Abstract:Objectives Rib failure and roof collapse in deep,soft-rock coal faces under ground pressure are addressed through investigation of seepage diffusion laws and field application of advance grouting for kilometer-deep mining.Methods Taking the 140504 working face of Kouzidong Mine as a case study,a fan-shaped grouting hole layout is designed for advance roof reinforcement with cement slurry.Using COMSOL Multiphysics,the variations in slurry diffusion radius and grouting pressure over time under double-hole grouting are simulated.FLAC3D is then employed to compare the vertical displacement of the surrounding rock before and after grouting,thereby evaluating the reinforcement effect.Results The results show that:(1)the slurry diffuses concentrically,with the highest concentration at the grouting hole,decreasing axi-symmetrically outward;the diffusion radius increases nonlinearly with time.(2)The maximum diffusion ra-dius is attained after 17 h of grouting.By varying the final hole spacing based on this radius,three rein-forcement scenarios—overlapping,tangent,and separated diffusion zones—are simulated;the tangent con-dition is adopted to determine the optimal grouting hole spacing.(3)The grouting pressure remains nearly constant near the injection point,then drops sharply and stabilizes symmetrically toward both sides.(4)Simulation indicates that roof grouting reduces the maximum vertical displacement by 21.4%,demonstrat-ing effective control of overlying-strata movement.(5)Field practice confirms that grouting reinforcement significantly reduces personnel requirements and increases the monthly face-advance rate by 62.4%.Based on actual grouting data,the final hole pressure should be no less than 8 MPa.Conclusions The findings provide a practical reference for the design and implementation of advance grouting reinforcement in kilometer-deep coal faces.

Abstract:Objectives Stability control of hydraulic supports is a major technical challenge in steeply in-clined coal seam mining.Influenced by variable geological conditions and changes in the mining environ-ment,supports are prone to operating in unstable states.Methods An improved YOLOv11n-Pose algorithm was employed to train the hydraulic support pose detection model,achieving holistic posture detection.To meet requirements for model lightweighting,the GhostNet network structure and RepConv modules were in-troduced into the algorithm's backbone.A self-designed C3k2-RVB-EMA attention mechanism module was incorporated to enhance model robustness.To improve overall model accuracy and convergence efficiency,a comparative analysis of prevalent loss functions—namely CIoU,GIoU,DIoU,EIoU,SIoU,and WIoU—was conducted.Based on this comparison,WIoU(Wise-IoU)was selected as the loss function for the model.Based on a binocular vision model and coordinate transformation relationships,data measurement for prop height,canopy pitch angle,and base deflection angle was achieved.Results The results indicate that the lightweight design reduced the model size by 30.26%compared to the original YOLOv11n-Pose al-gorithm model.The incorporation of the C3k2-RVB-EMA attention mechanism module and the WIoU loss function increased model accuracy by 1.7%.The improved algorithm model outperformed the existing algo-rithm models in generating support posture curves,keypoint positions,and output confidence values.In the posture measurement experiments,the maximum relative error of the proposed model's measurement results was within 5.52%.When deployed on an edge computing device platform,the proposed model exhibited ad-vantages over common models in terms of parameter count,computational load,size,and inference time.Conclusions The proposed improved algorithm model demonstrates high accuracy and robustness for holis-tic posture detection of supports in steeply inclined coal seams.Deploying the model on edge computing de-vices enables efficient inference,effectively balancing detection accuracy with lightweight deployment re-quirements.This provides a feasible technical pathway for posture detection of hydraulic supports in steeply inclined coal seams.

Abstract:Objectives Accurate prediction of mine water inflow is crucial for preventing water hazard acci-dents and ensuring safe production.This study aims to construct a water inflow prediction model suitable for mines in North China-type coalfields affected by water hazards from the underlying L1-4 limestone aqui-fer and Ordovician limestone aquifer.Methods Based on hydrogeological monitoring data from a typical coal mine in Henan Province,a coupled LSTM-Transformer model was proposed.The LSTM component cap-tures the dynamic temporal characteristics of mine water inflow,while the multi-head attention mechanism of the Transformer analyzes the complex temporal correlation between aquifer water level variations and mine water inflow.This framework enables accurate prediction of mine water inflow driven by dynamic wa-ter level changes.Results The coupled LSTM-Transformer model significantly outperformed LSTM,CNN,Transformer,and CNN-LSTM models in prediction accuracy,with a root mean square error(RMSE)of 20.91 m3/h,mean absolute error(MAE)of 16.08 m3/h,and mean absolute percentage error(MAPE)of 1.12%.Furthermore,compared to the single-factor water inflow prediction model,the two-factor(water level and water inflow)prediction model showed greater stability.Conclusions The LSTM-Transformer coupled model successfully overcomes the limitations of traditional methods in capturing the dynamic water level-discharge relationship within complex hydrogeological systems.It provides a solution for dynamic mine water inflow prediction with strong interpretability and robustness,offering a novel methodology for predict-ing water inflow under similar geological conditions.

