摘要：Room and pillar mining is an underground mining method that utilizes natural pillar support to control rock mass behavior,ensuring mine stability and a safe mine environment.This study specifically documents the influence of the intermediate principal stress component on the pillar behavior.So far only classical failure criteria ignoring the influence of the intermedi-ate principal stress component were used for underground pillar design.By using an extended Hoek-Brown failure criterion in comparison with the classical Hoek-Brown failure criterion,the influence of the intermediate principal stress component is documented by indicating those areas where the failure criterion is violated.This study demonstrates,that depending on the rock type,the intermediate principal stress component can have a significant effect.Ignoring this influence can lead to uneconomic pillar design and incorrect determination of the factor of safety.

摘要：This study focuses on steeply inclined and extremely thick coal seams(SIETCS)characterized by immense thickness,a steep inclination of coal seams(87°),and high horizontal stress.The geological conditions and mining technology associ-ated with SIETCS differ significantly from those of generally inclined coal seams,resulting in notable variations in roadway stress distributions.On SIETCS have predominantly examined the impact of rock layers flanking coal seams on rock bursts,with limited emphasis on SIETCS roadways.This study employs comprehensive methods,integrating numerical simula-tions,theoretical analyses,and field detections to investigate the stress distribution of SIETCS and the mechanisms of rock burst-induced vertical damage,subsequently validated in situ.The vertical stress in SIETCS is minimal,while horizontal stress is concentrated,leading to the formation of layered crack structures(LCS)that distribute above and below the road-ways.Additionally,elastic energy significantly concentrates within the LCS.Axial dynamic compressive stress and vertical dynamic tensile stress along the LCS diminish its stability,readily triggering failure.During the LCS failure process,the stored energy is released,converting into kinetic energy required for coal body ejection after reaching the minimum energy for failure and dissipative energy,ultimately leading to rock burst-induced vertical damage in roadways.On-site detection and analysis within SIETCS,along with historical rock burst data,confirm the existence of LCS and its role in inducing vertical rock burst damage.This research establishes essential foundations for preventing rock bursts within SIETCS.

摘要：Compared with blast mining only,blast mining after on-site hydraulic fracturing can make the mining easier and obtain better mining outcomes.To explore the effects of hydraulic fracturing on the blasting damages in coal seam,blasting experiments were carried out under biaxial confining pressure using the synthetic coal briquettes.The coal briquettes with the same mechanical properties as coal seam were prepared and the mica sheets with different radii and thicknesses were added to simulate the internal hydraulic fractures of different radii and openings.The internal damage distributions and stress attenuations of the coal briquette specimens with different hydraulic fracture radii and openings after the blasting were then measured using a rock ultrasonic tester and a static-dynamic strainmeter.Based on the rock blasting theory,the effects of hydraulic fractures with different radii and openings on the blast fracture propagation and coal seam damage were analyzed.The following conclusions are drawn:(1)The increases in hydraulic fracture radius mainly enhance the damages in the vertical direction to the hydraulic fracture,and can increase the vertical range of the severely damaged area by 20-25 cm.The increases in the hydraulic fracture opening mainly cause more severe damages along the direction of the hydraulic fracture and increase the horizontal range of the severely damaged area by 30 cm.(2)The area of the severely damaged area caused by blasting increases by 550 cm2 as the hydraulic fracture radius increased from 5 to 15 cm.As the hydraulic fracture opening increased from 2 to 10 mm,and the area of the severely damaged area caused by blasting increases by 650 cm2.Therefore,the hydraulic fracture opening has greater impacts on the severely damaged area.(3)The increase in the hydraulic fracture length reduces the compression phase attenuation of the blast stress in the radial direction.Both the increases of the hydraulic fracture length and opening increase the absolute value of the tensile phase in the radial direction.(4)Increasing the hydraulic fracture radius and opening can greatly promote the development of blast fractures and enhance the damages to coal seam.Therefore,the coal seam mining effect can be improved by increasing the radii or openings of hydraulic fractures to adjust the main action direction of blast fracture.

