Abstract:Based on the significant differences in roof structure fracture characteristics between gob-side entry retaining by roof cutting and coal-pillar mining,the mechanical response mechanism of the overburden under gob-side entry retaining by roof cutting was investigated.A physical similar-ity model of a coal mining panel in Shaanxi was constructed to track the dynamic development of fractures in different zones.The results show that the stress in the non-cutting coal pillar increases linearly,while the stress in the cutting-side coal pillar rises slowly in the early stage of mining and then accelerates.Although the roof cutting technique interrupts the short cantilever load path,the overburden load continues to be transferred to the deeper strata through a composite coal-pre-frac-tured plane structure.After the formation of a self-supporting masonry beam in the non-cutting roof,the vertical displacement and strain in the lower strata stabilize,while the horizontal displace-ment follows a"rapid-slow-rapid"sequence.The results also show that,at the end of mining,the maximum strain on the cutting side is 28.4％lower than that on the non-cutting side.The verti-cal displacement and strain in the upper strata are controlled by the key stratum,while the horizon-tal displacement is not affected.The cutting side develops 12.1％fewer fractures,which are mainly oriented within the range of 0°—65°.Field microseismic data further validate the failure mode of"compacted bulking gangue+residual roof micro-fracturing"on the cutting side.These results provide an important reference for clarifying the evolution of roof structure and fracture propagation under gob-side entry retaining by roof cutting conditions.

Abstract:The development and utilization of abandoned mines play a crucial role in advancing China's energy transition and achieving its"Dual Carbon"goals.From a top-level design perspec-tive,the concept of abandoned mine reuse is defined,considering China's national context and re-gional differences.This paper systematically presents a full-lifecycle development strategy,focus-ing on three primary utilization paths:resource-based,energy-based,and function-based.Follow-ing the guiding principle of"classified strategies and coordinated advancement",a phased and differ-entiated approach was proposed,led by pilot projects and supported by a comprehensive mecha-nism involving regional coordination,market regulation,technological innovation,and policy in-centives.The key scientific and technological challenges faced in the coordinated development and utilization of abandoned mines were systematically discussed,including dynamic multi-source detec-tion("sky-space-ground-storage"),underground space stability control,carbon migration pat-terns,three-dimensional carbon management,regional energy transition,and hybrid micro grid con-struction.Critical technologies spanning the entire chain,from resource detection to multifunctional development,were identified.This research offers a theoretical foundation and practical guidance for transforming abandoned mines from environmental burdens into strategic resources,contribut-ing to carbon neutrality and the high-quality development of regional economies.

Abstract:The discovery of oil and gas in the Lower Cambrian Qiongzhusi Formation shale of the Sichuan Basin has opened up a new frontier for shale gas reserve growth.To delineate the current in-situ stress characteristics of the Qiongzhusi Formation shale in the Jingyan area,southern Sich-uan,and their impact on hydraulic fractures,this study conducted a detailed interpretation of in-situ stress orientation and magnitude along well profiles using integrated multi-source data.A refined geological structure model and a heterogeneous geomechanical model were constructed.Building upon the constraints provided by single-well interpretations,a 3D simulation was performed to pre-dict the distribution of the current in-situ stress field.This clarified the distribution characteristics of in-situ stress in the study area and its influencing factors.Subsequently,horizontal well fracturing simulations were conducted to analyze the impact of current in-situ stress on fracture propagation.The main research findings are as follows.The magnitude of in-situ stress and the horizontal stress difference are primarily controlled by burial depth.Vertically,stress locally increases within the black shale-bearing layers 1,5,and 9 due to lithological influence.Planarly,the northwestern and southeastern parts of the study area exhibit higher values,while the middle part shows lower val-ues.In-situ stress magnitude and horizontal stress difference decrease near faults.NE-trending faults have a greater influence on stress magnitude compared to NW-trending faults.The larger the fault scale,the more pronounced the impact.Structural deformation has a relatively weak influence.For the target layer 7,the maximum horizontal principal stress,minimum horizontal principal stress,and vertical principal stress mainly range between 75-95,60-80,and 65-85 MPa,respec-tively.The horizontal stress difference primarily ranges between 11-16 MPa.The orientation of the maximum horizontal principal stress in the study area is predominantly concentrated between N75°-90°E.Influenced by structural deformation,the maximum horizontal principal stress orienta-tion slightly rotates counterclockwise in the southwestern plunging end of the Weiyuan Anticline.In the Tieshan Anticline area and the central pinch zone,the maximum horizontal principal stress ori-entation rotates clockwise by approximately 5°—10° due to fault influence.NE-trending faults have a greater impact on in-situ stress orientation than NW-trending faults.An increase in the minimum horizontal principal stress leads to a decrease in fracture length,width,height,and stimulated reser-voir volume.An increase in the horizontal stress difference results in an increase in fracture length but a decrease in fracture width,height,and stimulated reservoir volume.Better fracturing effec-tiveness is achieved when the well trajectory has a larger angle with the maximum horizontal princi-pal stress direction,and when the minimum horizontal principal stress and horizontal stress differ-ence are relatively small.The research results can provide a reference for the study of in-situ stress in shale reservoirs and the efficient exploration and development of shale gas.

