The deformation characteristics and thermal response of anchor rods are crucial for ensuring the stability and safety of surrounding rock support structures.However,existing research has predominantly concentrated on ...The deformation characteristics and thermal response of anchor rods are crucial for ensuring the stability and safety of surrounding rock support structures.However,existing research has predominantly concentrated on the mechanical performance of anchor rods,with limited attention to the coupled evolution of strain and temperature fields during tensile deformation.This knowledge gap hinders a comprehensive understanding of the synergistic mechanical-thermal response mechanisms in anchor rods under loading conditions.To address this limitation,the present study systematically investigated the evolution of strain and temperature fields,along with their correlation,during the test of micro-negative Poisson's ratio(NPR)and ordinary Poisson's ratio(PR)anchor rods.Digital image correlation(DIC)and infrared thermography(IRT)techniques were employed for this exploration.The uniaxial tensile tests were conducted at two different rates,and the ordinary PR anchor rod(Q235 anchor rod)was established as a control group for comparative analysis.The findings reveal that the micro-NPR anchor rod exhibit strain localization at multiple locations during the tensile process,whereas Q235 anchors show local strain concentration in only one region.The standard deviation evolution curves for both the strain and temperature field exhibit two distinct phases in the two anchor rods.The evolution patterns between these two types of curves are basically consistent.The two standard deviation curves for the micro-NPR anchor rod display a wavy increase in the second phase,while for the Q235 anchor rod,they increase steadily until the specimen is damaged.The correlation analysis reveals that the standard deviations of strain and temperature differences for both types of anchor rods are significantly correlated.These findings demonstrate the synergistic evolution mechanism of deformation and thermal response,providing a potential foundation for utilizing thermal monitoring to assess the stability of rock support structures.展开更多
Underground hydrogen storage has gained interest in recent years due to the enormous demand for clean energy.Hydrogen is more diffusive than air,with a smaller density and lower viscosity.These unique properties intro...Underground hydrogen storage has gained interest in recent years due to the enormous demand for clean energy.Hydrogen is more diffusive than air,with a smaller density and lower viscosity.These unique properties introduce distinctive hydrodynamic phenomena in hydrogen storage,one of which is fingering.Fingering could induce the fluid trapped in small clusters of pores,leading to a dramatic decrease in hydrogen saturation and a lower recovery rate.In this study,numerical simulations are performed at the microscopic scale to understand the evolution of hydrogen saturation and the impacts of injection and withdrawal cycles.Two sets of micromodels with different porosity(0.362 and 0.426)and minimum sizes of pore throats(0.362 mm and 0.181 mm)are developed in the numerical model.A parameter analysis is then conducted to understand the influence of injection velocity(in the range of 10^(-2)m/s to 10^(-5)m/s)and porous structure on the fingering pattern,followed by an image analysis to capture the evolution of the fingering pattern.Viscous fingering,capillary fingering,and crossover fingering are observed and identified under different boundary conditions.The fractal dimension,specific area,mean angle,and entropy of fingers are proposed as geometric descriptors to characterize the shape of the fingering pattern.When porosity increases from 0.362 to 0.426,the saturation of hydrogen increases by 26.2%.Narrower pore throats elevate capillary resistance,which hinders fluid invasion.These results underscore the importance of pore structures and the interaction between viscous and capillary forces for hydrogen recovery efficiency.This work illuminates the influence of the pore structures and the fluid properties on the immiscible displacement of hydrogen and can be further extended to optimize the injection strategy of hydrogen in underground hydrogen storage.展开更多
In-situ enlargement of super-large-span tunnels can intensify excavation-induced unloading in the surrounding rock,increasing deformation demand and failure risk during construction.This study combines laboratory mode...In-situ enlargement of super-large-span tunnels can intensify excavation-induced unloading in the surrounding rock,increasing deformation demand and failure risk during construction.This study combines laboratory model tests with FLAC3D simulations to evaluate the stabilizing role of prestressed anchor cables and to establish an energy-balance framework for support optimization.Comparative model tests of existing and enlarged tunnel sections,with and without anchors,show that reinforcement increases load-carrying capacity,reduces displacement,and confines damage to more localized zones.The numerical simulations reproduce displacement fields,shear-strain localization,and plastic-zone evolution with good agreement against the experimental observations.The energy framework is implemented in the in-situ simulations by quantifying unloading-related energy release in the rock mass and reinforcement work contributed by the anchors,and by introducing an energy release–reinforcement ratio as a stability indicator.Parametric analyses indicate that anchor length,spacing,and prestress influence stability in a nonlinear manner,with diminishing returns once reinforcement extends beyond the mechanically dominant deformation zone.An efficient parameter window is identified that improves deformation and yielding control while avoiding unnecessary reinforcement.The results provide an energy-consistent and design-oriented basis for prestressed anchorage selection in large-span tunnel expansion.展开更多
This study examines how native pore structures and loading conditions influencethe fracture size distribution and the predictability of catastrophic failure in rocks.Four lithologies with distinct pore characteristics...This study examines how native pore structures and loading conditions influencethe fracture size distribution and the predictability of catastrophic failure in rocks.Four lithologies with distinct pore characteristics,i.e.granite,limestone,red sandstone,and marble,were tested under uniaxial compression and Brazilian splitting.Nuclear magnetic resonance(NMR)was used to characterize pore structures,while acoustic emission(AE)monitoring captured the temporal evolution of microcracking.The relationships among pore properties,AE b-values,and failure predictability were systematically evaluated.Results show that the overall b-value is primarily controlled by native pore size rather than loading condition.Rocks with larger pores display higher b-value and greater temporal variability,whereas those with smaller pores exhibit lower and more stable b-value.To assess failure predictability,the AE count rate was incorporated into an inverse power law model.The model demonstrates higher predictive accuracy for high-porosity rocks.The average predicted failure time(t_(p))decreases monotonically with porosity:under uniaxial compression,t_(p)for granite,marble,limestone,and sandstone are 2.32,1.82,1.42,and 0.03,respectively;under Brazilian splitting,3.54,3.30,0.10,and 0.03.Among the four rock types,sandstone with the highest porosity exhibits the smallest discrepancy between predicted and actual failure time,whereas granite with the lowest porosity shows the largest.As porosity decreases,prediction accuracy progressively declines for limestone and marble.Overall,the findings indicate that native pore heterogeneity governs both fracture scaling behavior and failure predictability,and that these effects are largely independent of the loading conditions examined in this study.展开更多
Water-sand gushing(WSG)disasters in confinedaquifers pose significantchallenges to the utilization of deep underground spaces in soft soil areas.Since few studies have considered the impact of confined aquifer thickne...Water-sand gushing(WSG)disasters in confinedaquifers pose significantchallenges to the utilization of deep underground spaces in soft soil areas.Since few studies have considered the impact of confined aquifer thickness and confinedwater pressure on WSG disasters,a novel visual model test system was developed to investigate the influencingcharacteristics and mechanisms of the two aforementioned factors.The test results showed that the WSG process in clay aquiclude-confinedaquifer composite strata exhibits two prominent stages.First,the sand loss zone expands vertically in an ellipsoid shape.Then,it expands horizontally once the ellipsoid reaches the boundary of the clay layer.The sand loss continues until the overlying clay sinks to the bottom to clog the gushing crack,creating a large sinkhole at the surface.Increasing the confinedaquifer thickness can increase the vertical expansion of the ellipsoid and delay the clay-clogging effects,thereby considerably increasing the severity of sand loss,stratum deformation,and surface settlement.An increase in the confinedwater pressure markedly increases the hydraulic gradient along the seepage path,which contributes to increasing the gushing rates of water and sand.As a result,substantial sand loss occurs before the clay clogs the gushing crack,inducing more cracks and deeper sinkholes at the surface.All the aforementioned results provide insights into the effects of confinedaquifer on WSG disasters in clay aquiclude-confinedaquifer composite strata.展开更多
