Abstract:In order to accurately quantify and predict the evolution of slope stability of fault-containing slopes under the long-term effect of blasting vibration,and to realize the safe,efficient and sustainable mining of open-pit mines.Taking an open-pit mine as the engineering background,the dynamic characteristics of blasting seismic waves in time and space dimensions are investigated by on-site vibration test-ing and numerical calculations,and the propagation and attenuation laws of blasting seismic waves in the horizontal and vertical directions are studied to elucidate the mechanism of elevation amplification effect and the vibration isolation effect of faults;Hopkinson compres-sion rod impact test is used to study the crack expansion and damage deterioration laws of slope rock and soil bodies under the effect of cyclic blasting impacts.Established the quantitative relationship between the intensity and frequency of blasting vibration and the internal damage of the rock body,and established a dynamic damage degradation mathematical model of the slope geotechnical body;applied FLAC3D numerical simulation to study the characteristics of the dynamic response of the slope under the action of blasting vibration,and analyzed the potential landslide mode of the slope and the mechanism of destabilizing evolution,and put forward the calculation method of the stability of the slope containing faults under the action of blasting vibration,and analyzed the effect of the blast vibration on the stabil-ity of the slope quantitatively.Quantitatively analyze the effect of blasting vibration on slope stability,predict the number of blasting vibra-tion that the slope can withstand.The results show that:blasting vibration has a greater impact on slope stability,the maximum dynamic stress response of the slope under the action of blasting vibration is positively correlated with the amount of single shot,elevation differ-ence,and negatively correlated with the center of the blast distance;with the increase of the maximum dynamic stress of blasting vibration and the number of blasts,the damage parameter is an exponential function of the damage parameter is larger,and the rate of reduction of the dynamic-static coefficient of safety of the slope is a trend of the power function of the increase.Combined with engineering examples,it verifies the reasonableness of the calculation method of slope stability of fault-containing slopes under the action of blasting vibration,and provides a new perspective for the evaluation of slope stability of similar mines.

Abstract:Due to complex geological conditions and unevenly artificial lighting in underground coal mines,surveillance video images of-ten exhibit non-uniform illumination,detail loss,and low contrast.Moreover,existing enhancement algorithms frequently introduce color distortion and halo artifacts during processing.To address these issues,a mine image enhancement algorithm based on multi-scale fast bi-lateral filtering and wavelet fusion is proposed.First,homomorphic filtering is applied to preliminarily enhance the image and convert it into HSV space,where the hue component remains unchanged.A multi-scale fast bilateral filter is then constructed to extract the illumina-tion component from the brightness channel,and a dual gamma correction function is employed to enhance the illumination component.The reflection component,estimated according to Retinex theory,is further enhanced using a grayscale adjustment function and the Con-strained Contrast Adaptive Histogram Equalization(CLAHE)algorithm.Illumination and reflection components are subsequently fused by wavelet transform to obtain the enhanced brightness channel.In addition,a saturation correction function is designed to improve the satur-ation component and enhance the overall color representation of the mine image.Finally,the enhanced brightness and saturation compon-ents are combined with the hue component and transformed back from HSV to RGB space.Experimental results demonstrate that,com-pared with BPDHE,CLAHE,NPE,SRIE,BIMEF,and PnPRetinex algorithms,the proposed method achieves respective improvements of 25.31%,42.75%,9.59%,1.60%,and 41.26%in objective evaluation metrics including mean,average gradient,standard deviation,inform-ation entropy,and spatial frequency.The method effectively enhances illumination,details,and contrast of mine images while suppressing halo artifacts and color distortion.Moreover,when extracting illumination components,multi-scale fast bilateral filtering achieves an aver-age speed improvement of 87.29%compared with the classical bilateral filter.When YOLOv8 is applied to the enhanced images of mine workers,an average detection accuracy of 90%is obtained,representing a 40%increase compared with the original images and signific-antly improving the accuracy of intelligent detection.

Abstract:The mechanical and deformation behavior of deep high-stressed coal seams under ambient disturbance is different from that of shallow coal seams.Based on this,the effects of various disturbance schemes i.e.,high-pressurized water injection,depressurized borehole and cyclic loading-unloading,on failure mechanical behavior of gas-bearing coal under high confining pressure constraint are investigated experimentally.The results show that high-stressed coal tends to ductile state transformation without significant post-peak stress drop.Deep high-stressed coal dominated by shear and tensile fracture exhibited post-peak linear dilatancy behavior.Compared with the pure mechanical failure,the strength of coal with horizontal borehole and pressurized water is decreased by 29.1%and 4.1%,respectively,and their degradation mechanisms for coal strength and mechanical properties were different.The former is induced by the continuous in-crease of vertical deformation,resulting in borehole collapse and compaction zone formation.The latter is induced by pressurized water counteracting the normal stress of fracture surface,which promotes the rapid expansion of coal in horizontal direction,resulting in its dilatancy instability and subsequent shear failure.The dilatancy coefficient β=-1.524<0 at peak stress of coal within horizontal borehole also indicates that it is in a compacted state.The single yield surface model is used to prove the rationality of the post-peak compaction be-havior of high-stressed coal within horizontal borehole.The loading-unloading disturbance at constant amplitude plays a cyclic reinforce-ment effect on the mechanical properties of elastic high-stressed coal,and its strength is increased by 18.0%-27.0%with significant post-peak dilatancy.Due to the greater influence of unloading on coal deformation,the irreversible compaction strain(ΔεH,ΔεvandΔεh)in-creases with the increasing loading times,and manifests as strain hardening with the compression trend in all directions,which is contrary to the fatigue damage induced by cyclic loading-unloading on rock.The research results can provide reference for major engineering is-sues such as deep high-energy coal seam risk solving,three-dimensional fracture network reconstruction and seepage assessment.