摘要：In rock drilling and blasting,the misfire of electronic detonators will not only affect the rock fragmentation result but also bring serious potential safety hazards to engineering construction.An accurate and comprehensive understanding of the failure mechanisms of electronic detonators subjected to impact loading is of great significance to the reliability design and field safety use of electronic detonators.The spatial distribution characteristics and failure modes of misfired electronic detonators under different application scenarios are statistically analysed.The results show that under high impact loads,electronic detonators will experience failure phenomena such as rupture of the fuse head,fracture of the bridge wire,falling off of the solder joint,chip module damage and insufficient initiation energy after deformation.The lack of impact resistance is the primary cause of misfire of electronic detonators.Combined with the underwater impact resistance test and the impact load test in the adjacent blasthole on site,the formulas of the impact failure probability of the electronic detonator under different stress-strength distribution curves are deduced.The test and evaluation method of the impact resistance of electronic detonators based on stress-strength interference theory is proposed.Furthermore,the impact failure model of electronic detonators considering the strength degradation effect under repeated random loads is established.On this basis,the failure mechanism of electronic detonators under different application environments,such as open-pit blasting and underground blasting,is revealed,which provides scientific theory and methods for the reliability analysis,design and type selection of electronic detonators in rock drilling and blasting.

摘要：The study of the mechanical property and damage state of coal materials under compression is a fundamental area of research in underground mining engineering.Drawing upon the compaction effect and linear energy dissipation(LED)law,a novel compressive damage constitutive model for brittle coal is proposed.Utilizing the energy-defined damage method for mate-rials,the LED law is innovatively introduced to accurately characterize the energy dissipation during the loading process,and a novel formula for characterizing the damage variable of brittle coal is proposed.On this basis,considering that the constitutive model based on the hypothesis of strain equivalence is incapable of accurately describing the compaction effect exhibited by coal material during the compression process,a correction coefficient is proposed and apply it in the novel damage constitutive model.The established conventional monotone loading and single-cyclic loading-unloading uniaxial compression damage constitutive models have been validated using experimental data from cylindrical and cuboid coal specimens.In addition,compared with the constitutive model obtained via the traditional energy calculation method based on the hypothesis that the unloading curve is a straight line,the constitutive model employing LED law can describe the stress-strain state of brittle coal more precisely.This approach introduces a new perspective and enhances the convenience for constructing the constitutive model based on energy theory.

摘要：Geo-monitoring provides quantitative and reliable information to identify hazards and adopt appropriate measures timely.However,this task inherently exposes monitoring staff to hazardous environments,especially in underground settings.Since 2000s,robots have been widely applied in various fields and many studies have focused on establishing autonomous mobile robotic systems as well as solving the issue of underground navigation and mapping.However,only a few studies have conducted quantitative evaluations of these methods,and almost none have provided a systematic and comprehensive assessment of the suitability of mapping robots for underground geo-monitoring.In this study,a methodology for objective and quantitative assessment of the applicability of SLAM methods in underground geo-monitoring is proposed.This involves the development of an underground test field and some specific metrics,which allow detailed local accuracy analysis of point measurements,line segments,and areas using artificial targets.With this proposed methodology,a series of repeated experimental measurements has been performed with an autonomous driving robot and the selected LiDAR-and visual-based SLAM methods.The resulting point cloud was compared with the reference data measured by a total station and a terrestrial laser scanner.The accuracy and precision of the selected SLAM methods as well as the verifiability and reliability of the results are evaluated and discussed by analysing quantities such as the deviations of the control points coordinates,cloud-to-cloud distances between the test and reference point cloud,normal vector,centre point coordinates and area of the planar objects.The results demonstrate that the HDL Graph SLAM achieves satisfactory precision,accuracy,and repeatability with a mean cloud-to-cloud distance of 0.12 m(with a standard deviation of 0.13 m)in an 80 m closed-loop measurement area.Although RTAB-Map exhibits better plane-capturing capabilities,the measurement results reveal instability and inaccuracies.

