Abstract:In response to the engineering requirement for frequent speed switching of fixed-capacity belt conveyors in the vertical shaft skip loading,we proposed a kinematic analysis and control method based on a trapezoidal acceleration curve.The core objective of this method is to achieve smooth and precise control during the starting,stopping,and speed-changing processes of the fixed-capacity conveyor.By constraining the change rate of acceleration during both acceleration and deceleration phases,it theoretically avoids the mechanical impact and elastic vibration problems caused by abrupt acceleration and deceleration in traditional control strategies.A kinematic model covering all operational conditions,including constant speed,acceleration,and deceleration,was established.Analytical expressions for time,travel distance,velocity,and acceleration in each operational phase were systematically derived,providing a theoretical basis for accurately determining key motion parameters.To further validate the feasibility and superiority of the theoretical model,the actual design parameters and operating conditions of the main shaft hoisting system in the Maojiachuan Mine were combined.Detailed temporal sequence matching and simulation calculations were conducted for multiple feeding points at different distances,and differentiated control strategies were proposed for actual operating conditions at various stages.Application results demonstrate that the proposed trapezoidal acceleration control strategy not only significantly suppresses dynamic tension impact and vibration during speed transitions but also reduces the system's rest time from 25 seconds to 20 seconds,increasing overall operational efficiency by 4.6％.The findings provide theoretical foundation and practical guidance for achieving efficient,reliable,and safe automated collaborative operation between fixed-capacity belt conveyors and skip hoisting systems.

Abstract:To address the issue of drill pipe dropping caused by fractures in the male and female joints'threads,the drop mechanism for fractures at different thread positions is analyzed,leading to the proposal of a synchronous double-thread anti-drop technology.This design adopts a structure that combines synchronous double threads with a connecting rod,in which the primary thread bears the operational load.Should the primary thread fracture,the secondary thread and connecting rod maintain axial connectivity to prevent the drill tool dropping.The design principles for the male and female joints utilizing the synchronous double-thread system are introduced,and calculation methods are provided for the load-bearing capacity of the primary thread and the anti-drop capacity of the secondary thread and connecting rod.Performance tests conducted on Φ89 mm double-thread drill pipes demonstrated a torsional capacity of 34904 N·m and a tensile capacity of 1878 kN,representing 2.33 and 6.26 times the rated capacity of the matching drill rig,respectively.Following simulated fractures of the male and female joint threads,the residual tensile capacities measured 517 kN and 433 kN,corresponding to 1.72 and 1.44 times the rated tensile capacity of the drill rig.These values fully meet the safety requirements for drill string hoisting.The results confirm that the synchronous double-thread structure can resolve the problem of drill pipe dropping caused by joint fractures,enhancing the reliability of the drill pipe and the safety of construction operations.

Abstract:To overcome the insufficient feature extraction in existing fault diagnosis models when handling nonlinear,non-stationary signals under high-noise in underground mines,which compromises diagnostic accuracy,a dual-branch fusion model based on SwinT and SKNet is proposed for fault diagnosis of shearer rocker arm gears.The model extracts both global and local features through two parallel branches:a simplified Swin Transformer branch and a lightweight SKNet branch.The SwinT branch incorporates a Bottleneck Attention Module(BAM)to enhance its global feature representation.The SKNet branch utilizes depthwise separable convolutions and replaces fully connected layers with 1-dimension convolutions to reduce computational complexity,making the model suitable for deployment on mobile and edge devices.Tests conducted on the Taiyuan Heavy Industry rocker arm loading test bench show that the proposed method outperforms comparative models in both accuracy and precision.It maintains over 97％recognition accuracy even at a signal-to-noise ratio(SNR)of-6dB,demonstrating strong noise robustness.

