Rock spalling,considered an underground geological hazard that usually occurs after excavation in hard rock,threatens the safety of on-site operators and equipment.This study used an objective uncertainty-based model ...Rock spalling,considered an underground geological hazard that usually occurs after excavation in hard rock,threatens the safety of on-site operators and equipment.This study used an objective uncertainty-based model integrating six membership functions to evaluate rock spalling.Meanwhile,a new index,spalling coefficients,as a robust empirical method referring to the rich engineering experience of researchers,was proposed for spalling risk evaluation.Then,60 groups of the spalling dataset are collected from the literature to validate the perfor-mance of the proposed data-driven model and spalling coefficients.The results reveal that the constructed un-certainty model and spalling coefficients method can evaluate the spalling properly from different terms,which can be considered a valuable theoretical tool for underground hazard control and prevention.展开更多
Evaluation and prediction of the long-term behavior of abandoned mines have to consider complex interactions of different physical processes.The hydro-mechanical coupling plays an important role for potential short-an...Evaluation and prediction of the long-term behavior of abandoned mines have to consider complex interactions of different physical processes.The hydro-mechanical coupling plays an important role for potential short-and long-term environmental risks(e.g.surface subsidence,pollution of the biosphere,damage of the geological barrier,damage of groundwater regime).This work addresses challenges and key mechanisms in respect to longterm predictions for abandoned salt and potash mines and provides a general simulation concept.Exemplary,this concept is applied to a generic salt mine model characterized by hydro-mechanical coupling and visco-elasto as well as elasto-plastic material behavior.The concept considers time-depending rock mass and backfill material behavior.Long-lasting and large-scale fluid flow within solution-filled and backfilled cavities as well as a cavern due to creep induced convergence is simulated.A new coupling scheme between the numerical codes FLAC3D and Ansys Fluent is developed and employed for this purpose giving plausible and accurate results by efficient simulation duration.The presented workflow provides a step-by-step overview for assessing long-term safety of abandoned mines,starting with indication of main aspects determining the geomechanical and hydraulic pro-cesses followed by the exemplary model set-up,the choice of constitutive models,the simplification of the modelled mining process,the model calibration and the interpretation of the numerical results.Different model scenarios in respect to initial fluid saturation are simulated considering a partially saturated mine and a fully saturated mine,which leads to free fluid surface evolution up to the generation of excess of fluid pressure.展开更多
Rock failure is often governed by the initiation,propagation,and coalescence of fractures,particularly in hard rocks where fracturing,rather than plastic deformation,is the dominant failure mechanism.Therefore,predict...Rock failure is often governed by the initiation,propagation,and coalescence of fractures,particularly in hard rocks where fracturing,rather than plastic deformation,is the dominant failure mechanism.Therefore,predicting the explicit fracturing process is crucial when assessing rock mass stability for engineering applications.However,fracture mechanics are seldom employed in practical rock engineering design,primarily due to the limited understanding of complex fracturing processes in jointed rock masses and the absence of tools capable of accurately simulating these phenomena.Since the 1990s,a novel approach to modelling rock mass failure has emerged,utilizing a numerical code called FRACOD.This code,based on fracture mechanics principles,predicts the explicit fracturing processes in rocks.Over the past three decades,substantial progress has been made in advancing this method to the point where it can reliably predict rock mass stability at an engineering scale.FRACOD incorporates complex coupled processes,including thermal effects,rock mechanical response,and hydraulic flow,enabling it to address coupled problems commonly encountered in geothermal energy extraction,nuclear waste disposal,hydraulic fracturing,and underground LNG storage,etc.Numerous applications of FRACOD have been conducted over the last thirty years,including studies on borehole stability in deep geothermal reservoirs,pillar spalling under mechanical and thermal loading,and the prediction of tunnel and shaft stability,as well as the excavation disturbed zone(EDZ).This paper reviews the theoretical foundations of the fracture mechanics approach employed by FRACOD and highlights the most recent developments.It also presents several validation cases to demonstrate the accuracy of this approach.Additionally,a case study on geothermal energy development in the Cooper Basin,Australia,is included to illustrate the practical applications of this method.展开更多
In order to master the research status,hotspots and trends of mining surface deformation(MSD)in metal mines,exploring the green and sustainable development path of mines,2241 articles in the Web of Science database in...In order to master the research status,hotspots and trends of mining surface deformation(MSD)in metal mines,exploring the green and sustainable development path of mines,2241 articles in the Web of Science database in recent 30 years were visually analyzed with"metal mine"and"surface deformation"as search keywords.Draw the knowledge map of authors and hot keywords,and discuss the research progress and prospect of MSD based on the environmental impact.The results show that MSD research has experienced three stages:slow start,steady development and rapid development.MSD research involves the whole life cycle of mine mining damage source control,process monitoring and later restoration.MSD research keywords can be divided into five main clusters,among which subsidence prediction,backfilling mining,fracture failure,Geo-mechanical modeling and backfill materials are representative research hotspots.With the progress of the times,MSD research presents the evo-lution characteristics of iterative replacement,from shallow to deep,and subject integration.Furthermore,it puts forward three frontier research directions for the future:MSD intelligent early warning,mine intelligent backfilling-mining integration,mine ecological restoration and environmental governance throughout the whole life cycle.展开更多
The study examines empirical and numerical modeling methods that can be used to predict the depth of notch failure in bored raises excavated for Glencore’s Onaping Depth project within the Craig Mine complex in Sudbu...The study examines empirical and numerical modeling methods that can be used to predict the depth of notch failure in bored raises excavated for Glencore’s Onaping Depth project within the Craig Mine complex in Sudbury,Ontario,Canada,at depths between 1150 and 1915 m.These raises experienced significant notch growth throughout their entire length.A detailed assessment found four mechanisms of deterioration causing the notch growth.Of these mechanisms,stress fracturing and scouring contributed to most of the notch growth.These two mechanisms,when working together,magnify their individual effects,making their combined contributions difficult to predict using existing empirical approaches and numerical models.Hence,a new and innovative approach is presented to simulate the progressive notch failure observed in the Onaping Depth raises using FLAC3D.Due to the inability of FLAC3D to simulate rock fracturing directly,an iterative process is established where elements that meet a damage criterion considering cohesion and volumetric strain are removed from the model,and the model equilibrium is restabilized with additional damage forming.The final stabilized notches simulated with FLAC3D show a good agreement with the geometry observed in the raises.This representation of notch failure is more realistic,which is different from the conventional approach of using yielded elements to represent failure zones in continuum models.This work provides insight into deterioration in bored raises and establishes a framework for predicting deterioration and its growth,thereby enhancing the understanding of rock mass response to mining activities.展开更多
