The occurrence of top-down(TD)cracking has gradually become a prevalent issue in semi-rigid base asphalt pavements after prolonged service.A coupled simulation model integrating the finite difference method(FDM)and di...The occurrence of top-down(TD)cracking has gradually become a prevalent issue in semi-rigid base asphalt pavements after prolonged service.A coupled simulation model integrating the finite difference method(FDM)and discrete element method(DEM)was employed to investigate the mechanical behavior of asphalt pavement containing a pre-existing TD crack.The mesoscopic parameters of the model were calibrated based on the mixture modulus and the static mechanical response on the MLS66 test road.Finally,an analysis was performed to assess how variations in TD crack depth and longitudinal length affect the distribution patterns of transverse tensile stress,vertical shear stress,and vertical compressive stress.The results indicate that the vertical propagation of TD crack significantly increases both the tensile stress value and range on the middle surface,while the longitudinal development of TD crack has minimal impact.This phenomenon may result in more severe fatigue failure on the middle surface.With the vertical and longitudinal development of TD crack,the vertical shear stress and compressive stress show obvious"two-stage"characteristics.When the crack's vertical length reaches 40 mm,there is a sharp increase in stress on the upper surface.As the crack continues to propagate vertically,the growth of stress on the upper surface becomes negligible,while the stress in the middle and lower layers increased significantly.Conversely,for longitudinal development of TD crack,any changes in stress are insignificant when their length is less than 180 mm;however,as they continue to develop longitudinally beyond this threshold,there is a sharp increase in stress levels.These findings hold great significance for understanding pavement structure deterioration and maintenance behavior associated with TD crack.展开更多
As the mine depth around the world increases,the temperature of the surrounding rock of the mining workface increases significantly.To control the heat hazards,the hot water in the mining floor is developed during min...As the mine depth around the world increases,the temperature of the surrounding rock of the mining workface increases significantly.To control the heat hazards,the hot water in the mining floor is developed during mining to decrease the min-ing workface temperature while also developing geothermal energy.This method is called the co-exploitation of mine and geothermal energy(CMGE).The geothermal development may precipitate the large-scale failure of the nearby fault zone during the mining process.However,the evolution of shear slide and shear failure of fault under geothermal production/rein-jection during mining is missing.Therefore,a fully-coupled hydraulic mechanism(HM)double-medium model for CMGE was developed based on the measured data of the Chensilou mine.A comparative analysis of the mechanical response of fault between CMGE and single mining was conducted.The disturbance of geothermal production pressure and reinjection pressure under mining on fault stability were respectively expounded.The results indicate that:(1)The disturbance of geo-thermal reinjection amplifies the disturbance of mining on fault stability.The amplified effect resulted in a normal stress drop of the fault,further leading to a substantial increase in shear slide distance,failure area,and cumulative seismic moment of fault compared with the single mining process.(2)As the distance of reinjection well to the fault decreases,the fault failure intensity increases.Setting the production well within the fault is advantageous for controlling fault stability under CMGE.(3)The essence of the combined disturbance of CMGE on the nearby fault is the overlay of tensile stress disturbance on the fault rock mass of the mining and geothermal reinjection.Though the geothermal reinjection causes a minor normal stress drop of fault,it can result in a more serious fault failure under CMGE.This paper supplies a significant gap in understanding thenearby faults failure under CMGE.展开更多
Rock-like specimens containing a joint with different inclination angles and roughness were prepared using 3D printing technology.Then,true triaxial compression loading experiments were conducted on those jointed spec...Rock-like specimens containing a joint with different inclination angles and roughness were prepared using 3D printing technology.Then,true triaxial compression loading experiments were conducted on those jointed specimens.The increase in roughness leads to an increase in the axial strength and peak strain.With the increasing inclination angle,the axial strength initially decreases from 30°to 60°and then increases from 60°to 90°.While the peak strain first rises from 30°to 45°and then declines from 45°to 90°.The variation in failure mode results from differences in lateral stress on the joints under different strike directions.Specimens with joint strike parallel to the intermediate principal stress predominantly showed matrix or matrix-joint mixed shear failure,whereas those parallel to the minimum principal stress exhibited matrix shear failure.The analysis results of acoustic emission signals indicate the crack number and shear crack percentage increase with the increasing roughness and first decrease(30°to 60°),then increase(60°to 90°)with the increasing inclination angle.The research results can provide some guidance for the design and support of underground engineering with jointed surrounding rock.展开更多
Thermodynamically stable and ultra-thin “phase” at the interface, known as complexions, can significantly improve the mechanical properties of nanolayered composites. However, the effect of complexions features (e.g...Thermodynamically stable and ultra-thin “phase” at the interface, known as complexions, can significantly improve the mechanical properties of nanolayered composites. However, the effect of complexions features (e.g., crystalline orientation, crystalline structure and amorphous composition) on the plastic deformation remains inadequately investigated, and the correlation with the plastic transmission and mechanical response has not been fully established. Here, using atomistic simulations, we elucidate the different complexions-dominated plastic transmission and mechanical response. Complexions can alter the preferred slip system of dislocation nucleation, depending on the Schmid factor and interface structure. After nucleation, the dislocation density exhibits an inverse correlation with the stress magnitude, because the number of dislocations influences the initiation of plastic deformation and determines the stress release. For crystalline complexions with different structures and orientations, the ability of dislocation transmission is mainly dependent on the continuity of the slip system. The plastic transmission can easily proceed and exhibits relatively low flow stress when the slip system is well-aligned. In the case of amorphous complexions with different compositions, compositional variations impact the atomic percentage of shear transformation zones after loading, resulting in different magnitudes of plastic deformation. When smaller plastic deformation is produced, less stress can be released contributing to higher flow stress. These findings reveal the role of the complexions on plasticity behavior and provide valuable insights for the design of nanolayered composites.展开更多
Underground engineering in extreme environments necessitates understanding rock mechanical behavior under coupled high-temperature and dynamic loading conditions.This study presents an innovative multi-scale cross-pla...Underground engineering in extreme environments necessitates understanding rock mechanical behavior under coupled high-temperature and dynamic loading conditions.This study presents an innovative multi-scale cross-platform PFC-FDEM coupling methodology that bridges microscopic thermal damage mechanisms with macroscopic dynamic fracture responses.The breakthrough coupling framework introduces:(1)bidirectional information transfer protocols enabling seamless integration between PFC’s particle-scale thermal damage characterization and FDEM’s continuum-scale fracture propagation,(2)multi-physics mapping algorithms that preserve crack network geometric invariants during scale transitions,and(3)cross-platform cohesive zone implementations for accurate SHTB dynamic loading simulation.The coupled approach reveals distinct three-stage crack evolution characteristics with temperature-dependent density following an exponential model.High-temperature exposure significantly reduces dynamic strength ratio(60%at 800℃)and diminishes strain-rate sensitivity,with dynamic increase factor decreasing from 1.0 to 2.2(25℃)to 1.0-1.3(800℃).Critically,the coupling methodology captures fundamental energy redistribution mechanisms:thermal crack networks alter elastic energy proportion from 75%to 35%while increasing fracture energy from 5%to 30%.Numerical predictions demonstrate excellent experimental agreement(±8%peak stress-strain errors),validating the PFC-FDEM coupling accuracy.This integrated framework provides essential computational tools for predicting complex thermal-mechanical rock behavior in underground engineering applications.展开更多