摘要：Soot is a flocculent carbon nanoparticle that results the imperfect combustion of fossil fuel,and numerous studies are dedicated to the reduction of soot production to alleviate the associated environmental problems.However,soot as a functional material is also widely used in energy storage and superhydrophobic materials.As a partial oxidation technology,the entrained flow coal gasification process will produce part of the soot.It is important to separate soot from the coal gasification fine slag(CGFS)and understand its structural characteristics for soot utilization.For this purpose,two industrial typical pulverized coal gasification fine slag(PCGFS)and coal-water slurry gasification fine slag(WCGFS)were selected for this study.The results showed that both fine slags were rich in soot,and the dry ash free mass fraction of soot in PCGFS and WCGFS was 6.24％and 2.91％,respectively,and the soot of PCGFS had a hollow carbon nanosphere morphology,while the soot of WCGFS showed a flocculent irregular morphology.The average fringe length,fringe tortuosity,and fringe spacing of the soot were 0.84 nm,1.21,and 0.45 nm,respectively.Compared to the WCGFS,the soot particles of PCGFS have less continuity of molecular bonds within the lattice,the larger the defects within the lattice,the fewer isolated lattice carbon layers there are.This study provides important theoretical support for understanding the structural characteristics and next applications of soot in the entrained flow coal gasification fine slag.

摘要：The frequent or occasional impact loads pose serious threats to the service safety of conventional concrete structures in tunnel.In this paper,a novel three-dimensional mesoscopic model of steel fiber reinforced concrete(SFRC)is constructed by discrete element method.The model encompasses the concrete matrix,aggregate,interfacial transition zone and steel fibers,taking into account the random shape of the coarse aggregate and the stochastic distribution of steel fibers.It captures microscopic-level interactions among the coarse aggregate,steel fibers,and matrix.Subsequently,a comprehensive procedure is formulated to calibrate the microscopic parameters required by the model,and the reliability of the model is verified by comparing with the experimental results.Furthermore,a coupled finite difference method-discrete element method approach is used to construct the model of the split Hopkinson pressure bar.Compression tests are simulated on SFRC specimens with varying steel fiber contents under static and dynamic loading conditions.Finally,based on the advantages of DEM analysis at the mesoscopic level,this study analyzed mechanisms of enhancement and crack arrest in SFRC.It shed a light on the perspectives of interface failure process,microcrack propagation,contact force field evolution and energy analysis,offering valuable insights for related mining engineering applications.

摘要：The large amount of harmful particles in coal dust not only pollutes the production environment,affects the production efficiency and resource utilization of enterprises,but also poses a risk to human health.Effectively controlling coal dust is of great significance to clean production.Water-based dust suppressants are extensively employed to mitigate coal dust.This paper provides a comprehensive review of the water-based dust suppression materials for coal dust control.Accord-ing to the difference of mechanism,the dust suppressants are divided into wetting type,hygroscopic coalescence type,cohesive agglomeration type,and composite type.The evaluation methods for dust suppressants key properties such as wettability,permeability,moisture absorption and water retention,and consolidation are summarized.The review results show that coal dust suppressants are no longer limited to a single dust suppression function.For example,it is necessary to develop multi-functional coal suppressants to meet the needs for synergistic suppression both coal dust and coal spon-taneous combustion.Driven by the concept of green,low-carbon and sustainable development,attention should be paid to the development of bio-based environmentally friendly coal dust suppressants.In addition,the evaluation method system for the key performance of water-based dust suppressants should also be improved,and further research is necessary.

摘要：Coal is a versatile energy resource and was a driver of the industrial revolution that transformed the economies of Europe and North America and the trajectory of civilization.In this work,a technoeconomic analysis was performed for a coal-to-carbon-fiber manufacture process developed at the University of Kentucky's Center for Applied Energy Research.According to this process,coal,with decant oil as the solvent,was converted to mesophase pitch via solvent extraction,and the mesophase pitch was subsequently converted to carbon fiber.The total cost to produce carbon fibers from coal and decant oil via the solvent extraction process was estimated to be $11.50/kg for 50,000-tow pitch carbon fiber with a production volume of 3750 MT/year.The estimated carbon fiber cost was significantly lower than the current commercially available PAN-based carbon fiber price($20-$30/kg).With decant oil recycling rates of 50％and 70％in the solvent extraction process,the manufacturing cost of carbon fiber was estimated to be $9.90/kg and $9.50/kg of carbon fiber,respectively.A cradle-to-gate energy assessment revealed that carbon fiber derived from coal exhibited an embodied energy of 510 MJ/kg,significantly lower than that of conventionally produced carbon fiber from PAN.This notable difference is primarily attributed to the substantially higher conversion rate of coal-based mesophase pitch fibers into carbon fiber,surpassing PAN fibers by 1.6 times.These findings indicate that using coal for carbon fiber production through solvent extraction methods could offer a more energy-efficient and cost-competitive alternative to the traditional PAN based approach.