Abstract:Objectives In order to investigate the influence of different types of crack failures on the contact force characteristics and load sharing performance of the double-ring herringbone planetary gear train,Methods based on SolidWorks and ADAMS,a joint simulation study of faults was conducted.Precise vir-tual prototype models were respectively established for the healthy state and the double-ring herringbone planetary gear train with three different crack faults of penetrating,non-penetrating,and end-face penetrat-ing on the planet gear.The GSTIFF integration method was adopted to solve the tooth contact forces under healthy and different typical crack fault conditions,the load sharing coefficient of the system was calcu-lated,and the contact force characteristics of the internal and external meshing pairs in the time-frequency domain and the variation law of the load sharing performance of system were analyzed.Results The results indicated that in the healthy state,the contact forces of each gear pair exhibited stable cyclic variations.The simulated fundamental frequency differed from the meshing frequency by only 1%.The load sharing co-efficient of the internal and external meshing pairs were 1.006 and 1.007,demonstrating good load sharing performance of the system.In the presence of crack failures,when the depth of penetrating cracks extended to 30 mm,the load sharing coefficient of the internal and external meshing pairs increased by 6.2%and 9.2%respectively;when the angle of penetrating cracks extended to 60°,the load sharing coefficient of the internal and external meshing pairs increased by 6.6%and 7.8%respectively;when the effective length of non-penetrating cracks extended to 120 mm,the load sharing coefficient of the internal and external mesh-ing pairs increased by 4.3%and 4.1%respectively;and when the effective width of end-face penetrating cracks extended to 150 mm,the load sharing coefficient of the internal and external meshing pairs in-creased by 10.8%and 11.4%respectively.Conclusions As the degree of crack faults increased,the load sharing coefficient exhibited a gradual rise,indicating a gradual deterioration in load sharing performance.The external meshing load sharing performance of the system was more significantly impacted than the that of the internal meshing,and the presence of end-face penetrating cracks on the planet gear had a notably greater impact on the load sharing performance of system compared to penetrating and non-penetrating cracks.

Abstract:Objectives Taddress insufficient geological understanding of deep coal-measure gas exploration in the Turpan-Hami(Tuha)Basin,this study focuses on well K1—the deep coal-measure gas well—system-atically investigating its coal reservoir characteristics and exploration potential.The aim is to reveal the gas occurrence patterns and accumulation models in deep coal measures,providing a scientific basis for large-scale exploration and development.Methods Coal petrographic analysis,three-dimensional CT scanning,overburden pressure porosity-permeability experiments,and isothermal adsorption tests are conducted.Pa-rameters such as coal maceral composition,pore structure,and dynamic permeability changes are inte-grated for a comprehensive analysis of the reservoir physical properties.Geological conditions of the Junggar and Ordos Basins are compared,and logging data combined with coalbed methane resource prediction methods are used to evaluate the exploration potential of deep coal-measure gas in the Tuha Basin.Results Deep coal reservoirs in the Tuha Basin are predominantly low-to medium-rank coals(K1 well:Ro=0.64%～0.94%),with vitrinite content up to 80.96%.The coal exhibits intact yet soft structures,characterized by"low porosity,low permeability,and complex pore structures."Porosity ranges from 2.99%to 7.55%,and permeability varies from 0.044×10-3 to 13.52×10-3 μm2,both decreasing with depth.The reservoirs demon-strate a dual-phase gas storage mechanism of"microporous adsorption+macroporous/fracture free gas."Field gas content tests indicate a total gas content of 14.24 to 18.23 cm3/g in the main coal seams,with free gas accounting for 35%～40%.The desorption rates are rapid(adsorption times ranging from 4.06 to 5.01 days),demonstrating a"coexisting dual-phase,free gas-dominated"storage advantage.Two reservoir formation models are identified:(1)the northern piedmont"adjustment-type"gas reservoir and(2)the central sag"self-sourced and self-reservoired"gas reservoir.Compared to the Junggar and Ordos Basins,the Tuha Basin exhibits moderate thermal evolution,high free gas ratios,and rapid initial production effi-ciency.Conclusions The deep coal-measure gas in the Tuha Basin shows significant exploration potential.The main coal seams in the Taibei Sag(Xishanyao Formation)contain resources reserves exceeding 2.2 tril-lion m3.The Wenjisang structural belt and Xiaocao South Slope emerge as prioritized exploration targets due to their"high free gas ratios and low desorption resistance."