Laser-assisted drilling combined with full-size polycrystalline diamond compact(PDC)bit is considered a feasible solution to enhance the drilling performance of engineering machinery.In this method,determining the opt...Laser-assisted drilling combined with full-size polycrystalline diamond compact(PDC)bit is considered a feasible solution to enhance the drilling performance of engineering machinery.In this method,determining the optimal collaborative control parameters that support rapid drilling is crucial for improving the combined performance.This study used average drilling speed,average torque,and total specificenergy for quantitative analysis to characterize the efficiencyand economy of combined rock breaking.Given the advantage of the response surface methodology in providing high-precision predictions with limited experimental data,regression models of the average drilling speed,average torque,and total specificenergy were established.The results showed that as the laser power and irradiation time increased,the average drilling speed firstincreased rapidly and then leveled off,while the average torque decreased sharply before decelerating.The total specificenergy initially decreased and then increased,with the combined drilling outperforming conventional mechanical drilling within specific parameter ranges.As the weight on bit increased,both the average torque and total specificenergy first decreased and then increased.With rising rotating speed,the average torque exhibited a trend of initial increase,then decrease,and finalincrease,whereas the total specificenergy increased slowly at firstand then sharply.Both parameters exhibited optimal values at which the average torque and total specific energy remained at minimal levels.For granite combined drilling,the optimal performance was achieved at a laser power of 3000 W,irradiation time of 31 s,the weight on bit of 2.4 kN,and the rotating speed of 97 r/min.展开更多
Geological prospecting and the identification of adverse geological features are essential in tunnel construction,providing critical information to ensure safety and guide engineering decisions.As tunnel projects exte...Geological prospecting and the identification of adverse geological features are essential in tunnel construction,providing critical information to ensure safety and guide engineering decisions.As tunnel projects extend into deeper and more mountainous terrains,engineers face increasingly complex geological conditions,including high water pressure,intense geo-stress,elevated geothermal gradients,and active fault zones.These conditions pose substantial risks such as high-pressure water inrush,largescale collapses,and tunnel boring machine(TBM)blockages.Addressing these challenges requires advanced detection technologies capable of long-distance,high-precision,and intelligent assessments of adverse geology.This paper presents a comprehensive review of recent advancements in tunnel geological ahead prospecting methods.It summarizes the fundamental principles,technical maturity,key challenges,development trends,and real-world applications of various detection techniques.Airborne and semi-airborne geophysical methods enable large-scale reconnaissance for initial surveys in complex terrain.Tunnel-and borehole-based approaches offer high-resolution detection during excavation,including seismic ahead prospecting(SAP),TBM rock-breaking source seismic methods,fulltime-domain tunnel induced polarization(TIP),borehole electrical resistivity,and ground penetrating radar(GPR).To address scenarios involving multiple,coexisting adverse geologies,intelligent inversion and geological identification methods have been developed based on multi-source data fusion and artificial intelligence(AI)techniques.Overall,these advances significantly improve detection range,resolution,and geological characterization capabilities.The methods demonstrate strong adaptability to complex environments and provide reliable subsurface information,supporting safer and more efficient tunnel construction.展开更多
Excavation causes stress redistribution and affects the stress path during the shearing process of rock.The shear strength of rock varies under different stress paths,and the presence of defects reduces the shear stre...Excavation causes stress redistribution and affects the stress path during the shearing process of rock.The shear strength of rock varies under different stress paths,and the presence of defects reduces the shear strength.To further investigate this phenomenon,this study investigates the shear behaviour of rocks with different shear surface integrities under the influenceof different stress paths through laboratory tests and numerical simulations.The results indicate that the shear strength depends on the stress path and a decrease in the shear surface integrity reduces the degree of dependence.The cohesion and friction angle of the Mohr‒Coulomb criterion decrease with weakening of the shear surface integrity.For different stress paths,the direct shear strength is always greater than that of other shear stress paths.The pattern of changes in the acoustic emission count and cumulative count indirectly reflectsthe above findings.Numerical simulations further indicate that the different principal stress states and normal suppression effects during the shearing process lead to changes in the factors of crack propagation,resulting in different mechanical behaviours under various stress paths.For rocks with different integrity levels,the main reason for the different path dependences of shear strength is that the size of the area affected by shear is different.Shear failure will concentrate on the shear plane when the normal inhibition effect is greater.This study explores the mechanism of rock shear behaviour,providing a theoretical basis for establishing more accurate constitutive models and strength criteria.展开更多
To investigate the energy relief effect of real-time drilling in preventing rockburst in high-stress rock,a series of high-stress real-time drilling uniaxial compression tests were conducted on red sandstone specimens...To investigate the energy relief effect of real-time drilling in preventing rockburst in high-stress rock,a series of high-stress real-time drilling uniaxial compression tests were conducted on red sandstone specimens using the SG4500 drilling rig.Results showed that the mechanical behavior(i.e.peak strength and rockburst intensity)of the rock was weakened under high-stress real-time drilling and exhibited a downward trend as the drilling diameter increased.The real-time drilling energy dissipation index(ERD)was proposed to characterize the energy relief during high-stress real-time drilling.The ERD exhibited a linear increase with the real-time drilling diameter.Furthermore,the elastic strain energy of post-drilling rock showed a linear relationship with the square of stress across different stress levels,which also applied to the peak elastic strain energy and the square of peak stress.This findingreveals the intrinsic link between the weakening effect of peak elastic strain energy and peak strength due to high-stress real-time drilling,confirmingthe consistency between energy relief and pressure relief effects.By establishing relationships among rockburst proneness,peak elastic strain energy,and peak strength,it was demonstrated that high-stress real-time drilling reduces rockburst proneness through energy dissipation.Specifically,both peak elastic strain energy and rockburst proneness decreased with larger drill bit diameters,consistent with reductions in peak strength,rockburst intensity,and fractal dimensions of high-stress real-time drilled rock.These results validate the energy relief mechanism of real-time drilling in mitigating rockburst risks.展开更多
Thermochromic soft materials are flexible functional materials that adaptively tune optical properties(transmittance,reflectance,or scattering)with temperature for thermal modulation.Herein,a laminated thermochromic g...Thermochromic soft materials are flexible functional materials that adaptively tune optical properties(transmittance,reflectance,or scattering)with temperature for thermal modulation.Herein,a laminated thermochromic gel(DEE-DA)is synthesized by encapsulating a thermochromic hydrogel(DA)between two hydrophobic ionogels(DEE)in a stacked configuration.The synergy of multiple dynamic bonds endows the DEE-DA gel with exceptional mechanical properties and remarkable self-healing capability(98.8%at 30℃).More importantly,attributed to the temperature-responsive reversible cleavage and recombination of hydrogen bonds and borate ester bonds,DEE-DA gel demonstrates tunable transmittance with a light modulation efficiency of 85.45%.In response to the various external conditions,the gel can auto-adjust the optical properties to avoid sun irradiation or heat loss.Accordingly,the gel enables efficient dual-mode thermal modulation across a broad temperature range to realize thermal management.The research proposes gel thermochromism and laminated durability enhancement for adaptive materials in smart buildings and wearables.展开更多