Under external disturbances,the shear mechanical responses and debonding failure mechanisms at anisotropic interfaces of anchoring system composed of multiphase media are inherently difficult to characterize due to th...Under external disturbances,the shear mechanical responses and debonding failure mechanisms at anisotropic interfaces of anchoring system composed of multiphase media are inherently difficult to characterize due to the concealment nature of interfacial interactions.This study establishes an equivalent shear model for a bolt-resin-rock anchoring system and conducts direct shear tests under dynamic normal load(DNL)boundary from both laboratory experiments and discrete element method(DEM)simulations.The research investigates the influence of normal dynamic load amplitude(An)and rock type on shear strength parameters,elucidating the evolutionary characteristics and underlying mechanisms of shear load and normal displacement fluctuations induced by cyclic normal loading,with maximum shear load decreasing by 36.81%to 46.94%as An increases from 10%to 70%when rock type varies from coal to limestone.Through analysis of strain field evolution,the critical impact of rock type on localization of shear failure surface is revealed,with systematic summarization of differentiated wear characteristics,failure modes,and key controlling factors associated with shear failure surface.Mesoscopic investigations enabled by DEM simulations uncover the nonuniform distribution of contact force chains within the material matrix and across the anisotropic interfaces under various DNL boundaries,clarify rock type dependent crack propagation pathways,and quantitatively assess the damage extent of shear failure surface,with the anisotropic interface damage factor increasing from 34.9%to 56.6%as An rises from 10%to 70%,and decreasing from 49.6%to 23.4%as rock type varies from coal to limestone.展开更多
High-entropy alloys(HEA)are novel materials obtained by introducing chemical disorder through mixing multiple-principal components,performing rather attractive features together with charming and exceptional propertie...High-entropy alloys(HEA)are novel materials obtained by introducing chemical disorder through mixing multiple-principal components,performing rather attractive features together with charming and exceptional properties in comparison with traditional alloys.However,the trade-off relationship is still present between strength and ductility in HEAs,significantly limiting the practical and wide application of HEAs.Moreover,the preparation of HEAs by trial-and-error method is time-consuming and resource-wasting,hindering the high-speed and high-quality development of HEAs.Herein,the primary objective of this work is to summarize the latest advancements in HEAs,focusing on methods for predicting phase structures and the factors influencing mechanical properties.Additionally,strengthening and toughening strategies for HEAs are highlighted,thus maximizing their application potential.Besides,challenges and future investigation direction of HEAs are also identified and proposed.展开更多
Triply periodic minimal surfaces(TPMS)are structures with smooth surfaces and excellent energy absorption properties.Combining new functional materials,such as shape memory alloys,with TPMS structures provides a novel...Triply periodic minimal surfaces(TPMS)are structures with smooth surfaces and excellent energy absorption properties.Combining new functional materials,such as shape memory alloys,with TPMS structures provides a novel and promising research field.In this study,three TPMS structures(Gyroid,Diamond,and Primitive)of Cu-11.85Al-3.2Mn-0.1Ti alloy were printed by laser powder bed fusion,which is favorable for the fabrication of complex structures.The manufacturing fidelity,mechanical response,and superelastic properties of the three structures were investigated.Stress distributions in the three structures during compression were analyzed by finite element(FE)simulation.The three structures were equipped with high-quality,glossy surfaces and uniform pores.However,due to powder adhesion and forming steps,there were volumetric errors and dimensional deviations between the samples and the CAD models.The errors were within 1.6%for the Gyroid and Diamond structures.The dimensional deviations at the nodes in the three structures were less than 0.09 mm.The microstructures of all structures wereβ1´martensite,consistent with the cubic sample.Experimental results of compression showed that the structures underwent a layer-by-layer compression failure mode,and the Primitive structures exhibited a more pronounced oscillatory process.The Diamond structures showed the highest first fracture stress and strain of 164.67 MPa and 13.89%,respectively.It also possessed the lowest yield strength(61.97 MPa)and the best energy absorption properties(7.6 MJ/m3).Through the deformation analysis,the Gyroid and Diamond structures were found to fracture at a 45°direction,while the Primitive structures fractured horizontally.These findings were consistent with the results obtained from the FE simulation,which showed equivalent stress distributions.After applying various pre-strains,the Diamond structures displayed the highest superelastic strain of up to 3.53%.The superelastic recovery of all samples ranged from 63.5%to 71.5%.展开更多
To investigate the mechanical response during failure and the impact tendency characteristics of gangue-coal combined structure,uniaxial compression tests were conducted on nine groups of combined structures,each with...To investigate the mechanical response during failure and the impact tendency characteristics of gangue-coal combined structure,uniaxial compression tests were conducted on nine groups of combined structures,each with varying gangue thicknesses and positions.The response patterns of compressive strength,elastic modulus,pre-peak accumulated energy,elastic energy index,and impact energy index were systematically analyzed.Furthermore,a new index for evaluating the impact tendency of gangue-containing coal was proposed,and its effectiveness was verified.The findings are as follows:(1)As the gangue thickness increases,both the compressive strength and the pre-peak energy of the combined structure decrease,whereas the elastic modulus increases accordingly.When the gangue is located in the lower middle position,the combined structure exhibits the lowest compressive strength and elastic modulus but the highest pre peak energy.(2)As the gangue shifts toward the middle position of the combined structure,the failure mode gradually transitions from comple te“crushing”failure to an incomplete“point-type”failure.As gangue thickness further increases,the failure region evolves from overall failure to localized failure,with the degree of failure shifting from complete to incomplete.The K_(crc)value corresponding to“crushing”complete failure is higher and has a stronger impact tendency compared to“point-type”incomplete failure.(3)The proposed comprehensive impact instability evaluation index K_(crc)for the gangue-coal combined structure has shown a significant positive correlation with compressive strength(R_(c))and impact energy index(K_(E)),further verifyi ng its rationality in comprehensively assessing the impact tendency of gangue-containing coal bodies.Applying this index to the evaluation of gangue-containing coal seams provides a more accurate reflection of their impact tendency compared with the residual energy index,which has a wide range of potential applications and practical significance.展开更多
The effect of cold plastic deformation between solution treatment and artificial aging on the age-hardening response and mechanical properties of alloy was investigated by micro-hardness test,tensile test,optical micr...The effect of cold plastic deformation between solution treatment and artificial aging on the age-hardening response and mechanical properties of alloy was investigated by micro-hardness test,tensile test,optical microscopy（OM） and TEM observation.After solution treatment at 420 ℃ for 1 h,three kinds of pre-deformation strains,i.e.0,5% and 10%,were applied to extruded ZM61 bars.Age-hardening curves show that pre-deformation can significantly accelerate the precipitation kinetics and increase peak-hardness value;however,as pre-deformation strain rises from 5% to 10%,there is no gain in peak hardness value.The room temperature（RT） tensile properties demonstrate that increasing the pre-deformation degree can enhance the yield strength（YS） and ultimate tensile strength（UTS） but moderately reduce elongation（EL）;furthermore,the enhancement of YS is larger than that of UTS.No twin can be observed in 5% pre-deformed microstructure;however,a large number of twins are activated after 10% pre-deformation.The peak-aged TEM microstructure shows that pre-deformation can increase the number density of rod-shaped β 1 ＇ precipitates which play a key role in strengthening ZM61 alloy.展开更多