Abstract:To address the complexity and high-risk nature of the underground coal mine working environment,as well as difficulties and limited methods in monitoring the health of underground personnel,a multi-dimensional status monitoring and real-time risk early warning system is proposed based on smart wristbands,portable monitors,and intelligent information-capable miner's lamps.The system collects underground workers'real-time physiological parameters such as heart rate,body temperature,blood oxygen saturation,etc.,and environmental parameters such as methane and carbon monoxide concentrations.Data is uploaded to a surface server via the mine Internet of Things to build a unified monitoring platform.An innovative fatigue assessment model based on a back propagation neural network is established for data processing.By analyzing the correlation between physiological parameters and sweat pH,miners'fatigue levels was accurately estimated.Furthermore,by integrating a Conditional Score-based Diffusion Model for Imputation(CSDI),the system can fuse multi-dimensional data including physiological status,environment,and personnel location to achieve dynamic risk early warning and proactive health diagnosis.Test results show that the system has a fatigue assessment error within 0.05 and an early warning accuracy rate above 95％,significantly improving the safety and health management level of mine personnel.

Abstract:To address the challenges associated with unclear deformation mechanisms and support design difficulties for large chambers in soft rock strata in western China,an underground loading chamber in the Ordos mining area was investigated.An integrated approach combining three-dimensional numerical simulation(FLAC3D)and field monitoring was employed to analyze the stability and deformation evolution of the chamber after excavation and support.The simulation results reveal significant deformation at the chamber roof and its junction with the inclined shaft.The thickness of the plastic zone was determined to be approximately 6 m in the sidewalls,5 m in the roof,and 5.5 m in the floor,indicating a necessity for reinforcement using anchor cables with lengths of 7.5 to 8 m.Field monitoring data show that,the loads on bolts and cables increased rapidly upon support installation and then stabilized.Monitoring points inside the chamber stabilized in about 20 days,while those in stress concentration zones stabilized in about 15 days.All measured loads were below the ultimate breaking capacity,confirming the safety and reliability of the support system.The findings provide critical parameters and a theoretical basis for the support design of large chambers in soft rock strata in western China.

Abstract:The mining of extra-thick coal seams induces more intense responses in the overlying strata.To clarify the evolution laws of mining-induced fissures in the overburden,ensure safe and efficient production at the working face,and protect the surface ecological environment,taking the 2303 working face of Yongning Coal Mine in Xinjiang as the engineering background.The discrete element numerical simulation is employed to visually characterize the development features of overburden fissures under the extra-thick coal seam mining,revealing the evolution patterns of the water-conducting fissured zone and the caved zone as the working face advances.Combining with fractal geometry theory,the box-counting method is used to precisely quantify the fissure development intensity.The results show that after mining working face,the development heights of the caved zone and the water-conducting fissured zone are 51.10 m and 148.11 m,respectively,with caving-to-mining and fracturing-to-mining ratios of 5.77 and 16.63.As the working face advances,the height of the fissured zone undergoes a three-stage development of initiation-growth-stabilization,while the height of the caved zone undergoes two cycles of"sudden increase-gentle decrease"accompanied by the fracture of the main roof and sub-key strata.The development of mining-induced fissures in the overburden exhibits significant fractal characteristics.The overall fractal dimension dynamically changes in a saddle-shaped pattern("high at both ends,low in the middle")as the working face advances:the average fractal dimensions on both sides of the goaf(main fissured zones)are 1.001 and 0.978,respectively,constituting the primary water-conducting channels of the goaf.The fractal dimension in the bed separation development zone 150 m above the floor is 0.904,which is prone to forming groundwater accumulation spaces.By fitting the evolution curve of the fractal dimension,it is estimated that the fractal dimension peaks when the advance distance reaches 71.18 m,which precisely corresponds to the stage of large-scale roof caving.

Abstract:Accurate prediction of mine water inflow is crucial for the safe production and water hazard prevention in underground coal mines.Traditional prediction methods are limited by model assumptions and parameter sensitivity,making it difficult to meet engineering requirements for high prediction accuracy.Therefore,a new method for mine water inflow prediction is proposed based on improved complete ensemble empirical mode decomposition with adaptive noise(ICEEMDAN)and variational mode decomposition(VMD)secondary decomposition technology,combined with bidirectional long short-term memory(BiLSTM)and Transformer.Specifically,the original water inflow signal is decomposed into several intrinsic mode functions(IMFs)by ICEEMDAN at first.Then,the sparrow search algorithm(SSA)is introduced to optimize the key parameters of variational mode decomposition(VMD),and secondary decomposition is performed on the signal to achieve multi-scale feature extraction.Subsequently,BiLSTM captures short-term and long-term dependency features of the time-series data,while the Transformer's self-attention mechanism strengthens global feature correlation modeling.Experimental results show that this method significantly outperforms traditional prediction methods in both prediction accuracy and robustness,providing a new technical approach for mine water inflow monitoring and early warning.