This study investigates the influence of the elastic modulus(E)of the composite strata on the trough width coefficient(i).It is hypothesized that,in composite strata,the relationship between the trough width coefficie...This study investigates the influence of the elastic modulus(E)of the composite strata on the trough width coefficient(i).It is hypothesized that,in composite strata,the relationship between the trough width coefficient(i)and the stratum thickness(H)follows a piecewise linear trend.Specifically,within strata of identical elastic modulus(E),i exhibits a linear correlation with H,while variations in E affect the slope of this correlation.Building upon the non-iterative analytical method(NIAM)for evaluating tunnel excavation responses in composite strata,this study proposes two novel approaches:the crucial point method(CPM)and the standard curve method(SCM).These methods incorporate the elastic modulus into the estimation of i.The values of i obtained via NIAM and refined through CPM and SCM are validated against field data using the parameter K.The results are consistent with existing research findings,thereby confirming the reliability of the proposed methodology.Furthermore,the study investigates the relationship between tunnel depth(h0)and tunnel radius(R),and explores the interactions among the layer number of stratum(n),elastic modulus(E),and layer thickness(H).A reduction coefficient(η)is introduced to improve the model's accuracy.The proposed approach is applied to nine tunnel engineering cases,and comparisons with measured data demonstrate its accuracy and practical applicability.展开更多
Strong seismic excitation and fault dislocation are likely to occur simultaneously in high-intensity seismic zones,causing severe damage to tunnels crossing active fault zones.This paper aims to develop a novel analyt...Strong seismic excitation and fault dislocation are likely to occur simultaneously in high-intensity seismic zones,causing severe damage to tunnels crossing active fault zones.This paper aims to develop a novel analytical solution to determine the longitudinal mechanical responses of tunnels subjected to the combined effects of seismic waves and strike-slip faulting.Adopting the elastic springbeam model,the seismic waves are modelled as shear horizontal(SH)waves and the fault dislocation follows an S-shaped pattern;the superposition principle for free-fielddisplacements caused by both effects is assumed.In addition,the transmission and reflectionof seismic waves at the fault-rock geological interface and the tangential contact conditions at the tunnel-rock interface are considered.The analytical model is validated against numerical simulations,confirmingits accuracy in calculating tunnel responses.Moreover,a parametric study is conducted to evaluate the impact of key factors,including fault displacement,fault zone width,fault dip angle,earthquake frequency,rock conditions,tunnel lining stiffness,and tangential contact conditions,on tunnel responses.Compared with each effect alone,the combined effects of seismic waves and strike-slip faulting significantlychange the tunnel deformation and internal forces,leading to increased tunnel responses,especially within the fault zone and near the fault-rock interfaces.Depending on specificparameters,tunnel responses can be classifiedinto seismic-dominated,faulting-dominated,and seismic-faulting coupled responses on the basis of the relative contributions of each effect.The proposed analytical solution can be applied to quickly predict the longitudinal mechanical behaviour of tunnels under such combined effects in engineering applications.展开更多
The weak and broken roof,explosive control and other problems seriously restrict the promotion of non coal pillar self-forming roadway technology.In order to solve such problems,a new method of non coal pillar self-fo...The weak and broken roof,explosive control and other problems seriously restrict the promotion of non coal pillar self-forming roadway technology.In order to solve such problems,a new method of non coal pillar self-forming roadway through non-blasting roof cutting and pressure relief was proposed in this study.A systematic research system of"theoretical analysis-physical experiment-engineering verification"was constructed with the 9103 working face of Longmenta Coal Mine as the research object.Firstly,the theoretical analysis was conducted to reveal the roof cutting mechanics mechanism of rock mass weakened by dense drilling,establish the design criteria for key drilling parameters,and obtain the key design parameters of dense drilling in the test working face.Secondly,the physical model test was conducted to make clear that the dense drilling method can directionally cut off the goaf roof along the set position,reducing the stress and deformation of the roadway surrounding rock.Finally,the field engineering tests were conducted,and monitoring results showed that the pressure relief effect of the dense drilling method was comparable to that of the directional blasting method,achieving non coal pillar self-forming roadway mining under non blasting conditions.展开更多
Traditional mining in open pit mines often uses explosives,leading to environmental hazards,with flyrock being a critical issue.In detail,excess flying rock beyond the designated explosion area was identified as the p...Traditional mining in open pit mines often uses explosives,leading to environmental hazards,with flyrock being a critical issue.In detail,excess flying rock beyond the designated explosion area was identified as the primary cause of fatal and non-fatal blasting hazards in open pit mining.Therefore,the accurate and reliable prediction of flyrock becomes crucial for effectively managing and mitigating associated problems.This study used the Light Gradient Boosting Machine(LightGBM)model to predict flyrock in a lead-zinc mine,with promising results.To improve its accuracy,multi-verse optimizer(MVO)and ant lion optimizer(ALO)metaheuristic algorithms were introduced.Results showed MVO-LightGBM outperformed conventional LightGBM.Additionally,decision tree(DT),support vector machine(SVM),and classification and regression tree(CART)models were trained and compared with MVO-LightGBM.The MVO-LightGBM model excelled over DT,SVM,and CART.This study highlights MVO-LightGBM's effectiveness and potential for broader applications.Furthermore,a multiple parametric sensitivity analysis(MPSA)algorithm was employed to specify the sensitivity of parameters.MPSA results indicated that the highest and lowest sensitivities are relevant to blasted rock per hole and spacing with theγ=1752.12 andγ=49.52,respectively.展开更多
Aiming at the problem of dynamic instability of hard-brittle jointed rock surrounding in deep tunnel/roadway engineering,combining with the support concepts of"coupling rigidity with flexibility"and"ove...Aiming at the problem of dynamic instability of hard-brittle jointed rock surrounding in deep tunnel/roadway engineering,combining with the support concepts of"coupling rigidity with flexibility"and"overcoming rigidity by flexibility",the prevention and control method with"rigid-flexible coupling(R-F-C)"was put forward.Through numerical simulation calculation,the impact damage process,acoustic emission(AE)evolution characteristics,and element stress/displacement evolution characteristics of unsupported surrounding rock structure model,rigid supporting surrounding rock structure model,and"R-F-C"supporting surrounding rock structure model under horizontal bidirectional impact loading were compared and analyzed.Based on the theory of stress wave propagation,the dynamic instability catastrophe mechanism of three kinds of supporting structure models induced by horizontal bidirectional impact loading was revealed.Based on the Mohr-Coulomb strength theory,the stress discrimination methods of dynamic catastrophe of surrounding rock induced by horizontal bidirectional impact loading under three kinds of supporting structures were proposed.Combined with the above numerical simulation study,the explosion impact physical and mechanical test of"R-F-C"surrounding rock supporting plate structure was further designed and carried out.Finally,combined with the"conceptual model of ball-cliff potential energy instability",the energy driving theory and energy transformation mechanism of impact-induced rockburst under three kinds of supporting structures were discussed deeply.The research results provided a scientific basis for further promoting the effective application of"R-F-C"supporting structure in the prevention and control of dynamic instability of deep tunnel/roadway surrounding rock.展开更多
Based on inspection data,the authors analyze and summarize the main types and distribution characteristics of tunnel structural defects.These defects are classified into three types:surface defects,internal defects,an...Based on inspection data,the authors analyze and summarize the main types and distribution characteristics of tunnel structural defects.These defects are classified into three types:surface defects,internal defects,and defects behind the structure.To address the need for rapid detection of different defect types,the current state of rapid detection technologies and equipment,both domestically and internationally,is systematically reviewed.The research reveals that surface defect detection technologies and equipment have developed rapidly in recent years.Notably,the integration of machine vision and laser scanning technologies have significantly improved detection efficiency and accuracy,achieving crack detection precision of up to 0.1 mm.However,the non-contact rapid detection of internal and behind-the-structure defects remains constrained by hardware limitations,with traditional detection remaining dominant.Nevertheless,phased array radar,ultrasonic,and acoustic vibration detection technologies have become research hotspots in recent years,offering promising directions for detecting these challenging defect types.Additionally,the application of multisensor fusion technology in rapid detection equipment has further enhanced detection capabilities.Devices such as cameras,3D laser scanners,infrared thermal imagers,and radar demonstrate significant advantages in rapid detection.Future research in tunnel inspection should prioritize breakthroughs in rapid detection technologies for internal and behind-the-structure defects.Efforts should also focus on developing multifunctional integrated detection vehicles that can simultaneously inspect both surface and internal structures.Furthermore,progress in fully automated,intelligent systems with precise defect identification and real-time reporting will be essential to significantly improve the efficiency and accuracy of tunnel inspection.展开更多
