of carbonate rocks and analyzed the impact of stress loading direction and confining stress on stress sensitivity.The findings reveal that the stress loading direction significantly influences the stress sensitivity of fractured carbonate rocks.When a stress of 60 MPa is applied perpendicular to the fracture direction,the permeability reduction ratio can reach 17.32％.In contrast,when the same stress is applied parallel to the fracture direction,the permeability reduction ratio is only 4.82％.Furthermore,a simulation of UHS with cyclic injection and production of H2 in the target block was conducted.When both permeability and porosity stress sensitivity were considered,the working gas volume for UHS decreased by only 3.4％,demonstrating that fractured carbonate reservoirs are feasible candidates for constructing underground hydrogen storage.

摘要：Mining-induced surface subsidence often causes buried oil-gas pipelines deform,and the potential leakage risk can pose a safety hazard.In this work,a novel model for predicting the influence range of potential leakage risk from deformed pipelines was developed.First,the pipe instability deformation limit was corrected by the multi-indicator optimized screening method proposed in this paper.Then,the leakage risk influence radius of the pipe segment was defined by the failure probability.Next,the pipe segment' deformation and strength were assessed sequentially using the ratio and point methods.Combining the fuzzy logic inference method with the assessment results as input variable,and the failure probabilities as output vari-able,a quantitative assessment model for the pipeline leakage risk was established.Accordingly,the risk range and level of adjacent coal mines and surfaces were divided,and the verification method and forward countermeasures were proposed.Finally,an engineering case was used for analysis and verification.The results show that the gas pipeline with 650 m length was divided into seven regions and four risk levels.The influence radius of the risk levels from low to high were 12.75 m,25.5 m,38.25 m,and 51m,and the influence widths on the surface were 25.28 m,49.84 m,76.34 m,and 101.84 m,corre-spondingly.The nearest distances from the risk area to the mine and village were 212.65 m and 329.08 m.The assessment of potentially threatened areas is significantly simplified by the assessment model combined with pipeline deformation,which has great practical importance for risk management and disaster prevention in adjacent space.

摘要：Coal mining in groundwater-rich coal fields will trigger failure of overlying strata,resulting in the formation of water-conducting fracture zone(WCFZ)and potentially leading to water-inrush accidents.In this study,a reliability model with consideration of spatial variability and uncertainty of strength parameters was proposed to predict the failure behaviour of overlying strata during coal mining in groundwater-rich coalfields.Rock strength parameters,including cohesion,internal friction angle,uniaxial tensile strength,and softening coefficient,are treated as random variables to determine the rock fail-ure uncertainty.The experimental results of these geomechanical parameters at different positions are interpolated by the Kriging interpolation method.Spatially,the interpolated values are arranged as the average value of each random variable to demonstrate their autocorrelation.Furthermore,based on Mohr-Coulomb yield criterion,a performance function is deduced to calculate the failure probabilities of overburden rocks to evaluate the spatial scale of WCFZ.As a typical case,the failure features of adjacent overlying strata of No.7121 mining face in Qidong Coal Mine is analyzed.The results show that the risks of water-inrush are high when the mining face advances to 260-380 m and 1120-1240 m,which aligns with both field monitoring results and borehole observation results.The proposed model holds significant implications for prevention of water-inrush accidents in groundwater-rich coal mines.

摘要：Activated carbon,as a hydrogen storage material,possesses advantages such as low cost,high safety,lightweight,and good cycling performance.Zhundong coal,characterized by low calorific value,high volatility,and elevated reaction activity,stands out as an exceptional raw material for the production of activated carbon.This study employed Zhundong coal for the synthesis of hydrogen storage activated carbon,exploring the impact of acid treatment and varied activation conditions on Zhundong coal.The specific surface area of sample ZD-HK3-AC is 1980 m2/g,and the gravimetric hydrogen storage density reaches 0.91 wt％under the condition of 80bar at room temperature.The adsorption-desorption isotherms nearly overlapped,demonstrating excellent cycling performance and high mechanical strength.At the same time,the relationship between the pore structure parameters of activated carbon and hydrogen storage density was explored,revealing the mechanism of activated carbon adsorption and hydrogen storage.These findings hold significant guiding implications for the preparation and research of hydrogen storage materials utilizing activated carbon.

摘要：Coal seams in China are typically characterized by high coal seam gas content and low permeability,posing challenges for efficient coal seam gas extraction.However,achieving successful boreholes,especially in soft coal formations,remains a chal-lenge.The mechanisms underlying permeability improvement in different coal structures need further exploration.Therefore,this paper is focused on the fundamental principles of permeability improvement in soft coal through hydraulic punching,and in hard coal via hydraulic jet fracturing.Firstly,borehole instability results from a dynamic interplay of four factors:in situ stress,coal structure,mechanical properties of coal with fluid,and drilling technology.While borehole instability is inevitable,enhancing drilling tools,drilling media,and drilling processes can mitigate risks associated with buried and stuck drill pipes by ensuring effective discharge of drill cuttings through critical flow velocity and displacement.Secondly,permeability improvement in soft coal through hydraulic punching aims at pressure relief and capacity increase,while in hard coal,hydraulic jet fracturing induces crack formation within the coal seam.Finally,this study illustrates the dynamics of the granular arch in soft coal after hydraulic punching,shedding light on the complex processes involved.

