Investigating the damage evolution of surrounding rock under thermal shock cycles is crucial for ensuring the stability of engineering rock masses.This study performed Brazilian splitting tests on granite specimens un...Investigating the damage evolution of surrounding rock under thermal shock cycles is crucial for ensuring the stability of engineering rock masses.This study performed Brazilian splitting tests on granite specimens under varying temperature and cycle conditions,employing acoustic emission monitoring,digital image correlation,and three-dimensional scanning technology.A systematic analysis was conducted on the patterns of damage evolution,failure precursor,and response mechanisms under combined thermal and cyclic loading.Experimental results show that both P-wave velocity and tensile strength degrade significantly with increasing temperature and cycle count,with temperature having a more pronounced effect than cycle count.Notably,damage evolution exhibits a dual-threshold behavior in which degradation accelerates markedly above 400℃ and stabilizes after 5 thermal cycles.Fracture surfaces evolve from initially planar to rugged morphologies,with peak-valley height differences at 600℃ being approximately three times greater than those at 200℃.Furthermore,based on acoustic emission energy entropy analysis,we introduce a novel failure precursor indicator where the sustained increase and critical surge in average entropy serve as reliable early-warning signals for impending rock failure.These findings establish a solid theoretical basis and practical methodology for damage assessment and instability early-warning systems in high-temperature rock engineering.展开更多
Freeze-thaw cycles(FTCs)have an important effect on soil aggregate stability by altering soil structures,thereby influencing soil wind and water erosion on the eastern Qinghai-Tibet Plateau.However,the effects of FTCs...Freeze-thaw cycles(FTCs)have an important effect on soil aggregate stability by altering soil structures,thereby influencing soil wind and water erosion on the eastern Qinghai-Tibet Plateau.However,the effects of FTCs on the stability of these soils remain unclear.Here,we conducted freeze-thaw simulations in laboratory to investigate the effects of FTCs(0 to 15 cycles)on the wet-and dry-sieving aggregate stability of undisturbed sandy loam from Maqu county,which was treated with different initial soil moisture contents(1%to 25%in increments of 4%)and initial aggregate diameters(<2,2-5,5-10,and 10-15 mm).Results show that soil aggregates with initial diameters larger than 2 mm exhibit higher soil organic carbon contents(1.45%-1.57%)and silt contents(34.63%-35.52%)than those smaller than 2 mm(0.93%and 31.38%,respectively).The stability of both wet-and dry-sieving aggregates increases with larger initial diameters.Increasing initial soil moisture content from 1%to 25%reduces aggregate stability,with reductions of 2.4%-88.0%for wet-sieving aggregates and 2.1%-25.5%for dry-sieving aggregates(>2 mm).With increasing FTCs,wet-sieving aggregate(>2 mm)stability exhibits a fluctuating upward trend,with increases of 79.2%-87.4%after 15 FTCs,while dry-sieving aggregate(>2 mm)stability decreases significantly(5.7%-21.7%)upon the first FTC and remains unchanged thereafter.The stability of both the wet-and dry-sieving aggregates smaller than 2 mm remains unchanged with increasing FTCs(p>0.05).SOC content decreases by 22.3%on average with increasing FTCs from 1 to 15 and shows no significant correlations with wet-and dry-sieving aggregate stability.Higher silt content(r=0.39,p<0.05)and lower sand content(r=-0.38,p<0.05)enhances the wet-sieving aggregate stability of sandy loam.Frequent FTCs tend to improve wet-sieving aggregate stability but reduce dry-sieving aggregate stability in the sandy loam.The findings provide certain guidance for preventing freeze-thaw-induced wind erosion.展开更多
This study introduces superabsorbent polymers(SAP)into recycled concrete and,through freeze-thaw cycle tests,unconfined compressive strength tests,and nuclear magnetic resonance(NMR)analysis,evaluates the freeze-thaw ...This study introduces superabsorbent polymers(SAP)into recycled concrete and,through freeze-thaw cycle tests,unconfined compressive strength tests,and nuclear magnetic resonance(NMR)analysis,evaluates the freeze-thaw resistance and durability of recycled concrete samples under varying freeze-thaw cycles.The results indicate that an appropriate addition of SAP significantly enhances the freeze-thaw resistance of recycled concrete.After 200 freeze-thaw cycles,the RS0.6 sample retained good surface integrity,demonstrating the best performance.Compared to NAC,its mass loss decreased by 1.16%,the relative dynamic modulus improved by 7.01%,and the compressive strength loss rate decreased by 5.41%.Additionally,T2 spectrum analysis revealed that adding SAP optimized the pore structure of recycled concrete and mitigated pore development during freeze-thaw cycles.As the number of freeze-thaw cycles increased,the RS0.3 and RS0.6 samples demonstrated superior frost resistance compared to NAC.However,an excessive amount of SAP increased pore expansion during subsequent freeze-thaw cycles,ultimately weakening frost resistance.展开更多
The solar cycle(SC),a phenomenon caused by the quasi-periodic regular activities in the Sun,occurs approximately every 11 years.Intense solar activity can disrupt the Earth’s ionosphere,affecting communication and na...The solar cycle(SC),a phenomenon caused by the quasi-periodic regular activities in the Sun,occurs approximately every 11 years.Intense solar activity can disrupt the Earth’s ionosphere,affecting communication and navigation systems.Consequently,accurately predicting the intensity of the SC holds great significance,but predicting the SC involves a long-term time series,and many existing time series forecasting methods have fallen short in terms of accuracy and efficiency.The Time-series Dense Encoder model is a deep learning solution tailored for long time series prediction.Based on a multi-layer perceptron structure,it outperforms the best previously existing models in accuracy,while being efficiently trainable on general datasets.We propose a method based on this model for SC forecasting.Using a trained model,we predict the test set from SC 19 to SC 25 with an average mean absolute percentage error of 32.02,root mean square error of 30.3,mean absolute error of 23.32,and R^(2)(coefficient of determination)of 0.76,outperforming other deep learning models in terms of accuracy and training efficiency on sunspot number datasets.Subsequently,we use it to predict the peaks of SC 25 and SC 26.For SC 25,the peak time has ended,but a stronger peak is predicted for SC 26,of 199.3,within a range of 170.8-221.9,projected to occur during April 2034.展开更多
To investigate the strength degradation characteristics and microscopic damage mechanisms of moraine soil under hydro-thermo-mechanical coupling conditions,a series of X-ray Diffraction(XRD),standard triaxial testing,...To investigate the strength degradation characteristics and microscopic damage mechanisms of moraine soil under hydro-thermo-mechanical coupling conditions,a series of X-ray Diffraction(XRD),standard triaxial testing,Scanning Electron Microscopy(SEM),and Nuclear Magnetic Resonance(NMR)experiments were conducted.The mechanical property degradation laws and evolution characteristics of the microscopic pore structure of moraine soil under Freeze-Thaw(F-T)conditions were revealed.After F-T cycles,the stress-strain curves of moraine soil showed a strain-softening trend.In the early stage of F-T cycles(0–5 cycles),the shear strength and elastic modulus exhibited damage rate of approximately 10.33%±0.8%and 16.60%±1.2%,respectively.In the later stage(10–20 cycles),the strength parameters fluctuated slightly and tended to stabilize.The number of F-T cycles was negatively exponentially correlated with cohesion,while showing only slight fluctuation in the internal friction angle,thereby extending the Mohr-Coulomb strength criterion for moraine soil under F-T cycles.The NMR experiments quantitatively characterized the evolution of the internal pore structure of moraine soil under F-T cycles.As the number of F-T cycles increased,fine and micro pores gradually expanded and merged due to the frost-heaving effect during the water-ice phase transition,forming larger pores.The proportion of large and medium pores increased to 59.55%±2.1%(N=20),while that of fine and micro pores decreased to 40.45%±2.1%(N=20).The evolution of pore structure characteristics was essentially completed in the later stage of F-T cycles(10–20 cycles).This study provides a theoretical foundation and technical support for major engineering construction and disaster prevention in the Qinghai-Xizang Plateau.展开更多