Abstract:In-situ pyrolysis of tar-rich coal is an innovative coal utilization method that heats coal seams by isolating air to extract oil and gas resources.This approach plays a crucial role in improving domestic oil and gas supply and ensuring national energy security.To in-vestigate the temperature distribution pattern during the in-situ pyrolysis of tar-rich coal,a self-designed pyrolysis experimental apparatus was used to simulate the temperature field evolution in the underground pyrolysis process of tar-rich coal.Scanning Electron Microscopy(SEM)and 3D Microscopy(3DM)were employed to analyze the temperature response and thermal relaxation characteristics of the tar-rich coal seam and its overburden,revealing the heat transfer mechanisms within the strata during the pyrolysis process.The results show:Dur-ing the pyrolysis of tar-rich coal,the temperature at different locations increases non-linearly with time.The temperature variation in the coal seam and overburden follows a similar pattern,with diffusion in the vertical direction occurring faster than in the horizontal direction.Both the coal seam and overburden exhibit significant thermal relaxation.The temperature in the central area is higher and increases rap-idly,while the temperature at the periphery is lower with a slower rate of increase.The extent of thermal relaxation is related to the aniso-tropy of the coal-rock body and spatial position.The further the distance from the central axis of the pyrolysis zone,the longer the second-ary heating time of the strata.During the pyrolysis process,the development of pores and fractures in the pyrolyzed semi-coke,along with an increase in fracture network density,reduces the thermal conductivity of the tar-rich coal,forming sealed spaces and causing the reten-tion of pyrolysis tar within the coal matrix.At the same time,due to the high density and viscosity of the pyrolysis tar,it condenses in the lower sections of the coal seam and low-temperature areas,causing partial cementation of the semi-coke into lumps and forming insulat-ing layers.This reduces heat transfer efficiency,impacts the depth and rate of the pyrolysis reaction,and leads to a conical temperature dis-tribution pattern in the coal and overburden.The research findings provide significant theoretical support for the engineering practice of in-situ pyrolysis of tar-rich coal.

Abstract:Artificial cooling technology is one of the most effective methods for deep well heat damage management.The current cooling method is dominated by all-air cooling,which reveals many problems such as cooling effect of"near-cold and far-hot",huge energy con-sumption and so on,which is contrary to the national green mine development strategy.The assembled convection-radiation cooling sys-tem is a kind of local cooling device integrating support and cooling,which can be installed in the area of the working face that needs to be cooled to create a local comfortable thermal environment.In order to study the cooling effect of the assembled convection-radiation refri-geration system,theoretical analysis and CFD simulation methods were used to obtain the mathematical model of the system's cooling ca-pacity;the cooling mechanism of the system was analyzed to optimize the operating conditions;and the cooling effect of the system was evaluated by taking the working face of Zhangshuanglou Mine 7119 as an example.The results show that:the combination of assembled high-temperature mine convection-radiation cooling system and side-helm support system can realize the synchronization of roadway min-ing,support and environmental improvement,and improve the production efficiency and environmental comfort.The optimal operating conditions of the assembled high-temperature mine convection-radiation cooling system are as follows:the refrigerant flow rate is 0.2 m/s,the inlet air velocity is 0.6 m/s,the height of the air outlet is set at 60 mm,and the cooling capacity of the system is 269 W.The cooling ca-pacity of the system is 0.2 m/s,the inlet air velocity is 0.6 m/s,and the height of the air outlet is set at 60 mm.The cooling effect of the as-sembled high-temperature mine convection-radiation cooling system(to meet the demand for comfort)has been improved by 31%com-pared with the all-air type cooling method of the roadway,which can meet the demand for comfortable environment for the adapted work-ers in the quarry within the mining depth of 2000 m,and the system is able to maximize the thermal safety of the miners.At the same time,according to the cooling needs of the site,adjust the equipment installation spacing,local environmental control,and greatly save cooling energy consumption.The research can be used to guide the local environmental control of the mine quarry,the efficient and pre-cise cooling of the intelligent less manned working face,and the protection of miners'occupational health,which fully responds to the na-tional development strategy of green mines and helps the realization of the national dual-carbon goal.

