Abstract:The linearity of the mining face is crucial for the stability of surrounding rocks and the efficiency of coal recovery.To ad-dress the issue of establishing an accurate control model to achieve the optimal group straightening of the hydraulic supports during the mining process,which is affected by dynamic changes in the coal wall,roof and floor,a multi-agent decision model for group straightening of hydraulic supports is proposed based on Markov decision process(MDP).Each hydraulic support is treated as an agent,thus avoiding reliance on control models.A multi-agent decision model for group straightening of hydraulic supports is estab-lished,where the agents collaborate with each other to achieve optimal decisions for the group straightening using reinforcement learning(RL).Given that the actions during hydraulic supports straightening are continuous numerical,the twin delayed deep de-terministic policy gradient(TD3)algorithm is extended to the multi-agent straightening process of hydraulic supports.To overcome the slow convergence speed of straightening policies under multi-agent conditions,layer normalization is introduced into the Actor-Critic network structure.This helps to aggregate the inputs of each layer under a unified probability distribution,accelerating the con-vergence of the neural network weights.To solve the difficulty of determining the optimal policy for multi-agent,a global action op-timization(GAO)module is proposed,which globally optimizes the decision outcomes of multi-agent hydraulic supports,thereby achieving the optimal decision for hydraulic supports group straightening.Furthermore,based on the engineering practice of the coal mining face,a simulation platform for intelligent decision-making in group straightening of supports is developed using the Gym framework(OpenAI Gym).The experimental results show that the algorithm proposed in this paper significantly outperforms other algorithms in terms of the average value and standard deviation of linearity.When the number of"S-bend"grouped supports is sev-en,the proposed algorithm improves the coal mining face linearity by 86%compared to the MA-TD3 algorithm,and reduces the standard deviation by 71%.

Abstract:Aiming at the surrounding rock control problem of roof cutting and retaining roadway in 10605 working face of Wangjiazhai Coal Mine in Nayong County,the mechanical model of surrounding rock of roof cutting and retaining roadway is con-structed.The roof cutting parameters such as roof cutting strength,roof cutting height and roof cutting angle,and the key parameters of retaining roadway such as the length of reinforcing anchor cable and the spacing of reinforcing anchor cable are studied by numer-ical simulation.The results show that the greater the roof cutting strength,the smaller the roof subsidence;the larger the roof cutting height and the roof cutting angle,the roof subsidence is in the trend of decreasing first and then increasing;the length of the reinfor-cing anchor cable increases,and the convergence range between the roof and floor of the roadway decreases;the row spacing between reinforcing anchor cables increases,and the supporting effect gradually weakens.The practice results show that when the height of roof cutting is 15 m,the angle of roof cutting is 15°,the strength of roof cutting is in the middle,the length of reinforcing anchor cable is 15 m,and the row spacing between reinforcing anchor cables is 1 m,with the advancement of the working face,the average height of the retaining roadway is 2.39 m,and the average width is 3.43 m,which meets the requirements of the next work-ing face as the return air roadway.

Abstract:In order to explore the fatigue and damage characteristics of combined coal and rock mass under cyclic loading,fatigue failure tests under the combined action of high static stress and small-amplitude cyclic loading were carried out based on the RMT-150C test system.The fatigue and damage characteristics of rock-coal-rock combined coal and rock mass specimens under different stress amplitudes,and the variation laws of fatigue strength,hysteresis loop characteristics,axial strain,irreversible deformation with the number of cycles were studied to reveal the fatigue damage law of combined coal and rock mass and analyze the main control factors of fatigue failure.The results show that the fatigue failure of combined coal and rock mass is strictly controlled by the stress-strain under static loading,and the deformation required for fatigue failure should be approximately equal to the deformation of the post-peak part of the uniaxial compression stress-strain curve corresponding to the upper limit stress.The fatigue life of combined coal and rock mass decreases exponentially with the increase of the number of cycles,and the threshold value of the fatigue upper limit stress ratio of combined coal and rock mass is about 0.8,and the stress threshold value is about 22.5 MPa.During the fatigue test,the variation laws of axial strain,axial irreversible strain and damage degree of combined coal and rock mass with the number of cycles are basically similar.Specifically,for specimens that have not failed during the cycle process,there are two stages:initial ac-celeration and middle and late stage constant speed.For specimens that have failed during the cycle process,there are three stages:initial acceleration,middle stage constant speed and late stage acceleration.The disturbance amplitude has a significant influence on the fatigue mechanical properties of combined coal and rock mass.Increasing the amplitude will significantly increase the growth rate of axial strain,axial irreversible strain and damage degree in the middle stage constant speed,accelerate the damage and deteri-oration of coal and rock mass,and greatly shorten its fatigue life.