Because of the challenge of compounding lightweight,high-strength Ti/Al alloys due to their considerable disparity in properties,Al 6063 as intermediate layer was proposed to fabricate TC4/Al 6063/Al 7075 three-layer ...Because of the challenge of compounding lightweight,high-strength Ti/Al alloys due to their considerable disparity in properties,Al 6063 as intermediate layer was proposed to fabricate TC4/Al 6063/Al 7075 three-layer composite plate by explosive welding.The microscopic properties of each bonding interface were elucidated through field emission scanning electron microscope and electron backscattered diffraction(EBSD).A methodology combining finite element method-smoothed particle hydrodynamics(FEM-SPH)and molecular dynamics(MD)was proposed for the analysis of the forming and evolution characteristics of explosive welding interfaces at multi-scale.The results demonstrate that the bonding interface morphologies of TC4/Al 6063 and Al 6063/Al 7075 exhibit a flat and wavy configuration,without discernible defects or cracks.The phenomenon of grain refinement is observed in the vicinity of the two bonding interfaces.Furthermore,the degree of plastic deformation of TC4 and Al 7075 is more pronounced than that of Al 6063 in the intermediate layer.The interface morphology characteristics obtained by FEM-SPH simulation exhibit a high degree of similarity to the experimental results.MD simulations reveal that the diffusion of interfacial elements predominantly occurs during the unloading phase,and the simulated thickness of interfacial diffusion aligns well with experimental outcomes.The introduction of intermediate layer in the explosive welding process can effectively produce high-quality titanium/aluminum alloy composite plates.Furthermore,this approach offers a multi-scale simulation strategy for the study of explosive welding bonding interfaces.展开更多
Gas content serves as a critical indicator for assessing the resource potential of deep coal mines and forecasting coal mine gas outburst risks.However,existing sampling technologies face challenges in maintaining the...Gas content serves as a critical indicator for assessing the resource potential of deep coal mines and forecasting coal mine gas outburst risks.However,existing sampling technologies face challenges in maintaining the integrity of gas content within samples and are often constrained by estimation errors inherent in empirical formulas,which results in inaccurate gas content measurements.This study introduces a lightweight,in-situ pressure-and gas-preserved corer designed to collect coal samples under the pressure conditions at the sampling point,effectively preventing gas loss during transfer and significantly improving measurement accuracy.Additionally,a gas migration model for deep coal mines was developed to elucidate gas migration characteristics under pressure-preserved coring conditions.The model offers valuable insights for optimizing coring parameters,demonstrating that both minimizing the coring hole diameter and reducing the pressure difference between the coring-point pressure and the original pore pressure can effectively improve the precision of gas content measurements.Coring tests conducted at an experimental base validated the performance of the corer and its effectiveness in sample collection.Furthermore,successful horizontal coring tests conducted in an underground coal mine roadway demonstrated that the measured gas content using pressure-preserved coring was 34%higher than that obtained through open sampling methods.展开更多
Prepulse combined hydraulic fracturing facilitates the development of fracture networks by integrating prepulse hydraulic loading with conventional hydraulic fracturing.The formation mechanisms of fracture networks be...Prepulse combined hydraulic fracturing facilitates the development of fracture networks by integrating prepulse hydraulic loading with conventional hydraulic fracturing.The formation mechanisms of fracture networks between hydraulic and pre-existing fractures under different prepulse loading parameters remain unclear.This research investigates the impact of prepulse loading parameters,including the prepulse loading number ratio(C),prepulse loading stress ratio(S),and prepulse loading frequency(f),on the formation of fracture networks between hydraulic and pre-existing fractures,using both experimental and numerical methods.The results suggest that low prepulse loading stress ratios and high prepulse loading number ratios are advantageous loading modes.Multiple hydraulic fractures are generated in the specimen under the advantageous loading modes,facilitating the development of a complex fracture network.Fatigue damage occurs in the specimen at the prepulse loading stage.The high water pressure at the secondary conventional hydraulic fracturing promotes the growth of hydraulic fractures along the damage zones.This allows the hydraulic fractures to propagate deeply and interact with pre-existing fractures.Under advantageous loading conditions,multiple hydraulic fractures can extend to pre-existing fractures,and these hydraulic fractures penetrate or propagate along pre-existing fractures.Especially when the approach angle is large,the damage range in the specimen during the prepulse loading stage increases,resulting in the formation of more hydraulic fractures.展开更多
Bayesian-optimized lithology identification has important basic geological research significance and engineering application value,and this paper proposes a Bayesian-optimized lithology identification method based on ...Bayesian-optimized lithology identification has important basic geological research significance and engineering application value,and this paper proposes a Bayesian-optimized lithology identification method based on machine learning of rock visible and near-infrared spectral data.First,the rock spectral data are preprocessed using Savitzky-Golay(SG)smoothing to remove the noise of the spectral data;then,the preprocessed rock spectral data are downscaled using Principal Component Analysis(PCA)to reduce the redundancy of the data,optimize the effective discriminative information,and obtain the rock spectral features;finally,a Bayesian-optimized lithology identification model is established based on rock spectral features,optimize the model hyperparameters using Bayesian optimization(BO)algorithm to avoid the combination of hyperparameters falling into the local optimal solution,and output the predicted type of rock,so as to realize the Bayesian-optimized lithology identification.In addition,this paper conducts comparative analysis on models based on Artificial Neural Network(ANN)/Random Forest(RF),dimensionality reduction/full band,and optimization algorithms.It uses the confusion matrix,accuracy,Precison(P),Recall(R)and F_(1)values(F_(1))as the evaluation indexes of model accuracy.The results indicate that the lithology identification model optimized by the BO-ANN after dimensionality reduction achieves an accuracy of up to 99.80%,up to 99.79%and up to 99.79%.Compared with the BO-RF model,it has higher identification accuracy and better stability for each type of rock identification.The experiments and reliability analysis show that the Bayesian-optimized lithology identification method proposed in this paper has good robustness and generalization performance,which is of great significance for realizing fast,accurate and Bayesian-optimized lithology identification in tunnel site.展开更多
基金supported by State Key Laboratory for Geomechanics and Deep Underground Engineering,China University of Mining&Technology,Beijing(Grant No.SKLGDUEK2120)。
文摘The deformation characteristics and thermal response of anchor rods are crucial for ensuring the stability and safety of surrounding rock support structures.However,existing research has predominantly concentrated on the mechanical performance of anchor rods,with limited attention to the coupled evolution of strain and temperature fields during tensile deformation.This knowledge gap hinders a comprehensive understanding of the synergistic mechanical-thermal response mechanisms in anchor rods under loading conditions.To address this limitation,the present study systematically investigated the evolution of strain and temperature fields,along with their correlation,during the test of micro-negative Poisson's ratio(NPR)and ordinary Poisson's ratio(PR)anchor rods.Digital image correlation(DIC)and infrared thermography(IRT)techniques were employed for this exploration.The uniaxial tensile tests were conducted at two different rates,and the ordinary PR anchor rod(Q235 anchor rod)was established as a control group for comparative analysis.The findings reveal that the micro-NPR anchor rod exhibit strain localization at multiple locations during the tensile process,whereas Q235 anchors show local strain concentration in only one region.The standard deviation evolution curves for both the strain and temperature field exhibit two distinct phases in the two anchor rods.The evolution patterns between these two types of curves are basically consistent.The two standard deviation curves for the micro-NPR anchor rod display a wavy increase in the second phase,while for the Q235 anchor rod,they increase steadily until the specimen is damaged.The correlation analysis reveals that the standard deviations of strain and temperature differences for both types of anchor rods are significantly correlated.These findings demonstrate the synergistic evolution mechanism of deformation and thermal response,providing a potential foundation for utilizing thermal monitoring to assess the stability of rock support structures.