Abstract:In order to reveal the pressure distribution and fluid migration law of the gas lift reverse circulation washing flow field in drilling method,the ø5m advanced drilling of the north wind well in Taohutu coal mine was taken as the research background.Based on the relevant theories of fluid mechanics,a pressure mathematical model of the gas lift reverse circulation washing flow field was estab-lished,and the theoretical analytical solutions of the fluid pressure in the drill pipe annulus,bottom hole and inside the drill pipe were giv-en.Secondly,the CFD-DEM method(coupling computational fluid dynamics and discrete element method)was used to establish a numer-ical model of gas lift reverse circulation multiphase coupling well cleaning,verifying the correctness of the pressure model of the well cleaning flow field and obtaining the migration law of the fluid in the well cleaning flow field.Finally,based on the pressure mathematical model and theoretical analytical solution of the well cleaning flow field,the influence of factors such as gas content,mud density,mud vis-cosity,rock slag density,and slag content on the pressure of the well cleaning flow field was explored.The results indicate that:The aver-age radial flow velocity of the horizontal bottom hole fluid of the truncated cone drill bit is greater than the tangential flow velocity and the axial flow velocity;Rock debris undergoes dynamic cyclic transport at the bottom of the well,including spiral downward movement,accu-mulation at the bottom of the well,propulsion and suspension,adsorption and lifting.It is transported in the form of"low flow rate,high density"and"high flow rate,low density"in the liquid-solid and liquid-solid gas sections inside the drill pipe,respectively.The fluid pres-sure inside the drill pipe decreases approximately linearly along the wellhead direction.At the gas injection end,the fluid pressure drops sharply,and the pressure difference inside and outside the drill pipe reaches its maximum;The fluid pressure at the bottom of the well shows a trend of"first slightly decreasing,then significantly decreasing"from the outside to the inside,with a greater decrease in fluid pressure and rate in the effective adsorption zone at the bottom of the well.The gas content,mud density,and fluid pressure difference in-side and outside the drill pipe are positively correlated,while mud viscosity,rock slag density,liquid-solid and liquid-solid gas section slag content are negatively correlated.The sensitivity of various factors to the fluid pressure difference inside and outside the drill pipe can be summarized as follows:mud density>gas content>rock slag density>mud viscosity>liquid-solid section slag content>liquid-solid gas sec-tion slag content.The research results can provide useful theoretical references for solving the technical problem of low efficiency of gas lift reverse circulation well washing in Jurassic strata drilling method.

Abstract:Aiming at the problems of energy waste and low transportation efficiency caused by continuous high-speed operation of scraper conveyor in fully mechanized mining face,this paper combined with two-way coal cutting technology,systematically analyzed the opera-tion stage of scraper conveyor,established the energy consumption model of scraper conveyor,and proposed a speed control method based on load torque prediction and energy consumption optimization.Firstly,a coal quantity model is established to describe the dynamic char-acteristics of coal quantity changing with operating conditions.Then,according to the running resistance characteristics of the scraper con-veyor,the relationship between coal volume,driving force and running resistance is defined,and the energy consumption model of the scraper conveyor is built.In order to cope with the complex and variable operating conditions of fully mechanized mining face,a rough ra-dial basis neural network(RRBFNN)is introduced in this paper to accurately predict the load torque of the scraper conveyor and generate the key input variables required for the optimization model.On this basis,the improved particle swarm optimization algorithm(PSO)is used to optimize the running speed of the scraper conveyor with the goal of minimizing energy consumption.The improved algorithm bal-ances the global search and local search capabilities while introducing dynamic inertia factor,thus improving the optimization accuracy and convergence efficiency.Finally,the proposed method is validated with the actual data of Yujialiang 43101 fully mechanized mining face.The results show that the speed control method can effectively reduce the energy consumption of the scraper conveyor by 10.42%in one production cycle.

Abstract:A new kind of modified acrylic grouting material has been developed to address the limitations of traditional inorganic cement-based grouting materials in sealing fine pores,as well as the shortcomings of chemical grouting materials such as polyurethane and epoxy resin in terms of durability,cost,and environmental impact.This grouting material not only has strong permeability and good groutability,but also has low cost.The effects of retarder dosage and reaction temperature on the gel time of modified acrylate grouting material were studied in order to optimize the formula to adapt to different engineering conditions.By adjusting the mass fraction of lotion,the com-pressive strength,elongation at break and storage stability of sand consolidation body of slurry were evaluated,and the optimal mass frac-tion of lotion was determined to be 20%.In addition,the influence of acrylic lotion with different glass transition temperature on the prop-erties of grouting materials was compared to expand its application range.The results show that under the condition of water bearing sand layer,the best sand consolidation and water blocking effect is achieved when the water content of the slurry is below 89%.In water envir-onments with different pH values,the reaction rate of the slurry is slower in acidic environments and fastest in alkaline environments.The prepared modified acrylic grouting material can effectively fix sand and seal leaks,ensuring that the sealed sandstone maintains excellent compressive strength,providing a new technological approach for safe mining in coal mines.