Abstract:In order to find out the water source,channel and formation mechanism of water damage in the coal seam working face in the hidden outcrop area of Songxinzhuang Coal Mine,we analyzed the changing law of water level in the aquifer,combined with the hydrogeological conditions of the working face and the characteristics of the water inrush,and preliminarily judged the type of the water damage in the roof to be the water inrush from bed separation.Numerical modeling was used to study the formation location,shape and height of the separation space in the hidden outcrop area of the coal seam under the mining conditions of the working face,and numerical modeling and on-site measurements were used to obtain the development height of water-conducting fractured zone after the mining of the working face.The research results show that due to the significant differences in mechanical properties and physical characteristics of the overlying strata of the coal seam,a bed separation space is formed at the angle unconformity contact position after the working face is mined.When the water-conducting fracture zone develops to the upper aquifer,groundwater seeps through the fracture network into the bed separation space for recharge,forming a bed separation water body.Under the combined action of the pressure of the overlying rock layer and its own gravity,this water body breaks through the lower aquiclude rock layer and rushes into the working face,ultimately resulting in bed separation water damage.Regarding this formation mechanism,it is pro-posed to implement comprehensive prevention and control measures such as conducting advanced drainage of the aquifer in the roof of the hidden outcrop area,controlling the uniform mining speed of the working face to inhibit the excessive development of the wa-ter-conducting fracture zone,optimizing the mining limit and reasonably reducing the mining height.These measures can effectively reduce the accumulation scale and collapse risk of the bed separation water body.Research shows that due to significant differences in rock layer strength in the hidden outcrop area of the coal seam,bed separation water disasters are prone to occur.The proposed prevention and control measures can provide theoretical basis and technical support for water disaster prevention in working faces with similar geological conditions.

Abstract:To accurately identify unstable slopes in open-pit mines and analyze the influence mechanisms of rainfall infiltration on slope stability,this study focuses on a southern open-pit mine,integrating remote sensing monitoring and numerical simulation tech-nologies to investigate slope deformation response patterns under the coupling effect of rainfall-infiltration-mechanics.Utilizing the small baseline subset interferometric synthetic aperture radar(SBAS-InSAR),multitemporal radar images from August 2017 to November 2019 were processed to generate vertical deformation rate distribution maps and spatiotemporal evolution diagrams,com-bined with meteorological data to statistically analyze settlement differences between rainy and dry seasons at key monitoring points.A Comsol-based hydro-mechanical coupling model was developed to simulate pore water pressure,effective saturation,and plastic strain field evolution during rainfall infiltration.Additionally,migration patterns of wetting fronts were extracted,and the model ac-curacy was validated by assessing the impact of shear strength degradation on stability.Monitoring results reveal significant subsid-ence is concentrated in the southeastern slope,with a maximum rate of-177 mm/year,and the rainy-season settlement at key points is 3.9 times that in dry-season.Uplift was observed in the northwestern slope and pit bottom,with a maximum rate of 70 mm/year.Numerical simulations demonstrate that rainfall infiltration increases shallow pore water pressure by up to 120 kPa,driving wetting fronts depths of the two measured profiles to reach 1.6 and 1.8 m respectively under the action of rainfall.Effective saturation in shallow soil surged by 35%during rainfall,while deep layers exhibited a trend of decreasing first and then increasing due to mois-ture migration hysteresis.Shear strength decreased by 14%-22%,and plastic yield zones expanded to the mid-slope when the safety factor dropped to 1.412.Simulated displacements showed 89%correlation with InSAR-measured subsidence.The subsidence in the southeastern part of the mining area is mainly dominated by the progressive creep deformation triggered by rainfall.During the rainy season,the infiltration of rainwater leads to a significant increase in the effective saturation and pore water pressure of the shallow rock and soil,resulting in a decrease in shear strength and the formation of a highly plastic strain zone and coupled with the effect of gravity,it drives the slope to slide along the weak plane.