Conglomerate rock's complex and heterogeneous microstructure significantly affects its mechanical properties,especially under dynamic loading.However,research on their dynamic behavior and fracture mechanisms is l...Conglomerate rock's complex and heterogeneous microstructure significantly affects its mechanical properties,especially under dynamic loading.However,research on their dynamic behavior and fracture mechanisms is limited.Through uniaxial compression tests and split Hopkinson pressure bar(SHPB)impact tests,the dynamic compressive mechanical properties and fracture mechanisms of conglomerate rock were studied.Nanoindentation and high-resolution X-ray computed tomography were employed to analyze the micro-mechanical behavior and internal structure of the conglomerate rock.Results indicate significant differences in mechanical properties between different gravel particles and cementing materials,with initial fractures primarily distributed at the gravel-cement interfaces.The dynamic mechanical properties of conglomerate rocks exhibit a clear strain rate dependency.Based on the stress−strain curves and failure characteristics,the dynamic compressive mechanical behavior can be categorized into two types using a critical strain rate.The dynamic compressive strength,peak strain,and toughness of conglomerate rock increased with the strain rate,with the strength at 54 s−1 being 2.6 times that at 6 s−1.The dynamic compressive fracture mechanism of conglomerate rock is related to the strain rate and microstructure;at low strain rates,gravel distribution is the key factor,whereas at high strain rates,gravel content becomes critical.展开更多
Piezoelectric semiconductor(PSC)materials exhibit strong electromechanical coupling affected by free carriers,which makes their contact behavior essential for sensors,actuators,and electronic devices.Analytical models...Piezoelectric semiconductor(PSC)materials exhibit strong electromechanical coupling affected by free carriers,which makes their contact behavior essential for sensors,actuators,and electronic devices.Analytical models for three-dimensional(3D)PSC contact problems are still scarce,especially for conductive indenters.This work develops a semi-analytical framework to study the 3D frictionless contact between a conductive indenter and a PSC half-space.Fundamental solutions under a unit force and a unit electric charge are derived,and the corresponding frequency response functions are combined with a discrete convolution-fast Fourier transform(DC-FFT)algorithm to achieve an efficient semi-analytical contact model.The numerical results demonstrate that an increase in the surface charge density reduces the indentation pressure and modifies the electric potential distribution.A higher steady carrier concentration enhances the screening effect,suppresses the electromechanical coupling,and shifts the system response toward purely elastic behaviors.The sensitivity analysis shows that the indentation depth is dominated by the elastic constants,while the electric potential is mainly affected by the piezoelectric coefficient.Although the analysis is carried out with spherical indenters,the model is not limited to a specific indenter shape.It provides an effective tool for investigating complex 3D PSC contact problems and offers useful insights into the design of PSC materials-based devices.展开更多
Understanding the molecular responses of tea leaves to mechanical stress is crucial for elucidating the mechanisms of post-harvest quality formation during oolong tea processing.This study employed an integrated multi...Understanding the molecular responses of tea leaves to mechanical stress is crucial for elucidating the mechanisms of post-harvest quality formation during oolong tea processing.This study employed an integrated multi-omics strategy to characterize the changes and interactions among metabolomic(MB),transcriptomic(TX),and proteomic(PT)profiles in mechanically stressed tea leaves.Mechanical stress initially activated damage-associated molecular patterns(DAMPs),including Ca^(2+)signaling,jasmonic acid signaling,and glutathione metabolism pathways.These processes subsequently induced quality-related metabolic pathways(QRMPs),particularly α-linolenic acid and phenylalanine metabolism.Upregulated expression of LOX,ADH1,and PAR genes,together with the increased abundance of their encoded proteins,respectively promoted the accumulation of jasmine lactone,benzyl alcohol,and 2-phenylethanol.These findings indicate that mechanical stress influences the metabolite biosynthesis in tea leaves through coordinated molecular responses.This study provides new insights into the molecular mechanisms underlying tea leaf responses to mechanical stress and a foundation for future investigations into how early molecular events may contribute to post-harvest metabolic changes during oolong tea processing.展开更多
This study presents a framework involving statistical modeling and machine learning to accurately predict and optimize the mechanical and damping properties of hybrid granite-epoxy(G-E)composites reinforced with cast ...This study presents a framework involving statistical modeling and machine learning to accurately predict and optimize the mechanical and damping properties of hybrid granite-epoxy(G-E)composites reinforced with cast iron(CI)filler particles.Hybrid G-E composite with added cast iron(CI)filler particles enhances stiffness,strength,and vibration damping,offering enhanced performance for vibration-sensitive engineering applications.Unlike conventional approaches,this work simultaneously employs Artificial Neural Networks(ANN)for highaccuracy property prediction and Response Surface Methodology(RSM)for in-depth analysis of factor interactions and optimization.A total of 24 experimental test data sets of varying input factors(granite weight%,epoxy weight%,and CI filler weight%)were utilized to train and test the prediction models using an ANN approach and further analyze the interaction effects using RSM.Mechanical properties,including tensile,compressive,and flexural strength,elastic modulus,density and damping properties measured under various testing conditions,were set as output parameters for prediction.This study analyzed and optimized the performance of the ANN model using Bayesian Regularization and Levenberg-Marquardt algorithms to identify the best performing number of neurons in the hidden layer for achieving the highest prediction accuracy.The proposed ANN framework achieved an exceptional average determination coefficient(R2)exceeding 99%,with Bayesian Regularization demonstrating remarkable stability in the 22-neuron range and minimal variation across all properties.RSM and ANN form a powerful framework for predicting and optimizing hybrid G-E composite properties,enabling efficient design for vibration-critical applications with reduced experimental effort and performance optimization.展开更多
This study employed tri-component continuous monitoring data from 10 measurement points on both sides of a base isolation layer in the basement of a large-span high-rise building in Beijing,as well as from a free-fiel...This study employed tri-component continuous monitoring data from 10 measurement points on both sides of a base isolation layer in the basement of a large-span high-rise building in Beijing,as well as from a free-field station and roof frame,during a Mw 5.5 magnitude earthquake in Pingyuan,Shandong,in 2023.The H/V spectral ratio method was used to evaluate the structural dynamic response characteristics of the building and analyze the regulatory effect of the base-isolation layer on seismic waves.The results indicate that during the earthquake,the peak frequency of the free-field and the measurement points below the base-isolation layer was stable at 0.17 Hz,whereas the main frequency of the measurement points above the base-isolation layer increased to 0.75–1.18 Hz,which is 4–6 times greater than that of the points below.The amplitude was suppressed by more than 70%,confirming that the base isolation layer effectively isolated the low-frequency energy from the ground and increased the response frequency of the building.When the building was excited by an earthquake,a three-tier frequency gradient was formed throughout the building:“base-isolation layer(0.17 Hz)-main body(1.18 Hz)-roof frame(3.83 Hz)”,which can effectively avoid resonance of the entire building.In addition,the composite base-isolation device changed the dynamic characteristics of the structure.The resonance period was extended from 0.74 s(theoretical value without base isolation)to 5.9 s(calculated value),and the resonance frequency was reduced from 1.35 to 0.17 Hz.This finding indicates that the base-isolation layer can enhance seismic performance by increasing flexibility and damping.展开更多