Abstract:Physical model experiments are an important research method to reveal the mechanism of coal rock dynamic disasters,and the preparation of coal like physical model materials is the key to laying similar coal seams.For dynamic disasters such as coal and gas out-bursts,water inrush,etc.caused by fluid solid coupling and temperature loss,simulating the permeability performance of materials is the key to the experiment.To reasonably evaluate the similarity between simulated material permeability and raw coal,a method of using Pearson correlation coefficient between material pore structure and permeability during loading and unloading process for similarity evalu-ation was proposed,and coal like materials were configured for experimental verification.The results showed that:Correlation coefficient P can effectively reflect the similarity of the permeability performance between raw coal and coal like materials during the loading and un-loading process.The minimum correlation coefficients P for the porosity,permeability,and compressibility coefficient(CP)of the two coal samples were 0.624,0.913,and 0.888,respectively.The permeability performance remained strongly similar or extremely similar in over-all changes.During the loading and unloading process,the porosity and permeability of both coal samples are negatively correlated with confining pressure,and the permeability is highly sensitive to stress.CP of the two coal samples is negatively correlated with confining pressure,and CP value during unloading is higher than that during loading.The research results provide a basis for evaluating the similar-ity of permeability performance of coal like physical model materials,and have guiding significance for conducting physical model experi-mental research.

Abstract:In underground coal mine environments,factors such as suspended coal dust and artificial light sources often lead to low bright-ness or uneven illumination in surveillance video images,resulting in severe image degradation.Existing underground image enhance-ment methods are not ideal and may cause issues like overexposure at near light points and distortion at far light points.To address this,we propose an image enhancement method for non-uniform illumination in underground coal mines based on the glow model and SRLLIE al-gorithm.This method consists of three main parts:using the glow model for exposure reduction,generating illumination and reflectance maps with the SRLLIE algorithm,and optimizing the illumination map to obtain the enhanced image using the Retinex model.First,the glow model is applied to remove the influence of glare in the image,avoiding overexposure and resulting in a low-illumination image without glare.Based on this,the objective function of the low-illumination enhancement SRLLIE algorithm is improved,and the alternat-ing direction method of multipliers(ADMM)is used for iterative solving to obtain the illumination and reflectance maps that suppress overexposure while preserving structural details and removing low-light noise.Then,the illumination map is optimized using an S-shaped gamma correction function,further suppressing overexposed areas and enhancing the brightness of low-illumination regions.Finally,ac-cording to the Retinex theory,the optimized illumination map is multiplied by the denoised reflectance map to obtain the final enhanced image.To verify the effectiveness of the proposed algorithm,comparison experiments with relevant methods are conducted.The experi-mental results show that the proposed algorithm outperforms others in overall image quality,significantly enhancing image contrast,ef-fectively solving the problem of uneven illumination in underground coal mine images,and improving the clarity of surveillance images.This provides valuable decision support for coal mine safety production and the construction of intelligent mines.

Abstract:Hydraulic shearing is an important method in the development of hot dry rock geothermal energy.Studying the differences in the acoustic emission spectrum during fault slip in hot dry rock reservoirs with and without fluid involvement is of great significance for the impact range of hydraulic shearing engineering in hot dry rock geothermal exploitation and the site selection of production wells.To gain a deeper understanding of the acoustic emission frequency spectral characteristics during the shear slip process of granite fractures un-der different hydraulic coupling effects,a self-developed high-confining pressure large-displacement real-time dynamic shear-seepage test-ing device is used to conduct shear tests on dry and water-injected granite fracture samples,with the water in jection pressure gradient set to 5,6,and 8 MPa.The results indicate that normalized main frequency amplitude and ring count rate can effectively characterize the slid-ing characteristics during water injection.The acoustic emission signals produced by the dry fracture surfaces during the stick-slip process have significantly higher normalized main frequency amplitude and ring count rate compared to those of water-injected fracture surfaces.Moreover,as the water injection pressure increases,these two parameters show a negative correlation with the water injection pressure.Spectral analysis results indicate that water injection reduces the main frequency and amplitude of the acoustic emission signals.The acoustic emission signals of water-lubricated friction are generally lower in these two parameters compared to dry friction,and both the main frequency and amplitude decrease as the water injection pressure increases.The frequency of low-amplitude acoustic emission sig-nals and the main frequency are both affected by the water injection pressure,with the frequency of acoustic emission signals increasing as the water injection pressure increases,while the main frequency shows a decreasing trend.The reduction in the intensity of AE signals and the increase in the number of low-amplitude AE signals can be used as criteria to determine whether there is fluid involvement in fault slip.