摘要：Jerada coal mining generates extensive coal mine waste rock(CMWR)piles rich in valuable minerals,posing environmental challenges and economic opportunities.This study examines reprocessing feasibility through 3D geometallurgical charac-terization.Sampling used down the hole hammer drilling technique(DTH)and drone surveys for topographical precision.Over 620 samples from(T01,T02,T08)underwent comprehensive analyses including particle size distribution,x-ray fluorescence(XRF),total sulfur/carbon analysis(S/C),and inductively coupled plasma mass spectrometry(ICP-MS)for physical-chemical characterization.Mineralogical aspects were explored via optical microscopy(OM),X-ray diffraction(XRD),scanning electron microscopy(SEM),electron probe microanalysis(EPMA),and laser ablation inductively coupled plasma mass spectrometry(LA-ICP-MS).Quantitative mineral evaluation by scanning electron microscope(QEMSCAN)provided mineral insights.Chemical data was used in a 3D block model to quantify residual coal.Results for the three exam-ined CMWR piles(T01,T02,and T08)showed varying D80 from 160 to 300 μm,notable carbon content averaged 12.5 wt％(T01),16 wt％(T02),and 8.5 wt％(T08).Sulfur presence exceeded 1 wt％in T08,and potential environmental concerns due to iron sulfides.Anthracite liberation was below 30 wt％.3D modeling estimated a total volume of 7 Mm3,mainly from T08,equaling 11.2 Mt.With its high carbon content and substantial tonnages,re-exploitation or alternative applications could minimize these CMWR piles environmental impact.

摘要：To address issues such as inefficient top-coal drawing,challenges in simultaneously mining and drawing,and the need for intelligent control in extra-thick coal seams,this study examines the principles of top-coal drawing and explores automation and intelligent equipment solutions within the framework of the group coal drawing method.Numerical simulations were performed to investigate the impact of the Number of Drawing Openings(NDO)and rounds on top-coal recovery,coal draw-ing efficiency,and Top Coal Loss(TCL)mechanism.Subsequently,considering the recovery and coal drawing efficiency and by introducing the instantaneous gangue content and cumulative gangue content in simulations,the top-coal recovery,gangue content,and coal loss distribution when considering excessive coal drawing were analyzed.This established a foun-dation for determining the optimal NDO and shutdown timing.Finally,the key technical principle and automated control of a shock vibration and hyperspectral fusion recognition device were detailed,and an intelligent coal drawing control method based on this technology was developed.This technology enabled the precise control of the instantaneous gangue content(35％)during coal drawing.The top-coal recovery at the Tashan Mine 8222 working face increased by 14.78％,and the gangue content was controlled at～9％,consistent with the numerical simulation results.Thus,the reliability of the numerical simulation results was confirmed to a certain extent.Meanwhile,the single-group drawing method significantly enhanced the production capacity of the 8222 working face,achieving an annual output of 15 million tons.

摘要：To reveal the rock burst mechanism,the stress and failure characteristics of coal-rock strata under different advancing speeds of mining working face were explored by theoretical analysis,simulation,and engineering monitoring.The relationship between energy accumulation and release was analyzed,and a reasonable mining speed according to specific projects was recommended.The theoretical analysis shows that as the mining speed increases from 4 to 15 m/d,the rheological coefficient of coal mass ranges from 0.9 to 0.4,and the elastic energy of coal mass accumulation varies from 100 to 900 kJ.Based on the simulation,there is a critical advancing speed,the iteration numbers of simulation are less than 15,000 per mining 10 m coal seam,the overburden structure is obvious,the abutment pressure in coal mass is large,and the accumulated energy is large,which is easy to cause strong rock burst.When the iteration number is greater than 15,000,the static force of coal mass increases slightly,but there is no obvious rock burst.Based on engineering monitoring,the mining speed of a mine is less than 8 m/d,and the periodic weighting distance is about 17 m;as the mining speed is greater than 10 m/d,and the periodic weighting distance is greater than 20 m;as the mining speed is 3-8 m/d,and the range of high stress in surrounding rock is 48 m;as the advancing speed is 8-12 m/d,and the high-stress range in surrounding rock is 80 m.Moreover,as the mining speed is less than 8 cut cycles,the micro seismic energy is less than 10,000 J;as the mining speed is 12 cut cycles,the micro-seismic energy is about 20,000 J.In summary,the advancing speed is positively correlated with the micro seismic event;as the mining speed increases,the accumulated elastic energy of surrounding rock is greater,which is easy to cause rock burst.The comprehensive analysis indicates the daily advance speed of the mine is not more than 12 cut cycles.