Abstract:In order to improve the early strength of traditional double liquid grouting material and accelerate the setting time of slurry after double liquid mixing,using fly ash,quicklime and hydrated lime to modify traditional double liquid grouting materials,sulph-oaluminate cement-based double liquid grouting material(SACDL)was developed based on response surface method(RSM).Tak-ing the mass fraction of fly ash,quicklime and hydrated lime as variables,slurry fluidity,setting time,flexural and compressive strength as responses,and a polynomial model was established,and the early hydration mechanism was analyzed in combination with macroscopic properties and microscopic morphology.The results show that the optimal mass fraction of fly ash,quicklime and hydrated lime in SACDL is 0%,10.6%and 10%respectively,at this time,the fluidity,initial setting time,3 h flexural strength and 3 h compressive strength of SACDL reach 141.5 mm,19.4 min,2.3 MPa and 12.6 MPa respectively,the error between the predicted value and the actual value is small,and the model is in high agreement with the actual data;the interaction between quicklime and hydrated lime had significant effects on the fluidity,setting time,flexural strength and compressive strength of SACDL paste at dif-ferent ages,quicklime and hydrated lime greatly increased the concentration of Ca2+in the liquid phase,and provided an alkaline en-vironment for the reaction system,accelerating the hydration of dicalcium silicate(C2S)and tricalcium silicate(C3S),thereby im-proving the early strength of SACDL;however,fly ash is not suitable for SACDL,the incorporation of fly ash makes SACDL lack sufficient active silicate,resulting in a decrease in the production of ettringite(AFt),thereby reducing the strength of SACDL.

Abstract:To study the impact of irregular loads from the overburden dumping site on the stability of the coal pillar and slope in open-pit coal mining,this study selects Laiyegou Open-pit Mine in Ordos of Inner Mongolia as a case study.Based on the irregular geometric shape of the dumping site,the Mark-Bieniawski formula is optimized.Coupled with the physical and mechanical paramet-ers of the geotechnical body,numerical simulations of the coal pillar and slope under the load conditions of the dumping site are con-ducted.Rhino software is used for three-dimensional modeling and grid division,and FLAC3D is employed for calculation and ana-lysis based on displacement changes,plastic zone distribution,and slope sliding.The research results show that when the dumping site load is considered,the width of the supporting coal pillar is 2.9 m and the isolation coal pillar width is 8.88 m;without the dump-ing site load,the supporting coal pillar width is 2.8 m and the isolation coal pillar width is 8.29 m.The load from the dumping site exacerbates the deformation of the coal pillar.At a depth of 100 m during excavation,the roof subsidence reaches 7.3 mm,and the floor heave is 6.98 mm.At a depth of 150 m,the roof subsidence reaches 6.79 mm,and the floor heave is 7.63 mm.The slope dis-placement increases to 38.2 mm under the dumping site load,compared to 31.9 mm without the load.The load from the dumping site affects the stress and deformation of the coal pillar,especially during deep excavation,where the irregular load on the upper part causes significant deformation and stress concentration in the coal pillar,increasing the risk of instability.In areas with greater ex-cavation depths,the load increases slope displacement,affecting the slope stability and increasing the risk of landslides.After the mining of end-slope overlying rock,a goaf is formed within the slope,leading to a dramatic increase in the plastic zone area,primar-ily due to tensile failure.The maximum shear strain increment is concentrated in the excavation roof area,forming a"settlement and progressive landslide"risk.In the stability analysis of this scheme,the safety factor of the slope is greater than 1.5,meeting the design specifications.In the process of end-slope mining with irregular dumping site loads,a reasonable plan should be considered to reduce the safety risks caused by coal pillar deformation and slope instability.

