Bio-carbonation of reactive MgO has been regarded as a promising and eco-friendly method for construction and demolition waste(CDW)cementation in various geotechnical engineering applications.However,the beneficial ef...Bio-carbonation of reactive MgO has been regarded as a promising and eco-friendly method for construction and demolition waste(CDW)cementation in various geotechnical engineering applications.However,the beneficial effect of bio-carbonation of reactive MgO cemented CDW(BCM-samples)can be altered when exposed to wetting-drying cycles induced by extreme climate changes or groundwater fluctuations.To better understand the durability of BCM-samples and their underlying deterioration mechanisms,a series of BCM-samples was prepared to investigate their physical-mechanical performance and microstructure evolution subjected to the wetting-drying cycles.The results indicated that the wetting-drying cycles can deteriorate the BCM-samples,and their physical-mechanical behaviors change quickly at the cycle beginning and then smoothly after 2 cycles.With the increase in cycling,the apparent deterioration with efflorescence and microcrack development can be observed.The mass loss and water absorption rates increased while the dry density,compressional wave velocity,and unconfined compression strength decreased.Urea pre-hydrolysis treatment can significantly improve the durability of BCM-samples,as the more hydrated magnesia carbonates(HMCs)enhance the cementing effects.After 10 cycles,the UCS of pre-hydrolyzed samples decreased 25.4%to 4.45 MPa,while that of ordinary samples decreased 50.7%to 1.20 MPa.The deterioration of BCM-samples caused by wetting-drying cycles can be attributed to two factors.One of the main factors is the structural integrity changes caused by the rapid loss of soluble material at the initial cycling stages.Another factor is the decrease in cementation induced by the loss of brucite and HMCs at the following cycle stages.展开更多
The rock masses in the hydro-fluctuation zone of reservoir banks sustain wettingdrying cycles(WDC),thereby affecting the stability of the reservoir bank slope.In this paper,rock masses with argillaceous siltstone and ...The rock masses in the hydro-fluctuation zone of reservoir banks sustain wettingdrying cycles(WDC),thereby affecting the stability of the reservoir bank slope.In this paper,rock masses with argillaceous siltstone and silty mudstone interbedded in Badong Formation were taken as the research object to investigate the variation of strength parameters of soft and hard interbedded rock masses with WDC and dip angle through laboratory experiments and numerical experiments.Some attempts were made to reveal the mechanical properties deterioration mechanism of interbedded rock masses by quantitatively analyzing the contribution of strength parameters deterioration of hard rocks,soft rocks,and bedding planes to the strength parameters deterioration of rock masses.The results indicate that the logarithmic function could be used to describe the deterioration of each strength parameter of both argillaceous siltstone and silty mudstone and bedding plane with the number of WDC.The strength parameters of interbedded rock masses decrease as the number of WDC increases,with the largest decrease after the first cycle and then slowing down in the later cycles.The strength parameters initially decrease and then increase as the dip angles increase.The impact of deteriorated strength parameters of bedding planes and rocks on the deterioration of strength parameters of interbedded rock masses differs significantly with the dip angle,which can be divided into four typical ranges of different controlling factors.展开更多
Cracking affected by wetting-drying cycles is a major cause of shallow failure of soft rock slopes.Knowledge of rock tensile properties and cracking behaviors helps better assess the stability of soft rock slopes.This...Cracking affected by wetting-drying cycles is a major cause of shallow failure of soft rock slopes.Knowledge of rock tensile properties and cracking behaviors helps better assess the stability of soft rock slopes.This study aims to examine the cracking behaviors and tensile strength of silty mudstone under wetting-drying cycles.The wetting-drying cycle and Brazilian splitting tests were performed on silty mudstone considering various cycle number and amplitude.The cracking behaviors of wetting-drying cycles were analyzed by digital image correlation,three-dimensional(3D)scanning technology,and scanning electron microscopy.The results reveal a spiral-like pattern of crack ratio escalation in silty mudstone,with a higher crack ratio observed during drying than wetting.Tensile strength and fracture energy correlate negatively with cycle number or amplitude,with cycle number exerting a more pronounced effect.The variance of the maximum principal strain reflects stages of initial deformation,linear deformation,strain localization,and stable deformation.The formation of strain localization zones reveals the physical process of crack propagation.Crack tip opening displacement progresses through stages of slow growth,exponential growth,and linear growth,delineating the process from crack initiation to stable extension.Failure modes of silty mudstone primarily involve tensile and tensile-shear failure,influenced by the geometric parameters of cracks induced by wetting-drying cycles.Fracture surface roughness and fractal dimension increase with cycle number due to mineral dissolution,physical erosion,and nondirectional crack propagation.Hydration-swelling and dehydration-shrinkage of clay minerals,along with absorption-drying cracking,initiate and merge cracks,leading to degradation of the rock mechanical properties.The findings could provide insights for mitigating shallow cracking of soft rock slopes under wetting-drying cycles.展开更多