Abstract:The hydraulic fracturing process involves energy input,release,and dissipation.Investi-gating the energy evolution mechanisms and stimulation effects during fracturing processes can pro-vide theoretical foundations and technical support for the optimization of fracturing techniques in deep coal reservoirs.Taking the No.2 coal seam in the southern Yanchuan block in the eastern margin of the Ordos Basin as the research object,by optimizing the physical simulation method of true triaxial hydraulic fracturing,combined with numerical simulation and mathematical modeling,the stress distribution and fracture initiation and propagation characteristics of hydraulic fracturing in deep coalbeds are analyzed,revealing the evolution mechanism of input energy and its control effect on the fracturing effect.The results show the following:The optimization method for the physical simulation of true triaxial hydraulic fracturing,in which the borehole is filled with NaCl powder,re-inforced with anti-pull-resistant glue,and buffered with rubber gaskets on the outer side of the sample,has good reliability,which greatly reduces the probability and end effect of the sample breaking during stress loading and meets the needs of the physical simulation of hydraulic fracturing in deep coal.As the injection rate increases,the fracture creation effect changes from a small-scale,low-fracture width complex fracture network to a large-scale,medium-fracture width complex frac-ture network and then to ultralarge scale,high-fracture width simple fractures.A injection rate of 9 mL/min can form a fracture system with a high scale and fracture complexity.The fracture pres-sure point is the turning point from slow to fast expansion of the fracture zone.Comprehensively considering the effects of in situ stress and water pressure,a model of hydraulic fracturing stress dis-tribution is constructed.The calculation revealed that the transformation of circumferential stress from compressive stress to tensile stress is the driving force for the initiation of fracturing fractures.In the deep normal faulting stress regime,fractures not only form in the plane where the vertical stress and the maximum horizontal principal stress are located but also preferentially initiate near the wellbore parallel to the vertical stress direction.The energy of hydraulic fracturing physical simula-tion of fracture initiation comes from the accumulated input energy during the water pressure in-crease stage(stage Ⅱ).It consists of pressure energy and kinetic energy,and pressure energy is the main body of energy.The injection rate exhibits a quadratic relationship with both the input en-ergy and the dissipated energy,while it follows a logarithmic relationship with the energy input rate.Increasing injection rate can increase the energy input rate,but the energy input efficiency de-creases.There is a Gaussian distribution between the fracture rate and the energy input rate.When the energy input rate in Stage Ⅱ is between 0.70 and 1.15 J/s,the effect of physical simulation fracturing is the best.

Abstract:Investigating the destressing effects of different mining heights in lower protective layer of semi-coal rock under the influence of thick and hard key strata is of great significance for deter-mining a reasonable mining height,controlling gangue discharge,ensuring effective pressure relief,and achieving efficient production.Taking the 172105 lower protective layer of semi-coal rock in Jinling Coal Mine as an example,both physical similarity simulation and FLAC3D numerical model-ing were employed to reveal the fracture and movement patterns of key strata at varying mining heights,as well as their destressing effects on the protected seam.The results indicate that when the mining height is 0.8 m,the interlayer key stratum does not fracture;the overlying strata bend and subside smoothly as a whole,and the protected seam experiences insufficient destressing.When the mining height exceeds 1.15 m,the interlayer key stratum fractures,with the fracture zone developing upward to the bottom of the key sandstone stratum above seam No.2-1,resulting in significant destressing of the protected seam.It is found that when the thickness of the interlayer limestone key stratum is 8.0 m and the mining height is 1.15 m,the swelling deformation reaches 3.0‰;when the mining height increases to 1.9 m,the limestone key stratum fractures,the stress in the protected seam is reduced by 41.6％-70.2％,and the maximum swelling deformation of the protected seam increases to 23.3‰,achieving a significant pressure-relief effect.These results guide the determination of a reasonable mining height for the half-coal-half-rock protective seam at working face 172105 of Jinling Coal Mine and ensure efficient pressure relief of the protected seam.