基金supported by the National Key Research and Development Project(Grant No.2023YFE0110900)the National Natural Science Foundation of China(Grant Nos.42320104003,42477168).
文摘Underground hydrogen storage has gained interest in recent years due to the enormous demand for clean energy.Hydrogen is more diffusive than air,with a smaller density and lower viscosity.These unique properties introduce distinctive hydrodynamic phenomena in hydrogen storage,one of which is fingering.Fingering could induce the fluid trapped in small clusters of pores,leading to a dramatic decrease in hydrogen saturation and a lower recovery rate.In this study,numerical simulations are performed at the microscopic scale to understand the evolution of hydrogen saturation and the impacts of injection and withdrawal cycles.Two sets of micromodels with different porosity(0.362 and 0.426)and minimum sizes of pore throats(0.362 mm and 0.181 mm)are developed in the numerical model.A parameter analysis is then conducted to understand the influence of injection velocity(in the range of 10^(-2)m/s to 10^(-5)m/s)and porous structure on the fingering pattern,followed by an image analysis to capture the evolution of the fingering pattern.Viscous fingering,capillary fingering,and crossover fingering are observed and identified under different boundary conditions.The fractal dimension,specific area,mean angle,and entropy of fingers are proposed as geometric descriptors to characterize the shape of the fingering pattern.When porosity increases from 0.362 to 0.426,the saturation of hydrogen increases by 26.2%.Narrower pore throats elevate capillary resistance,which hinders fluid invasion.These results underscore the importance of pore structures and the interaction between viscous and capillary forces for hydrogen recovery efficiency.This work illuminates the influence of the pore structures and the fluid properties on the immiscible displacement of hydrogen and can be further extended to optimize the injection strategy of hydrogen in underground hydrogen storage.
基金funded by the National Key R&D Program of China,China(No.2024YFF0507903)the National Key Research and Development Program of China(Grant No.2024YFF0507904)the National Natural Science Foundation of China,China(Grant No.52379114).These supports are gratefully acknowledged.
文摘In-situ enlargement of super-large-span tunnels can intensify excavation-induced unloading in the surrounding rock,increasing deformation demand and failure risk during construction.This study combines laboratory model tests with FLAC3D simulations to evaluate the stabilizing role of prestressed anchor cables and to establish an energy-balance framework for support optimization.Comparative model tests of existing and enlarged tunnel sections,with and without anchors,show that reinforcement increases load-carrying capacity,reduces displacement,and confines damage to more localized zones.The numerical simulations reproduce displacement fields,shear-strain localization,and plastic-zone evolution with good agreement against the experimental observations.The energy framework is implemented in the in-situ simulations by quantifying unloading-related energy release in the rock mass and reinforcement work contributed by the anchors,and by introducing an energy release–reinforcement ratio as a stability indicator.Parametric analyses indicate that anchor length,spacing,and prestress influence stability in a nonlinear manner,with diminishing returns once reinforcement extends beyond the mechanically dominant deformation zone.An efficient parameter window is identified that improves deformation and yielding control while avoiding unnecessary reinforcement.The results provide an energy-consistent and design-oriented basis for prestressed anchorage selection in large-span tunnel expansion.
基金supported by the National Natural Science Foundation of China(Grant No.42172316)the Major National Science and Technology Project for Deep Earth(Grant No.2024ZD100380X)the Natural Science Foundation of Hunan Province of China(2025JJ20030).
文摘This study examines how native pore structures and loading conditions influencethe fracture size distribution and the predictability of catastrophic failure in rocks.Four lithologies with distinct pore characteristics,i.e.granite,limestone,red sandstone,and marble,were tested under uniaxial compression and Brazilian splitting.Nuclear magnetic resonance(NMR)was used to characterize pore structures,while acoustic emission(AE)monitoring captured the temporal evolution of microcracking.The relationships among pore properties,AE b-values,and failure predictability were systematically evaluated.Results show that the overall b-value is primarily controlled by native pore size rather than loading condition.Rocks with larger pores display higher b-value and greater temporal variability,whereas those with smaller pores exhibit lower and more stable b-value.To assess failure predictability,the AE count rate was incorporated into an inverse power law model.The model demonstrates higher predictive accuracy for high-porosity rocks.The average predicted failure time(t_(p))decreases monotonically with porosity:under uniaxial compression,t_(p)for granite,marble,limestone,and sandstone are 2.32,1.82,1.42,and 0.03,respectively;under Brazilian splitting,3.54,3.30,0.10,and 0.03.Among the four rock types,sandstone with the highest porosity exhibits the smallest discrepancy between predicted and actual failure time,whereas granite with the lowest porosity shows the largest.As porosity decreases,prediction accuracy progressively declines for limestone and marble.Overall,the findings indicate that native pore heterogeneity governs both fracture scaling behavior and failure predictability,and that these effects are largely independent of the loading conditions examined in this study.
基金financedby the National Natural Science Foundation of China(Grant No.52090083)the Shanghai Rising-Star Program(Grant No.23QB1404800).
文摘Water-sand gushing(WSG)disasters in confinedaquifers pose significantchallenges to the utilization of deep underground spaces in soft soil areas.Since few studies have considered the impact of confined aquifer thickness and confinedwater pressure on WSG disasters,a novel visual model test system was developed to investigate the influencingcharacteristics and mechanisms of the two aforementioned factors.The test results showed that the WSG process in clay aquiclude-confinedaquifer composite strata exhibits two prominent stages.First,the sand loss zone expands vertically in an ellipsoid shape.Then,it expands horizontally once the ellipsoid reaches the boundary of the clay layer.The sand loss continues until the overlying clay sinks to the bottom to clog the gushing crack,creating a large sinkhole at the surface.Increasing the confinedaquifer thickness can increase the vertical expansion of the ellipsoid and delay the clay-clogging effects,thereby considerably increasing the severity of sand loss,stratum deformation,and surface settlement.An increase in the confinedwater pressure markedly increases the hydraulic gradient along the seepage path,which contributes to increasing the gushing rates of water and sand.As a result,substantial sand loss occurs before the clay clogs the gushing crack,inducing more cracks and deeper sinkholes at the surface.All the aforementioned results provide insights into the effects of confinedaquifer on WSG disasters in clay aquiclude-confinedaquifer composite strata.
基金funded by the National Natural Science Foundation of China(Grand No.52325904)National Key Research and Development Program of China(Grant No.2023YFB2390200)the National Natural Science Foundation of China(Grant No.52309134).