Rock anisotropy caused by inherent structures like bedding,foliation,and micro-fractures directly influences strength,deformability,and stress distribution variations.These directional changes can affect the stability...Rock anisotropy caused by inherent structures like bedding,foliation,and micro-fractures directly influences strength,deformability,and stress distribution variations.These directional changes can affect the stability of rock engineering practices,such as underground openings and slopes,and dealing with the anisotropic rock masses(ARMs)is one of the significant challenges.The commonly used conventional classifications are solely based on the isotropic behavior of rock masses and are unsuitable for anisotropic ones.Despite the limitations of these classifications,engineers tend to oversimplify the situation and characterize or design the ARMs,ignoring the impact of anisotropy.This study presents a summary of geological conditions,mechanical behavior,and classification systems of ARMs,as well as a review of numerical modeling techniques that may be applicable in the design phase within such medium.ARM Rating(ARMR),or any other type of alternative classification system that considers the directions in which rocks act instead of just their strength levels,can facilitate improved feasibility analysis for complex geological conditions and supporting systems design in ARMs.Moreover,the failure criteria considering the anisotropic behavior reflect the nonlinear development with long-term depen-dence on rock strength.Such criteria may be applied to numerical methods,such as the discrete element method(DEM),which offers more or less realistic simulations of ARMs’responses.Nevertheless,establishing standard procedures for the characterization,classification,and design of ARMs,especially in deep underground aniso-tropic conditions,is in high demand.展开更多
Rock slope along motorways in the Higher Himalayan terrains are prone to various types of failure.In order to effectively mitigate these failures,a thorough assessment of rock mass behavior is entailed.The present res...Rock slope along motorways in the Higher Himalayan terrains are prone to various types of failure.In order to effectively mitigate these failures,a thorough assessment of rock mass behavior is entailed.The present research employs and compares widely practiced geo-mechanical classification schemes viz.,RQD,RMR,SMR,Q-slope,and GSI.A 23 km road cut section,along Sangla to Chitkul route,in Higher Himalayan region(India)has been taken up for this work.Total of 18 locations were selected,and their slope and rockmass properties were examined.Afterwards,the most influencing parameters in RMR,SMR,and Q-Slope were evaluated through a machine learning algorithm,i.e.,Random Forest.For RMRbasic,about 83%of rock-slopes were designated in good condition and rest were of Fair quality.Evaluation of slope mass rating along all 18-locations highlighted eight-sites as partially unstable,six-sites as partially stable.Remaining four locations varied between,Very Bad to Bad slope-conditions,necessitating the installation of mechanical supports and redesign of slopes.For SMR classification,feature importance analysis revealed the predominance of F3 variable,RQD and intact rock strength.Q-Slope approach was incorporated to identify the most stable steepest angle of the examined locations.For Q-Slope rating,Jn and RQD were found to have the most influence in classification of the slopes.Three zones on the basis of GSI-scores have been identified in the study area,i.e.,A(6595),B(4555),and C(2535).This study highlights the application of multiple geomechanical classification schemes,demonstrating how each approach can complement the others.展开更多
Geothermal resources,especially hot dry rock(HDR),hold the unparalleled potential to decarbonize energy systems and bolster the global clean energy transition.Despite five decades of development,enhanced geothermal sy...Geothermal resources,especially hot dry rock(HDR),hold the unparalleled potential to decarbonize energy systems and bolster the global clean energy transition.Despite five decades of development,enhanced geothermal systems(EGS)remain constrained by limited power generation capacity,obstructing the commercial viability of deep geothermal energy.A comprehensive understanding of the limitations throughout the system operation is crucial for facilitating large-scale commercial utilization of HDR geothermal energy.Here,we compare the drilling-enhanced geothermal system(D-EGS)and the excavation-enhanced geothermal system(E-EGS)regarding reservoir construction and heat extraction,identifying a critical bottleneck:D-EGS suffers from non-reproducible fractured reservoir construction due to its dependence on site-specific geology,while E-EGS overcomes this by creating universally adaptable caved thermal reservoirs through mining technologies.We further propose a groundbreaking Tiered Synergistic Mining of Geothermal Energy and Minerals(TSMGM)framework,which integrates conventional mining techniques with EGS to extract HDR and mineral resources simultaneously.By stratifying resources into low-(<50°C),medium-(50–100°C),and high-temperature(>100°C)stages,TSMGM facilitates sequential extraction of both geothermal energy and minerals,significantly reducing operational costs and environmental risks.Although the TSMGM confronts substantial scientific and technical barriers,its modular design and tiered temperature-gradient exploitation strategy may advance HDR energy commercialization and enable integrated multi-energy development,positioning TSMGM as a potential catalyst for global carbon neutrality efforts.展开更多
Columnar jointed rock mass(CJRM)combines and mosaic of slender rock columns with different height-to-width(H/W)ratios.Revealing the correlation of the mechanical behavior of individual rock columns with internal facto...Columnar jointed rock mass(CJRM)combines and mosaic of slender rock columns with different height-to-width(H/W)ratios.Revealing the correlation of the mechanical behavior of individual rock columns with internal factors(H/W ratio and material strength)and external factor(lateral pressure)is fundamental to understanding the deterioration of CJRM.We adopt a numerical scheme that combines a statistical meso-damage constitutive model with a finite element formulation based on finite deformation,which can simultaneously consider both material failure and structural instability of the rock columns.Compression tests of rock columns with different H/W ratios and material strengths under varying lateral pressures were conducted to analyze the macro-strength features and failure modes.The numerical results show that increasing the material strength can improve the macro-strength,while the effect of H/W ratio is the opposite.Both increases can promote the conversion of failure modes,and the evolution process is as follows:material failure-induced structural instability→synergy and competition between material failure and structural instability→structural instability-induced material failure.Notably,for the last failure mode,an increase in lateral pressure decreases the macro-strength of the rock column and heightens its instability risk.This finding provides new insights into the response of rocks with different H/W ratios under lateral pressure,extending beyond traditional material-based perspectives.According to the position of the failure mode demarcation line,the failure mode of the rock column can be regulated.展开更多
Time-delayed rockbursts abruptly release huge energy,characterized by suddenness,randomness,and destructiveness,leading to substantial damage to both lives and property.This study explores the occurrence of time-delay...Time-delayed rockbursts abruptly release huge energy,characterized by suddenness,randomness,and destructiveness,leading to substantial damage to both lives and property.This study explores the occurrence of time-delayed rockbursts through statistical analysis of case studies in deep tunnels,including an extremely intensive time-delayed rockburst case.Through on-site surveys,blasting vibration tests,numerical calculations,and true triaxial compression experiments,this study analyzes the main factors and prevention and control strategies of time-delayed rockbursts based on an extremely intense time-delayed rockburst case.The results show that most time-delayed rockbursts are of high intensity.Paramount factors influencing their occurrence consider in-situ stresses,structural planes,and dynamic disturbances.Both high in-situ stress and its gradients provide the necessary conditions for such events,while the presence of abundant structural planes and frequent dynamic disturbances largely increase the risk of rockburst potential.To mitigate the risk of time-delayed rockbursts,energy control strategies are essential,incorporating measures such as energy reduction,prerelease,energy transformation,and energy absorption.Additionally,wave-absorbed support technology can reduce the amplitude and frequency of dynamic disturbances,further decreasing the likelihood of a rockburst occurring.Time-delayed rockburst occurrence requires long disturbance durations,compared to immediate rockbursts.Long-term,continuous,and multiple dynamic events will cause significant damage accumulation and formation of microcracks in hard rock.This study offers insights into the mechanisms underpinning time-delayed rockbursts and proposes prevention strategies for their control.展开更多