Abstract:Fine-grained interlayers are common sedimentary features in tailings dams and exhibit hy-draulic properties that can substantially alter the water migration,thereby influencing long-term sta-bility and service performance.To clarify capillary water migration mechanisms in layered tailings,this study examined the effects of fine-grained interlayer position and thickness on capillary rise be-havior.A self-developed real-time monitoring system was used to conduct controlled laboratory model tests.Three comparative experimental groups were established by varying interlayer eleva-tion and thickness.Temporal changes in capillary rise height and moisture distribution were con-tinuously monitored to analyze staged migration behavior.The results demonstrate that capillary rise in layered tailings progresses through three stages:rapid ascent,gradual rise,and stabiliza-tion.Columns with higher interlayers achieve significantly higher final capillary rise heights than those with middle or lower interlayers.Increasing interlayer thickness delayes capillary water trans-mission and promotes sustained moisture accumulation within the interlayer,where water content remaines higher than in adjacent tailings.Fine-grained interlayers markedly regulates water migra-tion in both the underlying and overlying tailings.Capillary flow accelerates upon reaching the lower interlayer interface due to strong matrix suction,whereas a capillary barrier formes at the up-per interface,producing a discontinuous capillary zone.Continued water accumulation ultimately overcame this barrier,enabling upward penetration into the overlying tailings.These findings clarify the coupled mechanisms of capillary water migration and capillary barrier formation in lay-ered tailings.They provide a scientific basis for evaluating moisture redistribution and long-term stability risks in fine-grained tailings dams.

Abstract:The mixing process of resin is a critical stage for the formation of adequate anchoring force of bolts.As a common anchoring defect of bolt,the degree of eccentricity may affect the mix-ing state of resin and the mechanical characteristics of bolt.Therefore,this paper uses theoretical analysis,numerical simulation and laboratory test methods to explore the mixing state of anchoring under the condition of anchoring eccentricity,and analyzes the response characteristics of bolt reac-tion torque under different anchoring eccentricity.The results show that eccentric anchoring ad-versely affects the mixing state of the resin.This leads to reduced breakdown of the resin pouches,uneven distribution of the resin mixture,and decreased compactness and integrity of the cured an-choring structure.Consequently,the reaction torque response characteristics of bolt during mixing are affected,resulting in poorer stability of the cured structure and ultimately weakening the load-bearing capacity of the anchoring system.The reaction torque-time curve of the bolt during mixing exhibits a distinct segmented characteristic,initially showing a significant rise followed by a ten-dency to stabilize.When the bolt passing through the resin cartridge,the root mean square(RMS)value,crest factor and variance of the change rate of bolt reaction torque increase with the eccentric-ity.In the mixing stage after the bolt reaches the bottom,the mean value of bolt reaction torque in-creases with the bolt eccentricity.Taking the characteristic value of bolt reaction torque change rate and the mean value of reaction torque during the mixing process of resin as the index to identify the bolt eccentricity,a tentative idea of identifying the anchoring eccentricity based on bolt reaction torque was proposed.The research conclusions provide a theoretical reference for the future realiza-tion of non-destructive and rapid assessment of bolt anchoring quality.

Abstract:In order to reveal the permeability enhancement mechanism of coal treated by safe and environmental-friendly low-concentration acetic acid with considering multi-phase and multi-field ef-fects,a coupling theoretical model incorporating gas-water phases and stress-chemistry-temperature-diffusion-seepage fields was established to analyze the variation characteristics of cal-cite concentration,hydrogen ion concentration and temperature value of the coal affected by acetic acid.Through adopting the magnetic resonance and ultrasonic wave experimental tests,the im-provement principles of pore and seepage characteristics was investigated.Meanwhile,the chang-ing laws of effective air pressure and water pressure was revealed.The effects of acetic acid concen-tration,initial gas pressure,water saturation,Langmuir volume constant and ultimate adsorption expansion deformation on the permeability and gas extraction characteristics were further analyzed.The results show that:affected by acetic acid,the calcite concentration,H+concentration and tem-perature value of the coal both decrease.The calcite concentration and H+concentration drop to ap-proximately 550 and 0.07 mol/m3,respectively.The coal temperature decreases with the increasing gas drainage time due to the effects of dissolution of calcite and desorption of gas(about 0.942 4 times of the original).Acetic acid treatment contributes to pore and fracture development,resulting in 18 times of permeability increase after 120 d of gas drainage.The NMR spectra of coal samples all show decrease in micro-small and medium pore peaks and increase in large pore peaks.The ultra-sonic attenuation coefficients and ratios of coal samples W2-6％HAc,W3-12％HAc and W4-18％HAc rise.Among which,the increasing degree of W3-12％HAc is the highest,being about 1 583％and 1 388％.This is validated with the acetic acid treatment's permeability enhancement effect.At 120 d of gas extraction,the effective air pressure in treated coal decreases from 0.70 MPa to 0.23 MPa,while the effective water pressure reduces from 0.75 MPa to 0.06 MPa.With the in-creasing acetic acid concentration,ultimate adsorption expansion deformation and water saturation,the coal permeability increases significantly.The range of"low-temperature zone"around borehole decreases with bigger Langmuir volume constant and initial gas pressure,with the lowest tempera-ture value also drops.The results could provide references for obtaining enhancement mechanism of permeability and gas extraction efficiency in coal treated by acetic acid.