Changes in the soil environment induced by major global changes in climate are affecting carbon emissions in cold-temperate coniferous forests.A randomized block experiment simulating warming,rainfall increase and nit...Changes in the soil environment induced by major global changes in climate are affecting carbon emissions in cold-temperate coniferous forests.A randomized block experiment simulating warming,rainfall increase and nitrogen addition in a Larix gmelinii forest was carried out to study the effects on soil carbon,nitrogen,and CO_(2)flux during the thawing,growing,and freezing periods.Our study found that warming(0-2.0℃)increased soil organic carbon(SOC)and total nitrogen(STN),dissolved organic carbon(DOC)and dissolved organic nitrogen(DON),and microbial biomass carbon(MBC)and microbial biomass nitrogen(MBN).Warming played a direct role in regulating soil CO_(2)emissions,stimulated microbial and plant root respiration and soil CO_(2)flux rapidly increased.Rainfall increase initially increased soil carbon and nitrogen,but a 30%increase in mean annual rainfall caused losses of SOC,STN,DOC,and DON,while MBC and MBN accumulated.Soil CO_(2)emissions were regulated by MBC after an increase in rainfall,excess moisture inhibited microbial activity,and soil CO_(2)flux showed a trend of R2(20%rainfall increase)>R1(10%rainfall increase)>CK(control)>R3(30%rainfall increase).The addition of nitrogen increased SOC,STN,DOC,DON,MBC and MBN.Soil CO_(2)flux progressively decreased with nitrogen inputs(2.5,5.0 and 10.0 g m^(-2)a^(-1)),as more N intensified plant-microbe competition.Nitrogen addition indirectly regulated soil CO_(2)emissions by altering SOC and STN,with MBC and MBN acting as secondary regulators.The results highlight the role of cold-temperate coniferous forest soils in predicting carbon-climate feedback in high-latitude forest permafrost regions.展开更多
Urbanization significantly affects the balance of key elements such as water,heat,and carbon in cities.However,previous studies have not integrated these factors for comprehensive analysis.Here,we proposed a waterheat...Urbanization significantly affects the balance of key elements such as water,heat,and carbon in cities.However,previous studies have not integrated these factors for comprehensive analysis.Here,we proposed a waterheat-carbon(WHC)nexus model to provide a holistic understanding of urbanization's impacts.Furthermore,we employed the model to identify the mechanisms and response thresholds of urbanization through this coupling approach.Our findings reveal three key insights:(1)WHC exhibits a nonlinear,inverted S-shaped response to urbanization.(2)The mechanisms through which urbanization impacts WHC differ significantly across urbanization gradients.Acrossing urbanization gradients,the complexity of impact pathways increases,with direct effects becoming more pronounced and positive impact pathways emerging progressively.(3)We identified priority zones for restoration and protection based on the likelihood of units shifting between lower-risk and higher-risk categories.Our study enhances understanding of the WHC-urbanization nexus and highlights the importance of accounting for threshold effects and environmental interactions when examining the impact between urbanization and WHC.This framework can be adapted to other urban areas experiencing similar challenges.展开更多
The use of ultra-high molecular weight polyethylene(UHMWPE)composite in the design of lightweight protective equipment,has gained a lot of interest.However,there is an urgent need to understand the ballistic response ...The use of ultra-high molecular weight polyethylene(UHMWPE)composite in the design of lightweight protective equipment,has gained a lot of interest.However,there is an urgent need to understand the ballistic response mechanism and theoretical prediction model of performance.This paper explores the ballistic response mechanism of UHMWPE composite through experimental and simulation analyses.Then,a resistance-driven modeling method was proposed to establish a theoretical model for predicting the bulletproof performance.The ballistic response mechanism of UHMWPE composite encompassed three fundamental modes:local response,structural response,and coupled response.The occurrence ratio of these fundamental response modes during impact was dependent on the projectile velocity and laminate thickness.The bulletproof performance of laminate under different response modes was assessed based on the penetration depth of the projectile,the bulging height on the rear face of the laminate,the thickness of remaining sub-laminate,and residual velocity of the projectile.The absolute deviations of bulletproof performance indicator between theoretical value and experimental value were well within 11.13%,demonstrating that the established evaluation model possessed high degree of prediction accuracy.展开更多
The seismic stability of the rock slope at tunnel entrances is very intricate because of the interactions among geological structures and earthquakes.However,the local damage mechanism and the correlation mechanism of...The seismic stability of the rock slope at tunnel entrances is very intricate because of the interactions among geological structures and earthquakes.However,the local damage mechanism and the correlation mechanism of accumulated damage and landslide triggering are not clear.To investigate the correlation between the inherent frequency and seismic characteristics of a layered slope at a tunnel entrance from the perspective of the frequency domain,a three-dimensional finite element modal analysis and Fourier spectrum analysis of shaking table tests were carried out.This work takes the quarry slope at the tunnel entrance in Xiamen City as a case example.The study region is predominantly affected by strong seismic activity,where the rock is primarily composed of granite with varying degrees of weathering.The results show that the seismic energy below the tunnel is mostly focused on the lowfrequency ranges,whereas the energy above the tunnel is gradually transferred to the high-frequency range.By analyzing the peak spectrum value of high-order inherent frequencies for the slope,its seismic damage evolution can be effectively identified,including fracture initiation,accelerated deformation,and sliding instability stages.The seismic response of the slope includes multi-mode interactions,which mainly include bending,torsion,and combined deformation.There are magnification effects of elevation,slope surface,and structural plane in the slope.Moreover,the triggering mechanism of the local deformation and integral sliding for the landslide is identified,which indicates that the lining structure of the tunnel entrance is more prone to seismic damage.This work successfully investigated the seismic damage evolution and failure mechanism of the slope at tunnel entrances in the frequency domain.展开更多
The bridge piles located in high-steep slopes not only endure the loads from superstructure, but also the residual sliding force as well as the resistance from the slope. By introducing the Winkler foundation theory, ...The bridge piles located in high-steep slopes not only endure the loads from superstructure, but also the residual sliding force as well as the resistance from the slope. By introducing the Winkler foundation theory, the mechanical model of piles-soils-slopes system was established, and the equilibrium differential equations of pile were derived. Moreover, an analytic solution for identifying the model parameters was provided by means of power series method. A project with field measurement was compared with the proposed method. It is indicated that the lateral loads have great influences on the pile, the steep slope effect is indispensable, and reasonable diameter of the pile could enhance the bending ability. The internal force and displacements of pile are largely based upon the horizontal loads applied on pile, especially in upper part.展开更多
基金supported by National Key R&D Program of China(Grant No.2021YFB2601200)Open Fund of National Engineering Research Center of Highway Maintenance Technology(Changsha University of Science&Technology)(No.kfj230207).
文摘The occurrence of top-down(TD)cracking has gradually become a prevalent issue in semi-rigid base asphalt pavements after prolonged service.A coupled simulation model integrating the finite difference method(FDM)and discrete element method(DEM)was employed to investigate the mechanical behavior of asphalt pavement containing a pre-existing TD crack.The mesoscopic parameters of the model were calibrated based on the mixture modulus and the static mechanical response on the MLS66 test road.Finally,an analysis was performed to assess how variations in TD crack depth and longitudinal length affect the distribution patterns of transverse tensile stress,vertical shear stress,and vertical compressive stress.The results indicate that the vertical propagation of TD crack significantly increases both the tensile stress value and range on the middle surface,while the longitudinal development of TD crack has minimal impact.This phenomenon may result in more severe fatigue failure on the middle surface.With the vertical and longitudinal development of TD crack,the vertical shear stress and compressive stress show obvious"two-stage"characteristics.When the crack's vertical length reaches 40 mm,there is a sharp increase in stress on the upper surface.As the crack continues to propagate vertically,the growth of stress on the upper surface becomes negligible,while the stress in the middle and lower layers increased significantly.Conversely,for longitudinal development of TD crack,any changes in stress are insignificant when their length is less than 180 mm;however,as they continue to develop longitudinally beyond this threshold,there is a sharp increase in stress levels.These findings hold great significance for understanding pavement structure deterioration and maintenance behavior associated with TD crack.