Abstract:Objectives With increasing mining depth,deformation of tunnel surrounding rock due to high stress has become increasingly serious.This study aims to optimize borehole stress relief parameters for the sidewalls of the Licun Coal Mine roadway.Methods Based on actual engineering geological conditions,25 experimental schemes were designed using the Box-Behnken method.Numerical simulations using FLAC3D were performed to analyze the mechanical responses under different parameter combinations.Six evaluation indicators were selected based on technical and economic considerations:construction cost,convergence of the sidewalls,roof-to-floor convergence,maximum vertical stress,plastic zone area,and construction ef-ficiency.The analytic hierarchy process(AHP)and principal component analysis(PCA)were employed to determine the weights of each evaluation indicator.Results A comprehensive evaluation model for borehole stress relief parameters was established,overcoming limitations of single evaluation criteria and subjective bias,providing a systematic and accurate evaluation methodology.A multivariate second-order regression equation was developed,using normalized comprehensive scores as the response variable and borehole stress relief parameters as independent variables.The optimized borehole stress relief parameters were found to be:borehole diameter 0.1 m,depth 4 m,and spacing 1 m×1 m,achieving the greatest overall benefit.Conclusions The proposed model provides reasonable and feasible borehole stress relief para-meters,effectively controlling surrounding rock deformation while ensuring economic efficiency,and can serve as a reference for roadway surrounding rock control design.

Abstract:Objectives This study aims to achieve real-time early warning of potential risks in gas-coal over-lapping areas and ensure the safety of gas-coal cross mining.Methods Taking the Daniudi Gas Field and a coal mine in the Hujilt mining area of the Ordos Basin as the engineering background,this study investi-gates the deformation characteristics and vulnerable zones of natural gas wells affected by mining activities.A prediction method for controlling the safe avoidance distance of natural gas wells was established.By inte-grating 3ds Max digital modeling,the Unity3D engine,and C#programming,a three-dimensional visualiza-tion and risk early warning platform was developed,featuring six major functional modules for gas-coal model linkage display and cross-regional risk warning.Results The platform realizes 3D visualization based on virtual-real mapping,laying a solid foundation for early warning system design and development.Through the analysis of field monitoring data,the effects of overburden movement and surface subsidence on the deformation of overlying oil and gas pipelines were revealed,and a 3D visualization of regional sub-sidence contour zoning was constructed.Based on the proposed prediction method for safe avoidance dis-tance control,real-time visual early warning between natural gas wells and coal mining faces was achieved.Furthermore,a comprehensive risk prediction and early warning platform integrating surface subsidence monitoring,pipeline deformation monitoring,and safe distance monitoring of natural gas wells was estab-lished based on GNSS monitoring technology.Conclusions The visualization platform enables 3D display,data monitoring,and real-time early warning in gas-coal overlapping areas.It provides technical support for coordinated gas-coal mining and offers a scientific basis for disaster prevention and control in gas-coal over-lapping regions.

Abstract:Objectives To address the problems of severe air leakage and low gas extraction concentration in failed boreholes,a study was carried out on precision plugging technology and equipment for secondary grouting in single-channel failed boreholes.Methods An accurate detection device for locating borehole air leakage was developed.The specific leakage position was identified by measuring the gas extraction concen-tration at different positions along the pipe bottom.Based on this,precision plugging technology and equip-ment for secondary grouting at the pipe bottom of failed boreholes were designed.A total of 23 low-concentration failed boreholes in the 2-803 working face of Liyazhuang Coal Mine were treated using this technology.Results The developed equipment achieved a secondary grouting pressure of up to 2.0 MPa with good plugging performance.The sealing-section length and depth can be freely adjusted,and the entire de-vice is fully retrievable,making the process simple,efficient,and convenient for field application.Accord-ing to the differences in gas extraction concentration,the main leakage channel of the 2-803 working face was determined to be located 17～23 m from the borehole collar.After applying the technology,the average gas extraction concentration increased from 29.01%before grouting to 81.35%,80.47%and 70.66%after one day,one week,and one month,corresponding to increases of 1.8,1.77 and 1.44 times,respectively.The average pure gas extraction rate increased from 0.05m3/min to 0.161,0.158,and 0.141 m³/min,repre-senting increases of 2.2,2.16 and 1.82 times,respectively.Conclusions The proposed technology and equipment can achieve precision plugging of low-concentration failed boreholes,reduce gas control costs,and improve the effectiveness of gas extraction and management.