In cold regions,slope rocks are inevitably impacted by freeze-thaw,dry-wet cycles and their alternating actions,leading to strength weakening and pore degradation.In this study,the mechanical and microstructural prope...In cold regions,slope rocks are inevitably impacted by freeze-thaw,dry-wet cycles and their alternating actions,leading to strength weakening and pore degradation.In this study,the mechanical and microstructural properties of schist subjected to four conditions were investigated:freeze-thaw cycles in air(FTA),freeze-thaw cycles in water(FTW),dry-wet cycles(DW),and dry-wet-freeze-thaw cycles(DWFT).Uniaxial compressive strength(UCS),water absorption,ultrasonication,low-field nuclear magnetic resonance,and scanning electron microscopy analyses were conducted.The integrity attenuation characteristics of the longitudinal wave velocity,UCS,and elastic modulus were analyzed.The results showed that liquid water emerged as a critical factor in reducing the brittleness of schist.The attenuation function model accurately described the peak stress and static elastic modulus of schist in various media(R2>0.97).Different media affected the schist deterioration and half-life,with the FTW-immersed samples having a half-life of 28 cycles.Furthermore,the longitudinal wave velocity decreased as the number of cycles increased,with the FTW showing the most significant reduction and having the shortest half-life of 208 cycles.Moreover,the damage variables of compressive strength and elastic modulus increased with the number of cycles.After 40 cycles,the schist exposed to FTW exhibited the highest damage variables and saturated water content.展开更多
In cold regions,rock structures will be weakened by freeze-thaw cycles under various water immersion conditions.Determining how water immersion conditions impact rock deterioration under freeze-thaw cycles is critical...In cold regions,rock structures will be weakened by freeze-thaw cycles under various water immersion conditions.Determining how water immersion conditions impact rock deterioration under freeze-thaw cycles is critical to assess accurately the frost resistance of engineered rock.In this paper,freeze-thaw cycles(temperature range of-20℃-20℃)were performed on the sandstones in different water immersion conditions(fully,partially and non-immersed in water).Then,computed tomography(CT)tests were conducted on the sandstones when the freeze-thaw number reached 0,5,10,15,20 and 30.Next,the effects of water immersion conditions on the microstructure deterioration of sandstone under freezethaw cycles were evaluated using CT spatial imaging,porosity and damage factor.Finally,focusing on the partially immersed condition,the immersion volume rate was defined to understand the effects of immersion degree on the freeze-thaw damage of sandstone and to propose a damage model considering the freeze-thaw number and immersion degree.The results show that with increasing freeze-thaw number,the porosities and damage factors under fully and partially immersed conditions increase continuously,while those under non-immersed condition first increase and then remain approximately constant.The most severe freeze-thaw damage occurs in fully immersed condition,followed by partially immersed condition and finally non-immersed condition.Interestingly,the freeze-thaw number and the immersion volume rate both impact the microstructure deterioration of the partially immersed sandstone.For the same freeze-thaw number,the damage factor increases approximately linearly with increasing immersion volume rate,and the increasing immersion degree exacerbates the microstructure deterioration of sandstone.Moreover,the proposed model can effectively estimate the freeze-thaw damage of partially immersed sandstone with different immersion volume rates.展开更多
Approximately 3.44 billion tons of copper mine tailings(MT)were produced globally in 2018 with an increase of 45%from 2010.Significant efforts are being made to manage these tailings through storage facilities,recycli...Approximately 3.44 billion tons of copper mine tailings(MT)were produced globally in 2018 with an increase of 45%from 2010.Significant efforts are being made to manage these tailings through storage facilities,recycling,and reuse in different industries.Currently,a large portion of tailings are managed through the tailing storage facilities(TSF)where these tailings undergo hydro-thermal-mechanical stresses with seasonal cycles which are not comprehensively understood.This study presents an investigative study to evaluate the performance of control and cement-stabilized copper MT under the influence of seasonal cycles,freeze-thaw(F-T)and wet-dry(W-D)conditions,representing the seasonal variability in the cold and arid regions.The control and cement-stabilized MT samples were subjected to a maximum of 12 F-T and 12 W-D cycles and corresponding micro-and-macro behavior was investigated through scanning electron microscope(SEM),volumetric strain(εvT,wet density(r),moisture content loss,and unconfined compressive strength(UCS)tests.The results indicated the vulnerability of Copper MT to 67%and 75%strength loss reaching residual states with 12 F-T and 8 W-D cycles,respectively.Whereas the stabilized MT retained 39%-55%and 16%-34%strength with F-T and W-D cycles,demonstrating increased durability.This research highlights the impact of seasonal cycles and corresponding strength-deformation characteristics of control and stabilized Copper MT in cold and arid regions.展开更多
Solar activity plays an important role in influencing space weather,making it important to understand numerous aspects of spatial and temporal variations in the Sun's radiative output.High-performance deep learnin...Solar activity plays an important role in influencing space weather,making it important to understand numerous aspects of spatial and temporal variations in the Sun's radiative output.High-performance deep learning models and long-term observational records of sunspot relative numbers are essential for solar cycle forecasting.Using the multivariate time series of monthly sunspot relative numbers provided by the National Astronomical Observatory of Japan and two Informer-based models,we forecast the amplitude and timing of solar cycles 25 and 26.The main results are as follows:(1)The maximum amplitude of solar cycle 25 is higher than the previous solar cycle 24 and the following solar cycle 26,suggesting that the long-term oscillatory variation of sunspot magnetic fields is related to the roughly centennial Gleissberg cyclicity.(2)Solar cycles 25 and 26 exhibit a pronounced Gnevyshev gap,which might be caused by two non-coincident peaks resulting from solar magnetic flux transported by meridional circulation and mid-latitude diffusion in the convection zone.(3)Hemispheric prediction of sunspot activity reveals a significant northsouth asynchrony,with activity level of the Sun being more intense in the southern hemisphere.These results are consistent with expectations derived from precursor methods and dynamo theories,and further provide evidence for internal changes in solar magnetic field during the decay of the Modern Maximum.展开更多
The roughness of the fracture surface directly affects the strength,deformation,and permeability of the surrounding rock in deep underground engineering.Understanding the effect of high temperature and thermal cycle o...The roughness of the fracture surface directly affects the strength,deformation,and permeability of the surrounding rock in deep underground engineering.Understanding the effect of high temperature and thermal cycle on the fracture surface roughness plays an important role in estimating the damage degree and stability of deep rock mass.In this paper,the variations of fracture surface roughness of granite after different heating and thermal cycles were investigated using the joint roughness coefficient method(JRC),three-dimensional(3D)roughness parameters,and fractal dimension(D),and the mechanism of damage and deterioration of granite were revealed.The experimental results show an increase in the roughness of the granite fracture surface as temperature and cycle number were incremented.The variations of JRC,height parameter,inclination parameter and area parameter with the temperature conformed to the Boltzmann's functional distribution,while the D decreased linearly as the temperature increased.Besides,the anisotropy index(Ip)of the granite fracture surface increased as the temperature increased,and the larger parameter values of roughness characterization at different temperatures were attained mainly in directions of 20°–40°,60°–100°and 140°–160°.The fracture aperture of granite after fracture followed the Gauss distribution and the average aperture increased with increasing temperature,which increased from 0.665 mm at 25℃to 1.058 mm at 800℃.High temperature caused an uneven thermal expansion,water evaporation,and oxidation of minerals within the granite,which promoted the growth and expansion of microfractures,and reduced interparticle bonding strength.In particular,the damage was exacerbated by the expansion and cracking of the quartz phase transition after T>500℃.Thermal cycles contributed to the accumulation of this damage and further weakened the interparticle bonding forces,resulting in a significant increase in the roughness,anisotropy,and aperture of the fracture surface after five cycles.展开更多