Rockburst is a common dynamic geological hazard,frequently occurring in underground engineering(e.g.,TBM tunnelling and deep mining).In order to achieve rockburst monitoring and warning,the microseismic moni-toring te...Rockburst is a common dynamic geological hazard,frequently occurring in underground engineering(e.g.,TBM tunnelling and deep mining).In order to achieve rockburst monitoring and warning,the microseismic moni-toring technique has been widely used in the field.However,the microseismic source location has always been a challenge,playing a vital role in the precise prevention and control of rockburst.To this end,this study proposes a novel microseismic source location model that considers the anisotropy of P-wave velocity.On the one hand,it assigns a unique P-wave velocity to each propagation path,abandoning the assumption of a homogeneous ve-locity field.On the other hand,it treats the P-wave velocity as a co-inversion parameter along with the source location,avoiding the predetermination of P-wave velocity.To solve this model,three various metaheuristic multi-objective optimization algorithms are integrated with it,including the whale optimization algorithm,the butterfly optimization algorithm,and the sparrow search algorithm.To demonstrate the advantages of the model in terms of localization accuracy,localization efficiency,and solution stability,four blasting cases are collected from a water diversion tunnel project in Xinjiang,China.Finally,the effect of the number of involved sensors on the microseismic source location is discussed.展开更多
The inversion of the source mechanism is a critical step in revealing and understanding the mechanisms of rock mass failure and guiding the prevention and control of ground pressure disasters.Under conditions of high ...The inversion of the source mechanism is a critical step in revealing and understanding the mechanisms of rock mass failure and guiding the prevention and control of ground pressure disasters.Under conditions of high stress and strong blasting disturbances,the formation,clustering,and interconnection of internal cracks in the sur-rounding rock of tunnels are highly likely to induce rock mass failure.Investigating the failure mechanisms of tunnel surrounding rock induced by strong blasting disturbances is essential for achieving effective tunnel protection.In this study,acoustic emission(AE)monitoring technology was employed to capture micro-fracture signals from the surrounding rock in real time.The RA-AF ratio method was utilized to classify crack types,while discrete element numerical simulations were conducted to analyze crack propagation patterns under dynamic disturbances.The results indicate that tensile-type cracks dominate during the static stress-controlled stage of tunnel failure,whereas blasting disturbances significantly accelerate shear crack propagation.Stress waves traveling in different directions produce tensile reflection effects in straight wall regions,leading to the inter-connection of shallow cracks on the blast-facing side and the formation of macroscopic fracture zones.Based on these findings,optimization strategies for support design are proposed.Radial constraints should be enhanced on the blast-facing side to suppress shallow surrounding rock deformation,and support depth should be extended along principal stress directions to mitigate rock mass damage and diffusion caused by blasting disturbances.展开更多
The mechanical behavior of fractured rock mass is significantly different from that of intact rock mass,and it is of great significance to study the mechanical response and damage law of crack rock to clarify the occu...The mechanical behavior of fractured rock mass is significantly different from that of intact rock mass,and it is of great significance to study the mechanical response and damage law of crack rock to clarify the occurrence mechanism of deep geological disasters.Based on this,this paper prepared samples with cracks of different angles,simulated deep stress environment,and conducted triaxial compression test on the samples.Combined with crack strain theory and energy dissipation theory,the mechanical failure characteristics of the sample were analyzed.The results indicate that fractures significantly weaken the mechanical properties of the samples,with the strength of fractured rock decreasing by 53.85-64.67%compared to intact rock,and the strength of frac-tured sandstone samples slightly increases as the crack angle increases.The evolution of crack volume strain reflects the damage and failure processes of the rock,while the slope of the crack volume strain curve indicates the rate of crack growth.The crack initiation stress and damage stress divide the crack volume strain process into the crack closing compaction stage,linear elastic deformation stage and stable expansion stage.With the crack angle increases,both crack initiation stress and damage stress initially decrease and then increase.The sample with an angle of 45◦is the smallest,and the sample with an angle of 90◦is the largest,indicating that the sample with a prefabricated angle of 45◦is the most prone to failure.A mechanical crack propagation model was established to analyze the propagation behavior of the cracks,and the deflection propagation characteristics of the fractured sandstone are explained.Using damage mechanics and statistical theory,a multi-parameter damage evolution expression is developed.It is found that the slow damage growth stage of the sample with the crack angle of 45◦lasted the longest and exhibited the fastest damage growth rate,explaining why it is most prone to failure.The evolution trends of total absorbed energy,elastic strain energy,and dissipated strain energy closely align with the stages of microcrack evolution in the sandstone samples.The evolution of energy dissipation reflects the overall damage and failure trends of the sample,and the theoretical model developed can charac-terize the damage and failure characteristics at a certain stage.Finally,based on the law of crack volume strain,a constitutive model for specimen damage and failure is developed,which is consistent with the test results,thereby verifying its accuracy.展开更多
Three-dimensional deformation properties of cement stone are crucial for the stability and safety of shafts.To explore these properties,a series of true triaxial tests adopting common loading path(constant intermediat...Three-dimensional deformation properties of cement stone are crucial for the stability and safety of shafts.To explore these properties,a series of true triaxial tests adopting common loading path(constant intermediate principal stress and minimum principal stress)were performed on the cement stone samples.The relationship between principal strains was examined.To investigate the correlation between shear and volumetric strains,the strain paths within meridian plane are analyzed.Under low intermediate principal stress,the volumetric strain tends to develop with increasing intermediate principal stress.Conversely,under high intermediate principal stress,the shear strain tends to develop with increasing intermediate principal stress.To examine the Lode angle dependence of deformation,the concept of the deflection Lode angle under common loading path is first introduced.The strain paths within the deviatoric plane are then analyzed.The deflection Lode angle is negatively correlated with the intermediate principal stress.With increasing intermediate principal stress,the deflection Lode angle transitions from positive to negative.Furthermore,the Lode dependence of deformation decreases significantly as the minimum principal stress increases.展开更多
Coal mass consists of matrices and cleats,which exhibits significant difference in mechanical properties,such as uniaxial compressive strength and Young’s modulus.Understanding this difference is critical for a numbe...Coal mass consists of matrices and cleats,which exhibits significant difference in mechanical properties,such as uniaxial compressive strength and Young’s modulus.Understanding this difference is critical for a number of engineering applications,such as assessing the stability of cleated coal seam gas wellbores,underground exca-vation stability in coal seams,and estimating cleat aperture response during gas extraction and surface response to reservoir depletion.The conventional method of measuring coal mechanical properties using strain gauges or displacement transducers is impractical and unreliable as it only captures the value for the installed point.This study explores the use of a two-dimensional Digital Image Correlation(2D-DIC)method to quantify the areal deformation of coal matrix and cleat regions and their contribution to the bulk mechanical properties of coal.Cyclic uniaxial compression tests were performed on coal specimens from the Goonyella Middle Seam,Australia.The results from the DIC technique were initially validated against strain gauge and Advanced Video Exten-someter(AVE)measurements,showing minimal percentage differences:5%with the strain gauge;16.6%with the coal cleat region,12.03%with the coal matrix region,and 9.28%with the coal bulk region compared to AVE.These results demonstrate that DIC is a reliable and accurate method for measuring coal deformation.Comparative analysis of cleat,matrix,and overall coal surface regions revealed distinct variations in Young’s modulus,with ratios of E_(cleat):E_(matrix):E_(overall)=0.24:1.60:1.00.The calculated cleat and matrix moduli are 143.6 MPa and 1785.3 MPa respectively.The contributions of E_(matrix)and E_(cleat)to the overall Young’s modulus(E_(overall))were quantified,revealing that the matrix accounts for 56%(A=0.56)and the cleat for 44%(1-A=0.44)of the overall modulus.The compressibility of the cleat shows six times that of the coal matrix(C_(cleat):C_(matrix):C_(overall)=4.24:0.62:1.00),highlighting the critical role of cleats in coal deformation and stress-induced permeability changes.Furthermore,Poisson’s ratios computed from the DIC for the tested coal samples range from 0.19 to 0.33,showing strong agreement with reported values in the literature.By integrating DIC analysis with traditional mechanical testing,this study offers a robust approach to evaluating full-field deformation mechanisms in fractured materials.These findings advance the understanding of coal’s mechanical properties,which in turn supports more accurate geotechnical modeling,optimizes mining design,and enhances coal seam gas extraction strategies.展开更多