摘要：The formation of coalesced fractures critically alters the mechanical properties of the surrounding virgin material,signifi-cantly changing the stress distribution and deformation behavior of the rock mass.However,understanding the generation mechanism and accurate prediction of rock fracture growth remain challenging in many engineering projects.Despite,wide range of conventional approaches including field investigations,laboratory-scale tests,and numerical modeling,the complex geological conditions hinder their accurate determination.This study introduces a new robust and cost-effective holistic geophysical approach to determine fractures propagation and predict failure in coal-rock masses at laboratory scale applicable across scales.The proposed approach combines rock mechanics and Acoustic Emission(AE)testing systems to make useful correlation between AE source parameters and deformation kinetics.This correlation analyzes the spatiotemporal distribution of AE events to elucidate the evolution of fracture patterns in coal-rock specimens from a complex mining project.Results showed dense and complex fracturing networks within coal specimens due to higher density,compaction,and mechanical strength compared to rock samples.This is indicated by peak acoustic events at 80％-100％load versus minimal events at 0-15％load.Simulated fracture patterns closely matched observed acoustic events,identifying key lineaments(macro-cracks)representing the transition from microcracks to macro-fractures.The convergence of these lineaments indicated intensely deformed zones prone to failure,consistent with previous field investigations.Acoustic parameters describing critical dam-age revealed an inverse relationship between stress and AE event magnitude.At roughly 70％σmax,a dramatic fall is seen in acoustic parameters indicated the shift from small-scale to large-scale microfractures,ultimately leading to catastrophic failure of the samples.Furthermore,Single Link Cluster(SLC)analysis demonstrated strong correlation among AE events,spatial correlation length(ξ)and information entropy(H).Both increased significantly at the onset of loading and fluctu-ated in proximity to ultimate failure.Using the micro-crack density criterion and 3D-crack growth theory,changes in above parameters verified the cracks transformation process.These findings showed that,the proposed approach compared with the conventional approaches,can improve disaster control and management plans,predict critical failures,and save lives in global mining projects when applied to field-scale studies.

摘要：To investigate the effect of saturation on the storage-dissipation properties and failure characteristics of red sandstone,as well as the energy mechanism of rockburst prevention by water,a series of uniaxial compression and uniaxial loading-unloading tests were conducted under five saturation levels.The effect of saturation on the mechanical properties and elastic energy density was analyzed,and a method for obtaining peak energy density was proposed.The effect of saturation on the energy evolution was examined,and the energy mechanism of water in preventing rockburst was revealed.The results indicate that an increase in saturation of red sandstone decreases the input energy density,elastic energy density,dissipated energy density,peak strength and peak strain;the compaction phase of the stress-strain curve becomes shorter;the failure mode transitions from X-conjugate oblique shear to single oblique shear;the variation in the debris ejection trajectory is as follows:radiation →X-ray →oblique upward parabola → horizontal parabola → oblique downward parabola;the degree of failure intensity and fragmentation is decreased gradually.Elastic energy density is interconnected with both saturation and stress but independent of the loading path.Saturation exhibits a dual effect on the energy storage property,i.e.,increasing satura-tion increases the energy storage efficiency and reduces the energy storage capacity.The ratio of peak elastic energy density to peak input energy density remains constant irrespective of saturation levels.Water prevents rockburst by decreasing the energy storage capacity of surrounding rock,alleviating the stress of surrounding rock to reduce energy storage,and elevat-ing the energy release threshold of high-energy surrounding rock.The findings of this study contribute to understanding the effect of water on rock failure from an energy perspective,as well as provide theoretical guidance for rockburst prevention by water in deep tunnels.