Abstract:The illegal mining activities in the Muli Coalfield have severely damaged the ecological environment of the Qilian Mountains,which has aroused great concern of the Party Central Committee.This study analyzes the spatiotemporal differentiation patterns of vegeta-tion coverage in the entire Muli Coalfield and its four sub-mining areas(Jiangcang,Duosuo Gongma,Juhugeng,and Hushan)from 2019 to 2023,using Normalized Difference Vegetation Index(NDVI)remote sensing data.By integrating spatial-temporal comparison analysis,zoning statistics,trend analysis,and change detection methods,it evaluates the vegetation restoration outcomes of ecological restoration projects.Through regression analysis,residual analysis,quantile-based threshold classification,and comaparison analysis,the study dis-sects the driving mechanisms of NDVI variations spatially and temporally.It quantitatively identifies regions where human activities exert significant influences on NDVI and clarifies the net effects and regional disparities of ecological restoration interventions.The results show that:The average NDVI across the entire region increased from 0.58 to 0.62,with an annual growth rate of 6.9%.Among all sub-re-gions,the Juhugeng mining area showed the most significant vegetation restoration effect:its average NDVI rose from 0.38 to 0.51,and the proportion of area with high vegetation coverage(NDVI>0.5)increased from 36.7%to 54.2%.The area with significant NDVI im-provement between consecutive years exhibited a trend of initially increasing and then decreasing:the proportion of areas with significant NDVI increase in the Juhugeng and Jiangcang mining areas peaked during 2020-2021,reaching 26.1%and 13.1%respectively;while the Duosuo Gongma and Hushan mining areas reached their maximum values during 2021-2022,with proportions of 21.7%and 10.7%re-spectively.In terms of impact mechanisms,topography had stronger explanatory power for the spatial differentiation of NDVI than climat-ic factors.The proportions of areas where human activities exerted positive impacts on the temporal changes of NDVI in Juhugeng and Duosuo Gongma mining areas were 25.1%and 11.6%respectively,significantly higher than that in the surrounding areas(5.0%),high-lighting the dominant role of ecological restoration projects in improving vegetation coverage.The proportions of significant negative im-pacts in the above-mentioned mining areas(4.4%,6.2%,4.5%)were close to that in the surrounding areas(5.0%),indicating that ecologic-al restoration projects did not additionally exacerbate vegetation degradation.In summary,the ecological restoration projects in Muli Coalfield significantly improved vegetation coverage in the mining areas,but there existed regional heterogeneity and ecological vulnerab-ility.The negative impacts of human activities were within a controllable range and did not pose a significant obstacle to the overall pro-cess of ecological restoration.The ecological restoration of Muli Coalfield is not a one-time effort.In the future,it is necessary to formu-late differentiated dynamic monitoring and maintenance strategies for different mining areas,with special attention to areas with low ve-getation coverage and severe degradation.It is essential to explore the causes,adjust restoration measures in a timely manner,and strictly control the negative interference of other human activities to effectively cope with potential risks of ecological degradation and continu-ously consolidate the achievements of ecological restoration.These research outcomes not only provide practical technical methodologies for monitoring vegetation changes and evaluating restoration effectiveness in mining areas but also offer a replicable technical paradigm for ecological restoration efforts in the Muli Coalfield and other alpine mining regions.

Abstract:The accurate determination of the degree of mechanical property degradation of rock layers after hydraulic fracturing is the basis for revealing the pressure relief mechanism of hydraulic fracturing and evaluating the fracturing effect.To reveal the degradation law of rock hydraulic fracturing mechanical properties,a two-stage scheme of true triaxial hydraulic fracturing physical model experiment and rock mechanics testing experiment was designed separately In order to study the degradation law of mechanical properties of rock layers before and after hydraulic fracturing,a two-stage plan of true triaxial hydraulic fracturing physical model experiment and rock mechanics testing experiment was designed.CT scanning was used to reconstruct the three-dimensional morphology of fractures.Through true triaxi-al hydraulic fracturing physical model experiment,rock specimens containing hydraulic fracturing fractures were prepared;Uniaxial and triaxial compression tests,as well as Brazilian splitting tests,were conducted on rock specimens containing hydraulic fracturing fractures.The research results indicate that grooving can effectively reduce the pressure of crack rupture,increase the width of the groove,and im-prove the probability of crack initiation.However,if the groove spacing is too small,cracks are prone to merge;The higher the viscosity of the fracturing fluid,the faster the pumping pressure rises,and the higher the fracture pressure;The lower the displacement,the greater the proportion of liquid filtration,and the lower the crack rupture pressure.After the displacement increases,the crack initiation pressure signi-ficantly increases,and the time required for initiation is shorter.After hydraulic fracturing,the reduction coefficients of internal friction angle,cohesion,and tensile strength of the rock are 0.896,0.996,and 0.295,respectively;The relationship between the reduction coeffi-cient of elastic modulus was obtained.With the increase of confining pressure,the elastic modulus of both samples showed an increasing trend,and the growth rate gradually slowed down.However,the reduction coefficient showed a decreasing trend with the increase of con-fining pressure,but the rate of decrease slowed down;The tensile strength of the sample decreased by 70.49%after fracturing,which was 2.39 times that of the sample after fracturing.The significant decrease in tensile strength of the sample indicates that fracturing causes cracks and damage inside the sample.The standard deviation before and after fracturing increased by 1.87 times,indicating that the frac-turing process generates a large number of unevenly distributed cracks inside the sample,and there are significant differences in the num-ber and distribution characteristics of micro cracks,resulting in significant mechanical differences in the sample.