Insight into the growth of internal microstructure and surface morphology is critical for understanding the robustness of red sandstone artifacts in frigid environments.Since freeze–thaw(F-T)cycles can exacerbate the...Insight into the growth of internal microstructure and surface morphology is critical for understanding the robustness of red sandstone artifacts in frigid environments.Since freeze–thaw(F-T)cycles can exacerbate the surface deterioration of water-bearing sandstone,a series of investigation on fresh and weathered water-bearing sandstone samples with different F-T cycle numbers(i.e.0–100)is performed in this study,including three-dimensional(3D)laser scanning,scanning electron microscope(SEM)and computed tomography(CT)scanning tests,thermal property tests,Brazilian tests,and multi-field numerical simulations.Our results demonstrate that with increasing F-T cycles,the surface fractal dimension and specific surface area of red sandstone samples increase,and the pore size distribution inside rocks shifts from ultrananopores(10–100 nm)to micro-pores(0.1–100μm)and ultramicropores(100μm+).Spatially,the pores generated by the F-T cycles are more prominent near the surfaces of rock samples.Numerical simulation indicates that the uneven pore distribution leads to surface degradation.After 100 F-T cycles,the intergranular(IG)cement of the samples cracks,and the IG fractures are widened;eventually,due to the structural integrity weakening,the tensile strength is drastically reduced by over half.The thermal properties of the water-saturated sandstone can be improved during the F-T cycles,and a strong coefficient of determination of 0.98 exists between the fractal dimensions of sandstone surface and the tensile strength.When assessing the mechanical properties of stone artifacts under F-T cycles,the morphological damage of red sandstone should first be investigated when in situ sampling is inappropriate.展开更多
The mechanical behavior of cohesive soil is sensitized to drying-wetting cycles under confinements.However,the hydromechanical coupling effect has not been considered in current constitutive models.A macro-micro analy...The mechanical behavior of cohesive soil is sensitized to drying-wetting cycles under confinements.However,the hydromechanical coupling effect has not been considered in current constitutive models.A macro-micro analysis scheme is proposed in this paper to investigate the soil deformation behavior under the coupling of stress and drying-wetting cycles.A new device is developed based on CT(computerized tomography)workstation to apply certain normal and shear stresses on a soil specimen during drying-wetting cycles.A series of tests are conducted on a type of loess with various coupling of stress paths and drying-wetting cycles.At macroscopic level,stress sensor and laser sensor are used to acquire stress and strain,respectively.The shear and volumetric strain increase during the first few drying-wetting cycles and then become stable.The increase of the shear stress level or confining pressure would cause higher increase rate and the value of shear strain in the process of drying-wetting cycles.At microscopic level,the grayscale value(GSV)of CT scanning image is characterized as the proportion of soil particles to voids.A fabric state parameter is proposed to characterize soil microstructures under the influence of stress and drying-wetting cycle.Test results indicate that the macroand micro-responses show high consistence and relevance.The stress and drying-wetting cycles would both induce collapse of the soil microstructure,which dominants degradation of the soil mechanical properties.The evolution of the macro-mechanical property of soil exhibits a positive linear relationship with the micro-evolution of the fabric state parameter.展开更多
Sulfate attack-induced expansion of cement-treated aggregates in seasonally frozen regions is a well-known issue which causes continuous expansion in railway subgrades,and particularly in high-speed railways.According...Sulfate attack-induced expansion of cement-treated aggregates in seasonally frozen regions is a well-known issue which causes continuous expansion in railway subgrades,and particularly in high-speed railways.Accordingly,we investigated the influence of material proportions,the number of freeze-thaw(FT)cycles,and temperature gradients on the expansion mechanism of sulfate attack on cement-treated aggregates subjected to FT cycles.The conditions,laws,and dominant factors causing the expansion of aggregates were analyzed through swelling tests.The results indicate that under FT cycles,3%content cement-treated graded macadam only experiences slight deformation.The maximum strain of graded macadam attacked by 1%sodium sulfate content in each FT cycle is significantly larger than that of 3%content cement-treated graded macadam attacked by 1%sodium sulfate content.Using scanning electron microscopy,needle-like crystals were observed during sulfate attack of cement-treated graded macadam.Through quantitative analysis,we determined the recoverable and unrecoverable deformations of graded macadam under FT cycles.For graded macadam under sulfate attack,the expansion is mainly induced by periodic frost heave and salt expansion,as well as salt migration.For cement-treated graded macadam under sulfate attack,the expansion is mainly induced by chemical attack and salt migration.This study can serve as a reference for future research on the mechanics of sulfate attack on cement-treated aggregates that experience FT cycles,and provide theoretical support for methods that remediate the expansion induced by sulfate attack.展开更多
Solar cycles are fundamental to astrophysics,space exploration,technological infrastructure,and Earth's climate.A better understanding of these cycles and their history can aid in risk mitigation on Earth,while al...Solar cycles are fundamental to astrophysics,space exploration,technological infrastructure,and Earth's climate.A better understanding of these cycles and their history can aid in risk mitigation on Earth,while also deepening our knowledge of stellar physics and solar system dynamics.Determining the solar cycles between 1600 and 1700-especially the post-1645 Maunder Minimum,characterized by significantly reduced solar activity-poses challenges to existing solar activity proxies.This study utilizes a new red equatorial auroral catalog from ancient Korean texts to establish solar cycle patterns from 1623 to 1700.Remarkably,a further reevaluation of the solar cycles between 1610 and 1755 identified a total of 13 cycles,diverging from the widely accepted record of 12 cycles during that time.This research enhances our understanding of historical solar activity,and underscores the importance of integrating diverse historical sources into modern analyses.展开更多
As a negative electrode material for lithium-ion batteries,silicon monoxide(SiO)suffers from dramatic volume changes during cycling,causing excessive stress within the electrode and resulting in electrode deformation ...As a negative electrode material for lithium-ion batteries,silicon monoxide(SiO)suffers from dramatic volume changes during cycling,causing excessive stress within the electrode and resulting in electrode deformation and fragmentation.This ultimately leads to a decrease in cell capacity.The trends of volume expansion and capacity change of the SiO/graphite(SiO/C)composite electrode during cycling were investigated via in situ expansion monitoring.First,a series of expansion test schemes were designed,and the linear relationship between negative electrode expansion and cell capacity degradation was quantitatively analyzed.Then,the effects of different initial pressures on the long-term cycling performance of the cell were evaluated.Finally,the mechanism of their effects was analyzed by scanning electron microscope.The results show that after 50 cycles,the cell capacity decreases from 2.556 mAh to 1.689 mAh,with a capacity retention ratio(CRR)of only 66.08%.A linear relationship between the capacity retention ratio and thickness expansion was found.Electrochemical measurements and scanning electron microscope images demonstrate that intense stress inhibits the lithiation of the negative electrode and that the electrode is more susceptible to irreversible damage during cycling.Overall,these results reveal the relationship between the cycling performance of SiO and the internal pressure of the electrode from a macroscopic point of view,which provides some reference for the application of SiO/C composite electrodes in lithium-ion batteries.展开更多
Microorganisms actively participate in biogeochemical cycling processes and play a crucial role in maintaining the dynamic balance of hot spring ecosystems.However,the distribution of microbial functional genes and th...Microorganisms actively participate in biogeochemical cycling processes and play a crucial role in maintaining the dynamic balance of hot spring ecosystems.However,the distribution of microbial functional genes and their influencing factors in hot springs remain largely unclear.Therefore,this study investigated the microbial functional genes and their potential for controlling biogeochemical cycles(C,N,S,and P) in the hot Springs of Tengchong,China,using the Geochip method,a functional gene microarray technology.The examined hot springs have very different microbial functional genes.A total of 22 736 gene probe signals were identified,belonging to 567 functional genes and associated with 15 ecological functions,mainly involving stress response,carbon cycle,nitrogen cycle,sulfur cycle,phosphorus cycle and energy processes.The amyA,narG,dsrA and ppx genes were most abundant in carbon,nitrogen,sulfur and phosphorus cycles,respectively,and were significantly correlated with pH,temperature and SO_(4)^(2-).The diversity and abundance of detected gene probes were negatively correlated with temperature.The α-diversity(i.e.,Shannon index) was high at low temperature and low pH.Molecular functional interactions revealed by the gene connectivity levels were negatively correlated with temperature,pH and SO_(4)^(2-).These results suggested that the abundance,diversity and interactions of microbial functional genes were significantly influenced by geochemical parameters.-In addition,some genera possessed functional genes related to carbon,nitrogen,sulfur,and phosphorus cycles and can synergistically control the biogeochemical cycles of carbon,nitrogen,sulfur and phosphorus.These findings provide new insights into the functional potentials of microorganisms to participate in biogeochemical cycles and their responses to environmental factors in hot springs.展开更多