Abstract:To provide design basis for surrounding rock support of rock burst roadway in Binchang mining area,support materials and components commonly used in roadway support system were selected for static and impact dynamic load tests.We systematically analyzed the static mechanical properties of bolts,anchor cables,trays and metal meshes,as well as the mechanical response characteristics and failure modes under the action of impact dynamic load.The test results show that:under the action of static load,the ultimate bearing capacity of the bolt specimen is 293.7 kN,and the elongation rate is 12.5％.The tensile strength of the anchor cable specimen reaches 1980 MPa,and the elongation rate is 9.9％.The compression load-deformation curve of the bolt tray develops in multiple stages,and the maximum load is 386 kN.Under the action of drop hammer impact,the impact force-displacement curve of the bolt varies in three stages:the elastic stage,the plastic stage and the rebound stage.The bolt can withstand a maximum of 8 rounds of impacts,with an impact elongation rate of 9.98％,and its brittleness is enhanced.The impact force-displacement curve of the anchor cable develops in four stages:tightening,rapid growth,stable deformation and rebound.The maximum peak value of the impact force is 550 kN,the elongation rate under dynamic load is 1.57％,and the absorbed energy is 1.35×104 J.The impact force-displacement curves of the butterfly bolt tray and the W-shaped tray successively go through four stages:slow growth,linear growth,steady growth and sharp decay.Compared with the butterfly bolt tray,the W-shaped bolt has smaller impact resistance in early stage.The impact force-displacement curve of the metal mesh roughly goes through three stages:linear growth,violent fluctuation and rapid decay.With the increase of the impact energy,the peak value of the impact force basically shows an increasing trend,the deformation continues to increase,the mesh basically maintains its original shape,and it has good cushioning performance.

Abstract:To understand the overburden failure characteristics and fracture development patterns during the mining of extra-thick coal seams,and to further prevent safety incidents such as roof collapse and water inrush to guide production practices,this study focuses on a shallow-buried extra-thick working face in the 6-upper coal seam of Huangyuchuan Coal Mine.Using an integrated approach that includes theoretical analysis,numerical simulation,and field measurement,a comparative analysis was conducted on the displacement field,stress field,and fracture field of the mining-disturbed overburden.The results show that the overburden failure range of the extra-thick working face is approximately 150 m,with the initial caving span of the main roof being 44.74 m and the periodic caving span being 18.27 m.The failure profile of the overburden under strong mining conditions exhibits an"inverted funnel"shape,and fracture development displays distinct zonal expansion characteristics,which can be divided into:separation zone,fracture development zone,fracture closure zone,and stable zone.Mining-induced stress transmission in the overburden presents a saddle-shaped distribution,with stress concentration primarily occurring along the goaf boundary and in the central compaction zone.After the working face advances 180 m,the mining influence stabilizes into a periodic weighting phase,stress transmission upward attenuates,and mining-induced fractures are suppressed.The findings offer valuable insights for predicting overburden movement and failure height and for hazard prevention under strong mining conditions in shallow-buried extra-thick coal seams.

