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 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 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 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.

Abstract:Objectives Due to the limitations of traditional continuum mechanics and fracture mechanics,it is challenging to accurately reveal the spatial structural characteristics of deep surrounding rock,particu-larly under three-dimensional stress states and complex geological conditions.Methods Based on the dimen-sionless conditions derived from quai-resonance and pendulum wave phenomena,a"characteristic energy factor"was derived to reflect the energy evolution of deep rock masses.This factor describes the energy-bearing properties of deep surrounding rock from a statistical physics perspective.Statistical analysis of field monitoring and model test data revealed the spatial variation of the characteristic energy factor during zonal disintegration.Results Comparative analysis with Shemyakin's empirical formula for the farthest frac-ture zone radius and measurement data from the 3213 working face in an underground mine validated the scaling evolution relationship between the spatial structure of zonal disintegration and the characteristic en-ergy factor.This indicates that the evolution of the characteristic energy factor can reflect the spatial struc-tural characteristics of zonal disintegration.Conclusions The proposed model has a minimal number of pa-rameters,is easy to measure,and demonstrates strong practicality and applicability,making it well-suited for predictive analysis and support design in deep tunnel construction.Additionally,this model significantly simplifies calculations and provides a novel approach to improving safety in deep underground engineering.It holds considerable potential for future planning of deep tunnel construction and the development of sur-rounding rock support strategies.

Abstract:Objectives This study aims to evaluate the leaching characteristics of solidified heavy metal-contaminated soil under an open-unidirectional freezing condition in the shallow groundwater environment of seasonally frozen regions.Methods Active magnesium oxide(MgO)and fly ash were used to solidify/sta-bilize Pb-Cd composite contaminated soil.Freeze-thaw cycle tests and leaching toxicity tests were con-ducted under two unidirectional freezing conditions:open(with external water replenishment)and closed(without external water replenishment).Scanning electron microscopy(SEM)was employed to investigate the deterioration mechanism of freeze-thaw cycles on the leaching characteristics of the solidified/stabilized Pb-Cd contaminated soil.Results The results showed that under different freezing conditions,the frost heave and the leaching concentrations of Pb and Cd followed the same trend:open-unidirectional freez-ing>closed unidirectional freezing>constant temperature freezing.After 11 freeze-thaw cycles,compared with the open-unidirectional freezing group without stabilizer,the frost heave of the closed unidirectional freezing group and the open-unidirectional freezing group with stabilizer decreased by 38%and 83%,re-spectively.The leaching concentrations of Pb and Cd in the open-unidirectional freezing group with stabi-lizer were 5.62 mg/L and 1.09 mg/L,which were 1.99 and 1.58 times those of the closed unidirectional freezing group,and 5.21 and 2.53 times those of the constant temperature freezing group,exceeding the limits specified in the national soil quality standards.Conclusions Freeze-thaw cycles reduced the content of hydration products and increased internal pore development within the solidified soil,thereby signifi-cantly weakening the immobilization effect of MgO-fly ash on Pb and Cd.The deterioration effect was more pronounced under the open-unidirectional freezing condition.These findings provide references for improv-ing the design of solidification/stabilization processes and evaluating the long-term stability of contaminated soil in shallow groundwater environments of seasonally frozen regions.

Abstract:Objectives To illustrate the characteristics of longitudinal guided wave in resin bolts,the eigen-function expansion method was used to solve the longitudinal guided wave dispersion equations of a resin bolt.Methods The resin anchor bolt was considered as a typical double-layer cylindrical viscoelastic struc-ture.Based on the Hysteretic viscoelastic model,considering continuity boundary conditions,the acoustic field displacements were represented in the Legendre polynomial series form.Then the problem of solving the complex wave control partial differential equation system was transformed into the problem of eigen-value calculation through matrix transformation.The eigenvalue was the wave number,and the eigenvector was the displacement field distribution,the longitudinal guided wave dispersion relationship was estab-lished,and the analytical solution of the transcendental dispersion equation was obtained.Then the group velocity dispersion curve and attenuation curve could be plotted.The correctness of the presented method was verified by comparing the obtained group velocity and attenuation results of a free bolt with those of ex-isting literature.Based on the COMSOL software,the longitudinal guided waves in various resin bolts were simulated to illustrate the influences of resin layer thickness and bond length on the guided wave character-istics.Results The results showed that:(1)The thickness of the resin layer had a significant effect on the longitudinal guided waves.With the increase of layer thickness,the wave packet dispersion and waveform distortion of the recovered signal increased.The group velocity and amplitude ratio of guided waves de-crease with the increase of layer thickness,but the attenuation increased.(2)With the increase of bond length,the group velocity of guided waves in the resin bolt decreased,the amplitude ratio decreased,and the guided wave attenuation increased.Conclusions The group velocity of guided wave was approximately linear with the bond length,and quantitative judgment of the length of the resin bolt bond section can be made through changes in guided wave group velocity.

Abstract:Objectives To investigate the effect of high-temperature history on the compressive strength of desert sand concrete(DSC),compressive strength tests of DSC after exposure to high temperatures were conducted by considering the effects of desert sand replacement rate(DSRR),temperature,heating rate,and resting time.Methods X-ray diffraction(XRD)and scanning electron microscopy(SEM)were em-ployed to analyze the changes in the microstructure and phase composition of DSC after high-temperature exposure.Based on the back-propagation(BP)algorithm,an artificial neural network(ANN)for predict-ing the compressive strength of DSC after high temperature was developed by integrating particle swarm op-timization(PSO)and genetic algorithm(GA).The model was validated using ten-fold cross-validation.Re-sults The results indicated that the compressive strength of DSC decreased with increasing temperature,ac-companied by significant decomposition of hydration products and progressive propagation and interconnec-tion of microcracks.Longer resting time led to higher compressive strength,while higher heating rates ac-celerated the damage of DSC.The compressive strength reached its maximum when the DSRR was 20%.The mean absolute percentage errors(MAPE)of the three predictive models were all within 8%.A higher degree of model optimization resulted in smaller prediction errors.The hybrid PSO-GA neural network model achieved the highest prediction accuracy,with a root mean square error(RMSE)of 1.127 2,MAPE of 3.98%,and a determination coefficient(R2)of 0.987 8 for the 28-day compressive strength.Conclu-sions The proposed method significantly improves the prediction accuracy of the mechanical properties of DSC after exposure to high temperature.