Cyclic wetting-drying alternation has a significant influence on the strength and structure of soils.It is prone to causing soil softening and disintegration,highlighting the importance to improve the soil's resis...Cyclic wetting-drying alternation has a significant influence on the strength and structure of soils.It is prone to causing soil softening and disintegration,highlighting the importance to improve the soil's resistance to disintegration.This paper utilizes a self-developed disintegration test apparatus to analyze the disintegration characteristics of improved red soil under wet-dry cycles,focusing on the disintegration amount and ratio.Furthermore,XRD(X-ray diffraction),SEM(scanning electron microscope),tensile test,and contact angle test are employed to investigate the anti-disintegration behaviors of the improved red soil.The results show that the disintegrating amount and ratio of undisturbed and improved red soil are distinctly different under wet-dry cycles.Linear,stepped,constant and concave but perfect"S"shapes of the disintegrating ratio are observed in the cyclic tests.Cement and lime strengthen the red soil primarily through hydration reaction.The drop experiment confirms that cement plays a crucial role in restraining the disintegration.When the ameliorant content is low,the correlation between pore parameters and disintegration duration of red soil follows the order:mean shape coefficient>fractal dimension>probability entropy>area probability distribution index.With a high ameliorant content,the correlation remains similar,with slightly higher correlation for probability entropy.Under wet-dry cycle conditions,sludge and kaolin can improve the soil through the bonding of clay particles.The improved water repellency greatly enhances the resistance to disintegration of the altered red soil.The research provides valuable insights for the practical application of soil.展开更多
In cold-region environments,where complex stresses and mining disturbances occur,rock masses are frequently segmented into discontinuous bodies by fractured structural planes,leading to anisotropic physical and mechan...In cold-region environments,where complex stresses and mining disturbances occur,rock masses are frequently segmented into discontinuous bodies by fractured structural planes,leading to anisotropic physical and mechanical properties.To explore the evolution of microcracks,degradation characteristics,and failure modes of fractured rocks in cold regions under the influence of freeze-thaw cycles,integrating laboratory experiments with the damage mechanics of freeze-thaw cycles.A numerical model for freeze-thaw cycle damage in rocks with various fracture dip angles was developed.The study revealed that the freeze-thaw expansion force generated during the pore water-ice phase transition is the primary driving factor behind freeze-thaw cycle damage.The initiation and propagation of microcracks and micropores,the detachment of matrix particles,and the loosening of clay mineral structures result in the transformation of the rock from a dense to a porous state,causing significant degradation in macroscopic mechanical properties.As freeze-thaw cycles increase,both the uniaxial compressive strength and the deformation modulus of the rock decrease significantly,with the failure mode gradually shifting from brittle instability to brittle-plastic or plastic failure.The findings of this study offer a practical approach to uncovering the mechanical response mechanisms between freeze-thaw damage in fractured rocks and structural planes.展开更多
Numerous slope failures have been reported during periods of water level fluctuations.Understanding the influence of water on the creep behavior of joints is essential for evaluating the long-term stability of slopes....Numerous slope failures have been reported during periods of water level fluctuations.Understanding the influence of water on the creep behavior of joints is essential for evaluating the long-term stability of slopes.This study focuses on the effects of drying-wetting cycles and soaking conditions on the long-term behavior of sandstone joints.A total of 12 multi-stage shear creep tests are carried out on sandstone joints subjected to varying drying-wetting cycles under both soaking and un-soaking conditions.Based on the experimental results,the influences of drying-wetting cycles as well as soaking conditions on the microstructure,shear creep displacement,strength,and failure morphologies of sandstone joints are investigated comprehensively.Results indicate that increasing drying-wetting cycles not only yields larger shear creep displacements but also leads to a negative exponential decrease in the strength of sandstone joints.Besides,soaking conditions strongly influence the creep behavior of sandstone joints.The failure strength and long-term strength of sandstone joints for soaked samples decrease by 13.6%–29.0%and 19.4%–37.5%,respectively,as compared to unsoaked samples.Furthermore,four distinct stages in the shear creep process were identified according to the results obtained from multi-stage shear creep tests and computerized tomography scans,and three creep failure modes of sandstone joints are thus determined.Finally,the influence mechanism of drying-wetting cycles and soaking conditions on the creep failure modes of sandstone joints is revealed.Drying-wetting cycles and soaking conditions diminish the influence of asperities on the shear creep behavior of joints,thereby reducing the resistance of joints to long-term deformation.展开更多
The mechanical properties of bedding rock in cold regions are frequently affected by freeze-thaw(F-T)cycles and ani-sotropy.Research on the mechanical characteristics of rock damage under the combined action of F-T an...The mechanical properties of bedding rock in cold regions are frequently affected by freeze-thaw(F-T)cycles and ani-sotropy.Research on the mechanical characteristics of rock damage under the combined action of F-T and bedding angles is limited,and most traditional rock damage models cannot accurately capture these characteristics.We performed axial compression tests to ex-plore the strength characteristics of bedding slates at the bedding angles ofβ=0°,30°,45°,60°,and 90°under various F-T cycles.The experimental findings suggest that the elastic modulus and uniaxial compressive strength of the slate declined exponentially as the number of F-T cycles increased.Axial compressive strength was characterized by a U-shaped tendency with the bedding angle.This study proposes a damage model for the uniaxial compressive strength of transversely isotropic rock,which integrates the F-T effect,utilizing the enhanced anisotropic Hoek-Brown strength criterion and a statistical damage model.This model was validated using experimental data.This statistical damage model can precisely capture the dual attributes of rock mass strength reduction with F-T cy-cles and variations arising from the loading direction.展开更多
基金supported by National Natural Science Foundation of China (Nos.52264006,52364004,and 52464005)the Guizhou Provincial Science and Technology Foundation (No.GCC[2022]005-1)。
文摘Investigating the damage evolution of surrounding rock under thermal shock cycles is crucial for ensuring the stability of engineering rock masses.This study performed Brazilian splitting tests on granite specimens under varying temperature and cycle conditions,employing acoustic emission monitoring,digital image correlation,and three-dimensional scanning technology.A systematic analysis was conducted on the patterns of damage evolution,failure precursor,and response mechanisms under combined thermal and cyclic loading.Experimental results show that both P-wave velocity and tensile strength degrade significantly with increasing temperature and cycle count,with temperature having a more pronounced effect than cycle count.Notably,damage evolution exhibits a dual-threshold behavior in which degradation accelerates markedly above 400℃ and stabilizes after 5 thermal cycles.Fracture surfaces evolve from initially planar to rugged morphologies,with peak-valley height differences at 600℃ being approximately three times greater than those at 200℃.Furthermore,based on acoustic emission energy entropy analysis,we introduce a novel failure precursor indicator where the sustained increase and critical surge in average entropy serve as reliable early-warning signals for impending rock failure.These findings establish a solid theoretical basis and practical methodology for damage assessment and instability early-warning systems in high-temperature rock engineering.