摘要：Abrasiveness as an intrinsic property of rocks defines the extent of wear or loss when interacting with other materials.In engineering sectors like hard rock mining and tunnelling,comprehending rock abrasiveness holds paramount importance due to its direct effect on tool wear during excavation.Among the diverse methods for assessing rock abrasiveness,the Cer-char abrasivity test emerges as the most widely used approach.Over time,the Cerchar test has garnered substantial attention from scholars,who have delved into the factors influencing test results due to testing conditions and examined the connection between the physical-mechanical parameters of rocks and their abrasiveness.Recent advancements in testing instrument have expanded our ability to measure additional parameters during rock cutting or drilling,yielding fresh insights for abrasiveness assessment,tool wear prediction,tool performance evaluation and rock excavatability estimation.The Cerchar abrasivity test,coupled with recent developments in testing instrument and parameter measurement,holds promising potential for enhanc-ing our comprehension of rock abrasiveness and its practical implications.This review systematically traces the evolution of the test.It commences with an overview of the test origin and progression,emphasizing its pivotal role in assessing rock abrasiveness.Furthermore,it consolidates and categorizes the research contributions from various scholars regarding the test.This includes enhancements and refinements of the testing apparatus,as well as investigations into various testing orientations and their effects on different types of rocks.Moreover,this review illuminates the broader applications and interdisciplinary possibilities of this test,not only in material science but also in tribology.It underscores how the insights gleaned from the Cerchar test can be extrapolated to diverse areas of research beyond the scope of rock engineering.

摘要：The complex and diverse nature of coal mining sites,including different landforms and working conditions,presents chal-lenges for rehabilitation efforts.To address this,we conducted a comprehensive experimental study focusing on microbially induced calcium carbonate precipitation(MICP)remediation,considering the fracture characteristics of coal mining sites.The MICP-restored samples were subjected to confined/unconfined compressive strength,uniaxial/triaxial permeability,and souring tests to assess their restoration efficacy.The results showed that under similar mining conditions,the average depth of parallel fractures was 0.185 m for loess ridges,0.16 m for the valley,and 0.146 m for the blown-sand region,while the average depth for boundary fractures was 0.411 m for loess ridges,0.178 m for the valley,and 0.268 m for the blown-sand region.Notably,parallel fractures showed negligible filling in all landforms,whereas boundary fractures in the blown-sand region were completely filled with wind-deposited sand.The valley landform was filled with alluvium and wind-deposited sand,whereas the loess landform was filled with wind-deposited sand and loess.MICP-restored soil samples in all landforms achieved a strength comparable to remolded fracture-free soil samples.Across all landforms,the maximum permeability coefficient of MICP-restored soil samples closely matched that of remolded fracture-free soil samples.Under similar topo-graphic and rainfall conditions MICP restorations scoured 31.3 g on blown-sand region,19.3 g on loess ridges,and 17.6 g on valleys.These research findings provide an experimental foundation for MICP repair of coal mining ground fractures.

摘要：A kind of slow deformation wave is produced in the crust under the action of internal and external factors,which plays an important role in the formation and occurrence of earthquakes.In this paper,uniaxial compression tests are carried out on red sandstone samples with uniform texture.Displacement controlled loading methods are adopted,and the loading rates are 0.1 mm/min,0.5 mm/min and 1.0 mm/min,respectively.The micro-characterization method of speckle photography and DIC processing technology are adopted.The transfer characteristics of slow deformation and strain localization of red sandstone specimens during loading and deformation are discussed.The results show that the boundary advance velocity is proportional to the slow deformation transfer velocity with the change of position,so it can be considered that the slow deformation transfer velocity is equal to the particle motion transfer velocity.The formation and development of sample strain localization may be determined by the flow channel,nucleation and Luders zone evolution.The formation of the Luders band is related to the maximum value of the flow channel,and as deformation increases,the Luders band merges and develops with the maximum value of the nearby flow channel.By applying different loading rates,the influence of loading rate on the average transfer velocity of slow deformation was obtained;the slow deformation wave during seismic migration has similar characteristics to the deformation transfer in the experiment,therefore the research results have reference significance for further studies on the evolution characteristics of slow deformation waves and seismic migration.