Compacted clays are widely used as barriers in municipal solid waste(MSW)landfills due to their low permeability,and the hydro-mechanical behaviour of such materials can be greatly affected by environmental conditions...Compacted clays are widely used as barriers in municipal solid waste(MSW)landfills due to their low permeability,and the hydro-mechanical behaviour of such materials can be greatly affected by environmental conditions.In this study,a series of wetting-drying(W-D)cycle tests and hydraulic conductivity tests were conducted on compacted red clay-bentonite mixtures.Various concentrations of NaCl solution were introduced during wetting to investigate the chemical effects.Scanning electron microscopy(SEM)and mercury intrusion porosimetry(MIP)tests were performed to analyze the evolution of soil microstructure.Results indicate that the compacted mixtures undergo cumulative shrinkage during W-D cycles,reaching an elastic state after three cycles.The hydraulic conductivity decreases as the bentonite content increases,becoming lower than 1×10^(-9)m/s when the bentonite content exceeds 10%,which satisfies the requirement for waste barriers.For a given bentonite content,the relationship between the logarithm of hydraulic conductivity and the void ratio can be well described by a linear regression equation.Additionally,the hydraulic conductivity initially increases and then decreases during the W-D cycles,peaking during the second wetting process.The presence of NaCl solution accelerates microstructural evolution and cumulative shrinkage,particularly in pure red clay.Therefore,adding an appropriate amount of bentonite mitigates the effect of NaCl solution on the volume change.Furthermore,the addition of bentonite exhibits a dual effect:the lubrication effect dominates in the mixtures with low bentonite content,while the filling effect prevails as volume change decreases due to the restriction of aggregates rearrangement when the bentonite content is high enough to fill the macropores.展开更多
The degradation progress of recycled aggregate concrete(RAC) subjected to sulfate attack under wetting-drying cycles and flexural loading is studied. Three different stress ratios(0, 0.3 and 0.5) were applied in this ...The degradation progress of recycled aggregate concrete(RAC) subjected to sulfate attack under wetting-drying cycles and flexural loading is studied. Three different stress ratios(0, 0.3 and 0.5) were applied in this test. The variations of relative dynamic elastic modulus Erd and water-soluble SO2-4 contents in RAC were used to evaluate degradation progress. The changes in mineral products and microstructures of interior concrete were investigated by means of X-ray diffraction(XRD), the environmental scanning electron microscope(ESEM) and X-ray computed tomography(X-CT). The results indicate that flexural loading accelerates the degradation of RAC under sulfate attack and wetting-drying cycles by expediting the transmission of SO2-4 into interior concrete. Furthermore, the accelerated effect of flexural loading is more obvious with the increase of stress ratio, that is because higher stress ratios can accelerate the extension of microcracks and generate more channels for the transmission of SO2-4. Also, more expansive products(gypsum and ettringite) are generated by the reaction of Ca(OH)2 with SO2-4, which can further accelerate the degradation of RAC.展开更多
Soil aggregate is the basic structural unit of soil,which is the foundation for supporting ecosystem functions,while its composition and stability is significantly affected by the external environment.This study was c...Soil aggregate is the basic structural unit of soil,which is the foundation for supporting ecosystem functions,while its composition and stability is significantly affected by the external environment.This study was conducted to explore the effect of external environment(wetting-drying cycles and acidic conditions)on the soil aggregate distribution and stability and identify the key soil physicochemical factors that affect the soil aggregate stability.The yellow‒brown soil from the Three Gorges Reservoir area(TGRA)was used,and 8 wetting-drying conditions(0,1,2,3,4,5,10 and 15 cycles)were simulated under 4 acidic conditions(pH=3,4,5 and 7).The particle size distribution and soil aggregate stability were determined by wet sieving method,the contribution of environmental factors(acid condition,wetting-drying cycle and their combined action)to the soil aggregate stability was clarified and the key soil physicochemical factors that affect the soil aggregate stability under wetting-drying cycles and acidic conditions were determined by using the Pearson’s correlation analysis,Partial least squares path modeling(PLS‒PM)and multiple linear regression analysis.The results indicate that wetting-drying cycles and acidic conditions have significant effects on the stability of soil aggregates,the soil aggregate stability gradually decreases with increasing number of wetting-drying cycles and it obviously decreases with the increase of acidity.Moreover,the combination of wetting-drying cycles and acidic conditions aggravate the reduction in the soil aggregate stability.The wetting-drying cycles,acidic conditions and their combined effect imposes significant impact on the soil aggregate stability,and the wetting-drying cycles exert the greatest influence.The soil aggregate stability is significantly correlated with the pH,Ca^(2+),Mg^(2+),maximum disintegration index(MDI)and soil bulk density(SBD).The PLS‒PM and multiple linear regression analysis further reveal that the soil aggregate stability is primarily influenced by SBD,Ca^(2+),and MDI.These results offer a scientific basis for understanding the soil aggregate breakdown mechanism and are helpful for clarifying the coupled effect of wetting-drying cycles and acid rain on terrestrial ecosystems in the TGRA.展开更多