基金supported by National Natural Science Foundation of China(Grant No.42201080)Young Scientific and Technological Talents Program of Shaanxi Province(Grant No.2025ZC-KJXX-57)Special Scientific Research Program of the Shaanxi Provincial Department of Education(Grant No.21JK0967)。
文摘Freeze-thaw cycles(FTCs)have an important effect on soil aggregate stability by altering soil structures,thereby influencing soil wind and water erosion on the eastern Qinghai-Tibet Plateau.However,the effects of FTCs on the stability of these soils remain unclear.Here,we conducted freeze-thaw simulations in laboratory to investigate the effects of FTCs(0 to 15 cycles)on the wet-and dry-sieving aggregate stability of undisturbed sandy loam from Maqu county,which was treated with different initial soil moisture contents(1%to 25%in increments of 4%)and initial aggregate diameters(<2,2-5,5-10,and 10-15 mm).Results show that soil aggregates with initial diameters larger than 2 mm exhibit higher soil organic carbon contents(1.45%-1.57%)and silt contents(34.63%-35.52%)than those smaller than 2 mm(0.93%and 31.38%,respectively).The stability of both wet-and dry-sieving aggregates increases with larger initial diameters.Increasing initial soil moisture content from 1%to 25%reduces aggregate stability,with reductions of 2.4%-88.0%for wet-sieving aggregates and 2.1%-25.5%for dry-sieving aggregates(>2 mm).With increasing FTCs,wet-sieving aggregate(>2 mm)stability exhibits a fluctuating upward trend,with increases of 79.2%-87.4%after 15 FTCs,while dry-sieving aggregate(>2 mm)stability decreases significantly(5.7%-21.7%)upon the first FTC and remains unchanged thereafter.The stability of both the wet-and dry-sieving aggregates smaller than 2 mm remains unchanged with increasing FTCs(p>0.05).SOC content decreases by 22.3%on average with increasing FTCs from 1 to 15 and shows no significant correlations with wet-and dry-sieving aggregate stability.Higher silt content(r=0.39,p<0.05)and lower sand content(r=-0.38,p<0.05)enhances the wet-sieving aggregate stability of sandy loam.Frequent FTCs tend to improve wet-sieving aggregate stability but reduce dry-sieving aggregate stability in the sandy loam.The findings provide certain guidance for preventing freeze-thaw-induced wind erosion.
基金Funded by the Science and Technology Program of Gansu Province(Nos.25JRRA497,23ZDFA017)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB0950000)High-level Talent Funding of Kashi。
文摘This study introduces superabsorbent polymers(SAP)into recycled concrete and,through freeze-thaw cycle tests,unconfined compressive strength tests,and nuclear magnetic resonance(NMR)analysis,evaluates the freeze-thaw resistance and durability of recycled concrete samples under varying freeze-thaw cycles.The results indicate that an appropriate addition of SAP significantly enhances the freeze-thaw resistance of recycled concrete.After 200 freeze-thaw cycles,the RS0.6 sample retained good surface integrity,demonstrating the best performance.Compared to NAC,its mass loss decreased by 1.16%,the relative dynamic modulus improved by 7.01%,and the compressive strength loss rate decreased by 5.41%.Additionally,T2 spectrum analysis revealed that adding SAP optimized the pore structure of recycled concrete and mitigated pore development during freeze-thaw cycles.As the number of freeze-thaw cycles increased,the RS0.3 and RS0.6 samples demonstrated superior frost resistance compared to NAC.However,an excessive amount of SAP increased pore expansion during subsequent freeze-thaw cycles,ultimately weakening frost resistance.
基金supported by the Academic Research Projects of Beijing Union University(ZK20202204)the National Natural Science Foundation of China(12250005,12073040,12273059,11973056,12003051,11573037,12073041,11427901,11572005,11611530679 and 12473052)+1 种基金the Strategic Priority Research Program of the China Academy of Sciences(XDB0560000,XDA15052200,XDB09040200,XDA15010700,XDB0560301,and XDA15320102)the Chinese Meridian Project(CMP).
文摘The solar cycle(SC),a phenomenon caused by the quasi-periodic regular activities in the Sun,occurs approximately every 11 years.Intense solar activity can disrupt the Earth’s ionosphere,affecting communication and navigation systems.Consequently,accurately predicting the intensity of the SC holds great significance,but predicting the SC involves a long-term time series,and many existing time series forecasting methods have fallen short in terms of accuracy and efficiency.The Time-series Dense Encoder model is a deep learning solution tailored for long time series prediction.Based on a multi-layer perceptron structure,it outperforms the best previously existing models in accuracy,while being efficiently trainable on general datasets.We propose a method based on this model for SC forecasting.Using a trained model,we predict the test set from SC 19 to SC 25 with an average mean absolute percentage error of 32.02,root mean square error of 30.3,mean absolute error of 23.32,and R^(2)(coefficient of determination)of 0.76,outperforming other deep learning models in terms of accuracy and training efficiency on sunspot number datasets.Subsequently,we use it to predict the peaks of SC 25 and SC 26.For SC 25,the peak time has ended,but a stronger peak is predicted for SC 26,of 199.3,within a range of 170.8-221.9,projected to occur during April 2034.
基金support from the National Natural Science Foundation of China(Grant Nos.42107193,42077245)supported by the Sichuan Science and Technology Program(2025YFNH0008,2025YFNH0004)+1 种基金the State Key Laboratory of Geohazard Prevention and Geoenvironment Protection Independent Research Project(SKLGP2023Z006)the Everest Scientific Research Program 2.0:Research on mechanism and control of glacial lake outburst chain catastrophe in Qinghai-Xizang Plateau based on man-earth coordination perspective.
文摘To investigate the strength degradation characteristics and microscopic damage mechanisms of moraine soil under hydro-thermo-mechanical coupling conditions,a series of X-ray Diffraction(XRD),standard triaxial testing,Scanning Electron Microscopy(SEM),and Nuclear Magnetic Resonance(NMR)experiments were conducted.The mechanical property degradation laws and evolution characteristics of the microscopic pore structure of moraine soil under Freeze-Thaw(F-T)conditions were revealed.After F-T cycles,the stress-strain curves of moraine soil showed a strain-softening trend.In the early stage of F-T cycles(0–5 cycles),the shear strength and elastic modulus exhibited damage rate of approximately 10.33%±0.8%and 16.60%±1.2%,respectively.In the later stage(10–20 cycles),the strength parameters fluctuated slightly and tended to stabilize.The number of F-T cycles was negatively exponentially correlated with cohesion,while showing only slight fluctuation in the internal friction angle,thereby extending the Mohr-Coulomb strength criterion for moraine soil under F-T cycles.The NMR experiments quantitatively characterized the evolution of the internal pore structure of moraine soil under F-T cycles.As the number of F-T cycles increased,fine and micro pores gradually expanded and merged due to the frost-heaving effect during the water-ice phase transition,forming larger pores.The proportion of large and medium pores increased to 59.55%±2.1%(N=20),while that of fine and micro pores decreased to 40.45%±2.1%(N=20).The evolution of pore structure characteristics was essentially completed in the later stage of F-T cycles(10–20 cycles).This study provides a theoretical foundation and technical support for major engineering construction and disaster prevention in the Qinghai-Xizang Plateau.