Renewable energies including solar and wind are intermittent,causing difficulty in connection to conventional power grids due to instability of output duty.Compressed air energy storage(CAES)in underground caverns has...Renewable energies including solar and wind are intermittent,causing difficulty in connection to conventional power grids due to instability of output duty.Compressed air energy storage(CAES)in underground caverns has been considered a potential large-scale energy storage technology.In order to explore the gas injection char-acteristic of underground cavern,a detailed thermodynamic model of the system is established in the process modelling software gPROMS.The four subsystem models,i.e.the compressor,heat exchanger,underground cavern storage and expander,are connected with inlet-outlet equilibrium of flow rate/pressure/temperature to form an integrated CAES system model in gPROMS.The maximum air pressure and temperature in the cavern are focused to interrogate the critical condition of the cavern during the injection process.When analyzing the mass flow rate-pressure ratio relationship,it’s found that under specified operating conditions,an increase in mass flow rate can lead to a higher pressure ratio.Compression power demand also escalates significantly with increasing mass flow rates,underscoring the system’s energy-intensive nature.Additionally,the cooler outlet energy rate progressively decreases,becoming increasingly negative as the mass flow rate increases.These in-sights offer critical theoretical foundations for optimizing practical efficiency of CAES.展开更多
The dynamic response of fractured rock masses with tunnel-like holes under impact loading is critical for ensuring the stability of underground engineering structures.This study investigates the interplay between stre...The dynamic response of fractured rock masses with tunnel-like holes under impact loading is critical for ensuring the stability of underground engineering structures.This study investigates the interplay between stress waves,crack propagation,and hole defects in rock materials through a combined experimental and numerical approach.A novel Large Single Cleavage Semicircle Compression(LSCSC)test is designed using U-shaped holed specimens with prefabricated cracks,enabling precise measurement of crack propagation velocity via crack propagation gauges(CPGs).An extended peridynamic(XPD)model with a local strain based implementation is introduced to simulate dynamic fracture processes under varying tunnel orientations.The results demonstrate that hole defects significantly alter crack patterns and reduce fracture toughness,with an inverse correlation between crack propagation speed and fracture toughness.Notably,the specimen exhibits the highest susceptibility to failure when the tunnel is inclined at a 45°angle to the stress wave direction.The experimental and numerical results align closely,validating the XPD model’s capability to capture stress heterogeneity,crack initiation,and dynamic failure modes.This work provides critical insights into the fracture mechanisms of holed rock structures under dynamic loads,offering practical references for hazard mitigation in tunneling and underground engineering.展开更多
Under the conditions of underground coal gasification(UCG),the pore structure and mechanical properties of overlying rocks are crucial for the stability of surrounding strata.Therefore,it is of great significance to i...Under the conditions of underground coal gasification(UCG),the pore structure and mechanical properties of overlying rocks are crucial for the stability of surrounding strata.Therefore,it is of great significance to investigate the thermal damage of surrounding rocks.In this study,the variations in apparent characteristics,mass,P-wave velocity,porosity and strength of sandstone after high temperature from room temperature to 800◦C.The results indicate that the physical and mechanical properties of sandstone exhibit different degrees of variation after being subjected to high temperatures.Macropores complexity peaks at 400℃ then weakens due to crack network simplification,while mesopores regularity linearly increases with cementation loss.Porosity growth rate shows three-stage escalation through thresholds at 200◦C and 600℃,rising from 3.81%(25℃)to 18.70%(800℃).The mechanism of sandstone damage caused by high temperatures has been explored based on microscopic thin-section analysis,and the findings of the research can offer insights for the evaluation of rock damage in underground coal gasification.展开更多
Shale instability during shale drilling poses significant challenges that require effective additives to control swelling and enhance water-based drilling fluids.This study investigates the effectiveness of various sh...Shale instability during shale drilling poses significant challenges that require effective additives to control swelling and enhance water-based drilling fluids.This study investigates the effectiveness of various shale in-hibitors,both individually and in combination,and compares them to the latest innovation i.e,Natural Deep Eutectic Solvents(NADES)as a promising alternative.Various additives including Potassium Chloride(KCl),1-Ethyl-3-methylimidazolium chloride.([EMIM]Cl),SiO2 nanoparticles,amine terminated polyetheramine(ATPE),Okra mucilage,Choline Chloride:Urea Deep Eutectic Solvent(DES),and Citric acid:Glycerine Natural Deep Eutectic Solvent(CA NADES)and their combinations were subjected to rigorous examination to delineate their impact on shale stability and drilling fluid properties.Notably,CA NADES reduced mudcake thickness by 42.8%,filtrate volume by 40.3%,and linear swelling by 76.1%,while improving shale recovery by 51.7%.Among the additive combinations,SET B(0.5%KCl+0.5%ATPE)and SET G(0.5%KCl+0.5%[EMIM]Cl)demonstrated particularly effective performance.Surface tension measurements revealed favorable interfacial properties,X-ray diffraction analysis confirmed effective intercalation,and zeta potential assessments indicated improved colloidal stability.Overall,these findings highlight the critical role of optimized additive formulations in miti-gating shale instability and enhancing drilling fluid performance,offering promising strategies for more efficient and reliable drilling operation.展开更多
As the mining depth of coal resources increases,resulting in frequent mine earthquakes during mining.In this study,the rolling window ratio method is firstly chosen as the seismic phase recognition method to read the ...As the mining depth of coal resources increases,resulting in frequent mine earthquakes during mining.In this study,the rolling window ratio method is firstly chosen as the seismic phase recognition method to read the mine earthquake data received by the microseismic sensor.Secondly,the improved genetic algorithm is used as the optimization algorithm of the objective function to build the algorithmic framework of accurate inverse localization of mine earthquake.Finally,the accuracy of this algorithm for seismic source localization is validated using actual engineering cases.Results show that the first arrival time extraction by the rolling window ratio method has the advantages of high accuracy and fast algorithm operation speed.The Fast Fourier Transform-Butterworth joint noise reduction method has a good noise reduction effect,which successfully suppressing noise outside the mine earthquake signal and effectively improving the issue of excessive noise in the mine earthquake signal.Compared to microseismic monitoring data,the localization error for mine earthquakes remains within 5%.展开更多
基金funded by the National Science Foundation of China(42177164,52474121)the Distinguished Youth Science Foundation of Hunan Province of China(2022JJ10073).