Abstract:To reveal the coupled disaster-causing mechanism of overlying goaf and remnant coal pillars on abnormal roof weighting in underlying working faces and to ensure roof stability along with safe and efficient mining,we systematically investigated the mechanism of abnormal roof weighting under multi-seam remnant coal pillars at the 32302 working face of Chahasu Coal Mine.A comprehensive methodology integrating theoretical analysis,numerical simulation,and field monitoring was employed.A floor stress zoning model under the influence of remnant coal pillars was established,clarifying the characteristics of the shallow compression-shear composite stress concentration zone in the floor and the abnormal stress distribution patterns within a 50 m range ahead of and behind the coal pillars.Based on elastic thin-plate theory,a mechanical model of periodic roof weighting in the main roof was developed,revealing the mechanical evolution of roof instability:initial destabilization occurs when the face advances to 11.4 m,with significant instability characteristics observed at 15 m of advance.Combining with three-dimensional numerical simulation and field monitoring data of hydraulic support resistance,the stress superposition features and dynamic propagation paths induced by overlying goaf edges and remnant coal pillars were identified.Results show that the maximum increase in advance stress peak reaches 34.08％,and the concentrated stress beneath remnant coal pillars reaches 24.23 MPa.Based on these findings,a three-level zoning control criterion was proposed based on face advance position,dividing the area into:a 50 m warning zone ahead of the setup entry,a 20 m high-risk zone around the setup entry,and a 20 m pressure-relief zone behind the setup entry.The findings provide a reliable theoretical basis and technical guidance for roof disaster identification and regional control in working faces under multi-seam remnant coal pillars.

Abstract:To improve image recognition accuracy,a tramp metal recognition method for mining belt conveyors based on machine vision and coal flow height is proposed.A binocular vision system is used to acquire images of tramp metal on the belt conveyor.Distortion is corrected using a planar template method to enhance image quality.The DA-GANomaly model in machine vision is utilized to generate a tramp metal recognition model.Based on the inferred coal flow height value,the model learns the feature distribution of normal coal flow images and identifies the difference between images containing tramp metal and the normal image feature distribution,thereby determining the presence of tramp metal.The CIoU loss function is selected,and an anomaly score is assigned to assist the model in judging whether an image contains tramp metal.Based on the anomaly score value,automatic recognition of tramp metal on mining belt conveyors is achieved.The results show that the proposed method has high recognition accuracy and efficiency,achieving the highest number of successful recognitions among the tested models.It can quickly and accurately determine whether an image contains tramp metal,enabling the recognition of tramp metal on the conveyor.

Abstract:In order to investigate the effect of CO2 phase transition fracturing on the full aperture pore structure of the coal,coal samples before and after CO2 fracturing were selected from Liupanshui Danyun Coal Mine and Dahebian Coal Mine in Guizhou,China,and the pore characteristics and fractal properties of the coal body before and after fracturing were analyzed by mercury intrusion porosimetry,low-temperature N2 adsorption test,low-pressure CO2 adsorption test,combining with the fractal theories.The results show that the pore structure of the original coal samples is mainly composed of slit pores formed by the accumulation of flake-shaped particles,and after the CO2 phase transition fracturing,the number of micropores in the coal decreases,while the number of mesopores and macropores increases,the pore structure develops,producing a large number of ink-bottle shaped semi-open/open pores,with the micropores developing into medium pores,the medium pores developing into large pores,and the large pores developing into larger pores.In terms of fractal characteristics,CO2 phase change fracturing has different effects on the structures of micropores,mesopores and macropores,with micropores increasing in fractal dimension,becoming more complex and non-homogeneous,macropores decreasing in fractal dimension,becoming simpler and less non-homogeneous,and mesopores in the low-pressure zone(P/P0≥0.5)decreasing in fractal dimension,becoming simpler and less non-homogeneous.The fractal dimension of mesopores in the high-pressure region(P/P0<0.5)does not show any obvious pattern.The results of engineering applications show that CO2 phase transition fracturing technology can significantly reduce the attenuation coefficient of gas flow,increase the permeability coefficient and permeability,reduce the gas content,and improve the efficiency of gas extraction.

Abstract:Taking the Pingdingshan mining area,a typical deep mining region,as the engineering background,the gas occurrence characteristics controlled by geological structures were elucidated.Based on the distribution features of coal and gas outburst accidents and the evolutionary causes of compound dynamic disasters,it was revealed that in-situ stress,geological structures,and coal seam thickness variation zones are the key factors in monitoring and early warning for compound dynamic disasters.Consequently,a monitoring and early warning system based on the spectral acoustic method for such disasters,was introduced and applied to the driving faces of the Ji15-15080 transportation roadway and return airway at the No.8 Mine of Pingdingshan Tianan Coal Industry Co.,Ltd.Test results indicate that:the outburst risk indicators varied abnormally and exceeded the critical thresholds within a certain distance ahead of fault exposure,the locations exceeding the critical thresholds are distributed within coal thickness variation zones and dip angle change areas.Gas outburst and sudden coal extrusion indicators exceed critical values in fault influence zones and coal thickness variation zones,indicating the risk of dynamic disasters in these areas.The monitoring and early warning results are consistent with on-site working conditions.