基金supported by the National Natural Science Foundation of China(Nos.42171108 and 42101136)Sichuan Science and Technology Program(Nos.2024NSFSC2007 and2025YFHZ0273)Natural Science Starting Project of SWPU(No.2024QHZ029)。
文摘In cold regions,slope rocks are inevitably impacted by freeze-thaw,dry-wet cycles and their alternating actions,leading to strength weakening and pore degradation.In this study,the mechanical and microstructural properties of schist subjected to four conditions were investigated:freeze-thaw cycles in air(FTA),freeze-thaw cycles in water(FTW),dry-wet cycles(DW),and dry-wet-freeze-thaw cycles(DWFT).Uniaxial compressive strength(UCS),water absorption,ultrasonication,low-field nuclear magnetic resonance,and scanning electron microscopy analyses were conducted.The integrity attenuation characteristics of the longitudinal wave velocity,UCS,and elastic modulus were analyzed.The results showed that liquid water emerged as a critical factor in reducing the brittleness of schist.The attenuation function model accurately described the peak stress and static elastic modulus of schist in various media(R2>0.97).Different media affected the schist deterioration and half-life,with the FTW-immersed samples having a half-life of 28 cycles.Furthermore,the longitudinal wave velocity decreased as the number of cycles increased,with the FTW showing the most significant reduction and having the shortest half-life of 208 cycles.Moreover,the damage variables of compressive strength and elastic modulus increased with the number of cycles.After 40 cycles,the schist exposed to FTW exhibited the highest damage variables and saturated water content.
基金funding support from the National Natural Science Foundation of China(Grant No.12172019).
文摘In cold regions,rock structures will be weakened by freeze-thaw cycles under various water immersion conditions.Determining how water immersion conditions impact rock deterioration under freeze-thaw cycles is critical to assess accurately the frost resistance of engineered rock.In this paper,freeze-thaw cycles(temperature range of-20℃-20℃)were performed on the sandstones in different water immersion conditions(fully,partially and non-immersed in water).Then,computed tomography(CT)tests were conducted on the sandstones when the freeze-thaw number reached 0,5,10,15,20 and 30.Next,the effects of water immersion conditions on the microstructure deterioration of sandstone under freezethaw cycles were evaluated using CT spatial imaging,porosity and damage factor.Finally,focusing on the partially immersed condition,the immersion volume rate was defined to understand the effects of immersion degree on the freeze-thaw damage of sandstone and to propose a damage model considering the freeze-thaw number and immersion degree.The results show that with increasing freeze-thaw number,the porosities and damage factors under fully and partially immersed conditions increase continuously,while those under non-immersed condition first increase and then remain approximately constant.The most severe freeze-thaw damage occurs in fully immersed condition,followed by partially immersed condition and finally non-immersed condition.Interestingly,the freeze-thaw number and the immersion volume rate both impact the microstructure deterioration of the partially immersed sandstone.For the same freeze-thaw number,the damage factor increases approximately linearly with increasing immersion volume rate,and the increasing immersion degree exacerbates the microstructure deterioration of sandstone.Moreover,the proposed model can effectively estimate the freeze-thaw damage of partially immersed sandstone with different immersion volume rates.
基金the W.M.Keck Center for Nano-Scale Imaging in the Department of Chemistry and Biochemistry at the University of Arizona(Grant No.RRID:SCR_022884),with funding from the W.M.Keck Foundation Grant.
文摘Approximately 3.44 billion tons of copper mine tailings(MT)were produced globally in 2018 with an increase of 45%from 2010.Significant efforts are being made to manage these tailings through storage facilities,recycling,and reuse in different industries.Currently,a large portion of tailings are managed through the tailing storage facilities(TSF)where these tailings undergo hydro-thermal-mechanical stresses with seasonal cycles which are not comprehensively understood.This study presents an investigative study to evaluate the performance of control and cement-stabilized copper MT under the influence of seasonal cycles,freeze-thaw(F-T)and wet-dry(W-D)conditions,representing the seasonal variability in the cold and arid regions.The control and cement-stabilized MT samples were subjected to a maximum of 12 F-T and 12 W-D cycles and corresponding micro-and-macro behavior was investigated through scanning electron microscope(SEM),volumetric strain(εvT,wet density(r),moisture content loss,and unconfined compressive strength(UCS)tests.The results indicated the vulnerability of Copper MT to 67%and 75%strength loss reaching residual states with 12 F-T and 8 W-D cycles,respectively.Whereas the stabilized MT retained 39%-55%and 16%-34%strength with F-T and W-D cycles,demonstrating increased durability.This research highlights the impact of seasonal cycles and corresponding strength-deformation characteristics of control and stabilized Copper MT in cold and arid regions.
基金supported by the National Nature Science Foundation of China(12463009)the Yunnan Fundamental Research Projects(202301AV070007,202401AU070026)+2 种基金the"Yunnan Revitalization Talent Support Program"Innovation Team Project(202405AS350012)the Scientific Research Foundation Project of Yunnan Education Department(2023J0624,2024Y469)the GHfund A(202407016295)。
文摘Solar activity plays an important role in influencing space weather,making it important to understand numerous aspects of spatial and temporal variations in the Sun's radiative output.High-performance deep learning models and long-term observational records of sunspot relative numbers are essential for solar cycle forecasting.Using the multivariate time series of monthly sunspot relative numbers provided by the National Astronomical Observatory of Japan and two Informer-based models,we forecast the amplitude and timing of solar cycles 25 and 26.The main results are as follows:(1)The maximum amplitude of solar cycle 25 is higher than the previous solar cycle 24 and the following solar cycle 26,suggesting that the long-term oscillatory variation of sunspot magnetic fields is related to the roughly centennial Gleissberg cyclicity.(2)Solar cycles 25 and 26 exhibit a pronounced Gnevyshev gap,which might be caused by two non-coincident peaks resulting from solar magnetic flux transported by meridional circulation and mid-latitude diffusion in the convection zone.(3)Hemispheric prediction of sunspot activity reveals a significant northsouth asynchrony,with activity level of the Sun being more intense in the southern hemisphere.These results are consistent with expectations derived from precursor methods and dynamo theories,and further provide evidence for internal changes in solar magnetic field during the decay of the Modern Maximum.
基金funding support from the National Natural Science Foundation of China(Grant No.52274082)the Program of Qingjiang Excellent Young Talents,Jiangxi University of Science and Technology(Grant No.JXUSTQJBJ2020003)the Innovation Fund Designated for Graduate Students of Jiangxi Province(Grant No.YC2023-B215).
文摘The roughness of the fracture surface directly affects the strength,deformation,and permeability of the surrounding rock in deep underground engineering.Understanding the effect of high temperature and thermal cycle on the fracture surface roughness plays an important role in estimating the damage degree and stability of deep rock mass.In this paper,the variations of fracture surface roughness of granite after different heating and thermal cycles were investigated using the joint roughness coefficient method(JRC),three-dimensional(3D)roughness parameters,and fractal dimension(D),and the mechanism of damage and deterioration of granite were revealed.The experimental results show an increase in the roughness of the granite fracture surface as temperature and cycle number were incremented.The variations of JRC,height parameter,inclination parameter and area parameter with the temperature conformed to the Boltzmann's functional distribution,while the D decreased linearly as the temperature increased.Besides,the anisotropy index(Ip)of the granite fracture surface increased as the temperature increased,and the larger parameter values of roughness characterization at different temperatures were attained mainly in directions of 20°–40°,60°–100°and 140°–160°.The fracture aperture of granite after fracture followed the Gauss distribution and the average aperture increased with increasing temperature,which increased from 0.665 mm at 25℃to 1.058 mm at 800℃.High temperature caused an uneven thermal expansion,water evaporation,and oxidation of minerals within the granite,which promoted the growth and expansion of microfractures,and reduced interparticle bonding strength.In particular,the damage was exacerbated by the expansion and cracking of the quartz phase transition after T>500℃.Thermal cycles contributed to the accumulation of this damage and further weakened the interparticle bonding forces,resulting in a significant increase in the roughness,anisotropy,and aperture of the fracture surface after five cycles.