Raining and sun-shining processes in natural climate were simulated by water spraying and infrared lightshining alternately as wetting-drying cycles in accelerated durability test. The accelerating effects of the wet-...Raining and sun-shining processes in natural climate were simulated by water spraying and infrared lightshining alternately as wetting-drying cycles in accelerated durability test. The accelerating effects of the wet-ting-drying cycles and the variation of corrosion current density and corrosion potential of steel bar in concrete undersuch conditions were studied. The result shows that the main reason leading to accelerating corrosion of steel bar inconcrete is the wetting-drying cycles, which can cause the increase of corrosion potential difference between the an-ode and cathode of steel bar corrosion cell and the decrease of concrete resistance. Corrosion rate of the steel bar inconcrete under four typical conditions, including wetting-drying cycle, long time submerging in water, long time ex-posure to indoor and outdoor environment were measured and compared. The test results indicate that the corrosionrates under the four typical conditions are in the order of spraying and infrared light shining cycles, outdoor environ-ment, indoor environment, and submerging in water, respectively.展开更多
Alternating rainfall and evaporation in nature severely impact the shear strength of expansive soils.This study presents an instrument for simulating the effect of wetting–drying cycles on the strength of expansive s...Alternating rainfall and evaporation in nature severely impact the shear strength of expansive soils.This study presents an instrument for simulating the effect of wetting–drying cycles on the strength of expansive soils under different loads,and its testing error is verified.With this instrument,direct shear tests were performed on samples experiencing 0-6 cycles under vertical loads of 0 kPa,5 kPa,15 kPa,and 30 k Pa.The results found that this instrument provides a new method for evaluating the effects of wetting–drying cycles on soils,and this method represents actual engineering conditions more accurately than do preexisting methods.It accurately controls the water content within 1%while simulating the specified loads at different soil depths.Cohesion is significantly affected by wetting–drying cycles,while the friction angle is not as sensitive to these cycles.Decrease in shear strength can be attributed to the fissures in soils caused by wetting–drying cycles.The existence of vertical loads effectively restricts shrinkage fissuring and cohesion attenuation,consequently inhibiting the attenuation of shear strength.展开更多
Piliostigma reticulatum is a native woody shrub found in cropped fields in the Sahel and has been shown to increase crop productivity and soil quality. Frequently occurring drying and rewetting cycles (DRW) may alter ...Piliostigma reticulatum is a native woody shrub found in cropped fields in the Sahel and has been shown to increase crop productivity and soil quality. Frequently occurring drying and rewetting cycles (DRW) may alter the soil quality beneath these shrubs. We investigated the effect of DRW cycles on microbial community in soil beneath and outside the P. reticulatum canopy and the roles of this shrub in the adaptation of the microbial community to abiotic stress. Soils were incubated in a climate controlled chamber for 45 days, after exposure to 10 consecutive days of DRW cycles at 75% of water holding capacity (WHC). Basal respiration, β-glucosidase activity, microbial biomass carbon (MBC), and available nitrogen (;) were measured at 2, 30, and 45 days after soil exposed to the DRW cycles. MBC increased significantly two days after the DRW cycles and was greater for soil beneath the shrub canopy compared with soil outside the shrub canopy. PCA analysis based on basal respiration, microbial biomass carbon, available nitrogen, and β-Glucosidase activity resulted in a tight clustering in the beneath shrub soil samples. Soils incubated for more than 30 days after DRW cycles had higher available nitrogen content than soils incubated for less than 30 days. Soil from beneath the shrub canopy significantly improved soil resilience based on β-glucosidase activity. Soil from beneath the shrub canopy also had higher nutrient levels and greater microbial activity even when subjected to DRW cycles, potentially improving the ability of crops to withstand in-season drought when they are adjacent to shrubs. The work should bring our scientific community into a more comprehensive assessment of potential effects of a crop-shrub intercropping that may allow for increased crop yields in semi-arid ecosystems under drought conditions.展开更多