Abstract:Elucidating the adhesion mechanisms between cohesive soil and metal under slurry im-mersion is crucial for preventing clogging and cake formation on cutterhead in slurry shield tunnel-ing.Based on the response surface methodology,an experimental study was conducted to investi-gate the adhesive stress between cohesive soil and metal,considering three factors:bentonite con-tent ratio,initial consistency index,and slurry immersion time.A quadratic polynomial regression model for adhesive stress was established,and the variation patterns of adhesive stress under slurry immersion were analyzed.The results show that the initial consistency index of cohesive soil has the most significant influence on adhesive stress,with notable interactive effects between bentonite con-tent ratio and initial consistency index,as well as between initial consistency index and immersion time.The adhesive stress generally decreases with prolonged immersion time.Under short-term immersion,cohesive strata with lower initial water content are more prone to causing clogging and cake formation on cutterhead and other equipment.In contrast,under long-term immersion,cohe-sive strata with lower initial water content and higher bentonite content exhibit a more rapid reduc-tion in peak adhesive stress.The adhesion behavior at the cohesive soil-metal interface under slurry immersion is not solely determined by the water content of the soil.The findings provide insights for risk assessment and prevention of cutterhead clogging in slurry shield tunneling in cohesive strata.

Abstract:To investigate the failure characteristics of fractured rock masses with varying fracture orientations under external loading,uniaxial compression tests were conducted on rock-like models with loading directions at 25°,35°,45°,and 60°(superimposed fracture angle,β)relative to the fractures.Digital image correlation and acoustic emission techniques were employed.The results show that the compressive strength of the models decreases progressively with increasing β.Whenβ is small,normal stress dominates and makes Mode Ⅰ tensile fracture more likely to occur.Whenβ increases,Mode Ⅱ stress intensity factor dominates,leading to Mode Ⅱ shear fracture becoming the dominant mode.The damage of the model accumulates continuously in the first two deforma-tion stages,and after reaching the corresponding moment of model strength,the ringing count de-creases.The total energy release,average cumulative energy,and energy release rate of the model increase with the increase of β.The greater the rate of model destruction,the more intense the en-ergy release,confirming that rupture is the root cause of energy generation.The model with β=60° has the fewest peak frequency points and the most dispersed distribution.The model with β=35° have a higher distribution of quantities and a more severe damage evolution process.By introducing b-value error analysis,it was found that the sudden change in the b-value curve of the β=35° andβ=45° models at the end of the elastic deformation stage can serve as a precursor to rock mass frac-ture.These findings provide valuable theoretical support for engineering design and stability assess-ment of fractured rock masses.

Abstract:In recent years,significant breakthroughs have been made in the exploration of deep coal-bed methane(CBM)in North China,revealing substantial resource potential.However,the un-clear mechanism governing the differential enrichment of free gas has hindered"sweet spot"predic-tion and development planning.Focuses on the typical deep CBM blocks in North China,a ternary coupling mechanism of"burial depth-preservation-reservoir capacity"which controlls the enrich-ment of free gas in deep coal seams was elucidated systematically by geological analysis,experimen-tal testing,and numerical simulation.The results shows that burial depth exceeding the critical ad-sorption depth is a crucial prerequisite for free gas formation,favorable preservation conditions are the key to free gas retention and accumulation,and sufficient reservoir space determines the scale of free gas enrichment.These three factors form an inseparable organic whole,and the absence of any one condition leads to differential enrichment of free gas in deep coal seams.Typical blocks in the southern Ningwu Basin,the Yushe-Wuxiang Block of the Qinshui Basin,and the northern eastern margin of the Ordos Basin were selected for analysis.The results shows that in the southern Ningwu Basin,free gas enrichment is absent because the coal seam burial depth does not reach the critical depth for adsorption capacity.In the Yushe-Wuxiang Block of the Qinshui Basin,intense tectonic modification in later stages caused large-scale gas escape.In the Linxing-Shenfu Block on the northern eastern margin of the Ordos Basin,differences in reservoir capacity primarily governs the differential enrichment of free gas.The results of numerical simulations further indicate that the degree of free gas enrichment is a key controlling factor for the production of deep CBM wells.A higher degree of free gas enrichment is conducive to achieving higher productivity.The efficient ex-ploration and development of deep CBM require defining the optimal"sweet spot"depth window.Within this window,coal seams should possess both high gas content and a significant degree of free gas enrichment to ensure favorable resource composition and scale.Furthermore,it is essential to comprehensively evaluate the stress-strain characteristics and fracability of the coal seams to guaran-tee effective hydraulic fracturing and economic recoverability.This research provides a crucial theo-retical basis for selecting exploration areas and optimizing development strategies for deep CBM.It holds positive significance for promoting the scaled development of China's CBM industry.