基金supported by the National Natural Science Foundation of China(Grant Nos.41772304 and 42277171).
文摘Insight into the growth of internal microstructure and surface morphology is critical for understanding the robustness of red sandstone artifacts in frigid environments.Since freeze–thaw(F-T)cycles can exacerbate the surface deterioration of water-bearing sandstone,a series of investigation on fresh and weathered water-bearing sandstone samples with different F-T cycle numbers(i.e.0–100)is performed in this study,including three-dimensional(3D)laser scanning,scanning electron microscope(SEM)and computed tomography(CT)scanning tests,thermal property tests,Brazilian tests,and multi-field numerical simulations.Our results demonstrate that with increasing F-T cycles,the surface fractal dimension and specific surface area of red sandstone samples increase,and the pore size distribution inside rocks shifts from ultrananopores(10–100 nm)to micro-pores(0.1–100μm)and ultramicropores(100μm+).Spatially,the pores generated by the F-T cycles are more prominent near the surfaces of rock samples.Numerical simulation indicates that the uneven pore distribution leads to surface degradation.After 100 F-T cycles,the intergranular(IG)cement of the samples cracks,and the IG fractures are widened;eventually,due to the structural integrity weakening,the tensile strength is drastically reduced by over half.The thermal properties of the water-saturated sandstone can be improved during the F-T cycles,and a strong coefficient of determination of 0.98 exists between the fractal dimensions of sandstone surface and the tensile strength.When assessing the mechanical properties of stone artifacts under F-T cycles,the morphological damage of red sandstone should first be investigated when in situ sampling is inappropriate.
基金funded by National Key R&D Program of China(Grant No.2023YFC3007001)Beijing Natural Science Foundation(Grant No.8244053)China Postdoctoral Science Foundation(Grant No.2024M754065).
文摘The mechanical behavior of cohesive soil is sensitized to drying-wetting cycles under confinements.However,the hydromechanical coupling effect has not been considered in current constitutive models.A macro-micro analysis scheme is proposed in this paper to investigate the soil deformation behavior under the coupling of stress and drying-wetting cycles.A new device is developed based on CT(computerized tomography)workstation to apply certain normal and shear stresses on a soil specimen during drying-wetting cycles.A series of tests are conducted on a type of loess with various coupling of stress paths and drying-wetting cycles.At macroscopic level,stress sensor and laser sensor are used to acquire stress and strain,respectively.The shear and volumetric strain increase during the first few drying-wetting cycles and then become stable.The increase of the shear stress level or confining pressure would cause higher increase rate and the value of shear strain in the process of drying-wetting cycles.At microscopic level,the grayscale value(GSV)of CT scanning image is characterized as the proportion of soil particles to voids.A fabric state parameter is proposed to characterize soil microstructures under the influence of stress and drying-wetting cycle.Test results indicate that the macroand micro-responses show high consistence and relevance.The stress and drying-wetting cycles would both induce collapse of the soil microstructure,which dominants degradation of the soil mechanical properties.The evolution of the macro-mechanical property of soil exhibits a positive linear relationship with the micro-evolution of the fabric state parameter.
基金National Natural Science Foundation of China(Nos.42171130 and 42301158)Pilot Project of China’s Strength in Transportation for the Central Research Institute(No.QG2021-1-4-7)National Key Technology Research and Development Program of the Ministry of Science and Technology of China(No.2021YFB2601200).
文摘Sulfate attack-induced expansion of cement-treated aggregates in seasonally frozen regions is a well-known issue which causes continuous expansion in railway subgrades,and particularly in high-speed railways.Accordingly,we investigated the influence of material proportions,the number of freeze-thaw(FT)cycles,and temperature gradients on the expansion mechanism of sulfate attack on cement-treated aggregates subjected to FT cycles.The conditions,laws,and dominant factors causing the expansion of aggregates were analyzed through swelling tests.The results indicate that under FT cycles,3%content cement-treated graded macadam only experiences slight deformation.The maximum strain of graded macadam attacked by 1%sodium sulfate content in each FT cycle is significantly larger than that of 3%content cement-treated graded macadam attacked by 1%sodium sulfate content.Using scanning electron microscopy,needle-like crystals were observed during sulfate attack of cement-treated graded macadam.Through quantitative analysis,we determined the recoverable and unrecoverable deformations of graded macadam under FT cycles.For graded macadam under sulfate attack,the expansion is mainly induced by periodic frost heave and salt expansion,as well as salt migration.For cement-treated graded macadam under sulfate attack,the expansion is mainly induced by chemical attack and salt migration.This study can serve as a reference for future research on the mechanics of sulfate attack on cement-treated aggregates that experience FT cycles,and provide theoretical support for methods that remediate the expansion induced by sulfate attack.
基金supported by the National Natural Science Foundation of China (42388101)the CAS Youth Interdisciplinary Team (JCTD-2021-05)funded by the Youth Innovation Promotion Association, Chinese Academy of Sciences.
文摘Solar cycles are fundamental to astrophysics,space exploration,technological infrastructure,and Earth's climate.A better understanding of these cycles and their history can aid in risk mitigation on Earth,while also deepening our knowledge of stellar physics and solar system dynamics.Determining the solar cycles between 1600 and 1700-especially the post-1645 Maunder Minimum,characterized by significantly reduced solar activity-poses challenges to existing solar activity proxies.This study utilizes a new red equatorial auroral catalog from ancient Korean texts to establish solar cycle patterns from 1623 to 1700.Remarkably,a further reevaluation of the solar cycles between 1610 and 1755 identified a total of 13 cycles,diverging from the widely accepted record of 12 cycles during that time.This research enhances our understanding of historical solar activity,and underscores the importance of integrating diverse historical sources into modern analyses.
基金supported by the Fundamental Research Funds for the Central Universities(WK2090000055)Anhui Provincial Natural Science Foundation of China(2308085QG231).
文摘As a negative electrode material for lithium-ion batteries,silicon monoxide(SiO)suffers from dramatic volume changes during cycling,causing excessive stress within the electrode and resulting in electrode deformation and fragmentation.This ultimately leads to a decrease in cell capacity.The trends of volume expansion and capacity change of the SiO/graphite(SiO/C)composite electrode during cycling were investigated via in situ expansion monitoring.First,a series of expansion test schemes were designed,and the linear relationship between negative electrode expansion and cell capacity degradation was quantitatively analyzed.Then,the effects of different initial pressures on the long-term cycling performance of the cell were evaluated.Finally,the mechanism of their effects was analyzed by scanning electron microscope.The results show that after 50 cycles,the cell capacity decreases from 2.556 mAh to 1.689 mAh,with a capacity retention ratio(CRR)of only 66.08%.A linear relationship between the capacity retention ratio and thickness expansion was found.Electrochemical measurements and scanning electron microscope images demonstrate that intense stress inhibits the lithiation of the negative electrode and that the electrode is more susceptible to irreversible damage during cycling.Overall,these results reveal the relationship between the cycling performance of SiO and the internal pressure of the electrode from a macroscopic point of view,which provides some reference for the application of SiO/C composite electrodes in lithium-ion batteries.