基金supported by the Key Project of the National Natural Science Foundation of China(U23B2091)the National Key R&D Program of China(2022YFC2905600)+1 种基金the Youth Project of the National Natural Science Foundation of China(52304104 and 52404157)the Postdoctoral Fellowship Program of China Postdoctoral Science Foundation(GZB20240825).
文摘As the mine depth around the world increases,the temperature of the surrounding rock of the mining workface increases significantly.To control the heat hazards,the hot water in the mining floor is developed during mining to decrease the min-ing workface temperature while also developing geothermal energy.This method is called the co-exploitation of mine and geothermal energy(CMGE).The geothermal development may precipitate the large-scale failure of the nearby fault zone during the mining process.However,the evolution of shear slide and shear failure of fault under geothermal production/rein-jection during mining is missing.Therefore,a fully-coupled hydraulic mechanism(HM)double-medium model for CMGE was developed based on the measured data of the Chensilou mine.A comparative analysis of the mechanical response of fault between CMGE and single mining was conducted.The disturbance of geothermal production pressure and reinjection pressure under mining on fault stability were respectively expounded.The results indicate that:(1)The disturbance of geo-thermal reinjection amplifies the disturbance of mining on fault stability.The amplified effect resulted in a normal stress drop of the fault,further leading to a substantial increase in shear slide distance,failure area,and cumulative seismic moment of fault compared with the single mining process.(2)As the distance of reinjection well to the fault decreases,the fault failure intensity increases.Setting the production well within the fault is advantageous for controlling fault stability under CMGE.(3)The essence of the combined disturbance of CMGE on the nearby fault is the overlay of tensile stress disturbance on the fault rock mass of the mining and geothermal reinjection.Though the geothermal reinjection causes a minor normal stress drop of fault,it can result in a more serious fault failure under CMGE.This paper supplies a significant gap in understanding thenearby faults failure under CMGE.
基金Projects(52074259,52204132)supported by the National Natural Science Foundation of ChinaProject(104023002)supported by the Yunlong Lake Laboratory of Deep Underground Science and Engineering Project,China+2 种基金Project(BK20220157)supported by Natural Science Foundation of Jiangsu Province of ChinaProject(2023JJ40285)supported by Hunan Provincial Natural Science Foundation of ChinaProject(22B0469)supported by Scientific Research Foundation of Hunan Provincial Education Department,China。
文摘Rock-like specimens containing a joint with different inclination angles and roughness were prepared using 3D printing technology.Then,true triaxial compression loading experiments were conducted on those jointed specimens.The increase in roughness leads to an increase in the axial strength and peak strain.With the increasing inclination angle,the axial strength initially decreases from 30°to 60°and then increases from 60°to 90°.While the peak strain first rises from 30°to 45°and then declines from 45°to 90°.The variation in failure mode results from differences in lateral stress on the joints under different strike directions.Specimens with joint strike parallel to the intermediate principal stress predominantly showed matrix or matrix-joint mixed shear failure,whereas those parallel to the minimum principal stress exhibited matrix shear failure.The analysis results of acoustic emission signals indicate the crack number and shear crack percentage increase with the increasing roughness and first decrease(30°to 60°),then increase(60°to 90°)with the increasing inclination angle.The research results can provide some guidance for the design and support of underground engineering with jointed surrounding rock.
基金supported by the National Natural Science Foundation of China(Nos.U23A20543,52071124)the Natural Science Foundation of the Hebei Province(No.E2021202135).
文摘Thermodynamically stable and ultra-thin “phase” at the interface, known as complexions, can significantly improve the mechanical properties of nanolayered composites. However, the effect of complexions features (e.g., crystalline orientation, crystalline structure and amorphous composition) on the plastic deformation remains inadequately investigated, and the correlation with the plastic transmission and mechanical response has not been fully established. Here, using atomistic simulations, we elucidate the different complexions-dominated plastic transmission and mechanical response. Complexions can alter the preferred slip system of dislocation nucleation, depending on the Schmid factor and interface structure. After nucleation, the dislocation density exhibits an inverse correlation with the stress magnitude, because the number of dislocations influences the initiation of plastic deformation and determines the stress release. For crystalline complexions with different structures and orientations, the ability of dislocation transmission is mainly dependent on the continuity of the slip system. The plastic transmission can easily proceed and exhibits relatively low flow stress when the slip system is well-aligned. In the case of amorphous complexions with different compositions, compositional variations impact the atomic percentage of shear transformation zones after loading, resulting in different magnitudes of plastic deformation. When smaller plastic deformation is produced, less stress can be released contributing to higher flow stress. These findings reveal the role of the complexions on plasticity behavior and provide valuable insights for the design of nanolayered composites.
基金supported by the National Natural Science Foundations of China(Nos.12272411 and 42007259)the State Key Laboratory for GeoMechanics and Deep Underground Engineering,the China University of Mining&Technology(No.SKLGDUEK2207)the Department of Science and Technology of Shaanxi Province(Nos.2022KXJ-107 and 2022JC-LHJJ-16).
文摘Underground engineering in extreme environments necessitates understanding rock mechanical behavior under coupled high-temperature and dynamic loading conditions.This study presents an innovative multi-scale cross-platform PFC-FDEM coupling methodology that bridges microscopic thermal damage mechanisms with macroscopic dynamic fracture responses.The breakthrough coupling framework introduces:(1)bidirectional information transfer protocols enabling seamless integration between PFC’s particle-scale thermal damage characterization and FDEM’s continuum-scale fracture propagation,(2)multi-physics mapping algorithms that preserve crack network geometric invariants during scale transitions,and(3)cross-platform cohesive zone implementations for accurate SHTB dynamic loading simulation.The coupled approach reveals distinct three-stage crack evolution characteristics with temperature-dependent density following an exponential model.High-temperature exposure significantly reduces dynamic strength ratio(60%at 800℃)and diminishes strain-rate sensitivity,with dynamic increase factor decreasing from 1.0 to 2.2(25℃)to 1.0-1.3(800℃).Critically,the coupling methodology captures fundamental energy redistribution mechanisms:thermal crack networks alter elastic energy proportion from 75%to 35%while increasing fracture energy from 5%to 30%.Numerical predictions demonstrate excellent experimental agreement(±8%peak stress-strain errors),validating the PFC-FDEM coupling accuracy.This integrated framework provides essential computational tools for predicting complex thermal-mechanical rock behavior in underground engineering applications.
基金support from the National Natural Science Foundation of China(Nos.51504247,52174092,51904290,and 52074259)the Natural Science Foundation of Jiangsu Province,China(No.BK20220157)+1 种基金the Fundamental Research Funds for the Central Universities,China(No.2022YCPY0202)the China University of Mining and Technology(CUMT)Open Sharing Fund for Large-scale Instruments and Equipment(No.DYGX-2025-47)is gratefully acknowledged.