文摘Rock spalling,considered an underground geological hazard that usually occurs after excavation in hard rock,threatens the safety of on-site operators and equipment.This study used an objective uncertainty-based model integrating six membership functions to evaluate rock spalling.Meanwhile,a new index,spalling coefficients,as a robust empirical method referring to the rich engineering experience of researchers,was proposed for spalling risk evaluation.Then,60 groups of the spalling dataset are collected from the literature to validate the perfor-mance of the proposed data-driven model and spalling coefficients.The results reveal that the constructed un-certainty model and spalling coefficients method can evaluate the spalling properly from different terms,which can be considered a valuable theoretical tool for underground hazard control and prevention.
文摘Evaluation and prediction of the long-term behavior of abandoned mines have to consider complex interactions of different physical processes.The hydro-mechanical coupling plays an important role for potential short-and long-term environmental risks(e.g.surface subsidence,pollution of the biosphere,damage of the geological barrier,damage of groundwater regime).This work addresses challenges and key mechanisms in respect to longterm predictions for abandoned salt and potash mines and provides a general simulation concept.Exemplary,this concept is applied to a generic salt mine model characterized by hydro-mechanical coupling and visco-elasto as well as elasto-plastic material behavior.The concept considers time-depending rock mass and backfill material behavior.Long-lasting and large-scale fluid flow within solution-filled and backfilled cavities as well as a cavern due to creep induced convergence is simulated.A new coupling scheme between the numerical codes FLAC3D and Ansys Fluent is developed and employed for this purpose giving plausible and accurate results by efficient simulation duration.The presented workflow provides a step-by-step overview for assessing long-term safety of abandoned mines,starting with indication of main aspects determining the geomechanical and hydraulic pro-cesses followed by the exemplary model set-up,the choice of constitutive models,the simplification of the modelled mining process,the model calibration and the interpretation of the numerical results.Different model scenarios in respect to initial fluid saturation are simulated considering a partially saturated mine and a fully saturated mine,which leads to free fluid surface evolution up to the generation of excess of fluid pressure.
文摘Rock failure is often governed by the initiation,propagation,and coalescence of fractures,particularly in hard rocks where fracturing,rather than plastic deformation,is the dominant failure mechanism.Therefore,predicting the explicit fracturing process is crucial when assessing rock mass stability for engineering applications.However,fracture mechanics are seldom employed in practical rock engineering design,primarily due to the limited understanding of complex fracturing processes in jointed rock masses and the absence of tools capable of accurately simulating these phenomena.Since the 1990s,a novel approach to modelling rock mass failure has emerged,utilizing a numerical code called FRACOD.This code,based on fracture mechanics principles,predicts the explicit fracturing processes in rocks.Over the past three decades,substantial progress has been made in advancing this method to the point where it can reliably predict rock mass stability at an engineering scale.FRACOD incorporates complex coupled processes,including thermal effects,rock mechanical response,and hydraulic flow,enabling it to address coupled problems commonly encountered in geothermal energy extraction,nuclear waste disposal,hydraulic fracturing,and underground LNG storage,etc.Numerous applications of FRACOD have been conducted over the last thirty years,including studies on borehole stability in deep geothermal reservoirs,pillar spalling under mechanical and thermal loading,and the prediction of tunnel and shaft stability,as well as the excavation disturbed zone(EDZ).This paper reviews the theoretical foundations of the fracture mechanics approach employed by FRACOD and highlights the most recent developments.It also presents several validation cases to demonstrate the accuracy of this approach.Additionally,a case study on geothermal energy development in the Cooper Basin,Australia,is included to illustrate the practical applications of this method.
基金supported by the Guizhou Provincial Science and Technology Department Innovation Talent Team Construction Project(Qiankehe talent CXTD[2025]025)Qiankehe Platform Talents(GCC[2023]056)+4 种基金Guizhou Provincial Basic Research Program(Natural Sci-ence)(Qianke He Foundation-ZK[2024]Key 022)Guizhou Provincial Department of Education 2023 Annual College Science and Technology Innovation Team(Guizhou Education Technology[2023]055)Project of Cultivation for young top-motch Talents of Beijing Municipal In-stitutions(BPHR202203036)Guizhou Science and Technology Plan Project(Qianke Science Support[2023]General 122)Yuxiu Inno-vation Project of NCUT(2024NCUTYXCX209).
文摘In order to master the research status,hotspots and trends of mining surface deformation(MSD)in metal mines,exploring the green and sustainable development path of mines,2241 articles in the Web of Science database in recent 30 years were visually analyzed with"metal mine"and"surface deformation"as search keywords.Draw the knowledge map of authors and hot keywords,and discuss the research progress and prospect of MSD based on the environmental impact.The results show that MSD research has experienced three stages:slow start,steady development and rapid development.MSD research involves the whole life cycle of mine mining damage source control,process monitoring and later restoration.MSD research keywords can be divided into five main clusters,among which subsidence prediction,backfilling mining,fracture failure,Geo-mechanical modeling and backfill materials are representative research hotspots.With the progress of the times,MSD research presents the evo-lution characteristics of iterative replacement,from shallow to deep,and subject integration.Furthermore,it puts forward three frontier research directions for the future:MSD intelligent early warning,mine intelligent backfilling-mining integration,mine ecological restoration and environmental governance throughout the whole life cycle.
文摘The study examines empirical and numerical modeling methods that can be used to predict the depth of notch failure in bored raises excavated for Glencore’s Onaping Depth project within the Craig Mine complex in Sudbury,Ontario,Canada,at depths between 1150 and 1915 m.These raises experienced significant notch growth throughout their entire length.A detailed assessment found four mechanisms of deterioration causing the notch growth.Of these mechanisms,stress fracturing and scouring contributed to most of the notch growth.These two mechanisms,when working together,magnify their individual effects,making their combined contributions difficult to predict using existing empirical approaches and numerical models.Hence,a new and innovative approach is presented to simulate the progressive notch failure observed in the Onaping Depth raises using FLAC3D.Due to the inability of FLAC3D to simulate rock fracturing directly,an iterative process is established where elements that meet a damage criterion considering cohesion and volumetric strain are removed from the model,and the model equilibrium is restabilized with additional damage forming.The final stabilized notches simulated with FLAC3D show a good agreement with the geometry observed in the raises.This representation of notch failure is more realistic,which is different from the conventional approach of using yielded elements to represent failure zones in continuum models.This work provides insight into deterioration in bored raises and establishes a framework for predicting deterioration and its growth,thereby enhancing the understanding of rock mass response to mining activities.
基金funded by the Natural Sciences and Engineering Research Council of Canada(NSERC)Alliance grant,project ALLRP 597619-24.