Abstract:Clarifying the flow and accumulation patterns of pressure-relief gas in goafs is essential for ensuring mine safety.In this study,based on a working face in the Binchang mining area,the in-fluence of varying mining heights on overlying strata fractures and gas migration was investigated through numerical simulations,which was verified by gas drainage data at field.The results demon-strate a positive correlation between mining height and the extent of fracture development in overly-ing strata.As mining height increased,the rotational space for overlying strata expanded,thereby promoting fracture generation,with significant increases in fracture density,separation volume,fractal dimension,and connectivity coefficient.Greater mining heights leaded to expanding of pres-sure-relief gas migration range,with a more pronounced effect on gas mobility in the middle and up-per zones.Based on the characteristics of fracture evolution and gas flow,the distribution of pres-sure-relief gas in mining-disturbed overlying strata was classified into three distinct zones:the lower diffusion zone,the middle ascending zone,and the upper advection zone.A identifying criterion-in-tegrated approach between the fracture field and seepage field was established using threshold val-ues of fracture density,separation volume,fractal dimension,connectivity coefficient,and gas en-richment rate for each zone.The result shows that as mining height increased from 5 m to 15 m,the spatial extent of gas migration zones expanded by an average of 112.6％.Among them,the promotion effect of mining height on middle ascending zone and upper advection zone is much greater than that of lower diffusion zone.The gas drainage effects of directional drilling in the test working face were good with pure gas flow rate of 0-14.43 m3/min.Drainage efficiency across zones follows the order:middle zone＞lower zone＞upper zone.And the ratio of drainage vol-ume of pressure-relief gas about this drilling site to the absolute gas emission of the working face presented stepped growth characteristic.These findings verified the feasibility of proposed zonal classification method and the rationality of borehole layout,offering theoretical support for optimiz-ing gas drainage strategies.

Abstract:Millimeter-scale fractures in the hydraulic fracture network of shale reservoirs are impor-tant pathways for shale gas seepage.It is of great significance to investigate the characteristics of proppant migration and settlement in these millimeter-scale fractures and the supporting perfor-mance of proppants after settlement.Based on the coupled methods of computational fluid dynamics(CFD)with discrete element method(DEM),and finite difference method(FDM)with DEM,a numerical research approach was proposed to comprehensively explore proppant migration in frac-tures and their supporting effect on fractures after settlement.First,the geometric model of the frac-ture surface for split shale was obtained through laser scanning,and a CFD-DEM model for the proppants transport carried by fracturing fluid within millimeter-aperture fracture was established.The transport characteristics of proppants under different parameters were analyzed and the settle-ment distribution of proppants was obtained.Then,a shale model with millimeter-aperture fracture was established,and the proppants obtained in CFD-DEM simulation were imported into the frac-ture of the shale model.The evolution of fracture aperture under stress,the stress-bearing character-istics of proppants,and the damage law of fracture surfaces were investigated.The research results indicate that smaller proppant particle size,higher fracturing fluid flow rate,and higher fracturing fluid viscosity are more conducive to proppant migration.When mixed proppants with different par-ticle sizes are used,the settlement of large-sized proppants hinders the migration of small-sized prop-pants,thereby forming settlement zones.The proportion of proppants that mainly bear stress is small,and they are mainly distributed in areas where the fracture surfaces have large inclination.There is no obvious correlation between the compression amount of fracture aperture and the prop-pant coverage rate on fracture surfaces,but it is significantly affected by stress magnitude and prop-pant size.Under the action of stress,stress concentration occurs around proppants,leading to ten-sile and shear damage to fracture surfaces.Tensile failure is the main damage form of fracture sur-faces,and the damage volume increases with the increase of proppant particle size.

Abstract:As a new rock breaking method,liquid oxygen transient expansion rock breaking technol-ogy shows significant potential in safety,vibration control and environmental protection perfor-mance.However,there are still some disputes on the energy release mechanism,safety boundary and process reliability.The reaction essence of the transient expansion process of liquid oxygen was systematically discussed,and the energy release mode of"combustion driven+phase transition dominated"was defined;A quantitative calculation method for the phase transition combustion ratio of liquid oxygen was proposed,which reveals that the vaporization expansion of liquid oxygen ac-counts for the main part of energy release;A test method for electrostatic sensitivity of liquid oxy-gen charge was proposed,the critical ignition energy of liquid oxygen charge under test conditions was determined,and it was proved that oil pollution would significantly improve its electrostatic sensitivity.Based on this,a method of eliminating electrostatic by equipotential grounding was pro-posed.Based on the above mechanism cognition,a tungsten wire mediated transient high tempera-ture ignition technology was developed to realize the intrinsic safety of the excitation source;The technology of subsection vibration reduction and detonation was invented according to the law of liq-uid oxygen phase change;The flying rock control method of top energy suppression and bottom en-ergy release and the flexible gradient plugging technology are proposed to effectively suppress flying rocks and reduce punching phenomenon;In addition,the mixed expansion of liquid oxygen and liq-uid nitrogen was explored to control the process of energy release.The field engineering application shows that the liquid oxygen transient expansion rock breaking technology has successfully realized the high-efficiency,low vibration and no flying rock breaking operation in the environment of urban foundation pit and earth rock mining,and verified the feasibility and engineering applicability of the technology.This study lays a theoretical and methodological foundation for the theoretical improve-ment,safety standardization and large-scale engineering application of liquid oxygen transient ex-pansion rock breaking technology.