Abstract:Objectives In order to accurately detect mask wearing in public places and provide humanized re-minders based on the detection results,a fast mask wearing detection solution was constructed to cope with the dual demands of detection speed and accuracy in the real-world scenarios.Methods Firstly,Fast Spa-tial Pyramid Pooling was improved by replacing the original convolution with deep convolution to achieve the purpose of lightweight the Fast Spatial Pyramid Pooling.Secondly,a self-calibrating channel attention mechanism was proposed,which consists of two levels of channel interactions.The first level of interactions was used to obtain the correlation between neighboring channels and channel weights were computed based on the correlation,and the second level of interactions was used to calibrate the channel weights obtained from the first level of interactions over a larger range of channels.This mechanism has been applied to the Neck part of the network.Thirdly,Weighted Bi-directional Feature Pyramid Network was improved by intro-ducing fusion paths for large-scale feature maps and small-scale feature maps,which aimed to enrich the detail information in the fused small-scale feature maps.Finally,GhostConv module and C3Ghost module were separately utilized to replace the Conv module and C3 module in the Backbone and Neck parts respec-tively,which aimed to reduce the computation and parameters of the network and finally lightweight the Backbone and Neck.Results According to the results on the self-made datasets and the public datasets Moxa3K,the solution in this paper separately improved mAP by 3.1%and 2.9%,reduced parameters by 46.8%and 46.8%,and improved detection speed by 25%and 29.1%when comparing with YOLOv5s.Con-clusions The experimental results demonstrated the effectiveness of the proposed solution.

Abstract:Objectives To address issues in rock mass microfracture grouting for reinforcement and seepage control,this study investigated nano-modified Portland cement-based grouting materials.Methods A nano-modified grouting material was developed using Taguchi-grey correlation optimization combined with or-thogonal tests.Signal-to-noise ratio analysis based on the Taguchi method was applied to systematically evaluate the effects of nano-CaCO3,polycarboxylate superplasticizer,ultrafine fly ash,and water-cement ratio on the grouting material's viscosity,bleeding rate,setting time,and 28 d stone body strength.Re-sults The orthogonal tests showed that the material prepared under the optimal ratio from Taguchi-grey cor-relation optimization exhibited excellent fluidity and mechanical properties,ensuring injectability and rein-forcement performance.Signal-to-noise ratio analysis indicated:nano-CaCO3 significantly increased viscos-ity while reducing bleeding rate;28 d stone strength first increased and then decreased with increasing nano-CaCO3 content.Polycarboxylate superplasticizer reduced viscosity but prolonged setting time and slightly increased bleeding rate,with minor effect on 28 d strength.Ultrafine fly ash also decreased viscos-ity but was unfavorable for shortening setting time or improving 28 d strength.The water-cement ratio had the most pronounced effect on bleeding rate,setting time,and 28 d strength:increasing water-cement ratio improved fluidity but prolonged setting and reduced 28 d strength.Conclusions The developed nano-modified Portland cement-based grouting material demonstrated good fluidity,stability,and mechanical per-formance.These findings provide theoretical and experimental guidance for material selection in practical grouting engineering.