Abstract:The drilling cuttings method is an important means to determine and predict the risk of coal and rock dynamic disasters such as rock burst.Accurately obtaining the variation law of drilling cuttings is one of the keys to understanding the stress state of coal.In order to further understand the failure process of coal body in drilling process,this study introduces the calculation formula of drilling cuttings based on elastic theory,designs the discrete element model of coal body drilling simulation,carries out drilling simulation experiments under different influencing factors,and puts forward the simulation method of indirectly reflecting the drilling cuttings by the number of discrete particles.The variation laws of the number of discrete particles under different mechanic-al properties of coal body,confining pressures and hole diameters are revealed.The results show that:the discrete element model based on PFC3D can effectively simulate the cutting process of the drill bit,the simulation results are basically consistent with the laws obtained by the test,and the number of discrete particles is approximately positively correlated with the amount of drilling cut-tings.According to the failure range,the failure area can be approximately divided into drilling failure area and deformation failure area,the drilling failure area is related to the geometric characteristics of the drill pipe,and the deformation failure area is related to the mechanical properties and confining pressure characteristics of the coal body.The mean value of discrete particles in the model is negatively correlated with the strength coefficient and elastic modulus coefficient.In practical application,the influence of mechanic-al properties such as softness and hardness of coal samples on the drilling cuttings index method should also be paid attention to.Un-der the condition of different lateral pressure coefficients,the mean value of discrete particles in coal is approximately linear.When the lateral pressure coefficient increases from 1.1 to 1.4,the high displacement area of the hole wall gradually changes from circle to ellipse,and the mean value of discrete particles increases by 8.7%.There is a certain proportion relationship between the mean value of discrete particles in coal under different hole diameter conditions.When the hole diameter increases sequentially from 20 mm to 24,28 and 32 mm,the phenomenon of borehole stress concentration increases significantly,the displacement of the hole wall in-creases significantly,and the amount of discrete particles increases by 17.3%,23.6%,16.7%,respectively.

Abstract:The uniaxial compression experiment under low pressure environment was carried out by using tectonic coal samples.The acoustic emission response characteristics of coal fracture in low pressure environment were obtained by using fast Fourier trans-form(FFT)and wavelet packet decomposition.The results show that when the loading stress of coal increases,the acoustic emission spectrum becomes more abundant,and the overall trend shows a left shift.When the gas pressure increases,the frequency spectrum of the acoustic emission signal gradually transitions from the initial low-frequency high-energy state to the high-frequency low-en-ergy state,and its frequency range gradually narrows.At the same time,the original complex multi-peak shape is gradually simpli-fied into a single peak shape.As the stress increases,the proportion of acoustic emission energy in the frequency band of 0-4.38 kHz gradually increases,while the acoustic emission energy in other frequency bands gradually decreases.The signal energy proportion in the two frequency bands of 2.92-4.38 kHz and 4.38-5.84 kHz has the most obvious response trend to stress change.When the air pressure changes,the proportion of acoustic emission energy in the three frequency bands of 2.92-4.38 kHz,4.38-5.84 kHz and 7.30-8.76 kHz shows a significant response trend with the change of air pressure.This phenomenon shows that the two frequency bands of 2.92-4.38 kHz and 4.38-5.84 kHz are the characteristic frequency bands of tectonic coal fracture process.

Abstract:Coal seam reservoirs contain a large number of weakly consolidated interfaces such as cleats,bedding,and natural frac-tures,which,along with complex pore structures,make the prediction of fracture propagation patterns during hydraulic fracturing challenging.Understanding the intersection and expansion rules of hydraulic fractures with coal seam weakly consolidated interfaces can facilitate comprehensive and effective permeability enhancement in coal seams through fracturing.We establish a model for the expansion of hydraulic fractures on weakly consolidated interfaces based on the cohesive element method,considering the occur-rence of weakly consolidated interfaces and their distance from the perforations,analyze the impact of different approach angles and strengths of weakly consolidated interfaces on the intersection and expansion patterns of hydraulic fractures at different length to dis-tance ratios(the ratio of the weakly consolidated interface length(L)to the distance(D)from the injection point to the center of the interface).The results indicate that when the length to distance ratio(L/D)is 1/3,2/3,1/1,as the approach angle increases,so does the fracture deflection angle;when L/D is 1/3 or 2/3,the total fracture length gradually decreases with increasing approach angle;when the aspect ratio is 1/1,the total fracture length gradually increases with the increase of the approach angle;when the approach angle is≤15°,hydraulic fractures are more likely to extend along the direction of the weakly consolidated interfaces after intersec-tion,whereas when the approach angle is≥30°,hydraulic fractures tend to penetrate the weakly consolidated interfaces;the fracture width is maximum when the approach angle is 30°;as the strength of the weakly consolidated interfaces increases,both the fracture deflection angle and the modified fracture length show an increasing trend.