文摘Under external disturbances,the shear mechanical responses and debonding failure mechanisms at anisotropic interfaces of anchoring system composed of multiphase media are inherently difficult to characterize due to the concealment nature of interfacial interactions.This study establishes an equivalent shear model for a bolt-resin-rock anchoring system and conducts direct shear tests under dynamic normal load(DNL)boundary from both laboratory experiments and discrete element method(DEM)simulations.The research investigates the influence of normal dynamic load amplitude(An)and rock type on shear strength parameters,elucidating the evolutionary characteristics and underlying mechanisms of shear load and normal displacement fluctuations induced by cyclic normal loading,with maximum shear load decreasing by 36.81%to 46.94%as An increases from 10%to 70%when rock type varies from coal to limestone.Through analysis of strain field evolution,the critical impact of rock type on localization of shear failure surface is revealed,with systematic summarization of differentiated wear characteristics,failure modes,and key controlling factors associated with shear failure surface.Mesoscopic investigations enabled by DEM simulations uncover the nonuniform distribution of contact force chains within the material matrix and across the anisotropic interfaces under various DNL boundaries,clarify rock type dependent crack propagation pathways,and quantitatively assess the damage extent of shear failure surface,with the anisotropic interface damage factor increasing from 34.9%to 56.6%as An rises from 10%to 70%,and decreasing from 49.6%to 23.4%as rock type varies from coal to limestone.
基金supported by the National Natural Science Foundation of China(Nos.52375451,52005396)Shandong Provincial Natural Science Foundation,China(Nos.ZR2023YQ052,ZR2023ME087)+6 种基金Shandong Provincial Technological SME Innovation Capability Promotion Project,China(No.2023TSGC0375)Young Taishan Scholars Program of Shandong Province,China(No.tsqn202306041)Guangdong Basic and Applied Basic Research Foundation,China(No.2023 A1515010044)Shandong Provincial Youth Innovation Team,China(No.2022KJ038)Open Project of State Key Laboratory of Solid Lubrication,China(No.LSL-22-11)Young Talent Fund of University Association for Science and Technology in Shaanxi,China(No.20210414)Qilu Youth Scholar Project Funding of Shandong University,China。
文摘High-entropy alloys(HEA)are novel materials obtained by introducing chemical disorder through mixing multiple-principal components,performing rather attractive features together with charming and exceptional properties in comparison with traditional alloys.However,the trade-off relationship is still present between strength and ductility in HEAs,significantly limiting the practical and wide application of HEAs.Moreover,the preparation of HEAs by trial-and-error method is time-consuming and resource-wasting,hindering the high-speed and high-quality development of HEAs.Herein,the primary objective of this work is to summarize the latest advancements in HEAs,focusing on methods for predicting phase structures and the factors influencing mechanical properties.Additionally,strengthening and toughening strategies for HEAs are highlighted,thus maximizing their application potential.Besides,challenges and future investigation direction of HEAs are also identified and proposed.
基金Supported by National Natural Science Foundation of China(Grant Nos.52275333,52375335,and U22A202494)the Stabilization Support Project of AVIC Manufacturing Technology Institute(Grant No.KZ571801)+1 种基金the Fundamental Research Funds for the Central Universities(Grant No.2020kfyXJJS088)the Young Elite Scientists Sponsorship Program by CAST(Grant No.YESS20200381).
文摘Triply periodic minimal surfaces(TPMS)are structures with smooth surfaces and excellent energy absorption properties.Combining new functional materials,such as shape memory alloys,with TPMS structures provides a novel and promising research field.In this study,three TPMS structures(Gyroid,Diamond,and Primitive)of Cu-11.85Al-3.2Mn-0.1Ti alloy were printed by laser powder bed fusion,which is favorable for the fabrication of complex structures.The manufacturing fidelity,mechanical response,and superelastic properties of the three structures were investigated.Stress distributions in the three structures during compression were analyzed by finite element(FE)simulation.The three structures were equipped with high-quality,glossy surfaces and uniform pores.However,due to powder adhesion and forming steps,there were volumetric errors and dimensional deviations between the samples and the CAD models.The errors were within 1.6%for the Gyroid and Diamond structures.The dimensional deviations at the nodes in the three structures were less than 0.09 mm.The microstructures of all structures wereβ1´martensite,consistent with the cubic sample.Experimental results of compression showed that the structures underwent a layer-by-layer compression failure mode,and the Primitive structures exhibited a more pronounced oscillatory process.The Diamond structures showed the highest first fracture stress and strain of 164.67 MPa and 13.89%,respectively.It also possessed the lowest yield strength(61.97 MPa)and the best energy absorption properties(7.6 MJ/m3).Through the deformation analysis,the Gyroid and Diamond structures were found to fracture at a 45°direction,while the Primitive structures fractured horizontally.These findings were consistent with the results obtained from the FE simulation,which showed equivalent stress distributions.After applying various pre-strains,the Diamond structures displayed the highest superelastic strain of up to 3.53%.The superelastic recovery of all samples ranged from 63.5%to 71.5%.
基金Project(52274130)supported by the National Natural Science Foundation of ChinaProject(ZR2024ZD22)supported by the Major Basic Research Project of the Shandong Provincial Natural Science Foundation,China+1 种基金Project(2023375)supported by the Guizhou University Research and Innovation Team,ChinaProject(LH[2024]-026)supported by the Guizhou Science and Technology Plan Project,China。
文摘To investigate the mechanical response during failure and the impact tendency characteristics of gangue-coal combined structure,uniaxial compression tests were conducted on nine groups of combined structures,each with varying gangue thicknesses and positions.The response patterns of compressive strength,elastic modulus,pre-peak accumulated energy,elastic energy index,and impact energy index were systematically analyzed.Furthermore,a new index for evaluating the impact tendency of gangue-containing coal was proposed,and its effectiveness was verified.The findings are as follows:(1)As the gangue thickness increases,both the compressive strength and the pre-peak energy of the combined structure decrease,whereas the elastic modulus increases accordingly.When the gangue is located in the lower middle position,the combined structure exhibits the lowest compressive strength and elastic modulus but the highest pre peak energy.(2)As the gangue shifts toward the middle position of the combined structure,the failure mode gradually transitions from comple te“crushing”failure to an incomplete“point-type”failure.As gangue thickness further increases,the failure region evolves from overall failure to localized failure,with the degree of failure shifting from complete to incomplete.The K_(crc)value corresponding to“crushing”complete failure is higher and has a stronger impact tendency compared to“point-type”incomplete failure.(3)The proposed comprehensive impact instability evaluation index K_(crc)for the gangue-coal combined structure has shown a significant positive correlation with compressive strength(R_(c))and impact energy index(K_(E)),further verifyi ng its rationality in comprehensively assessing the impact tendency of gangue-containing coal bodies.Applying this index to the evaluation of gangue-containing coal seams provides a more accurate reflection of their impact tendency compared with the residual energy index,which has a wide range of potential applications and practical significance.
基金Project(2007CB613700) supported by the National Basic Research Program of ChinaProject(50725413) supported by the National Natural Science Foundation of China+2 种基金Project(CDJXS11132228) supported by the Fundamental Research Funds for the Central Universities,ChinaProjects(2010DFR50010,2008DFR50040) supported by International Cooperation Program,ChinaProjects (CSTC2009AB4008,2010CSTC-HDLS) supported by Chongqing Sci & Tech Program,China
文摘The effect of cold plastic deformation between solution treatment and artificial aging on the age-hardening response and mechanical properties of alloy was investigated by micro-hardness test,tensile test,optical microscopy（OM） and TEM observation.After solution treatment at 420 ℃ for 1 h,three kinds of pre-deformation strains,i.e.0,5% and 10%,were applied to extruded ZM61 bars.Age-hardening curves show that pre-deformation can significantly accelerate the precipitation kinetics and increase peak-hardness value;however,as pre-deformation strain rises from 5% to 10%,there is no gain in peak hardness value.The room temperature（RT） tensile properties demonstrate that increasing the pre-deformation degree can enhance the yield strength（YS） and ultimate tensile strength（UTS） but moderately reduce elongation（EL）;furthermore,the enhancement of YS is larger than that of UTS.No twin can be observed in 5% pre-deformed microstructure;however,a large number of twins are activated after 10% pre-deformation.The peak-aged TEM microstructure shows that pre-deformation can increase the number density of rod-shaped β 1 ＇ precipitates which play a key role in strengthening ZM61 alloy.