Abstract:Objectives This study aims to investigate the impact of the optimized arrangement of abrasive grains on the subsurface damage of BK7 optical glass during grinding with diamond wheels.Using the maxi-mum crack depth as an evaluation index,the effects of different grain arrangement methods,grain sizes,and maximum cutting thicknesses of single abrasive grains on the subsurface damage depth of optical glass materials were studied.Methods The study conducted grinding experiments on BK7 optical glass using dia-mond wheels with an orderly arrangement of abrasive grains.Initially,the genetic algorithm was used to op-timize the arrangement of abrasive grains.Afterwards,grinding wheels were manufactured using this opti-mized method,and grinding experiments were carried out with two different particle sizes(40/45 mesh and 120/140 mesh),with varying wheel speeds,worktable feed rates,and grinding depths as experimental con-ditions.A vertical machining center was used for grinding experiments,and the grinding process was mea-sured and analyzed.Results Through the genetic algorithm,the optimal arrangement of the grinding wheel abrasive grains was that the axial distance K was 2 mm,the circumferential spacing ƒ was 0.3 mm,and the arrangement angle α was 50°.The experimental results showed that the optimized arrangement of abra-sive grains in the grinding wheel resulted in a smaller crack depth in the ground BK7 optical glass com-pared to other arrangement methods.The subsurface damage depth decreased with the increase of grain size and increased with the increase of the maximum cutting thickness of abrasive grains.The subsurface dam-age of BK7 optical glass after grinding was observed using section polishing and scanning electron micros-copy,and the subsurface damage values were calculated using Image-Pro Plus 6.0 software.Conclusions The study concluded that the use of an optimized arrangement of abrasive grains can significantly reduce the subsurface damage depth of BK7 optical glass.This indicated that the diamond wheel with an orderly ar-rangement of abrasive grains had a significant effect on improving the grinding quality of optical glass,which had important practical application value for the efficient and high-quality grinding of optical compo-nents.

Abstract:Objectives Gaps in existing wastewater treatment carbon-footprint research are addressed in the present study—namely the omission of CO₂ emissions originating from fossil-derived organic carbon in influ-ent wastewater that are released during biological treatment by activated sludge,and the lack of comprehen-sive life-cycle-level evaluation of carbon-reduction pathways.A life-cycle assessment is conducted to ana-lyze and evaluate the carbon footprint of municipal wastewater treatment.Methods An improved carbon-footprint accounting model is developed to identify the key emission sources across the full process of repre-sentative A/A/O(anaerobic/anoxic/oxic)wastewater treatment plants,and integrated,system-level mitiga-tion strategies are proposed.Taking a typical wastewater treatment plant as a case study,a life cycle assess-ment(LCA)method is applied to establish a system encompassing four unit processes:primary treatment,biological treatment,advanced treatment,and sludge treatment.The eFootprint software,along with the CLCD and Ecoinvent databases is used to quantify the carbon footprint.A novel aspect includes the ac-counting of CO2 emissions derived from fossil-origin organic carbon in wastewater during biological treat-ment via the activated sludge process.Based on one year of actual operational data,a sensitivity analysis is conducted to identify key influencing factors.Results The total carbon footprint of the plant is found to be 5.11×10⁻¹ kg CO₂e/m³.The carbon footprint of the four unit processes is ranked as follows:biological treat-ment>sludge treatment>advanced treatment>preliminary treatment.Biological and sludge treatments together account for 73%of the total,identifying them as the primary carbon emission units.From an inventory per-spective,the contributions are ranked as follows:electricity consumption>material consumption>pollutant emissions>direct emissions.Electricity and material consumption are identified as the core influencing fac-tors,with indirect emissions collectively accounting for 82%.Conclusions Based on the carbon footprint ac-counting model constructed in this study,which incorporates fossil-derived CO2 emissions,biochemical treatment and sludge treatment have been identified as the key units for emission reduction,with electricity consumption and material consumption being the primary focuses for management.Accordingly,short-and long-term coordinated emission reduction strategies are proposed:short-term measures include improving equipment energy efficiency,optimizing operational processes,and adopting low-cost material alternatives;long-term strategies involve process upgrades,implementing intelligent control systems,and optimizing the energy mix.This approach provides actionable pathways for carbon emission reduction in wastewater treat-ment plants.

Abstract:Objectives Under strong seismic excitation,soil often exhibits pronounced nonlinear dynamic characteristics,which can exacerbate damage to embedded structures.Methods To investigate the seismic input method that accounts for the nonlinear behavior of layered soils and the influencing factors affecting the dynamic response of underground structures,a modeling approach was developed to simulate seismic motions in layered soils.This approach enables iterative updating of material parameters at various soil depths,thereby reflecting the spatial distribution characteristics of real soil properties.For the dynamic analysis of soil-structure systems,an equivalent linear soil model was nested within the Mohr-Coulomb model to establish a viscoelastic-plastic model.A complete seismic response analysis procedure for a lay-ered soil-structure system considering soil nonlinearity was proposed.Using a specific engineering case,a nonlinear seismic response analysis was conducted to examine the effects of burial depth and soil param-eters on the seismic performance of underground structures.Results The results indicate that,under com-bined static and dynamic loads,the relative displacement difference between the top and bottom of the structure decreases with increasing burial depth.Under identical burial conditions,dynamic bending mo-ments induced by seismic loading contribute more significantly to the overall structural response than shear forces.Moreover,when the surface acceleration time history remains constant,the internal force response of the structure decreases as the soil shear modulus increases.Conclusions For double-layer underground structures,seismic actions cause greater shear and bending moment responses in the upper-layer central columns,which should be carefully considered in seismic design.In soft-soil environments,attention should be paid to the dynamic bending moment response,and effective reinforcement measures should be implemented.