文摘Rock anisotropy caused by inherent structures like bedding,foliation,and micro-fractures directly influences strength,deformability,and stress distribution variations.These directional changes can affect the stability of rock engineering practices,such as underground openings and slopes,and dealing with the anisotropic rock masses(ARMs)is one of the significant challenges.The commonly used conventional classifications are solely based on the isotropic behavior of rock masses and are unsuitable for anisotropic ones.Despite the limitations of these classifications,engineers tend to oversimplify the situation and characterize or design the ARMs,ignoring the impact of anisotropy.This study presents a summary of geological conditions,mechanical behavior,and classification systems of ARMs,as well as a review of numerical modeling techniques that may be applicable in the design phase within such medium.ARM Rating(ARMR),or any other type of alternative classification system that considers the directions in which rocks act instead of just their strength levels,can facilitate improved feasibility analysis for complex geological conditions and supporting systems design in ARMs.Moreover,the failure criteria considering the anisotropic behavior reflect the nonlinear development with long-term depen-dence on rock strength.Such criteria may be applied to numerical methods,such as the discrete element method(DEM),which offers more or less realistic simulations of ARMs’responses.Nevertheless,establishing standard procedures for the characterization,classification,and design of ARMs,especially in deep underground aniso-tropic conditions,is in high demand.
基金Anusandhan National Research Foundation(ANRF)(previously,Science and Engineering Research Board-SERB),India for the grant CRG/2022/002509.
文摘Rock slope along motorways in the Higher Himalayan terrains are prone to various types of failure.In order to effectively mitigate these failures,a thorough assessment of rock mass behavior is entailed.The present research employs and compares widely practiced geo-mechanical classification schemes viz.,RQD,RMR,SMR,Q-slope,and GSI.A 23 km road cut section,along Sangla to Chitkul route,in Higher Himalayan region(India)has been taken up for this work.Total of 18 locations were selected,and their slope and rockmass properties were examined.Afterwards,the most influencing parameters in RMR,SMR,and Q-Slope were evaluated through a machine learning algorithm,i.e.,Random Forest.For RMRbasic,about 83%of rock-slopes were designated in good condition and rest were of Fair quality.Evaluation of slope mass rating along all 18-locations highlighted eight-sites as partially unstable,six-sites as partially stable.Remaining four locations varied between,Very Bad to Bad slope-conditions,necessitating the installation of mechanical supports and redesign of slopes.For SMR classification,feature importance analysis revealed the predominance of F3 variable,RQD and intact rock strength.Q-Slope approach was incorporated to identify the most stable steepest angle of the examined locations.For Q-Slope rating,Jn and RQD were found to have the most influence in classification of the slopes.Three zones on the basis of GSI-scores have been identified in the study area,i.e.,A(6595),B(4555),and C(2535).This study highlights the application of multiple geomechanical classification schemes,demonstrating how each approach can complement the others.
基金supported by the National Natural Science Foundation Project(51627804)the Projects of Talents Recruitment of GDUPT(XJ2022000801)+1 种基金the Science and Technology Plan of Maoming(2023034)the Project of Guangdong Provincial Higher Education Institute(24GYB45).
文摘Geothermal resources,especially hot dry rock(HDR),hold the unparalleled potential to decarbonize energy systems and bolster the global clean energy transition.Despite five decades of development,enhanced geothermal systems(EGS)remain constrained by limited power generation capacity,obstructing the commercial viability of deep geothermal energy.A comprehensive understanding of the limitations throughout the system operation is crucial for facilitating large-scale commercial utilization of HDR geothermal energy.Here,we compare the drilling-enhanced geothermal system(D-EGS)and the excavation-enhanced geothermal system(E-EGS)regarding reservoir construction and heat extraction,identifying a critical bottleneck:D-EGS suffers from non-reproducible fractured reservoir construction due to its dependence on site-specific geology,while E-EGS overcomes this by creating universally adaptable caved thermal reservoirs through mining technologies.We further propose a groundbreaking Tiered Synergistic Mining of Geothermal Energy and Minerals(TSMGM)framework,which integrates conventional mining techniques with EGS to extract HDR and mineral resources simultaneously.By stratifying resources into low-(<50°C),medium-(50–100°C),and high-temperature(>100°C)stages,TSMGM facilitates sequential extraction of both geothermal energy and minerals,significantly reducing operational costs and environmental risks.Although the TSMGM confronts substantial scientific and technical barriers,its modular design and tiered temperature-gradient exploitation strategy may advance HDR energy commercialization and enable integrated multi-energy development,positioning TSMGM as a potential catalyst for global carbon neutrality efforts.
基金supported in part by the National Natural Science Foundation of China(4227233052079019)+1 种基金the Liaoning Province Science and Technology Plan Joint Program(Applied Basic Research Project)(2023JH2/101700340)the Fundamental Research Funds for the Central Universities(DUT24ZD135).
文摘Columnar jointed rock mass(CJRM)combines and mosaic of slender rock columns with different height-to-width(H/W)ratios.Revealing the correlation of the mechanical behavior of individual rock columns with internal factors(H/W ratio and material strength)and external factor(lateral pressure)is fundamental to understanding the deterioration of CJRM.We adopt a numerical scheme that combines a statistical meso-damage constitutive model with a finite element formulation based on finite deformation,which can simultaneously consider both material failure and structural instability of the rock columns.Compression tests of rock columns with different H/W ratios and material strengths under varying lateral pressures were conducted to analyze the macro-strength features and failure modes.The numerical results show that increasing the material strength can improve the macro-strength,while the effect of H/W ratio is the opposite.Both increases can promote the conversion of failure modes,and the evolution process is as follows:material failure-induced structural instability→synergy and competition between material failure and structural instability→structural instability-induced material failure.Notably,for the last failure mode,an increase in lateral pressure decreases the macro-strength of the rock column and heightens its instability risk.This finding provides new insights into the response of rocks with different H/W ratios under lateral pressure,extending beyond traditional material-based perspectives.According to the position of the failure mode demarcation line,the failure mode of the rock column can be regulated.
基金supported by the National Natural Science Foundation of China(Grant Nos.52222810 and 52178383).
文摘Time-delayed rockbursts abruptly release huge energy,characterized by suddenness,randomness,and destructiveness,leading to substantial damage to both lives and property.This study explores the occurrence of time-delayed rockbursts through statistical analysis of case studies in deep tunnels,including an extremely intensive time-delayed rockburst case.Through on-site surveys,blasting vibration tests,numerical calculations,and true triaxial compression experiments,this study analyzes the main factors and prevention and control strategies of time-delayed rockbursts based on an extremely intense time-delayed rockburst case.The results show that most time-delayed rockbursts are of high intensity.Paramount factors influencing their occurrence consider in-situ stresses,structural planes,and dynamic disturbances.Both high in-situ stress and its gradients provide the necessary conditions for such events,while the presence of abundant structural planes and frequent dynamic disturbances largely increase the risk of rockburst potential.To mitigate the risk of time-delayed rockbursts,energy control strategies are essential,incorporating measures such as energy reduction,prerelease,energy transformation,and energy absorption.Additionally,wave-absorbed support technology can reduce the amplitude and frequency of dynamic disturbances,further decreasing the likelihood of a rockburst occurring.Time-delayed rockburst occurrence requires long disturbance durations,compared to immediate rockbursts.Long-term,continuous,and multiple dynamic events will cause significant damage accumulation and formation of microcracks in hard rock.This study offers insights into the mechanisms underpinning time-delayed rockbursts and proposes prevention strategies for their control.
基金supported by the National Natural Science Founda-tion of China under Grant Nos.42472351,42177140,52404127,and 42207235the Natural Science Foundation of Hubei Province under Grant No.2024AFD359+1 种基金the Young Elite Scientist Sponsorship Program by CAST under Grant No.YESS20230742the China Postdoctoral Science Foundation Program under Grant No.2024T170684.