基金Project(51978674)supported by the National Natural Science Foundation of China。
文摘Conglomerate rock's complex and heterogeneous microstructure significantly affects its mechanical properties,especially under dynamic loading.However,research on their dynamic behavior and fracture mechanisms is limited.Through uniaxial compression tests and split Hopkinson pressure bar(SHPB)impact tests,the dynamic compressive mechanical properties and fracture mechanisms of conglomerate rock were studied.Nanoindentation and high-resolution X-ray computed tomography were employed to analyze the micro-mechanical behavior and internal structure of the conglomerate rock.Results indicate significant differences in mechanical properties between different gravel particles and cementing materials,with initial fractures primarily distributed at the gravel-cement interfaces.The dynamic mechanical properties of conglomerate rocks exhibit a clear strain rate dependency.Based on the stress−strain curves and failure characteristics,the dynamic compressive mechanical behavior can be categorized into two types using a critical strain rate.The dynamic compressive strength,peak strain,and toughness of conglomerate rock increased with the strain rate,with the strength at 54 s−1 being 2.6 times that at 6 s−1.The dynamic compressive fracture mechanism of conglomerate rock is related to the strain rate and microstructure;at low strain rates,gravel distribution is the key factor,whereas at high strain rates,gravel content becomes critical.
基金Project supported by the National Natural Science Foundation of China(No.12402113)the Sichuan Science and Technology Program(No.2024NSFSC0037)。
文摘Piezoelectric semiconductor(PSC)materials exhibit strong electromechanical coupling affected by free carriers,which makes their contact behavior essential for sensors,actuators,and electronic devices.Analytical models for three-dimensional(3D)PSC contact problems are still scarce,especially for conductive indenters.This work develops a semi-analytical framework to study the 3D frictionless contact between a conductive indenter and a PSC half-space.Fundamental solutions under a unit force and a unit electric charge are derived,and the corresponding frequency response functions are combined with a discrete convolution-fast Fourier transform(DC-FFT)algorithm to achieve an efficient semi-analytical contact model.The numerical results demonstrate that an increase in the surface charge density reduces the indentation pressure and modifies the electric potential distribution.A higher steady carrier concentration enhances the screening effect,suppresses the electromechanical coupling,and shifts the system response toward purely elastic behaviors.The sensitivity analysis shows that the indentation depth is dominated by the elastic constants,while the electric potential is mainly affected by the piezoelectric coefficient.Although the analysis is carried out with spherical indenters,the model is not limited to a specific indenter shape.It provides an effective tool for investigating complex 3D PSC contact problems and offers useful insights into the design of PSC materials-based devices.
基金supported by the National Key Research and Development Program of China(2022YFD2101101)the Earmarked Fund for CARS-19+2 种基金the National Natural Science Foundation of China(32402634)the Modern Agricultural(Tea)Industry Technology System of Fujian Province,China(2025 No.593)the Special Fund for Science and Technology Innovation of Fujian Zhang Tianfu Tea Development Foundation,China(FJZTF01)。
文摘Understanding the molecular responses of tea leaves to mechanical stress is crucial for elucidating the mechanisms of post-harvest quality formation during oolong tea processing.This study employed an integrated multi-omics strategy to characterize the changes and interactions among metabolomic(MB),transcriptomic(TX),and proteomic(PT)profiles in mechanically stressed tea leaves.Mechanical stress initially activated damage-associated molecular patterns(DAMPs),including Ca^(2+)signaling,jasmonic acid signaling,and glutathione metabolism pathways.These processes subsequently induced quality-related metabolic pathways(QRMPs),particularly α-linolenic acid and phenylalanine metabolism.Upregulated expression of LOX,ADH1,and PAR genes,together with the increased abundance of their encoded proteins,respectively promoted the accumulation of jasmine lactone,benzyl alcohol,and 2-phenylethanol.These findings indicate that mechanical stress influences the metabolite biosynthesis in tea leaves through coordinated molecular responses.This study provides new insights into the molecular mechanisms underlying tea leaf responses to mechanical stress and a foundation for future investigations into how early molecular events may contribute to post-harvest metabolic changes during oolong tea processing.
文摘This study presents a framework involving statistical modeling and machine learning to accurately predict and optimize the mechanical and damping properties of hybrid granite-epoxy(G-E)composites reinforced with cast iron(CI)filler particles.Hybrid G-E composite with added cast iron(CI)filler particles enhances stiffness,strength,and vibration damping,offering enhanced performance for vibration-sensitive engineering applications.Unlike conventional approaches,this work simultaneously employs Artificial Neural Networks(ANN)for highaccuracy property prediction and Response Surface Methodology(RSM)for in-depth analysis of factor interactions and optimization.A total of 24 experimental test data sets of varying input factors(granite weight%,epoxy weight%,and CI filler weight%)were utilized to train and test the prediction models using an ANN approach and further analyze the interaction effects using RSM.Mechanical properties,including tensile,compressive,and flexural strength,elastic modulus,density and damping properties measured under various testing conditions,were set as output parameters for prediction.This study analyzed and optimized the performance of the ANN model using Bayesian Regularization and Levenberg-Marquardt algorithms to identify the best performing number of neurons in the hidden layer for achieving the highest prediction accuracy.The proposed ANN framework achieved an exceptional average determination coefficient(R2)exceeding 99%,with Bayesian Regularization demonstrating remarkable stability in the 22-neuron range and minimal variation across all properties.RSM and ANN form a powerful framework for predicting and optimizing hybrid G-E composite properties,enabling efficient design for vibration-critical applications with reduced experimental effort and performance optimization.
基金supported by the Deep Earth Probe and Mineral Resources Exploration-National Science and Technology Major Project(Grant No.2025ZD005100)by Beijing Geolight Technology Co.,Ltd.under the project“The Impact of Strong Ground Motion on Buildings”(YF-202520).
文摘This study employed tri-component continuous monitoring data from 10 measurement points on both sides of a base isolation layer in the basement of a large-span high-rise building in Beijing,as well as from a free-field station and roof frame,during a Mw 5.5 magnitude earthquake in Pingyuan,Shandong,in 2023.The H/V spectral ratio method was used to evaluate the structural dynamic response characteristics of the building and analyze the regulatory effect of the base-isolation layer on seismic waves.The results indicate that during the earthquake,the peak frequency of the free-field and the measurement points below the base-isolation layer was stable at 0.17 Hz,whereas the main frequency of the measurement points above the base-isolation layer increased to 0.75–1.18 Hz,which is 4–6 times greater than that of the points below.The amplitude was suppressed by more than 70%,confirming that the base isolation layer effectively isolated the low-frequency energy from the ground and increased the response frequency of the building.When the building was excited by an earthquake,a three-tier frequency gradient was formed throughout the building:“base-isolation layer(0.17 Hz)-main body(1.18 Hz)-roof frame(3.83 Hz)”,which can effectively avoid resonance of the entire building.In addition,the composite base-isolation device changed the dynamic characteristics of the structure.The resonance period was extended from 0.74 s(theoretical value without base isolation)to 5.9 s(calculated value),and the resonance frequency was reduced from 1.35 to 0.17 Hz.This finding indicates that the base-isolation layer can enhance seismic performance by increasing flexibility and damping.