摘要：The displacement of groundwater resulting from mining disturbances and water withdrawals during coal production can lead to the compression of loose aquifers,leading to surface subsidence and threatening the safe production of coal mines.To thoroughly analyze the effects of non-mining factors on groundwater loss and subsidence in loose aquifers,the study area is divided into an aquifer system based on existing geological and hydrogeological data.A three-dimensional integrated subsidence observation network,designated the"sky-ground-underground"system,was constituted through the utilization of distributed fiber-optic sensor technology as the principal methodology.This approach was further enhanced through the integration of time-series InSAR technology,which was complemented by the utilization of conventional leveling,ground-based measurement techniques,and groundwater monitoring.The objective was to investigate the combined subsidence patterns of the strata and the surface.The findings suggest that the principal factor responsible for surface subsidence in the study area is the sustained compression of the fourth aquifer and the lower section of the third aquiclude.It has been observed that seasonal fluctuations in the deformation of the shallow aquifer occur.Furthermore,the weakening of clay in the deep-buried aquifer has been observed,with the degree of weakening correlating with groundwater mobility,thereby exacerbating surface subsidence.The compression observed in the fourth aquifer is primarily attributed to the loss of water from the aquifer.The study area has been observed to exhibit continuous surface sinking.The confirmation of a functional relationship between surface subsidence and the third aquiclude and fourth aquifers serves to reinforce the conclusion that declines in water levels in the fourth aquifer and the weakening of clay in the third aquiclude represent the primary factors contributing to surface subsidence.

摘要：Constructing underground structures in coastal regions poses significant challenges,particularly due to seawater intrusion,which can cause corrosion and threaten the safety and stability of the caverns and surrounding facilities.A crucial aspect of preventing seawater intrusion lies in accurate mapping of the geological structure of the reservoir area and its proximity to the coastline.This study uses reflection seismic data,borehole ultrasonic imaging,and core samples to identify geological features that influence subsurface stability.The seismic profile revealed a V-shaped or concave-down structure associated with faults,suggesting a down-dropped block within the subsurface.Seismic facies analysis identified chaotic,high-amplitude reflections within basement rocks,indicating highly fractured and faulted zones,possibly including mylonitic rocks.A novel approach is proposed that combines borehole ultrasonic imaging with fractal theory,integrating core photos,seismic attributes,and geophysical analysis.A functional relationship was established between the joint surface density and the joint information dimension within the borehole.Additionally,a relationship was established between fault information dimension and borehole joint surface density.Results showed that the joint information dimensions within the identified fault zones consisttently exceeded 1.775.By applying a threshold of joint information dimension greater than 1.775,15 small-scale structural prediction zones were identified.Subsequent analysis of core photos from the predicted regions confirmed the presence of relatively long fractured zones,demonstrating the high accuracy of the proposed method in identifying small-scale structures.This study presents a comprehensive method for mapping geological structures in coastal areas,providing an essential reference for the identification and management of small-scale features in underground engineering projects.

摘要：With the increasing availability and sophistication of computer hardware and software,computational modelling has become a cornerstone in the understanding of geomaterials mechanical behaviours over recent decades.Numerous researchers have sought to develop and refine various simulation models to accurately represent the mechanical behav-iour and fracturing mechanisms in rocks.It is the purpose of this review paper to present a comprehensive overview of the most advanced numerical approaches,including continuum methods,discrete element methods,and combined finite-discrete element methods,which have been widely used in the rock engineering fields to simulate fracture processes in layered rock.The fundamentals of each simulation technique are elucidated,focusing particularly on approaches that model fracture initiation,propagation,and the effects of discontinuities in rock masses.This discussion is supplemented by a concise summary of application work,highlighting both laboratory-scale models of layered rock failure and simula-tions of fracturing behaviour in geoengineering projects involving layered rock masses.

摘要：Coal mining accidents are a major concern worldwide,necessitating effective safety measures and comprehensive analysis to prevent future accidents.Our proposed solution is the first attempt for Indian mines,inspired by the potential of Natural Language Processing(NLP)that can read and analyze vast repositories of accident records in seconds.In combination with machine learning(ML),NLP algorithms can extract unstructured text by eliminating manual data entry errors,reading poorly scanned reports,and understanding multiple versions of the event and cluster documents based on types that would otherwise take months to collate.In the case of accident records,it can be an asset in capturing recurring issues,contributing factors,and high-risk areas,enabling proactive measures to be taken to prevent future accidents.The heart of the study lies in applying two ML algorithms called latent Dirichlet allocation(LDA)and RAKE(Rapid Automatic Keyword Extraction).LDA is a topic modeling technique for clustering accidents based on descriptions.RAKE generates root cause analysis through keywords from accident descriptions and remedies suggested by inspection officers.Both are unsupervised learning techniques that do not require any training on labeled datasets.AI and NLP can significantly enhance the process of creating Swiss Cheese Models and Logic Sequences of Contributory Factors Diagrams by automating the extraction,classification,and analysis of data from incident reports and other relevant documents.Data for analysis in this study came from the Directorate General of Mines Safety(DGMS),India records from 2010 to 2015.