Abstract:Safety inspection of coal mine shafts is the core link of coal mine safety checks,which is of great significance for achiev-ing safe production in coal mines and ensuring the personal safety of miners.Aiming at the deficiencies of intelligent safety inspec-tion robots in coal mines in terms of positioning accuracy and multi-robot collaboration,a fusion positioning and collaborative opera-tion model for inspection robots based on multi-source positioning information fusion and navigation-following control method is proposed.To address the issues of unstable positioning signals and low positioning accuracy in underground mines,this study ad-opts three positioning systems,namely inertial navigation system,liDAR positioning system and ultra-wideband positioning system,for underground positioning.The data information of the three positioning systems is fused through the extended Kalman filter and weighted fusion to perform the navigation and positioning of inspection robots.In the long and complex underground environment,the inspection of a single robot is extremely difficult and time-consuming.Safety inspections often need to be carried out through the collaborative operation of multiple robots.To achieve more efficient and coordinated multi-robot collaborative operations,the re-search adopts the navigation-following control method for multi-robot formation and improves the navigation-following control method by using the graph theory method based on directed graphs,obtaining an improved navigation-following control algorithm based on graph theory for robot collaborative operation formation.In the simulation experiment,it was proposed that the maximum root mean square error value of the trajectory obtained by the model in the x direction was 0.578 m,the average root mean square er-ror value was 0.295 m,and the maximum root mean square error value in the y direction was 0.155 m.Both had relatively small er-rors,indicating that the proposed model had high positioning accuracy.In the experimental results of different scenarios,the mean maximum value of the x-component position error of the robot using the model proposed in the research in the L-shaped roadway is 0.380 m,and the mean maximum value of the x-component position error in the connecting roadway is 0.442 m.It still has a relat-ively small error,further verifying that the model has superior positioning performance.Furthermore,the research results indicate that after adding obstacles,the maximum offset of the four follower robots in obstacle avoidance is within 1.025 meters,with a relat-ively small error.After obstacle avoidance,the follower robot quickly converges to the ideal trajectory.Both the obstacle avoidance and recovery time are approximately 20 seconds,demonstrating a relatively fast convergence speed.

Abstract:Aiming at the asymmetric failure phenomenon of inclined strata roadway,theoretical analysis and FLAC3D numerical sim-ulation method are used to study the bearing capacity and deformation and failure law of roadway under the influence of different strata dip angles and different positions of roadway,and the asymmetric deformation and failure mechanism of surrounding rock of inclined strata roadway is revealed.The results show that the bearing capacity of different positions around the roadway is different under the condition of different strata dip angles.The existence of structural plane reduces the stability of surrounding rock of road-way.When the shear stress at this position is greater than the shear strength,slip failure will occur.When the position of the road-way is fixed,there is the most unfavorable strata dip angle βmin.When the position of the structural plane coincides with βmin,the bear-ing capacity of the surrounding rock is the weakest,which is the most unfavorable to the stability of the roadway.Through the optim-ization of the roadway support scheme,the design of"anchor net+36 U shed+anchor cable beam+grouting"composite support scheme is designed,and the deformation of surrounding rock is effectively controlled.