Abstract:Objectives To clarify the sensitivity characteristics and damage mechanisms of deep coalbed methane(CBM),a study on sensitivity evaluation and damage mechanisms is conducted.Methods The deep CBM reservoirs in the Daji Block of the Ordos Basin is investigated in this study.Petrographic thin-section analysis,X-ray diffraction(XRD),and scanning electron microscopy(SEM)are employed to characterize the deep CBM reservoirs and identify potential sensitivity-inducing factors.Laboratory experi-ments are conducted to evaluate the fluid and stress sensitivity of the deep coal samples,thereby elucidat-ing the mechanisms of damage associated with sensitivity effects.Results(1)The coal maceral composition in the study area is dominated by vitrinite,with a low inertinite content and an absence of liptinite.The in-organic components are mainly quartz and clay minerals,with quartz content at 22.60%and clay minerals at 57.05%(predominantly kaolinite).The pore structure is characterized by abundant cast membrane pores,cellular pores,and gas pores,with well-developed fractures that are mostly filled by clay minerals or calcite.The porosity and permeability are relatively low,and pore connectivity is poor.(2)The CBM res-ervoir exhibits velocity sensitivity,water,salt,alkali,and stress sensitivity.The velocity sensitivity index is 82.64%,indicating strong damage.The water,salt,and alkali sensitivity indices are 53.90%,57.00%,and 63.50%,respectively,representing moderately strong damage.The stress sensitivity coefficient ranges from 0.692 9 to 0.938 3,indicating moderately strong to strong damage.However,no acid sensitivity dam-age is observed,and acid treatment can enhance permeability.(3)The high-temperature,high-pressure,and high-stress environment of deep CBM reservoir leads to low rock mechanical strength,making them highly susceptible to stress sensitivity damage.The high content of pyrite,kaolinite,and illite in the min-eral composition tends to autogenous cementation under complex fluid conditions,causing pore and fracture blockage that hinders gas production.Furthermore,high-salinity formation water is prone to salt precipita-tion and crystallization blockages during drilling and production.Conclusions The findings improve the ra-tionale for designing working fluid systems and production regimes.This is of positive significance for en-hancing coal reservoir protection and increasing coalbed methane production.

Abstract:Objectives To address the problem that the pullout resistance of the steel at the tail of resin an-chor bolts in coal mine roadways cannot be fully utilized,a variable-section anchor bolt with a hollow tail is proposed,and its load-bearing characteristics under pullout loads are investigated.Methods Theoretical analysis was employed to examine the internal force distribution,failure modes,and elastic bearing capac-ity of the anchorage segment of the variable-section anchor bolt under pullout loads.This revealed the influ-ence of the hollow section on the bolt's bearing performance.The theoretical findings were validated through laboratory pullout tests.Results Compared to conventional bolts,the hollow section causes a nonlin-ear increase in the axial force distribution of the bolt and an increase in the maximum shear stress at the resin-rock interface.The magnitude of these changes grows with the size of the hollow section.Two failure modes are identified for the variable-section anchor bolt:debonding at the resin-rock interface and bolt frac-ture at the variable-section.Based on their occurrence conditions,formulas for calculating the elastic bear-ing capacity and the critical state equation for each failure mode were derived.By comparing the elastic bearing capacity and safety under the two failure modes,debonding at the resin-rock interface is estab-lished as the primary failure mode.When this debonding occurs,the elastic bearing capacity of the variable-section anchor bolt decreases with increasing hollow section size:initially it declines gradually,then accelerates,showing a negative exponential decay pattern.Conclusions These findings provide theo-retical guidance for improving the economic efficiency of coal roadway support systems and addressing the low steel utilization problem in conventional anchor bolts.