Abstract:Mechanical behaviors of deformation,rupture,and ejection failure of coal with impact inclination under uniaxial compression were investigated.Uniaxial compression tests were conducted on coal with impact inclination at different loading rates.The classification characteristics of post-peak stress drop in coal samples have been identified.Based on the 3D reconstruction of the primary fracture of coal samples through CT scanning,the distinct mechanisms of instability failure of coal samples with various stress drop types are analyzed.Based on the non-contact full-field strain measurement results,the pre-peak and post-peak fracture evolution and the fracture-ejection rule of coal samples are analyzed.The stress change and transformation characteristics of the coal sample ejection region are statistically calcu-lated.The ejection mode of the coal body is disclosed,and the classification characteristics of the fracture-ejection and the stress drop type of the coal sample ejection mode are obtained.Additionally,the correlation between the existing impact tendency index of coal sample and the impact kinetic energy of post-peak ejection is analyzed,and Wsdr is established to characterize the intensity of post-peak ejection of coal sample.The results show that:Post-peak stress drop of coal samples can be divided into three types:continuous drop,stepped drop and in-stantaneous drop,and the post-peak stress drop type of coal samples is closely related to the development of primary fractures.Surface crack propagation before the impact inclined coal ejection has the nonlinear characteristics of slow and accelerated crack propagation,and the incubation time of classⅠ,classⅡand classⅢimpact ejection decreases successively.Coal with impact inclination can be classified into local ejection,regional through-out ejection and global instability ejection.Coal samples of ClassⅠ,ⅡandⅢare dominated by loc-al ejection,regional through-out ejection and global instability ejection respectively.The coal sample has two types of ejection modes:par-ent power source and ejection block power source.The same stress drop type coal sample can be caused by parent power source or ejec-tion block power source.Proposed index Wsdr has a linear positive correlation with the ejection kinetic energy.

Abstract:In the sealing section of double-prevention boreholes along the coal seam,the coal mass is characterized by a significant pres-ence of pores and fracture structures,forming seepage channels through which air from the roadway infiltrates the extraction boreholes,thereby affecting the gas extraction efficiency.Based on the structural characteristics of the coal mass in the sealing section of double-pre-vention boreholes,a self-developed triaxial permeability testing platform for coal was utilized to design and conduct permeability experi-ments on coal samples with combined pore-fracture structures.The experiments measured and calculated parameters such as porosity,gas seepage velocity,pressure gradient,permeability,and effective stress during the permeability process.The influence of effective stress on coal permeability was analyzed,and the permeability behavior of coal in the sealing section of double-prevention boreholes was explored.The results indicate that:Under the action of stress,the skeletal structure within the fractured coal sample undergoes deformation,with in-ternal particles experiencing dislocation and further fracturing.This reduces the number of gas seepage channels,leading to a decrease in permeability.As the load continues to increase,the coal structure becomes relatively compacted and densified,and the sensitivity of per-meability to changes in porosity diminishes,gradually stabilizing.The pressure gradient shows a significant decreasing trend with increas-ing seepage velocity.At low seepage velocities,the relationship between the two exhibits a clear Darcy phenomenon.At higher velocities,the seepage velocity-pressure gradient curve gradually deviates from linearity,conforming to the Forchheimer relationship.Gas flow in the sealing section of double-prevention boreholes is partitioned between the fractured zone and the broken zone of the coal mass.When gas flows through coal with a single pore size,it creeps along the surface of the coal particles,and changes in the structure of the seepage chan-nels have a relatively small impact on resistance.However,at the transition interface of coal with dual-combination pore sizes,abrupt changes occur in the pore structure of the coal mass.During the gas permeation process,the flow velocity is redistributed,generating addi-tional inertial resistance and causing significant fluctuations in nonlinear laminar flow.Effective stress can effectively characterize the in-hibitory effect on seepage velocity.As effective stress increases,sliding between fractured coal particles and deformation or breakage of the particles themselves may occur,resulting in continuous compaction and densification of the skeletal structure.This leads to the closure of pore seepage channels and a linear decrease in gas seepage velocity.A pore-throat expansion-contraction model was developed to theor-etically analyze the relationship between effective stress and seepage velocity,with experimental results aligning well with theoretical pre-dictions.Effective stress is the key factor causing changes in coal permeability.The permeability k of the sample decreases with increas-ing effective stress σe.At the interface of dual-pore-size combined coal media,significant differences in pore structure result in pro-nounced nonlinear fluctuations in gas flow.These fluctuations also lead to greater variations in coal permeability with changes in effective stress.The above research indicates that the degree of coal fragmentation during gas migration can characterize the permeability properties of the coal seam,serving as a basis for quantifying the structural parameters of the coal in the sealing section of double-prevention bore-holes.This provides important theoretical guidance for optimizing borehole arrangement and grouting parameters in the sealing section of double-prevention boreholes along the coal seam.