Abstract:Advanced detection of water abundance in rock strata ahead of roadway excavation is critical for ensuring mining safety.Conventional mine electrical prospecting techniques,constrained by axial observation system layouts,suffer from insufficient azi-muthal discrimination of electrical anomalies,significantly limiting their practical application efficacy.To address this technical bot-tleneck,a novel triaxial apparent resistivity detection method for roadway excavation is proposed and its detection workflow is delin-eated.By establishing a theoretical model of an infinite low-resistivity slab-shaped anomaly within a full-space homogeneous medi-um,a three-dimensional observation coordinate system including roadway axial(x),lateral(y),and vertical(z)directions was con-structed to derive analytical expressions for triaxial apparent resistivity responses.Numerical simulations and theoretical analysis were conducted to investigate the influence of slab-shaped anomaly attitude parameters(azimuth and dip angles)on triaxial apparent resistivity response characteristics.The study reveals that:the x-direction apparent resistivity curves exhibit stable"H-type"pattern,independent of anomaly azimuth and dip angles,though their anomaly amplitudes and detection pole distances at extremum points are significantly affected by attitude parameters;y-direction curves demonstrate high sensitivity to azimuth angles but negligible de-pendence on dip angles,with their curve types predominantly governed by azimuth variations;z-direction curves display comple-mentary behavior to y-direction responses,showing high sensitivity to dip angles while remaining largely unaffected by azimuth vari-ations,with curve types primarily determined by dip parameters.Compared to traditional axial electrical methods,the proposed ap-proach enables multi-dimensional electrical characterization of anomaly attitudes,preserving conventional axial method advantages while achieving enhanced anomaly resolution by integrated interpretation of triaxial apparent resistivity.

Abstract:In order to realize the real-time monitoring,prediction and early warning of coal and gas outburst danger in coal roadway heading face,Malan Mine has installed and deployed the KJ1521 coal and gas outburst prediction and early warning system,and we carried out the research on the difference distribution of time-frequency domain parameters of micro-seismic signals under different scenarios and outburst danger response characteristics.The results show that under normal monitoring,there are differences in the quantitative distribution of time-frequency domain parameters of micro-seismic signals in different regions,but the qualitative laws are basically the same.The time-frequency domain parameter distributions of micro-seismic signals in special scenarios such as mi-cro-seismic sensor movement,non-vertical installation of sensor and sensor short circuit correspond to low and high value anomalies of waveform amplitude and duration,low value anomalies of rise time,and low value anomalies of peak frequency 50 Hz and below,respectively;the reasonable threshold range set for the time-frequency domain parameters of the micro-seismic signal can effectively filter out the noise signal caused by the abnormal state of the sensor,and improve the accuracy of the response of the micro-seismic signal to coal and gas outburst.When the coal roadway heading face encounters fault structure,the rise time mean and duration mean of effective micro-seismic signal show high value anomaly,the amplitude mean shows local high value fluctuation,and the peak fre-quency mean shows low value anomaly.The average amplitude,rise time,duration and peak frequency of micro-seismic signals show the precursory characteristics of high value anomaly when the roadway is excavated through stress concentration area.

Abstract:Asymmetric large deformation and damage are prone to occur in the goaf during the mining process of close distance and thick coal seams,which seriously affects the safe and efficient production of the mine.Therefore,taking the 30503 working face of Tashan Coal Mine as the engineering background,a research method combining on-site measurement,theoretical analysis,and nu-merical simulation is adopted to study the deformation and damage laws of the goaf during the mining process of the working face,reveal its deformation and failure mechanism,and propose stability control technology for the goaf.The study results show that in-fluenced by adjacent goaf and filling roadway,the goaf presents significant asymmetric deformation,with a deformation of 800 mm in the middle and upper parts of the solid coal support and coal pillar support,and obvious floor heave;theoretical analysis finds that repeated mining results in the formation of a composite structure of"low-level cantilever beam+high-level masonry beam"in the overlying rock,which causes a significant increase in surrounding rock stress due to fracture and subsidence;establishing a stress transfer model for the high and low roofs,deriving the vertical stress distribution function,and verifying that the peak stress(23.1 MPa)borne by the coal pillar far exceeds its bearing capacity(11.9 MPa),the composite structure of the upper and lower roof panels and the instability of the coal pillar lead to the asymmetric deformation of the gob-side roadway;through FLAC3D numerical simulation,different reinforcement support schemes are compared for 4 types of anchor rods and 4 types of grouting depths(2-5 m),and the op-timal solution is 2 m grouting reinforcement on the side of the coal pillar(to enhance the stiffness and shear strength of the fracture surface)combined with 4 optimized anchor rods on the two sides(with an inter-row spacing of 1.2 m×2.0 m and a 15° inclined an-choring for the first/fourth rows),which achieves a 20%improvement in control effect compared to conventional support;after be-ing applied on-site,the distance between the two sides of the roadway decreased by 50%(the peak value dropped from 800 mm to 400 mm),and the distance of the roof and floor movement decreased by 40%(the peak value dropped from 520 mm to 312 mm),sig-nificantly improving the stability of the roadway.