Abstract:A suitable collector is the core for efficient flotation of fine coal particles.However,the selection logic of traditional surfactants limits the investigation into the interaction mechanism be-tween oxygen-containing functional groups on coal surfaces and reagent groups.This study com-bined simulation and experimental methods to systematically analyze the adsorption behavior and flo-tation enhancement mechanism of composite collectors on coal surfaces.Density Functional Theory(DFT)simulations showed that the average adsorption energies of water molecules,n-d ode cane,n-tetradecane,and methyl linoleate with hydrophilic characteristic units of coal were-0.34,-0.36,-0.38,and-0.46 eV,respectively.The adsorption stability followed the order:methyl linoleate＞n-tetradecane＞n-dodecane＞water molecules,indicating that hydrocarbon oils cannot easily replace the adsorption of methyl linoleate on the hydrophilic sites of coal.The ad-sorption energies of the three reagents were-0.56 eV(n-dodecane),-0.79 eV(n-tetradecane),and-0.84 eV(methyl linoleate),confirming that although methyl linoleate reduces the adsorp-tion sites of hydrocarbon oils,it can improve the overall adsorption stability by adsorbing hydrocar-bon oils,thereby enhancing the collecting effect.In terms of interaction forces,the adsorption be-tween coal and water molecules or methyl linoleate is dominated by hydrogen bonds combined with van der Waals forces,while the interaction with hydrocarbon oils mainly relies on van der Waals forces.These forces significantly improve the adsorption capacity and diffusivity of the reagent.Molecular dynamics(MD)simulations verified that methyl linoleate can increase the distance be-tween water molecules in the system and improve coal hydrophobicity.Flotation experiments showed that when the mass ratio of n-tetradecane to methyl linoleate was 1∶1 with a total dosage of 1 200 g/t,the clean coal yield reached 89.20％,accompanied by an increase in tailings ash content and enhanced separation selectivity.In conclusion,methyl linoleate can strengthen coal hydropho-bic modification and hydrocarbon oil adsorption,thereby improving flotation efficiency.This study provides theoretical support and practical solutions for reagent regulation in coal slime flotation.

Abstract:In order to investigate the dynamical evolution characteristics of the swelling stress dur-ing the CO2 adsorption process in coal,embarking on the key technical challenges such as the air-tightness of the device,the effectiveness of the confinement system and the reliability of the dyna-mometer,a test apparatus for coal adsorption-induced swelling stress has been developed,which in-tegrates the axial confinement system,the data monitoring system,the pore pressure control sys-tem and the temperature control system.The results show that the developed coal adsorption-in-duced swelling stress test device has excellent air-tightness and axial confinement capability,is ca-pable of achieving more than 95％axial deformation of coal samples and enables dynamic testing of gas pressure and coal swelling stress within 10 MPa.The experiments of coal swelling stress under CO2 are conducted based on this device to analyze its dynamical evolution characteristics.The dy-namical evolution curve of adsorption-induced swelling stress in coal during CO2 adsorption over time exhibits three pattern types.When the CO2pressure is low,there is no significant mechanical damage effect due to the adsorbed gas in the coal,resulting in the curve that is primarily character-ized by two stages:The reduction of the compressive stress due to gas injection and the subsequent increase in swelling stress due to gas adsorption,presenting a type-Ⅰ curve with a distinct Lang-muir curve characteristics.As the gas pressure increases,the mechanical damage caused by the"erosion"effect of gas adsorption leads to a decrease in swelling stress,forming a type-Ⅱ curve.Once the stress reduction due to mechanical damage exceeds the stress increase due to adsorption swelling,the swelling stress after adsorption equilibrium is significantly lower than the initial value,presenting a type-Ⅲ curve.A dual Langmuir model for the dynamical evolution of the adsorption-induced swelling stress has been developed,which takes into account the coal mechanical damage,can accurately fit the evolution relationship of the swelling stress over time.