基金funded by the Science and Technology Programme of Inner Mongolia Autonomous Region(Grant No.:2023YFDZ0026 and 2024KYPT0003)the 2024 Postgraduate Research and Innovation Programme of Inner Mongolia Agricultural University。
文摘Changes in the soil environment induced by major global changes in climate are affecting carbon emissions in cold-temperate coniferous forests.A randomized block experiment simulating warming,rainfall increase and nitrogen addition in a Larix gmelinii forest was carried out to study the effects on soil carbon,nitrogen,and CO_(2)flux during the thawing,growing,and freezing periods.Our study found that warming(0-2.0℃)increased soil organic carbon(SOC)and total nitrogen(STN),dissolved organic carbon(DOC)and dissolved organic nitrogen(DON),and microbial biomass carbon(MBC)and microbial biomass nitrogen(MBN).Warming played a direct role in regulating soil CO_(2)emissions,stimulated microbial and plant root respiration and soil CO_(2)flux rapidly increased.Rainfall increase initially increased soil carbon and nitrogen,but a 30%increase in mean annual rainfall caused losses of SOC,STN,DOC,and DON,while MBC and MBN accumulated.Soil CO_(2)emissions were regulated by MBC after an increase in rainfall,excess moisture inhibited microbial activity,and soil CO_(2)flux showed a trend of R2(20%rainfall increase)>R1(10%rainfall increase)>CK(control)>R3(30%rainfall increase).The addition of nitrogen increased SOC,STN,DOC,DON,MBC and MBN.Soil CO_(2)flux progressively decreased with nitrogen inputs(2.5,5.0 and 10.0 g m^(-2)a^(-1)),as more N intensified plant-microbe competition.Nitrogen addition indirectly regulated soil CO_(2)emissions by altering SOC and STN,with MBC and MBN acting as secondary regulators.The results highlight the role of cold-temperate coniferous forest soils in predicting carbon-climate feedback in high-latitude forest permafrost regions.
基金funded by the National Forestry and Grassland Administration(Grant No.2023132050)National Forestry and Grassland Administration(Grant No.2019132703)+1 种基金National Science Foundation of China(Grants No.42171093,42101250)Fengyun 3 Satellite Ground Application Project(Grants No.FY-2(03)-AS-12.09-ZT,FY-APP-2021.0407)。
文摘Urbanization significantly affects the balance of key elements such as water,heat,and carbon in cities.However,previous studies have not integrated these factors for comprehensive analysis.Here,we proposed a waterheat-carbon(WHC)nexus model to provide a holistic understanding of urbanization's impacts.Furthermore,we employed the model to identify the mechanisms and response thresholds of urbanization through this coupling approach.Our findings reveal three key insights:(1)WHC exhibits a nonlinear,inverted S-shaped response to urbanization.(2)The mechanisms through which urbanization impacts WHC differ significantly across urbanization gradients.Acrossing urbanization gradients,the complexity of impact pathways increases,with direct effects becoming more pronounced and positive impact pathways emerging progressively.(3)We identified priority zones for restoration and protection based on the likelihood of units shifting between lower-risk and higher-risk categories.Our study enhances understanding of the WHC-urbanization nexus and highlights the importance of accounting for threshold effects and environmental interactions when examining the impact between urbanization and WHC.This framework can be adapted to other urban areas experiencing similar challenges.
基金supported by the National Key Research and Development of China(Grant No.2022YFB4601901)the National Natural Science Foundation of China(Grant No.12122202)。
文摘The use of ultra-high molecular weight polyethylene(UHMWPE)composite in the design of lightweight protective equipment,has gained a lot of interest.However,there is an urgent need to understand the ballistic response mechanism and theoretical prediction model of performance.This paper explores the ballistic response mechanism of UHMWPE composite through experimental and simulation analyses.Then,a resistance-driven modeling method was proposed to establish a theoretical model for predicting the bulletproof performance.The ballistic response mechanism of UHMWPE composite encompassed three fundamental modes:local response,structural response,and coupled response.The occurrence ratio of these fundamental response modes during impact was dependent on the projectile velocity and laminate thickness.The bulletproof performance of laminate under different response modes was assessed based on the penetration depth of the projectile,the bulging height on the rear face of the laminate,the thickness of remaining sub-laminate,and residual velocity of the projectile.The absolute deviations of bulletproof performance indicator between theoretical value and experimental value were well within 11.13%,demonstrating that the established evaluation model possessed high degree of prediction accuracy.
基金funded by the National Natural Science Foundation of China(52574084)the Key Research and Development Projects of Guangdong Province(2019B111108001)+5 种基金the Guangdong Basic and Applied Basic Research Foundation(2024A1515010045)the Natural Science Foundation of Jiangsu Province(BK20231217)the Independent research project of the State Key Laboratory of Subtropical Building and Urban Science(2023ZB15)the Key Laboratory of Geomechanics and Geotechnical Engineering Safety,Chinese Academy of Sciences(SKLGME023001)the Open Research Fund Program of the State Key Laboratory of Hydroscience and Engineering(sklhse-KF-2025-D-02)the Special Project on Basic and Applied Basic Research of the Guangzhou Municipal Science and Technology Bureau(2025A04J3992)。
文摘The seismic stability of the rock slope at tunnel entrances is very intricate because of the interactions among geological structures and earthquakes.However,the local damage mechanism and the correlation mechanism of accumulated damage and landslide triggering are not clear.To investigate the correlation between the inherent frequency and seismic characteristics of a layered slope at a tunnel entrance from the perspective of the frequency domain,a three-dimensional finite element modal analysis and Fourier spectrum analysis of shaking table tests were carried out.This work takes the quarry slope at the tunnel entrance in Xiamen City as a case example.The study region is predominantly affected by strong seismic activity,where the rock is primarily composed of granite with varying degrees of weathering.The results show that the seismic energy below the tunnel is mostly focused on the lowfrequency ranges,whereas the energy above the tunnel is gradually transferred to the high-frequency range.By analyzing the peak spectrum value of high-order inherent frequencies for the slope,its seismic damage evolution can be effectively identified,including fracture initiation,accelerated deformation,and sliding instability stages.The seismic response of the slope includes multi-mode interactions,which mainly include bending,torsion,and combined deformation.There are magnification effects of elevation,slope surface,and structural plane in the slope.Moreover,the triggering mechanism of the local deformation and integral sliding for the landslide is identified,which indicates that the lining structure of the tunnel entrance is more prone to seismic damage.This work successfully investigated the seismic damage evolution and failure mechanism of the slope at tunnel entrances in the frequency domain.
基金Project(51408066)supported by the National Natural Science Foundation of China
文摘The bridge piles located in high-steep slopes not only endure the loads from superstructure, but also the residual sliding force as well as the resistance from the slope. By introducing the Winkler foundation theory, the mechanical model of piles-soils-slopes system was established, and the equilibrium differential equations of pile were derived. Moreover, an analytic solution for identifying the model parameters was provided by means of power series method. A project with field measurement was compared with the proposed method. It is indicated that the lateral loads have great influences on the pile, the steep slope effect is indispensable, and reasonable diameter of the pile could enhance the bending ability. The internal force and displacements of pile are largely based upon the horizontal loads applied on pile, especially in upper part.