基金supported by grants from the National Natural Science Foundation of China(Nos.42172339,91951205)。
文摘Microorganisms actively participate in biogeochemical cycling processes and play a crucial role in maintaining the dynamic balance of hot spring ecosystems.However,the distribution of microbial functional genes and their influencing factors in hot springs remain largely unclear.Therefore,this study investigated the microbial functional genes and their potential for controlling biogeochemical cycles(C,N,S,and P) in the hot Springs of Tengchong,China,using the Geochip method,a functional gene microarray technology.The examined hot springs have very different microbial functional genes.A total of 22 736 gene probe signals were identified,belonging to 567 functional genes and associated with 15 ecological functions,mainly involving stress response,carbon cycle,nitrogen cycle,sulfur cycle,phosphorus cycle and energy processes.The amyA,narG,dsrA and ppx genes were most abundant in carbon,nitrogen,sulfur and phosphorus cycles,respectively,and were significantly correlated with pH,temperature and SO_(4)^(2-).The diversity and abundance of detected gene probes were negatively correlated with temperature.The α-diversity(i.e.,Shannon index) was high at low temperature and low pH.Molecular functional interactions revealed by the gene connectivity levels were negatively correlated with temperature,pH and SO_(4)^(2-).These results suggested that the abundance,diversity and interactions of microbial functional genes were significantly influenced by geochemical parameters.-In addition,some genera possessed functional genes related to carbon,nitrogen,sulfur,and phosphorus cycles and can synergistically control the biogeochemical cycles of carbon,nitrogen,sulfur and phosphorus.These findings provide new insights into the functional potentials of microorganisms to participate in biogeochemical cycles and their responses to environmental factors in hot springs.
基金financially supported by the National Natural Science Foundation of China(Grant No.42102303)the Natural Science Foundation of Yunnan Province,China(Grant No.202401CF070174)the Xingdian Talent Support Program(Grant No.C619300A130).
文摘Cyclic wetting-drying alternation has a significant influence on the strength and structure of soils.It is prone to causing soil softening and disintegration,highlighting the importance to improve the soil's resistance to disintegration.This paper utilizes a self-developed disintegration test apparatus to analyze the disintegration characteristics of improved red soil under wet-dry cycles,focusing on the disintegration amount and ratio.Furthermore,XRD(X-ray diffraction),SEM(scanning electron microscope),tensile test,and contact angle test are employed to investigate the anti-disintegration behaviors of the improved red soil.The results show that the disintegrating amount and ratio of undisturbed and improved red soil are distinctly different under wet-dry cycles.Linear,stepped,constant and concave but perfect"S"shapes of the disintegrating ratio are observed in the cyclic tests.Cement and lime strengthen the red soil primarily through hydration reaction.The drop experiment confirms that cement plays a crucial role in restraining the disintegration.When the ameliorant content is low,the correlation between pore parameters and disintegration duration of red soil follows the order:mean shape coefficient>fractal dimension>probability entropy>area probability distribution index.With a high ameliorant content,the correlation remains similar,with slightly higher correlation for probability entropy.Under wet-dry cycle conditions,sludge and kaolin can improve the soil through the bonding of clay particles.The improved water repellency greatly enhances the resistance to disintegration of the altered red soil.The research provides valuable insights for the practical application of soil.
基金supported by the National Key Research and Development Program of China(No.2022YFC2903902)the National Natural Science Foundation of China(Nos.52374157 and 52174070)+1 种基金the Young Elite Scientists Sponsorship Program by CAST(No.2023QNRC001)the Key Science and Technology Project of Ministry of Emergency Management of the People’s Republic of China(No.2024EMST080802).
文摘In cold-region environments,where complex stresses and mining disturbances occur,rock masses are frequently segmented into discontinuous bodies by fractured structural planes,leading to anisotropic physical and mechanical properties.To explore the evolution of microcracks,degradation characteristics,and failure modes of fractured rocks in cold regions under the influence of freeze-thaw cycles,integrating laboratory experiments with the damage mechanics of freeze-thaw cycles.A numerical model for freeze-thaw cycle damage in rocks with various fracture dip angles was developed.The study revealed that the freeze-thaw expansion force generated during the pore water-ice phase transition is the primary driving factor behind freeze-thaw cycle damage.The initiation and propagation of microcracks and micropores,the detachment of matrix particles,and the loosening of clay mineral structures result in the transformation of the rock from a dense to a porous state,causing significant degradation in macroscopic mechanical properties.As freeze-thaw cycles increase,both the uniaxial compressive strength and the deformation modulus of the rock decrease significantly,with the failure mode gradually shifting from brittle instability to brittle-plastic or plastic failure.The findings of this study offer a practical approach to uncovering the mechanical response mechanisms between freeze-thaw damage in fractured rocks and structural planes.
基金financial support from the National Natural Science Foundation of China(Grant Nos.52479108,52408391)the Fundamental Research Funds for the Central Universities(2042024kf0032)+1 种基金the Postdoctoral Fellowship Program(Grade C)of China Postdoctoral Science Foundation(Grant No.GZC20241283)the Natural Science Foundation of Hubei Province,China(No.2024AFB160)。
文摘Numerous slope failures have been reported during periods of water level fluctuations.Understanding the influence of water on the creep behavior of joints is essential for evaluating the long-term stability of slopes.This study focuses on the effects of drying-wetting cycles and soaking conditions on the long-term behavior of sandstone joints.A total of 12 multi-stage shear creep tests are carried out on sandstone joints subjected to varying drying-wetting cycles under both soaking and un-soaking conditions.Based on the experimental results,the influences of drying-wetting cycles as well as soaking conditions on the microstructure,shear creep displacement,strength,and failure morphologies of sandstone joints are investigated comprehensively.Results indicate that increasing drying-wetting cycles not only yields larger shear creep displacements but also leads to a negative exponential decrease in the strength of sandstone joints.Besides,soaking conditions strongly influence the creep behavior of sandstone joints.The failure strength and long-term strength of sandstone joints for soaked samples decrease by 13.6%–29.0%and 19.4%–37.5%,respectively,as compared to unsoaked samples.Furthermore,four distinct stages in the shear creep process were identified according to the results obtained from multi-stage shear creep tests and computerized tomography scans,and three creep failure modes of sandstone joints are thus determined.Finally,the influence mechanism of drying-wetting cycles and soaking conditions on the creep failure modes of sandstone joints is revealed.Drying-wetting cycles and soaking conditions diminish the influence of asperities on the shear creep behavior of joints,thereby reducing the resistance of joints to long-term deformation.
基金supported by the Qingdao Postdoctoral Science Foundation(No.862205040054)the International Research Fellowship from the Japan Society for the Promotion of Science(Postdoctoral Fellowships for Research in Japan(Standard))the National Natural Science Foundation of China(No.52078093).
文摘The mechanical properties of bedding rock in cold regions are frequently affected by freeze-thaw(F-T)cycles and ani-sotropy.Research on the mechanical characteristics of rock damage under the combined action of F-T and bedding angles is limited,and most traditional rock damage models cannot accurately capture these characteristics.We performed axial compression tests to ex-plore the strength characteristics of bedding slates at the bedding angles ofβ=0°,30°,45°,60°,and 90°under various F-T cycles.The experimental findings suggest that the elastic modulus and uniaxial compressive strength of the slate declined exponentially as the number of F-T cycles increased.Axial compressive strength was characterized by a U-shaped tendency with the bedding angle.This study proposes a damage model for the uniaxial compressive strength of transversely isotropic rock,which integrates the F-T effect,utilizing the enhanced anisotropic Hoek-Brown strength criterion and a statistical damage model.This model was validated using experimental data.This statistical damage model can precisely capture the dual attributes of rock mass strength reduction with F-T cy-cles and variations arising from the loading direction.