Abstract:The vigorous development of the resource utilization technology and industry for bulk industrial solid wastes(BISWs)is a key initiative for implementing China's"dual carbon"strategy and promoting the circular economy.This paper systematically reviews the technolog-ical pathways and engineering application scenarios for the resource utilization of four typical industrial solid wastes,including fly ash,steel slag,red mud and alkali slag.The technology for preparing geopolymers derived from industrial solid wastes is the focus of analysis.A pro-spective discussion of the development directions of BISWs resource utilization technologies is conducted from three perspectives:multi-source solid waste synergistic utilization,multi-field comprehensive synergistic utilization,and integration of resource utilization with carbon emis-sion reduction.The analysis indicates that the resource utilization technology of BISWs is an e-merging sector with broad development prospects.It can be applied in construction materials,agricultural materials,environmental protection materials,recovery of valuable components,and the preparation of high-value-added products and other fields,with huge development po-tential.From the perspective of large-scale industrial application scenarios,production of con-struction materials and green mine backfilling have emerged as priority directions for the re-source utilization of BISWs."Multi-source synergy,multi-field integration and the unity of pollution reduction and carbon mitigation"represent the overarching development trend.First-ly,the joint utilization of different solid wastes such as slag,steel slag and fly ash is promoted by the synergy of solid waste sources,which is characterized by"component complementarity and activity synergy".Secondly,guided by the"value gradient"application fields,the limita-tions of single-sector utilization are overcome to establish an integrated a comprehensive utili-zation system.Thirdly,focused on the dual objective of"pollution reduction and carbon miti-gation",the integration of resource utilization and carbon emission reduction goals is promoted by connecting solid waste carbonation with CO2 mineralization through functional synergy.This study provides theoretical support and practical references for technological development,industrialization promotion and formulation of relevant policies in the BISWs resource utiliza-tion industry,thereby contributing to China's"dual carbon"goals and the construction of a Beautiful China.

Abstract:After undergoing a series of mining activities such as overburden removal,excavation,dumping,and reclamation,the original natural strata,landforms,landscapes,and other key ecologi-cal elements in open-pit coal mines undergo profound structural changes,resulting in a unique large-scale artificial ecosystem.This paper analyzed the spatial heterogeneity of ecological factors such as hydrothermal conditions,topography,and rock-soil strata in open-pit coal mines,as well as their en-vironmental effects,across three scales:regional,mine-scale,and local dump-site scales.At the re-gional scale,an analytical method based on the hydrothermal coordination index was established.It was found that the hydrothermal conditions of open-pit coal mine ecosystems in arid and semi-arid re-gions of China exhibit significant spatial differences.Hydrothermal coordination directly affects the ef-fectiveness of vegetation restoration in mining areas and should be considered as one of the key factors in planning the production capacity layout of open-pit mines.At the mine scale,changes in elevation and slope before and after mining in typical open-pit coal mines were analyzed.Based on Sentinel-2 satellite atmospheric water vapor data and Envi-met numerical simulations,it was revealed that an"inversion effect"forms in open-pit mines at night,which exacerbates the upward migration and accu-mulation of dust from the mine pit towards the temperature inversion layer.During the daytime,an"M-shaped wet island effect"characterized by"high in the removal area-low in the excavation area-high in the dumping area"emerges,while a"dry island effect"occurs at night.These phenomena ex-acerbate the loss of surface soil moisture in the mining area.At the local dump-site scale,a typical particle-size segregation phenomenon was observed on the step slopes of reconstructed dump strata,with the particle-size distribution along the slope direction conforming to the Rosin-Rammler distribu-tion function.The reconstructed dump strata exhibit a typical vertical differentiation feature of"or-dered structure in the lower part and disordered structure in the upper part".Under the influence of particle-size segregation,a vertical permeability gradient is formed in the reconstructed dump strata,and the internal seepage field shows nonlinear migration characteristics dominated by"preferential channel migration-retention at heterogeneous interfaces".Such a disordered structure lacks the condi-tions to impede groundwater infiltration,making it difficult to restore the phreatic water level.There-fore,the systematic implementation of ecological restoration in open-pit mines should also include sci-entific reconstruction of dump strata to control seepage conditions in the restored strata and prevent risks of solute migration pollution.This study holds significant theoretical importance for understand-ing the evolution mechanisms of mining ecosystems,optimizing mining design,and formulating eco-logical protection and restoration measures for mining areas.