文摘Laser-assisted drilling combined with full-size polycrystalline diamond compact(PDC)bit is considered a feasible solution to enhance the drilling performance of engineering machinery.In this method,determining the optimal collaborative control parameters that support rapid drilling is crucial for improving the combined performance.This study used average drilling speed,average torque,and total specificenergy for quantitative analysis to characterize the efficiencyand economy of combined rock breaking.Given the advantage of the response surface methodology in providing high-precision predictions with limited experimental data,regression models of the average drilling speed,average torque,and total specificenergy were established.The results showed that as the laser power and irradiation time increased,the average drilling speed firstincreased rapidly and then leveled off,while the average torque decreased sharply before decelerating.The total specificenergy initially decreased and then increased,with the combined drilling outperforming conventional mechanical drilling within specific parameter ranges.As the weight on bit increased,both the average torque and total specificenergy first decreased and then increased.With rising rotating speed,the average torque exhibited a trend of initial increase,then decrease,and finalincrease,whereas the total specificenergy increased slowly at firstand then sharply.Both parameters exhibited optimal values at which the average torque and total specific energy remained at minimal levels.For granite combined drilling,the optimal performance was achieved at a laser power of 3000 W,irradiation time of 31 s,the weight on bit of 2.4 kN,and the rotating speed of 97 r/min.
基金supported by the National Natural Science Foundation of China(Grant Nos.52021005,52325904,and 51991391)。
文摘Geological prospecting and the identification of adverse geological features are essential in tunnel construction,providing critical information to ensure safety and guide engineering decisions.As tunnel projects extend into deeper and more mountainous terrains,engineers face increasingly complex geological conditions,including high water pressure,intense geo-stress,elevated geothermal gradients,and active fault zones.These conditions pose substantial risks such as high-pressure water inrush,largescale collapses,and tunnel boring machine(TBM)blockages.Addressing these challenges requires advanced detection technologies capable of long-distance,high-precision,and intelligent assessments of adverse geology.This paper presents a comprehensive review of recent advancements in tunnel geological ahead prospecting methods.It summarizes the fundamental principles,technical maturity,key challenges,development trends,and real-world applications of various detection techniques.Airborne and semi-airborne geophysical methods enable large-scale reconnaissance for initial surveys in complex terrain.Tunnel-and borehole-based approaches offer high-resolution detection during excavation,including seismic ahead prospecting(SAP),TBM rock-breaking source seismic methods,fulltime-domain tunnel induced polarization(TIP),borehole electrical resistivity,and ground penetrating radar(GPR).To address scenarios involving multiple,coexisting adverse geologies,intelligent inversion and geological identification methods have been developed based on multi-source data fusion and artificial intelligence(AI)techniques.Overall,these advances significantly improve detection range,resolution,and geological characterization capabilities.The methods demonstrate strong adaptability to complex environments and provide reliable subsurface information,supporting safer and more efficient tunnel construction.
基金support from the Postgraduate Research&Practice Innovation Program of Jiangsu Province,China(Grant No.KYCX24_2822)the Graduate Innovation Program of China University of Mining and Technology(Grant No.2024WLKXJ205)the National Natural Science Foundation of China(Grant No.52474157).
文摘Excavation causes stress redistribution and affects the stress path during the shearing process of rock.The shear strength of rock varies under different stress paths,and the presence of defects reduces the shear strength.To further investigate this phenomenon,this study investigates the shear behaviour of rocks with different shear surface integrities under the influenceof different stress paths through laboratory tests and numerical simulations.The results indicate that the shear strength depends on the stress path and a decrease in the shear surface integrity reduces the degree of dependence.The cohesion and friction angle of the Mohr‒Coulomb criterion decrease with weakening of the shear surface integrity.For different stress paths,the direct shear strength is always greater than that of other shear stress paths.The pattern of changes in the acoustic emission count and cumulative count indirectly reflectsthe above findings.Numerical simulations further indicate that the different principal stress states and normal suppression effects during the shearing process lead to changes in the factors of crack propagation,resulting in different mechanical behaviours under various stress paths.For rocks with different integrity levels,the main reason for the different path dependences of shear strength is that the size of the area affected by shear is different.Shear failure will concentrate on the shear plane when the normal inhibition effect is greater.This study explores the mechanism of rock shear behaviour,providing a theoretical basis for establishing more accurate constitutive models and strength criteria.
基金supported by the National Natural Science Foundation of China(Grant No.42077244)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(Grant No.KYCX24_0434).
文摘To investigate the energy relief effect of real-time drilling in preventing rockburst in high-stress rock,a series of high-stress real-time drilling uniaxial compression tests were conducted on red sandstone specimens using the SG4500 drilling rig.Results showed that the mechanical behavior(i.e.peak strength and rockburst intensity)of the rock was weakened under high-stress real-time drilling and exhibited a downward trend as the drilling diameter increased.The real-time drilling energy dissipation index(ERD)was proposed to characterize the energy relief during high-stress real-time drilling.The ERD exhibited a linear increase with the real-time drilling diameter.Furthermore,the elastic strain energy of post-drilling rock showed a linear relationship with the square of stress across different stress levels,which also applied to the peak elastic strain energy and the square of peak stress.This findingreveals the intrinsic link between the weakening effect of peak elastic strain energy and peak strength due to high-stress real-time drilling,confirmingthe consistency between energy relief and pressure relief effects.By establishing relationships among rockburst proneness,peak elastic strain energy,and peak strength,it was demonstrated that high-stress real-time drilling reduces rockburst proneness through energy dissipation.Specifically,both peak elastic strain energy and rockburst proneness decreased with larger drill bit diameters,consistent with reductions in peak strength,rockburst intensity,and fractal dimensions of high-stress real-time drilled rock.These results validate the energy relief mechanism of real-time drilling in mitigating rockburst risks.
基金supported by the Yunlong Lake Laboratory of Deep Underground Science and Engineering Project(104024004)the National Natural Science Foundation of China(62288102)+2 种基金the Key Project of Basic Research Program of Jiangsu Province(BK20243036)the State Key Laboratory of Mechanics and Control for Aerospace Structures(Nanjing University of Aeronautics and astronautics)(MCAS-E-0124K01)the Cultivation Program for the Excellent Doctoral Dissertation of Nanjing Tech University(2023-06)。
文摘Thermochromic soft materials are flexible functional materials that adaptively tune optical properties(transmittance,reflectance,or scattering)with temperature for thermal modulation.Herein,a laminated thermochromic gel(DEE-DA)is synthesized by encapsulating a thermochromic hydrogel(DA)between two hydrophobic ionogels(DEE)in a stacked configuration.The synergy of multiple dynamic bonds endows the DEE-DA gel with exceptional mechanical properties and remarkable self-healing capability(98.8%at 30℃).More importantly,attributed to the temperature-responsive reversible cleavage and recombination of hydrogen bonds and borate ester bonds,DEE-DA gel demonstrates tunable transmittance with a light modulation efficiency of 85.45%.In response to the various external conditions,the gel can auto-adjust the optical properties to avoid sun irradiation or heat loss.Accordingly,the gel enables efficient dual-mode thermal modulation across a broad temperature range to realize thermal management.The research proposes gel thermochromism and laminated durability enhancement for adaptive materials in smart buildings and wearables.
基金support from the National Natural Science Foundation of China(Grant No.52278387).