文摘Rockburst is a common dynamic geological hazard,frequently occurring in underground engineering(e.g.,TBM tunnelling and deep mining).In order to achieve rockburst monitoring and warning,the microseismic moni-toring technique has been widely used in the field.However,the microseismic source location has always been a challenge,playing a vital role in the precise prevention and control of rockburst.To this end,this study proposes a novel microseismic source location model that considers the anisotropy of P-wave velocity.On the one hand,it assigns a unique P-wave velocity to each propagation path,abandoning the assumption of a homogeneous ve-locity field.On the other hand,it treats the P-wave velocity as a co-inversion parameter along with the source location,avoiding the predetermination of P-wave velocity.To solve this model,three various metaheuristic multi-objective optimization algorithms are integrated with it,including the whale optimization algorithm,the butterfly optimization algorithm,and the sparrow search algorithm.To demonstrate the advantages of the model in terms of localization accuracy,localization efficiency,and solution stability,four blasting cases are collected from a water diversion tunnel project in Xinjiang,China.Finally,the effect of the number of involved sensors on the microseismic source location is discussed.
基金supported by the National Key Research and Development Program of China(2023YFC2907204)the Na-tional Natural Science Foundation of China(52174142)the Science and Technology Program of Liaoning Province(2023JH1/10400004).
文摘The inversion of the source mechanism is a critical step in revealing and understanding the mechanisms of rock mass failure and guiding the prevention and control of ground pressure disasters.Under conditions of high stress and strong blasting disturbances,the formation,clustering,and interconnection of internal cracks in the sur-rounding rock of tunnels are highly likely to induce rock mass failure.Investigating the failure mechanisms of tunnel surrounding rock induced by strong blasting disturbances is essential for achieving effective tunnel protection.In this study,acoustic emission(AE)monitoring technology was employed to capture micro-fracture signals from the surrounding rock in real time.The RA-AF ratio method was utilized to classify crack types,while discrete element numerical simulations were conducted to analyze crack propagation patterns under dynamic disturbances.The results indicate that tensile-type cracks dominate during the static stress-controlled stage of tunnel failure,whereas blasting disturbances significantly accelerate shear crack propagation.Stress waves traveling in different directions produce tensile reflection effects in straight wall regions,leading to the inter-connection of shallow cracks on the blast-facing side and the formation of macroscopic fracture zones.Based on these findings,optimization strategies for support design are proposed.Radial constraints should be enhanced on the blast-facing side to suppress shallow surrounding rock deformation,and support depth should be extended along principal stress directions to mitigate rock mass damage and diffusion caused by blasting disturbances.
基金supported by the Postdoctoral Fellowship Program of CPSF under Grant No.GZB20230451 and 2024T170578National Natural Science Foundation of China Grant.No 52374222+1 种基金National major science and technology project for deep earth Grant No.2024ZD1003903Basic and Applied Basic Research Project of Guangdong Province(2024A1515010992).
文摘The mechanical behavior of fractured rock mass is significantly different from that of intact rock mass,and it is of great significance to study the mechanical response and damage law of crack rock to clarify the occurrence mechanism of deep geological disasters.Based on this,this paper prepared samples with cracks of different angles,simulated deep stress environment,and conducted triaxial compression test on the samples.Combined with crack strain theory and energy dissipation theory,the mechanical failure characteristics of the sample were analyzed.The results indicate that fractures significantly weaken the mechanical properties of the samples,with the strength of fractured rock decreasing by 53.85-64.67%compared to intact rock,and the strength of frac-tured sandstone samples slightly increases as the crack angle increases.The evolution of crack volume strain reflects the damage and failure processes of the rock,while the slope of the crack volume strain curve indicates the rate of crack growth.The crack initiation stress and damage stress divide the crack volume strain process into the crack closing compaction stage,linear elastic deformation stage and stable expansion stage.With the crack angle increases,both crack initiation stress and damage stress initially decrease and then increase.The sample with an angle of 45◦is the smallest,and the sample with an angle of 90◦is the largest,indicating that the sample with a prefabricated angle of 45◦is the most prone to failure.A mechanical crack propagation model was established to analyze the propagation behavior of the cracks,and the deflection propagation characteristics of the fractured sandstone are explained.Using damage mechanics and statistical theory,a multi-parameter damage evolution expression is developed.It is found that the slow damage growth stage of the sample with the crack angle of 45◦lasted the longest and exhibited the fastest damage growth rate,explaining why it is most prone to failure.The evolution trends of total absorbed energy,elastic strain energy,and dissipated strain energy closely align with the stages of microcrack evolution in the sandstone samples.The evolution of energy dissipation reflects the overall damage and failure trends of the sample,and the theoretical model developed can charac-terize the damage and failure characteristics at a certain stage.Finally,based on the law of crack volume strain,a constitutive model for specimen damage and failure is developed,which is consistent with the test results,thereby verifying its accuracy.
基金the National Natural Science Foundation of China under Grants#42141010.
文摘Three-dimensional deformation properties of cement stone are crucial for the stability and safety of shafts.To explore these properties,a series of true triaxial tests adopting common loading path(constant intermediate principal stress and minimum principal stress)were performed on the cement stone samples.The relationship between principal strains was examined.To investigate the correlation between shear and volumetric strains,the strain paths within meridian plane are analyzed.Under low intermediate principal stress,the volumetric strain tends to develop with increasing intermediate principal stress.Conversely,under high intermediate principal stress,the shear strain tends to develop with increasing intermediate principal stress.To examine the Lode angle dependence of deformation,the concept of the deflection Lode angle under common loading path is first introduced.The strain paths within the deviatoric plane are then analyzed.The deflection Lode angle is negatively correlated with the intermediate principal stress.With increasing intermediate principal stress,the deflection Lode angle transitions from positive to negative.Furthermore,the Lode dependence of deformation decreases significantly as the minimum principal stress increases.
文摘Coal mass consists of matrices and cleats,which exhibits significant difference in mechanical properties,such as uniaxial compressive strength and Young’s modulus.Understanding this difference is critical for a number of engineering applications,such as assessing the stability of cleated coal seam gas wellbores,underground exca-vation stability in coal seams,and estimating cleat aperture response during gas extraction and surface response to reservoir depletion.The conventional method of measuring coal mechanical properties using strain gauges or displacement transducers is impractical and unreliable as it only captures the value for the installed point.This study explores the use of a two-dimensional Digital Image Correlation(2D-DIC)method to quantify the areal deformation of coal matrix and cleat regions and their contribution to the bulk mechanical properties of coal.Cyclic uniaxial compression tests were performed on coal specimens from the Goonyella Middle Seam,Australia.The results from the DIC technique were initially validated against strain gauge and Advanced Video Exten-someter(AVE)measurements,showing minimal percentage differences:5%with the strain gauge;16.6%with the coal cleat region,12.03%with the coal matrix region,and 9.28%with the coal bulk region compared to AVE.These results demonstrate that DIC is a reliable and accurate method for measuring coal deformation.Comparative analysis of cleat,matrix,and overall coal surface regions revealed distinct variations in Young’s modulus,with ratios of E_(cleat):E_(matrix):E_(overall)=0.24:1.60:1.00.The calculated cleat and matrix moduli are 143.6 MPa and 1785.3 MPa respectively.The contributions of E_(matrix)and E_(cleat)to the overall Young’s modulus(E_(overall))were quantified,revealing that the matrix accounts for 56%(A=0.56)and the cleat for 44%(1-A=0.44)of the overall modulus.The compressibility of the cleat shows six times that of the coal matrix(C_(cleat):C_(matrix):C_(overall)=4.24:0.62:1.00),highlighting the critical role of cleats in coal deformation and stress-induced permeability changes.Furthermore,Poisson’s ratios computed from the DIC for the tested coal samples range from 0.19 to 0.33,showing strong agreement with reported values in the literature.By integrating DIC analysis with traditional mechanical testing,this study offers a robust approach to evaluating full-field deformation mechanisms in fractured materials.These findings advance the understanding of coal’s mechanical properties,which in turn supports more accurate geotechnical modeling,optimizes mining design,and enhances coal seam gas extraction strategies.