Abstract:The theoretical calculation of the height development of water conducting fracture zones under fully mechanized top coal caving conditions is crucial for the prevention and control of water hazard in coal mine roofs.With the advancement of thick top coal caving technology,existed empirical formulas cannot fully meet the prediction of water conducting fracture zone height in thick and extra-thick coal layers.Based on the measured values of the height of water conducting fracture zones in 185 sets of thick and extra-thick coal seams in China,according to the lithology of the overlying rock,the data is divided into three categories:hard,medium hard,and weak.Four mathematical models,including guideline-like formula,linear regression,quadratic regression,and DoseResp function,are used to fit and analyze the data.The model reliability is analyzed using the goodness of fit R2.Under hard overburden conditions,the goodness-of-fit is DoseResp model>quadratic regression model=linear regression model>guideline-like model.Under medium hard and weak overburden conditions,the performance of the goodness-of-fit is DoseResp model>quadratic regres-sion model>linear regression model>guideline-like model.Furthermore,the mean absolute percentage error(MAPE)method is adopted to compare the reliability of the newly fitted formulas with those specified in the Guidelines for Coal Pillar Layout and Min-ing Under Buildings.Water Bodies,Railways and Main Shafts/Tunnels(hereinafter referred to as the Guidelines).For hard overbur-den,the accuracy of the four new fitted formulas was higher than that of the existing formulas in the Guidelines;for medium hard overburden conditions,the accuracy of the four new fitted formulas was better than that of the existing formulas in the Guidelines,and the DoseResp model performed the best.For weak overburden conditions,the guideline-like formulas and the DoseResp model are better than the existing formulas in the Guidelines.Applying the newly fitted formulas to specific mines,the DoseResp function has good applicability in predicting the height development of water conducting fracture zones in thick and extra-thick different over-burden rocks(hard,medium hard and weak),followed by the guideline-like model,and both predictions are better than the formulas in the Guidelines.

Abstract:Controlling the oxidation rate during the latent period of spontaneous combustion plays an important role in the efficient inhibition of coal spontaneous combustion.In order to suppress coal spontaneous combustion while meeting the environmental re-quirements of inhibitor materials,experiments on room-temperature and low-temperature inhibition of coal spontaneous combustion using composite environmentally friendly inhibitors were conducted.Common halide salt inhibitors and composite environmentally friendly chemical inhibitors were selected for comparative analysis of gas products(CO,CO2)and oxygen consumption during room-temperature and low-temperature oxidation of coal samples;then,Fourier transform infrared spectroscopy and electron paramagnet-ic resonance spectroscopy were used to analyze the changes in oxygen-containing functional groups and free radical contents of coal samples before and after treatment with the new composite environmentally friendly inhibitor.The macroscopic experimental results show that during the oxidation stage at room temperature,the cumulative production of CO and CO2 in the coal samples treated with the new type of composite environmentally friendly inhibitor decreases more significantly.In the low-temperature oxidation stage,compared with halide salt inhibitors,the new type of composite environmentally friendly can significantly reduce the generation of CO and CO2 in coal samples,and the oxygen consumption is the lowest.Through the microscopic test results,it can be found that the content of oxygen-containing functional groups and alkyl groups in the coal sample will significantly decrease after treatment with the new type of composite environmentally friendly inhibitor.In addition,the concentration of free radicals in the coal samples will also be significantly reduced after treatment with the new type of composite environmentally friendly inhibitor.Combining the res-ults of macroscopic experiments and microscopic tests,it can be concluded that the new type of composite environmental-friendly in-hibitor has a significantly better inhibitory effect on coal spontaneous combustion than the commonly used halide salt inhibitors.It can effectively reduce the generation of gas products and oxygen consumption during coal oxidation,and at the same time,it can ef-fectively lower the oxidation activity of active groups in coal under normal temperature and heating conditions,revealing its poten-tial efficacy in replacing halide salt inhibitors in preventing coal spontaneous combustion.