文摘This study investigates the influence of the elastic modulus(E)of the composite strata on the trough width coefficient(i).It is hypothesized that,in composite strata,the relationship between the trough width coefficient(i)and the stratum thickness(H)follows a piecewise linear trend.Specifically,within strata of identical elastic modulus(E),i exhibits a linear correlation with H,while variations in E affect the slope of this correlation.Building upon the non-iterative analytical method(NIAM)for evaluating tunnel excavation responses in composite strata,this study proposes two novel approaches:the crucial point method(CPM)and the standard curve method(SCM).These methods incorporate the elastic modulus into the estimation of i.The values of i obtained via NIAM and refined through CPM and SCM are validated against field data using the parameter K.The results are consistent with existing research findings,thereby confirming the reliability of the proposed methodology.Furthermore,the study investigates the relationship between tunnel depth(h0)and tunnel radius(R),and explores the interactions among the layer number of stratum(n),elastic modulus(E),and layer thickness(H).A reduction coefficient(η)is introduced to improve the model's accuracy.The proposed approach is applied to nine tunnel engineering cases,and comparisons with measured data demonstrate its accuracy and practical applicability.
基金supported by the National Natural Science Foundation of China(No.41941018)Shanghai Gaofeng Discipline Construction Funding.
文摘Strong seismic excitation and fault dislocation are likely to occur simultaneously in high-intensity seismic zones,causing severe damage to tunnels crossing active fault zones.This paper aims to develop a novel analytical solution to determine the longitudinal mechanical responses of tunnels subjected to the combined effects of seismic waves and strike-slip faulting.Adopting the elastic springbeam model,the seismic waves are modelled as shear horizontal(SH)waves and the fault dislocation follows an S-shaped pattern;the superposition principle for free-fielddisplacements caused by both effects is assumed.In addition,the transmission and reflectionof seismic waves at the fault-rock geological interface and the tangential contact conditions at the tunnel-rock interface are considered.The analytical model is validated against numerical simulations,confirmingits accuracy in calculating tunnel responses.Moreover,a parametric study is conducted to evaluate the impact of key factors,including fault displacement,fault zone width,fault dip angle,earthquake frequency,rock conditions,tunnel lining stiffness,and tangential contact conditions,on tunnel responses.Compared with each effect alone,the combined effects of seismic waves and strike-slip faulting significantlychange the tunnel deformation and internal forces,leading to increased tunnel responses,especially within the fault zone and near the fault-rock interfaces.Depending on specificparameters,tunnel responses can be classifiedinto seismic-dominated,faulting-dominated,and seismic-faulting coupled responses on the basis of the relative contributions of each effect.The proposed analytical solution can be applied to quickly predict the longitudinal mechanical behaviour of tunnels under such combined effects in engineering applications.
基金Project(2024YFC2909500)supported by the National Key Research and Development Program of ChinaProjects(42377148,52204164)supported by the National Natural Science Foundation of ChinaProject(2022XJSB03)supported by the Fundamental Research Funds for the Central Universities,China。
文摘The weak and broken roof,explosive control and other problems seriously restrict the promotion of non coal pillar self-forming roadway technology.In order to solve such problems,a new method of non coal pillar self-forming roadway through non-blasting roof cutting and pressure relief was proposed in this study.A systematic research system of"theoretical analysis-physical experiment-engineering verification"was constructed with the 9103 working face of Longmenta Coal Mine as the research object.Firstly,the theoretical analysis was conducted to reveal the roof cutting mechanics mechanism of rock mass weakened by dense drilling,establish the design criteria for key drilling parameters,and obtain the key design parameters of dense drilling in the test working face.Secondly,the physical model test was conducted to make clear that the dense drilling method can directionally cut off the goaf roof along the set position,reducing the stress and deformation of the roadway surrounding rock.Finally,the field engineering tests were conducted,and monitoring results showed that the pressure relief effect of the dense drilling method was comparable to that of the directional blasting method,achieving non coal pillar self-forming roadway mining under non blasting conditions.
基金funded by the Key Laboratory of Geological Safety of Coastal Urban Underground Space,Ministry of Natural Resources of China(Grant No.BHKF2022Y02)Natural Science Foundation of Guangdong Province,China(Grant No.2024A1515011162)Natural Science Foundation of Shandong Province,China(Grant No.ZR2024QE021).
文摘Traditional mining in open pit mines often uses explosives,leading to environmental hazards,with flyrock being a critical issue.In detail,excess flying rock beyond the designated explosion area was identified as the primary cause of fatal and non-fatal blasting hazards in open pit mining.Therefore,the accurate and reliable prediction of flyrock becomes crucial for effectively managing and mitigating associated problems.This study used the Light Gradient Boosting Machine(LightGBM)model to predict flyrock in a lead-zinc mine,with promising results.To improve its accuracy,multi-verse optimizer(MVO)and ant lion optimizer(ALO)metaheuristic algorithms were introduced.Results showed MVO-LightGBM outperformed conventional LightGBM.Additionally,decision tree(DT),support vector machine(SVM),and classification and regression tree(CART)models were trained and compared with MVO-LightGBM.The MVO-LightGBM model excelled over DT,SVM,and CART.This study highlights MVO-LightGBM's effectiveness and potential for broader applications.Furthermore,a multiple parametric sensitivity analysis(MPSA)algorithm was employed to specify the sensitivity of parameters.MPSA results indicated that the highest and lowest sensitivities are relevant to blasted rock per hole and spacing with theγ=1752.12 andγ=49.52,respectively.
基金Project(2023AH051167)supported by the Natural Science Research Project of Anhui Educational Committee,ChinaProject(AHBP2024B-04)supported by the Foundation of Anhui Engineering Research Center of New Explosive Materials and Blasting Technology,China+1 种基金Project(GXZDSYS2023103)supported by the Open Fund for Anhui Key Laboratory of Mining Construction Engineering,ChinaProjects(52274071,52404155)supported by the National Natural Science Foundation of China。
文摘Aiming at the problem of dynamic instability of hard-brittle jointed rock surrounding in deep tunnel/roadway engineering,combining with the support concepts of"coupling rigidity with flexibility"and"overcoming rigidity by flexibility",the prevention and control method with"rigid-flexible coupling(R-F-C)"was put forward.Through numerical simulation calculation,the impact damage process,acoustic emission(AE)evolution characteristics,and element stress/displacement evolution characteristics of unsupported surrounding rock structure model,rigid supporting surrounding rock structure model,and"R-F-C"supporting surrounding rock structure model under horizontal bidirectional impact loading were compared and analyzed.Based on the theory of stress wave propagation,the dynamic instability catastrophe mechanism of three kinds of supporting structure models induced by horizontal bidirectional impact loading was revealed.Based on the Mohr-Coulomb strength theory,the stress discrimination methods of dynamic catastrophe of surrounding rock induced by horizontal bidirectional impact loading under three kinds of supporting structures were proposed.Combined with the above numerical simulation study,the explosion impact physical and mechanical test of"R-F-C"surrounding rock supporting plate structure was further designed and carried out.Finally,combined with the"conceptual model of ball-cliff potential energy instability",the energy driving theory and energy transformation mechanism of impact-induced rockburst under three kinds of supporting structures were discussed deeply.The research results provided a scientific basis for further promoting the effective application of"R-F-C"supporting structure in the prevention and control of dynamic instability of deep tunnel/roadway surrounding rock.