基金supported by National Natural Science Foundation of China Excellent Young Scientists Fund Program,Deep Earth Probe and Mineral Resources Exploration-National Science and Technology Major Project(grant No.2024ZD1004105)Shandong Excellent Young Scientists Fund Program(Overseas)(grant No.2022HWYQ-020)Shenzhen Science and Technology Program(grant No.JCYJ20220530141016036,GJHZ20240218113359001).
文摘Renewable energies including solar and wind are intermittent,causing difficulty in connection to conventional power grids due to instability of output duty.Compressed air energy storage(CAES)in underground caverns has been considered a potential large-scale energy storage technology.In order to explore the gas injection char-acteristic of underground cavern,a detailed thermodynamic model of the system is established in the process modelling software gPROMS.The four subsystem models,i.e.the compressor,heat exchanger,underground cavern storage and expander,are connected with inlet-outlet equilibrium of flow rate/pressure/temperature to form an integrated CAES system model in gPROMS.The maximum air pressure and temperature in the cavern are focused to interrogate the critical condition of the cavern during the injection process.When analyzing the mass flow rate-pressure ratio relationship,it’s found that under specified operating conditions,an increase in mass flow rate can lead to a higher pressure ratio.Compression power demand also escalates significantly with increasing mass flow rates,underscoring the system’s energy-intensive nature.Additionally,the cooler outlet energy rate progressively decreases,becoming increasingly negative as the mass flow rate increases.These in-sights offer critical theoretical foundations for optimizing practical efficiency of CAES.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.12402483,52078467,52204104,12272247)China Postdoctoral Science Foundation(Grant No.2024M752113)Major R&D project of Zhejiang Provincial Department of Transportation under(Grant no.2025ZD001).
文摘The dynamic response of fractured rock masses with tunnel-like holes under impact loading is critical for ensuring the stability of underground engineering structures.This study investigates the interplay between stress waves,crack propagation,and hole defects in rock materials through a combined experimental and numerical approach.A novel Large Single Cleavage Semicircle Compression(LSCSC)test is designed using U-shaped holed specimens with prefabricated cracks,enabling precise measurement of crack propagation velocity via crack propagation gauges(CPGs).An extended peridynamic(XPD)model with a local strain based implementation is introduced to simulate dynamic fracture processes under varying tunnel orientations.The results demonstrate that hole defects significantly alter crack patterns and reduce fracture toughness,with an inverse correlation between crack propagation speed and fracture toughness.Notably,the specimen exhibits the highest susceptibility to failure when the tunnel is inclined at a 45°angle to the stress wave direction.The experimental and numerical results align closely,validating the XPD model’s capability to capture stress heterogeneity,crack initiation,and dynamic failure modes.This work provides critical insights into the fracture mechanisms of holed rock structures under dynamic loads,offering practical references for hazard mitigation in tunneling and underground engineering.
基金the National Natural Science Foundation of China(No.42307244 and 42230704)Xuzhou Research Program Youth Science and Technology Project(KC23044)Open Fund of State Key Laboratory of Geological Disaster Prevention and Geological Environment Protection(SKLGP2024K022).
文摘Under the conditions of underground coal gasification(UCG),the pore structure and mechanical properties of overlying rocks are crucial for the stability of surrounding strata.Therefore,it is of great significance to investigate the thermal damage of surrounding rocks.In this study,the variations in apparent characteristics,mass,P-wave velocity,porosity and strength of sandstone after high temperature from room temperature to 800◦C.The results indicate that the physical and mechanical properties of sandstone exhibit different degrees of variation after being subjected to high temperatures.Macropores complexity peaks at 400℃ then weakens due to crack network simplification,while mesopores regularity linearly increases with cementation loss.Porosity growth rate shows three-stage escalation through thresholds at 200◦C and 600℃,rising from 3.81%(25℃)to 18.70%(800℃).The mechanism of sandstone damage caused by high temperatures has been explored based on microscopic thin-section analysis,and the findings of the research can offer insights for the evaluation of rock damage in underground coal gasification.
基金YUTP Grant 015LC0-535 for providing financial assistance for this study.
文摘Shale instability during shale drilling poses significant challenges that require effective additives to control swelling and enhance water-based drilling fluids.This study investigates the effectiveness of various shale in-hibitors,both individually and in combination,and compares them to the latest innovation i.e,Natural Deep Eutectic Solvents(NADES)as a promising alternative.Various additives including Potassium Chloride(KCl),1-Ethyl-3-methylimidazolium chloride.([EMIM]Cl),SiO2 nanoparticles,amine terminated polyetheramine(ATPE),Okra mucilage,Choline Chloride:Urea Deep Eutectic Solvent(DES),and Citric acid:Glycerine Natural Deep Eutectic Solvent(CA NADES)and their combinations were subjected to rigorous examination to delineate their impact on shale stability and drilling fluid properties.Notably,CA NADES reduced mudcake thickness by 42.8%,filtrate volume by 40.3%,and linear swelling by 76.1%,while improving shale recovery by 51.7%.Among the additive combinations,SET B(0.5%KCl+0.5%ATPE)and SET G(0.5%KCl+0.5%[EMIM]Cl)demonstrated particularly effective performance.Surface tension measurements revealed favorable interfacial properties,X-ray diffraction analysis confirmed effective intercalation,and zeta potential assessments indicated improved colloidal stability.Overall,these findings highlight the critical role of optimized additive formulations in miti-gating shale instability and enhancing drilling fluid performance,offering promising strategies for more efficient and reliable drilling operation.
基金supported by the Shandong Energy Group(No.SNKJ2022A01-R26).
文摘As the mining depth of coal resources increases,resulting in frequent mine earthquakes during mining.In this study,the rolling window ratio method is firstly chosen as the seismic phase recognition method to read the mine earthquake data received by the microseismic sensor.Secondly,the improved genetic algorithm is used as the optimization algorithm of the objective function to build the algorithmic framework of accurate inverse localization of mine earthquake.Finally,the accuracy of this algorithm for seismic source localization is validated using actual engineering cases.Results show that the first arrival time extraction by the rolling window ratio method has the advantages of high accuracy and fast algorithm operation speed.The Fast Fourier Transform-Butterworth joint noise reduction method has a good noise reduction effect,which successfully suppressing noise outside the mine earthquake signal and effectively improving the issue of excessive noise in the mine earthquake signal.Compared to microseismic monitoring data,the localization error for mine earthquakes remains within 5%.