Abstract:Compared to conventional observation stations,continuous GNSS monitoring stations in mining areas can better capture dy-namic subsidence characteristics of the ground surface.However,the practical application is constrained by the excessive number of GNSS stations required and the high associated costs.To explore the feasibility of constructing surface dynamic subsidence models using con-tinuous GNSS observations from a limited number of stations,the surface subsidence monitoring project in the Loess Plateau mining area was used as a case study.By plotting dynamic subsidence curves and their corresponding velocity and acceleration variation curves,it was found that their distribution characteristics closely matched those of the Boltzmann angular function and its first-order and second-order derivatives.Therefore,the Boltzmann angular function with its"S-shaped"distribution characteristic was selected to construct the surface dynamic subsidence model.Two parameters-the relative position angle x and eccentricity angle y-were introduced to describe the relative positional relationship between monitoring stations and the dynamic boundary of the working face.The four parameters of the Boltzmann model(A1,A2,a,b)were inverted using GNSS time-series observation data,and the physical significance and variation characteristics of each parameter were elucidated.Based on this,a Boltzmann model for surface dynamic subsidence was constructed using GNSS time-series observation data acquired during the working face advancement.Analysis of how model parameters vary with the working face ad-vancement position(parameter x)revealed that these parameters'temporal changes tend toward stable values as surface subsidence in-creases.This model enables precise prediction of subsequent subsidence.Further analysis revealed that the spatial variation of Boltzmann model parameters across GNSS stations on the main fault plane conforms to Gaussian distribution characteristics.Observation data from no fewer than five GNSS stations can stably fit Gaussian function parameters,enabling the establishment of a Boltzmann prediction model for dynamic subsidence at any surface point.Field data validation demonstrates that the Boltzmann model constructed from time-series ob-servations at a small number of stations(no fewer than five)exhibits excellent parameter determinacy and prediction accuracy.This provides an effective approach for dynamic monitoring and prediction of surface subsidence in western mining areas.

Abstract:The seepage effect of leaching solution in the process of in-situ leaching mining may lead to the deterioration of the mechanical properties of the aquifuge,and affect the safety of coal uranium co-mining.Taking the conglomerate aquifuge of Jurassic Zhiluo Forma-tion in Inner Mongolia as the research object,the physicochemical properties and mechanical deterioration mechanism under acid leaching environment were discussed.The mass and metal cation concentration of tometer.The variation characteristics of mineral composition and microstructure conglomerate in sulfuric acid solution were measured by electronic balance and atomic absorption spectropho of conglom-erate with immersion time were analyzed by XRD and SEM.Triaxial compression tests were carried out to study the mechanical response of conglomerate under different immersion time.The evolution laws of parameters such as peak stress,elastic modulus,axial strain and dissipation energy density were analyzed.The coupling relationship between mechanical parameters and physicochemical parameters was quantified based on correlation analysis.The results show that the mass of conglomerate first increases and then decreases with the acid etching time.The concentration of metal cations in the solution is consistent with the mass change trend,and the concentration of Ca2+is the highest,indicating that the chemical reaction between calcite and sulfuric acid is an important factor leading to the deterioration of mechanical properties of conglomerate.Acid corrosion gradually dissolves the conglomerate cement,expands the internal fractures,and increases the pores,resulting in changes in the rock microstructure.The peak stress,elastic modulus and yield stress of the conglomerate increased briefly in the initial stage(1 d)and then gradually decreased.After 20 days of immersion,the peak stress decreased by 26.69%compared with the natural state,and the peak volumetric strain decreased significantly,indicating that the specimen changed from brittle failure to ductile failure mode.The growth rate of dissipative energy density in the post-peak stage presents the characteristics of"slow-fast-slow",and the failure process of the specimen is more gentle under the action of long-time acid leaching.The peak stress,elastic mod-ulus and total strain energy density have a strong positive correlation(r>0.8),and the metal cation concentration can be used as a character-ization parameter for the deterioration of mechanical properties of conglomerate.

Abstract:In order to improve the dust removal efficiency of the long-pressure and short-pumping local ventilation excavation face,the distribution characteristics of the wind flow field of the excavation face and the dust control effect of the whole process of cutting and tun-neling of the comprehensive excavator was quantitatively analyzed,and the optimal deployment position of the dust removal duct in the excavation roadway section was optimized.Firstly,according to the force analysis of dust particles under the action of wind flow,the dust particle movement model in the roadway wind flow considering the dust flow characteristics such as the roadway wind flow state and particle size was constructed.The section of the excavation face was divided into nine dust-producing areas to truly restores the dust-gen-erating process in the cutting process of the excavation face.Tthe N-S model and model of the wind flow field of the fully mechanized ex-cavation face combined,the numerical model of wind flow and dust migration of the fully integrated excavation face under the whole pro-cess of cutting and tunneling of the comprehensive excavator was established by taking the Baode coal mine 81205 Glue Transportation Slot comprehensive excavation face as the research object.On this basis,the dust removal ducts were simulated and analyzed under the conditions of different dust source areas,which were located in the"upper position of the roadway","the upper position of the roadway side gang"and the"middle position of the roadway side gang"under the conditions of different dust source areas.The results showed that the dust migration and diffusion in the roadway under the conditions of dust generation sources in different cutting areas showed obvious differences,and the change trend of dust migration and diffusion under the simulated conditions was basically the same,indicating that the subdivision of dust sources in the head-on section of the excavation face by the palace grid cutting method was more sand experimental uitable for the actual cutting and dust production process of the excavation face.Under the simulation and test conditions,the dust removal duct was located in the upper part of the roadway side,the driver's position(10 m away from the excavation face)was in the vortex negat-ive pressure area,and the wind speed and flow field in the personnel operation area(28 m away from the excavation face)was stable,which was the most conducive to dust control,and the dust removal duct was located in the upper part of the roadway.The dust removal duct was located in the upper part of the roadway side and the breathing height position(1.5m height from the roadway floor),the dust concentration value was the lowest,the dust diffusion area and the total dust diffusion area were the smallest,and it was more obvious when the comprehensive excavator cuted the upper and middle areas of the head-on section of the excavation face.