Abstract:In the complex tunnel environments of coal mines,traditional centralized vehicle dispatch systems suffer from inherent problems of high deployment costs and significant response delays due to reliance on standalone controllers;concurrently,existing positioning technologies fail to achieve continuous cross-base-station vehicle tracking while lacking real-time monitoring capabilit-ies for violations such as speeding and red-light running.To address these challenges,a distributed intelligent traffic control system based on joint scheduling units was constructed,the study designs a master base station(integrated with intelligent scheduling al-gorithms)and multi-slave base station collaborative architecture;the master station actively polls ultra-wideband(UWB)vehicle pos-itioning data from slave stations via TCP/IP protocols,dynamically generating traffic light control commands based on configurable locking and unlocking distance ranges to achieve centralized-controller-free distributed decision-making;supports modular deploy-ment configurations including"master-slave pairs"for straight sections,"master-dual-slave"for T-junctions,and"master-triple-slave"for crossroads,while significantly reducing hardware construction costs through base station reuse technology enabling single stations to serve dual joint scheduling units;the study develops a seamless roaming positioning mechanism utilizing the maximum ranging distance cross-coverage,allowing vehicle cards to synchronously scan neighboring base stations and triggering positioning base station handover when consecutively entering a new station ranging zone three times,thereby eliminating trajectory voids ex-ceeding 10 seconds in traditional solutions;the study establishes a violation recognition model that calculates real-time vehicle speed via UWB ranging displacement differentiation combined with traffic light state machines for dynamic red-light violation detection.Field validation at Shanxi Datong Coal Mine demonstrates that:traffic light control accuracy exceeding 99.3%,speeding detection rate no less than 98.2%,red-light violation recognition reaching 99.1%,and positioning handover time stabilized within 2 seconds in multi-base-station scenarios,fully verifying the excellent performance in dispatch control accuracy,safety supervision comprehens-iveness,and positioning continuity of the system.

Abstract:The pipe jacking rescue method is to form an emergency life passage safely and efficiently by jacking a prefabricated pipe through the caving and collapse blockage area.In order to study the macro-mesoscopic mechanical properties of the caving body un-der the action of pipe jacking under the conditions of different pipe jacking depths and particle sizes of the caving body,combining the similar simulation test and numerical simulation test of jacking pipe in caving body,the effects of pipe jacking burial depth and particle size of caving body on the resistance of jacking pipe and particle displacement are explored,and the macro-mesoscopic para-meters of caving body are further investigated from the viewpoints of coordination number,force chain and energy of caving body.The results show that:the jacking resistance and particle displacement as a whole increase with the increase of particle size of caving body and pipe jacking burial depth,and the displacement zone is mainly divided into the extrusion and disturbance zone in front of and behind the pipe opening and the shear sliding zone directly above the pipe opening;the amplitude of the fluctuation of the co-ordination number and the difference of the drop increase with the increase of particle size of caving body and pipe jacking burial depth,and the force chain in front of the pipe opening is damaged and continuously expanded,thus forming a shear sliding surface;with the increase of particle size of caving body and pipe jacking burial depth,the elastic potential energy,kinetic energy and dissipa-tion energy are positively correlated in the jacking process,and the jacking is mainly divided into the early small strain disturbance stage and large strain shear sliding stage.

Abstract:To effectively manage and utilize the vast amount of ventilation data in coal mines and meet the national demand for intel-ligent mining systems,the development of knowledge graphs and intelligent question-answering(Q&A)systems is a critical step in the intelligent transformation of mine ventilation.Using techniques like web scraping and classification analysis,knowledge data from the mine ventilation domain is collected and integrated with expert input to build an ontology model.This model serves as the foundation for constructing the mine ventilation knowledge graph,with 6 935 entity annotations and vertical relationship associ-ations completed.Based on this knowledge graph,a vector-based intelligent Q&A framework was designed.Through the creation of question intent identification rules and answer templates,a vector-based Q&A model was developed.To verify its applicability,200 professional questions related to mine ventilation were tested.The results show an overall accuracy of 95%for the model,with 97%accuracy for single-turn questions and 93%for multi-turn continuous questions.Compared to rule-based models,the vector-based model demonstrates significant advantages in multi-turn interactions.Future research will further improve the accuracy by integrat-ing large language models for enhanced semantic analysis.This intelligent Q&A system will reduce the workload of ventilation per-sonnel,increase management efficiency,and provide vital support for the full implementation of intelligent ventilation systems in coal mines.