Abstract:Objectives This study is conducted to investigate the coupled evolution of reservoir porosity-permeability and multiple CO2 trapping mechanisms in the CO2-brine-rock system,with the unclear syner-gistic mechanisms among different trapping methods and the sensitivity of key geological and engineering parameters during CO2 sequestration in saline aquifers being addressed.Methods A 100-year numerical simulation(including a 10-year injection period)is performed using the TOUGHREACT software with the ECO2N module.The model is applied to the deep saline aquifer of the Ordovician Majiagou Formation in the Gubei Mine of the Huainan Coalfield.Furthermore,a parameter sensitivity analysis is designed to fur-ther elucidate the influence of key geological(reservoir anisotropy,salinity)and engineering(CO2 injec-tion rate)factors on the efficiency of these CO2 trapping mechanisms.Results Results demonstrate that the maximum lateral extent of the CO2 plume reaches approximately 1000 meters over the simulation period.CO2 injection reduces pH to 5.36 near the injection well,leading to the dissolution of dolomite,which re-leases Mg²⁺ and inhibits calcite precipitation.This indirectly enhances dissolution processes,resulting in porosity and permeability increases of 0～0.52%and 0～1.6%,respectively.Structural trapping is identified as the dominant mechanism,followed by residual(16.9%),solubility(3.9%),and mineral trapping(0.5%).Sensitivity analysis indicates that higher CO2 injection rates enhance the overall storage capacity.Greater initial brine salinity intensifies buoyancy-driven migration,thereby increasing structural trapping,while salt-out effects suppresse solubility trapping.When the horizontal-to-vertical permeability ratio(kh/kv)increases from 1 to 100,residual and solubility trapping rise by 43.1%and 34.3%,respectively.An in-creased kh/kv ratio alters CO₂ distribution and phase partitioning,shifting the dominant trapping mecha-nism from structural dominance to a combination of physical and geochemical processes.Conclusions Struc-tural trapping is confirmed as the primary mechanism for CO2 sequestration in deep saline aquifers.Geo-chemical reactions influence the porosity-permeability structure through a cycle of mineral dissolution,ion migration,and precipitation.Reservoir anisotropy,brine salinity,and CO2 injection rate can be optimized to regulate fluid flow pathways and phase distribution,thereby enhancing the storage effectiveness of mul-tiple CO2 trapping mechanisms.

Abstract:Objectives In order to study the effect of various clearances on the dynamic characteristics of parallel mechanisms,the dynamic model of the 3-PRS parallel mechanism with mixing clearances of rotat-ing pairs and spherical pairs was established and the dynamic analysis was carried out in this paper.Meth-ods Firstly,kinematic analysis was conducted on the position,velocity and acceleration of the 3-PRS paral-lel mechanism;the kinematic models of the clearance rotating pair and the clearance spherical pair based on the"contact-separation"two-state model were established.Secondly,the Flores contact model and the modified Coulomb friction model were used to establish the contact force model.Then,the Newton-Euler method was used to establish the dynamic model of the 3-PRS parallel mechanism with mixed clearance.Fi-nally,through simulation experiments,the influences of mixed clearance,different clearance values,and different drives on the dynamic characteristics of the parallel mechanism were compared and analyzed.Re-sults The results showed that the motion trajectories of the mechanism with mixed clearance and the mecha-nism without clearance in the ideal state tended to be consistent as a whole.However,the mixed clearance causesed the mechanism to deviate from the ideal position during motion,resulting in fluctuations in veloc-ity and more frequent sudden changes in acceleration.By comparing different clearance values,when the clearance increased,the later the mechanism reached stable operation time,the greater the position offset,the greater the speed fluctuated,and the more unstable the mechanism operated.By comparing different drives,when the drive amplitude decreased,the mechanism reached stable operation earlier,the position and speed curves were smoother,and the mechanism was more stable.Conclusions The research results showed that the mixed clearance had a serious impact on the moving speed,acceleration and other dy-namic characteristics of the parallel mechanism.This research could provide a method and theoretical basis for analyzing the actual movement of the 3-PRS parallel mechanism and the control of clearance errors.