Abstract:The residual gas pressure of coal seam is one of the key indexes of regional outburst prevention effect test.The success rate of direct borehole measurement is low,and it is generally obtained by indirect calculation using Langmuir equation,but it has many test para-meters,long period and large error.In order to obtain the residual gas pressure of coal seam more accurately and quickly,on the basis of theoretical analysis,the self-built quantitative gas supply device is used to quantitatively compensate the gas volume of the test tank and measure the coal seam gas pressure,and the gas pressure value of coal seam measured by the experiment is compared and analyzed with the gas pressure value of coal seam calculated theoretically and measured on site.The results show that:Under constant temperature(con-sistent with the temperature of the coal seam),after compensating the gas amount,the gas pressure inside the test vessel exhibited a charac-teristic pattern of rapid increase-slow decrease-and eventual equilibrium stabilization.The relative error between the experimentally measured coal seam gas pressure value and the theoretically calculated coal seam gas pressure value is 4.46%-9.21%.The relative error between the experimentally measured coal seam gas pressure value and the coal seam gas pressure measured on site is 2.73%-5.56%.Compared with the indirect method of Langmuir equation,this method can exclude the influence of temperature and moisture on the pres-sure measurement results,and the test parameters are less and the test time is shorter.Compared with borehole measurement,this method does not need to be sealed and is not limited by the location of pressure measurement.The research results can provide a new method for coal mine to accurately and quickly obtain the residual gas pressure value of pre-pumped coal seam,and provide technical support for coal mine gas extraction standard evaluation and anti-outburst measures effect inspection.

Abstract:Membrane distillation MD technology occupies an important position in the zero-discharge treatment process system of high-mineralization mine water due to its unique advantages,such as low operating pressure and the efficient utilization of low-grade heat sources.It is one of the key technical units for constructing an economical and efficient treatment process.However,the lack of high-per-formance MD membranes has hindered its industrial application.The vapor-induced phase separation(VIPS)technique was used to re-place the traditional liquid-induced phase separation technique to prepare hydrophobic microporous polyvinylidene fluoride(PVDF)mem-branes,which were then applied to the membrane distillation technology for treating high-mineralization mine water.By coordinately reg-ulating parameters such as the temperature,humidity,and exposure time during the VIPS process,the optimization of the membrane struc-ture and performance was achieved.Using characterization methods such as scanning electron microscopy,porosity testing,and pore size analyzer,the effects of different parameter conditions on the membrane structure were monitored.The synergistic effects among multiple factors were comprehensively analyzed by the response surface method.High-salt simulated water and the actual high-mineralization mine water from the Ningdong Mining Area were used to test the actual performance of the optimized VIPS membrane during the membrane distillation process.The results indicate that:Elevating temperature accelerates the phase separation rate during VIPS,reduces the forma-tion of nodular structures on the membrane surface,and facilitates the development of larger pore sizes and higher porosity.However,ex-cessively high temperature constrains the enhancement of porosity.Increased humidity promotes the intrusion rate of non-solvents in VI-PS,which contributes to enlarged pore sizes,elevated porosity,and improved membrane flux;conversely,excessively high humidity res-ults in pore closure.Exposure time primarily governs the progression of phase separation:insufficient phase separation occurs with overly short exposure time,whereas pore collapse is induced by overly long exposure time.An appropriate exposure time helps to form a uni-form and high-performance membrane.There are also interactions of different degrees among the parameters.The synergistic effect between temperature and exposure time is the most significant,followed by that between temperature and humidity,while the interaction between humidity and time is weak.Finally,the VIPS membrane was prepared using the optimized parameters of a temperature of 40℃,a humidity of 70%,and an exposure time of 15 min,and its treatment performance was evaluated using a direct contact membrane distilla-tion device.The test results showed that the average fluxes of the membrane reached 14.75 L/(m2·h)and 14.03 L/(m2·h),respectively,and the rejection rate was above 99.9%,remaining stable throughout the test period.The scanning electron microscopy images of the mem-brane surface before and after the test showed no obvious attachment of pollutants,and the contact angle measurement data remained stable at around 110°before and after the test,indicating that the membrane has good anti-wetting and anti-fouling capabilities and exhib-its excellent performance.