Abstract:Given the challenges in quantitatively analyzing complex ionic species within high-salinity mine water and the dominance of SO42-in both concentration and material erosivity,we investigated the effect of SO42-concentration on the mechanical behavior of coal gangue-based filling materials.We prepared specimens using coal gangue and simulated mine water(sodium sulfate solution at 0-30000 mg/L SO42-)as core components,adding a curing agent for consolidation,then tested compressive strength and performed SEM microscopy across curing ages.Results demonstrate that during days 1～7,moderate SO42-boosts strength whereas excess concentrations weaken it,and by days 14～28,the 30000 mg/L SO42-group achieves optimal enhancement;SEM imaging at 28 days reveals escalating SO42-concentrations drive denser interlaced networks of ettringite crystals and C-S-H gels while visibly reducing pores,aligning consistently with macroscopic strength progression.Specimens fabricated with sodium sulfate solution outperform tap-water counterparts in compressive strength,confirming the feasibility of the dual-waste filling material.

Abstract:To address the severe surrounding rock deformation and challenging support issues in deep semi-coal rock gob-side roadways of gently inclined coal seams under high in-situ stress conditions,we took the gob-side roadway of Ⅱ7226S working face in Renlou Coal Mine as an engineering case.Methods including theoretical analysis,numerical simulation,and field testing were employed to investigate the deformation and failure patterns of semi-coal rock gob-side roadway surrounding rock under mining influence,analyze the deformation mechanism,and a surrounding rock control scheme was proposed combining high-strength pre-stressed bolt-cable support with grouting modification reinforcement.The results show a negative correlation between roof deflection in the gob-side roadway and the bearing capacity of the coal pillar,so the roof subsidence can be controlled through enhancing the pillar bearing capacity.Under conventional bolt-cable support,significant stress differences exist between the two ribs of the roadway,leading to asymmetric deformation.The coal rib tends to slide and bulge along the coal-rock weak interface,with severe deformation and overall shear failure occurring on the pillar rib.After optimizing the support design and incorporating grouting modification reinforcement,the stress difference between the two ribs is reduced,the surrounding rock stress environment improves,and deformation is significantly reduced.Field verification in the test section confirms satisfactory control of the roadway surrounding rock.

Abstract:Current methods for determining borehole spacing in gas extraction using boreholes instead of roadways mainly rely on goaf gas migration simulations and field experience.They lack systematic multi-field coupling analysis and insufficiently consider risk factors beyond gas concentration.To address this issue,the 2-105 working face in Tenghui Coal Mine was selected as a test site for integrated simulation and field measurement.First,gas migration patterns in the goaf under different borehole spacings were simulated to establish a baseline spacing range.Subsequently,a comprehensive optimization was conducted by coupling the temperature field,oxygen concentration field,and airflow field in the goaf.Finally,field measurements were carried out to validate the simulation results.The study shows that the borehole spacing based solely on gas field simulation is 25 m.However,multi-field coupling analysis reveals that larger spacing increases air leakage and oxygen concentration,leading to the expansion of the spontaneous combustion zone and the migration of high-temperature areas.Therefore,a dynamic extraction strategy with a spacing of 20 m is proposed.Field measurements indicate that when boreholes are located 15～35 m from the working face,the gas concentration at the upper corner remains below 0.8％,with the maximum differences of 0.9％in oxygen concentration and 0.8 K in temperature,showing minor deviations from the simulation results and confirming the accuracy of the simulation.