Abstract:Objectives This study aims to reasonably predict the threshold at which the dynamic load of high-speed trains may cause'activation'of the foundation in mined-out areas.Methods A combination of theoretical analysis and numerical simulation was employed to systematically investigate the determination of foundation'activation'in mined-out areas beneath high-speed railways,the dynamic loads imposed by trains,and the corresponding calculations of train speed and axle load.Based on the'activation'criteria and dynamic load analysis,a method for calculating the critical load of high-speed railway foundations above mined-out areas was established and applied to engineering practice to obtain the critical load,corre-sponding critical static axle load,and critical train speed.Numerical simulations using MIDAS software were conducted to determine the height of water-conducting fractured zones and the range of critical loads,thereby verifying the feasibility and accuracy of the proposed method and theoretical calculations.Results The results indicate that when a high-speed train passes over a mined-out area,the critical load is 26.60 t.For a designed static axle load is 17 t,the corresponding critical speed is 188.24 km/h;for a designed speed of 250 km/h,the critical static axle load is 15.20 t.When the train operates below the critical load of 26.60 t,the foundation in the mined-out area is unlikely to be'activated'.However,if the train simulta-neously runs at the design speed of 250 km/h and a static axle load of 17 t,the load reaches 29.75 t,ex-ceeding the calculated critical load.In this case,treatment of the mined-out area is necessary to ensure the safety of both the railway and the train.Conclusions The findings provide valuable guidance for the con-struction and treatment schemes of high-speed railway foundations above mined-out areas.

Abstract:Objectives Aiming at the problems of large air gap flux density waveform distortion and high torque ripple of traditional symmetrical magnetic pole permanent magnet synchronous motor(PMSM),a novel rotor of asymmetric interleaved magnetic pole PMSM was proposed.Methods The equivalent magnetic circuit model of the motor considering non-uniform air gap and leakage flux was established.Combined with the winding function theory,the analytical expressions of air gap flux density and torque ripple coefficient were derived.The influence law of rotor magnetic pole parameters on the amplitude of flux density harmon-ics and suppressing torque ripple was analyzed.By using the finite element method,the air gap flux den-sity amplitude,cogging torque and output torque of the motor were taken as the optimization objectives.The structural parameters of the rotor eccentricity,magnetic pole deflection angle and moving distance were optimized.The optimal matching parameters was obtained.The prototype was experimentally verified,and the electromagnetic characteristics and output performance before and after optimization were com-pared.Results The results showed that when the rotor eccentricity was 10.5 mm,the deflection angle of the rotor magnetic pole was 4.5 °,and the moving distance was 0.1 mm,the air gap flux density waveform dis-tortion rate was reduced by 53.3%.The cogging torque and torque ripple were reduced by 24.4%and 56.3%,respectively.The average output torque was increased by 1.6%.The relative error between the ex-perimental value and the simulation value of the cogging torque and the output torque of the prototype were 6.06%and 2.30%respectively.The difference between the results was small,which verified the effective-ness of the finite element analysis method.Conclusions the new structure and magnetic pole parameter opti-mization method proposed in this paper could effectively reduce the harmonic content of the air gap mag-netic density.The torque ripple was suppressed and the motor operation performance was improved.A theo-retical reference for the analysis and optimization of PMSM torque ripple was provided.

Abstract:Objectives Cleats serve as the primary conduits for fluid production and the key storage spaces for free gas in deep coal seams.Their characteristics directly influence methane occurrence state and flow capacity.Methods Through detailed drill core descriptions and CT scanning,cleats in the deep coal seams of the central-eastern Ordos Basin were systematically characterized.By integrating analyses of coal macroli-thotypes,mineral content,and vitrinite reflectance(Ro),formation mechanisms and main controlling fac-tors of cleats were comprehensively investigated.Results The results indicate that cleat development is con-trolled by macrolithotypes,mineral content,and coal metamorphism degree.Cleat frequency decreases pro-gressively from bright to dull coal,with cleats most developed in bright coal(averaging 19.7 cleats per 5 cm)and largely absent in dull coal.Cleats are confined to vitrinite and do not penetrate other components.An increase in mineral content gradually reduces cleat development.Cleats are most developed when the vi-trinite reflectance(Ro)ranges between 1.2%and 1.8%.Based on temporal matching analysis and the stress field evolution during major tectonic events,it is inferred that the face cleats in the study area trend NW-SE.Spatial distribution of these controlling factors was used to delineate cleat development zones,showing most intensive development in the central study area.Conclusions This study clarifies controlling factors and spatial distribution patterns of cleats in deep coal seams,confirming the dominant influence of coal macrolithotypes,mineral content,and metamorphism degree on cleat development.The findings provide a scientific basis for deep resource exploration and development.