文摘Based on inspection data,the authors analyze and summarize the main types and distribution characteristics of tunnel structural defects.These defects are classified into three types:surface defects,internal defects,and defects behind the structure.To address the need for rapid detection of different defect types,the current state of rapid detection technologies and equipment,both domestically and internationally,is systematically reviewed.The research reveals that surface defect detection technologies and equipment have developed rapidly in recent years.Notably,the integration of machine vision and laser scanning technologies have significantly improved detection efficiency and accuracy,achieving crack detection precision of up to 0.1 mm.However,the non-contact rapid detection of internal and behind-the-structure defects remains constrained by hardware limitations,with traditional detection remaining dominant.Nevertheless,phased array radar,ultrasonic,and acoustic vibration detection technologies have become research hotspots in recent years,offering promising directions for detecting these challenging defect types.Additionally,the application of multisensor fusion technology in rapid detection equipment has further enhanced detection capabilities.Devices such as cameras,3D laser scanners,infrared thermal imagers,and radar demonstrate significant advantages in rapid detection.Future research in tunnel inspection should prioritize breakthroughs in rapid detection technologies for internal and behind-the-structure defects.Efforts should also focus on developing multifunctional integrated detection vehicles that can simultaneously inspect both surface and internal structures.Furthermore,progress in fully automated,intelligent systems with precise defect identification and real-time reporting will be essential to significantly improve the efficiency and accuracy of tunnel inspection.
基金Opening Foundation of Key Laboratory of Explosive Energy Utilization and Control,Anhui Province(BP20240104)Graduate Innovation Program of China University of Mining and Technology(2024WLJCRCZL049)Postgraduate Research&Practice Innovation Program of Jiangsu Province(KYCX24_2701)。
文摘Because of the challenge of compounding lightweight,high-strength Ti/Al alloys due to their considerable disparity in properties,Al 6063 as intermediate layer was proposed to fabricate TC4/Al 6063/Al 7075 three-layer composite plate by explosive welding.The microscopic properties of each bonding interface were elucidated through field emission scanning electron microscope and electron backscattered diffraction(EBSD).A methodology combining finite element method-smoothed particle hydrodynamics(FEM-SPH)and molecular dynamics(MD)was proposed for the analysis of the forming and evolution characteristics of explosive welding interfaces at multi-scale.The results demonstrate that the bonding interface morphologies of TC4/Al 6063 and Al 6063/Al 7075 exhibit a flat and wavy configuration,without discernible defects or cracks.The phenomenon of grain refinement is observed in the vicinity of the two bonding interfaces.Furthermore,the degree of plastic deformation of TC4 and Al 7075 is more pronounced than that of Al 6063 in the intermediate layer.The interface morphology characteristics obtained by FEM-SPH simulation exhibit a high degree of similarity to the experimental results.MD simulations reveal that the diffusion of interfacial elements predominantly occurs during the unloading phase,and the simulated thickness of interfacial diffusion aligns well with experimental outcomes.The introduction of intermediate layer in the explosive welding process can effectively produce high-quality titanium/aluminum alloy composite plates.Furthermore,this approach offers a multi-scale simulation strategy for the study of explosive welding bonding interfaces.
基金supported by the National Natural Science Foundation of China(Nos.51827901,42477191,and 52304033)the Fundamental Research Funds for the Central Universities(No.YJ202449)+1 种基金the Open Research Fund of State Key Laboratory of Geomechanics and Geotechnical Engineering,Institute of Rock and Soil Mechanics,Chinese Academy of Sciences(No.SKLGME022009)the China Postdoctoral Science Foundation(No.2023M742446).
文摘Gas content serves as a critical indicator for assessing the resource potential of deep coal mines and forecasting coal mine gas outburst risks.However,existing sampling technologies face challenges in maintaining the integrity of gas content within samples and are often constrained by estimation errors inherent in empirical formulas,which results in inaccurate gas content measurements.This study introduces a lightweight,in-situ pressure-and gas-preserved corer designed to collect coal samples under the pressure conditions at the sampling point,effectively preventing gas loss during transfer and significantly improving measurement accuracy.Additionally,a gas migration model for deep coal mines was developed to elucidate gas migration characteristics under pressure-preserved coring conditions.The model offers valuable insights for optimizing coring parameters,demonstrating that both minimizing the coring hole diameter and reducing the pressure difference between the coring-point pressure and the original pore pressure can effectively improve the precision of gas content measurements.Coring tests conducted at an experimental base validated the performance of the corer and its effectiveness in sample collection.Furthermore,successful horizontal coring tests conducted in an underground coal mine roadway demonstrated that the measured gas content using pressure-preserved coring was 34%higher than that obtained through open sampling methods.
基金financially supported by,the Fundamental Research Funds for the Central Universities(Grant No.2023QN1064)the China Postdoctoral Science Foundation(Grant No.2023M733772)Jiangsu Funding Program for Excellent Postdoctoral Talent(Grant No.2023ZB847)。
文摘Prepulse combined hydraulic fracturing facilitates the development of fracture networks by integrating prepulse hydraulic loading with conventional hydraulic fracturing.The formation mechanisms of fracture networks between hydraulic and pre-existing fractures under different prepulse loading parameters remain unclear.This research investigates the impact of prepulse loading parameters,including the prepulse loading number ratio(C),prepulse loading stress ratio(S),and prepulse loading frequency(f),on the formation of fracture networks between hydraulic and pre-existing fractures,using both experimental and numerical methods.The results suggest that low prepulse loading stress ratios and high prepulse loading number ratios are advantageous loading modes.Multiple hydraulic fractures are generated in the specimen under the advantageous loading modes,facilitating the development of a complex fracture network.Fatigue damage occurs in the specimen at the prepulse loading stage.The high water pressure at the secondary conventional hydraulic fracturing promotes the growth of hydraulic fractures along the damage zones.This allows the hydraulic fractures to propagate deeply and interact with pre-existing fractures.Under advantageous loading conditions,multiple hydraulic fractures can extend to pre-existing fractures,and these hydraulic fractures penetrate or propagate along pre-existing fractures.Especially when the approach angle is large,the damage range in the specimen during the prepulse loading stage increases,resulting in the formation of more hydraulic fractures.
基金support from the National Natural Science Foundation of China(Grant Nos:52379103 and 52279103)the Natural Science Foundation of Shandong Province(Grant No:ZR2023YQ049).
文摘Bayesian-optimized lithology identification has important basic geological research significance and engineering application value,and this paper proposes a Bayesian-optimized lithology identification method based on machine learning of rock visible and near-infrared spectral data.First,the rock spectral data are preprocessed using Savitzky-Golay(SG)smoothing to remove the noise of the spectral data;then,the preprocessed rock spectral data are downscaled using Principal Component Analysis(PCA)to reduce the redundancy of the data,optimize the effective discriminative information,and obtain the rock spectral features;finally,a Bayesian-optimized lithology identification model is established based on rock spectral features,optimize the model hyperparameters using Bayesian optimization(BO)algorithm to avoid the combination of hyperparameters falling into the local optimal solution,and output the predicted type of rock,so as to realize the Bayesian-optimized lithology identification.In addition,this paper conducts comparative analysis on models based on Artificial Neural Network(ANN)/Random Forest(RF),dimensionality reduction/full band,and optimization algorithms.It uses the confusion matrix,accuracy,Precison(P),Recall(R)and F_(1)values(F_(1))as the evaluation indexes of model accuracy.The results indicate that the lithology identification model optimized by the BO-ANN after dimensionality reduction achieves an accuracy of up to 99.80%,up to 99.79%and up to 99.79%.Compared with the BO-RF model,it has higher identification accuracy and better stability for each type of rock identification.The experiments and reliability analysis show that the Bayesian-optimized lithology identification method proposed in this paper has good robustness and generalization performance,which is of great significance for realizing fast,accurate and Bayesian-optimized lithology identification in tunnel site.