Abstract:To address the structural instability of corrugated steel pipe culverts in open-pit mines caused by asymmetric backfilling under heavy-duty transportation,a modular repair technology utilizing an I-beam framework was proposed,Through integrating the numerical simulation and field measurements,a three-dimensional finite element model was established with Midas GTS NX to investigate of progressive deformation behavior in corrugated steel pipe culverts under asymmetric backfill conditions.A modular I-beam reinforcement design was developed based on structural damage characteristics.Rapid repair of the damaged area was achieved through standardized component prefabrication,progressive installation techniques,and a cooperative load-transfer mechanism between the new and old structures.The reinforcement effectiveness was verified via static load testing and model calibration.The results indicate:Firstly,asymmetric backfilling caused lateral displacement of 321.6 mm and a peak arch-foot stress of 359 MPa,leading to local buckling instability;Secondly,after reinforcement with the I-steel frame,the vertical displacement of the arch crown(23.8 mm)and circumferential stress at the arch foot(247 MPa)were restored to the original design levels(24.5 mm,255 MPa),and the maximum displacement under dynamic loads met the L/300 limit requirement;Thirdly,the relative displacement error between numerical simulation and static load tests was 3.5％,verifying the reliability of the model.Therefore,the I-beam frame reinforcement technology can rapidly and effectively restore the load-bearing capacity of damaged culvert structures.

Abstract:To support the optimal design and application of vibratory feeders,we investigated the vibration characteristics and stability of single-mass and dual-mass inertial vibratory feeders.After establishing the dynamic models and differential equations for both types of feeders,we calculated their rigid-body dynamic responses using Laplace transforms,and simulated the coupling force between the material and the feeder via the EDEM discrete element method.Finally,we analyzed the amplitude-frequency response curves under different material loads based on actual engineering parameters.The results show that the required excitation force for the dual-mass feeder is only 20％of that for the single-mass feeder,demonstrating significant energy-saving potential.Within the material coupled mass range of 0～1 t,the amplitude variation rate of the dual-mass feeder(8.82％)is much lower than that of the single-mass feeder(32.35％),indicating superior stability.This enhanced stability originates from the dual-mass feeder's operation in the sub-resonance region,where the leftward shift of the amplitude-frequency curve caused by increased material mass counterbalances the amplitude reduction effect,thereby establishing a stable amplitude zone.These findings provide valuable insights for optimizing vibrating feeder design.

Abstract:To optimize the stability of gob-side entry retaining by roof cutting and pressure relief in deep mines,based on the 360606 working face of Huainan Xinji No.1 Coal Mine,we focused on the full-lifecycle evolution law of floor heave in the entry and proposed control strategies.A comprehensive approach involving theoretical analysis,mechanical modeling,and FLAC3D numerical simulation was employed.Theoretical analysis revealed the mechanism of floor heave at each stage:during roadway excavation,due to stress redistribution,the floor heave was 118 mm;during primary mining,influenced by abutment pressure,it increased to 351.6 mm;during secondary mining,due to bending instability of the immediate floor,it reached 836.9 mm.Numerical simulations indicated that during secondary mining,the peak vertical stress reached 44 MPa,and the plastic zone extended to 40 m ahead of the working face,with high-stress concentration and plastic zone expansion exacerbating floor heave.Based on these findings,a"advanced-lagged-stabilized"phased collaborative control strategy was proposed,and roof cutting parameters were optimized to adjust the stress field.After on-site application,floor heave was reduced to 474 mm,representing a 43.3％decrease compared to the theoretical value,the roadway deformation was effectively controlled.

Abstract:In order to improve the stability and safety of roadway in mining engineering,through 60 years of sustained global research optimization,the mining engineering community has established a robust theoretical-practical framework for gob-side entry retaining and surrounding rock control.We analyzed the application of gob-side entry retaining in different mining modes,such as forward,regressive and reciprocating mining.At the same time,we elaborated on the five key surrounding rock control technologies of gob-side entry retaining,namely surface support,anchorage,modification,pressure relief and joint control.On this basis,we further discussed the application scenarios of filling and roof-cutting gob-side entry retaining.In particular,in the practice of filling gob-side entry retaining,by comparing with other filling materials and methods,the unique properties of high water material and their application characteristics in the filling process were deeply analyzed.Experiments and field data proved that the filling technology of high water material can effectively strengthen the structural strength of roadway,significantly reduce the risk of safety accidents,and significantly improve the recovery rate of coal resources.In addition,we also studied the construction technology,including the key elements of material proportioning and filling methods.