Abstract:Coal-gas compound dynamic disasters(hereinafter referred to as"compound disas-ter")is a catastrophic behavior in which the energy of the"gas-containing coal seam-surround-ing rock"system is violently released under deep mining disturbance.At present,there is still a lack of in-depth analysis on the interaction of energy between coal seams and surrounding rocks,especially the mechanism of surrounding rocks in compound disaster.By conducting physical simulation experiments on the instability of gas-containing coal rock structures under different geo-stress and coal rock strength differences,the energy conversion law of compound disaster was analyzed,and the mechanism of the elastic performance of surrounding rocks was mainly explored.A critical criterion model for rock instability was constructed based on dis-turbance response criteria,and the critical conditions for rock instability and the effect of rock energy accumulation on compound disaster were quantitatively determined.The experimental results show that the evolution of disasters is dominated by the energy feedback path between the surrounding rock and coal,which is manifested as:under high geo-stress and low roof strength conditions,the surrounding rock accumulates higher residual elastic performance due to enhanced energy storage capacity;The residual elastic energy of the two promotes mutual destruction through the bidirectional transmission mechanism of"coal-surrounding rock",leading to an increase in the degree of damage to the coal and roof,which in turn makes it easi-er for the ejected holes to expand upwards,ultimately significantly enhancing the intensity and risk of disasters.Theoretical results indicate that both low strength and high impact prone sur-rounding rocks are prone to instability under disturbance due to weak energy storage capacity and low threshold for plastic zone expansion,and are more likely to exacerbate coal damage through energy transfer;Although enhancing the strength of coal and rock can increase the critical stress of surrounding rock instability,the impact tendency increases synchronously,which may in turn reduce the critical value of instability and form a contradiction in prevention and control.Although the increase in support strength can only enhance the energy storage ca-pacity of the surrounding rock to a limited extent,it mainly releases elastic energy in a control-lable area by constraining deformation,reducing the risk of energy transfer to the coal body.Although increasing the excavation radius will significantly expand the plastic zone radius and elastic energy storage,it will not directly increase the risk of disasters.However,when disas-ters occur,the concentrated release of a large amount of elastic energy may increase the inten-sity of the disaster.The research proposes a"medium modification unloading energy dissipa-tion"prevention and control strategy,providing theoretical basis for the prediction and preven-tion of deep compound disaster.

Abstract:The middle and upper reaches of the Yellow River basin serve as a significant energy resource enrichment zone in China,possessing substantial reserves of carbon-based resources such as coal,oil,and natural gas.With the sustained growth of China's energy demand and the progressive depletion of resources in traditional energy production areas in the eastern re-gion,this area has evolved into a pivotal strategic zone for safeguarding national energy securi-ty.Currently,the intensifying contradiction between large-scale,high-intensity,and pro-longed mining activities and the region's complex and fragile ecological environment has signifi-cantly constrained the secure exploitation of carbon-based resources and the sustainable devel-opment of the regional economy and society.Focusing on the synergistic evolution mechanisms and damage effects of geological structure-hydrological cycle-ecological environment during re-source exploitation,and based on the concept of systems science,this study proposes the sci-entific connotation,key issues,and research framework for geological support of coordinated exploitation of superimposed carbon-based resources at the basin scale.The main contents are as follows.Conduct systematic study the spatial distribution patterns and coupling relation-ships between carbon-based resources(including coal and coal series resources,oil and gas re-sources,and biomass)and eco-environmental-hydrogeological systems at the basin scale.Clar-ify the baseline characteristics of pre-exploitation geological conditions and multi-sphere(such as atmosphere,hydrosphere,and biosphere)structural elements.Analyze the spatiotemporal evolution patterns of geological conditions and the dynamic response characteristics of multi-sphere structure-function during superimposed resource exploitation.Reveal the feedback mechanisms among geological occurrence conditions,resource exploitation disturbances,and eco-environmental damage.Investigate the spatiotemporal multi-source information fusion and active-passive collaborative monitoring methods for deep-shallow-surface geological structures and extract multi-dimensional dynamic information on geological structures,hydrological cycle processes,and ecological elements under resource development disturbances.Construct a ba-sin-scale multi-sphere structure-function coupling evolution model,develop an intelligent pre-diction and comprehensive evaluation platform,and achieve whole-process dynamic monitoring and trend prediction of the synergistic evolution of geological-hydrological-ecological multi-sys-tems during superimposed carbon-based resource exploitation.Propose an optimized allocation strategy for coordinated development of oil-gas,coal,and biomass resources based on the geo-logical occurrence characteristics and spatial distribution patterns of superimposed carbon-based resources at the basin scale.Develop damage mitigation engineering technologies that harmonize resource exploitation with basin hydro-ecological environments.Construct a large-scale,diversified,and functional comprehensive utilization model for underground spaces crea-ted by resource exploitation.Establish a full life-cycle geological support and damage mitiga-tion strategy with corresponding engineering technology systems,encompassing the"pre-ex-ploitation,during-exploitation,and post-exploitation"phases.The research can provide scien-tific guidance for secure and efficient resource extraction,thereby supporting the implementa-tion of the national strategy for ecological protection and high-quality development in the Yellow River basin.