Effects of earthworm casts on soil nutrient dynamics and their responses to changing moisture availability in subtropical ecosystems remain poorly understood.This study aimed to examine short-term carbon(C)and nitroge...Effects of earthworm casts on soil nutrient dynamics and their responses to changing moisture availability in subtropical ecosystems remain poorly understood.This study aimed to examine short-term carbon(C)and nitrogen(N)dynamics and their interactions with wetting-drying cycles in three different structural forms(i.e.,granular,globular,and heap-like)of Amynthas earthworm casts.The rates of C and N mineralization in the earthworm casts were examined under two different wetting-drying cycles(i.e.,2-d and 4-d wetting intervals)using a rainfall simulation experiment.After three simulated rainfall events,subsamples of the earthworm casts were further incubated for 4 d for the determination of CO2 and N2O fluxes.The results of this study indicated that the impacts of wetting-drying cycles on the short-term C and N dynamics were highly variable among the three cast forms,but wetting-drying cycles significantly reduced the cumulative CO2 and N2O fluxes by 62%-83%and 57%-85%,respectively,when compared to the control without being subjected to any rainfall events.The C mineralization rates in different cast forms were affected by the amount of organic substrates and N content in casts,which were associated with the food preference and selection of earthworms.Meanwhile,the cumulative N2O fluxes did not differ among the three cast forms.Repeated wetting and drying of casts not only enhanced aggregate stability by promoting bonds between the cast particles,but also inhibited microbial survival and growth during the prolonged drying period,which together hindered decomposition and denitrification.Our findings demonstrated that the interactions between the structural forms,aggregate dynamics,and C and N cycling in the earthworm casts were highly complex.展开更多
Loess landslides are major hazards in the Chinese Loess Plateau(CLP).The loess in this region is frequently subjected to repeated wetting–drying(W-D)cycles due to climatic factors,which significantly increases the li...Loess landslides are major hazards in the Chinese Loess Plateau(CLP).The loess in this region is frequently subjected to repeated wetting–drying(W-D)cycles due to climatic factors,which significantly increases the likelihood of landslides.Therefore,investigating the shear behavior and microstructural evolution of loess under climate-induced W-D cycles is crucial to understanding the mechanisms of loess landslides.In this study,Malan loess is analyzed using unsaturated triaxial tests,resistivity tests,scanning electron microscopy,and mercury intrusion porosimetry.The test results show that shear strength decreases with increased W-D cycles,and the degradation effect is more pronounced under lower confining pressure.The variations in conductive pathways indicate that electrical resistivity can effectively reflect the structural damage of loess during W-D cycles,which is associated with increased direct point contacts and spaced pores.Aggregation of clay particles and growth of cracks during the W-D cycles can further destabilize the loess microstructure.As the confining pressure increases,crushed particles rearrange and convert spaced pores into intergranular pores.The number and peak intensity of dominant spaced pores decrease,resulting in a more stable structure.This study clarifies the mechanisms of loess landslides under W-D cycles and provides theoretical support for landslide prevention and control in the CLP.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
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
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(F–T)cycle-induced cracking in silty clays poses a significant risk to engineering stability.Although the individual addition of fly ash(FA)or sisal fiber(SF)provides partial solutions,their simultaneous ...Freeze–thaw(F–T)cycle-induced cracking in silty clays poses a significant risk to engineering stability.Although the individual addition of fly ash(FA)or sisal fiber(SF)provides partial solutions,their simultaneous application may result in a synergistic effect to compensate for their respective shortcomings.In this study,the effects of SF and FA on the mechanical properties,crack resistance,water retention,and erosion resistance of improved soil were systematically investigated through unconfined compressive strength(UCS)tests,crack evolution analysis,simulated rainfall erosion tests,and microscopic characterization(laser particle size analysis and nitrogen adsorption).The results reveal that the volumetric stability of FA particles significantly inhibits cracking in soil after F–T cycles.However,FA contributes only slightly to soil strength and erosion resistance.SF,on the other hand,plays a substantial role in increasing both soil strength and erosion resistance.The synergy between FA and SF results in the simultaneous increase in crack resistance,erosion resistance,and strength.FA improves the aggregate stability during F–T cycles,whereas SF reinforces the bonds between these aggregates.A comprehensive evaluation of the improved soil during F–T cycles using the entropy weight-TOPSIS method reveal that the combination of 10%FA+18 mm SF performed the best,achieving a 246%higher composite score than the unmodified soil did.With respect to this optimal combination,compared with the unmodified soil,the SF–FA-improved soil exhibits a 30%reduction in the average crack width,a 30%reduction in the erosion rate,and a 46%increase in strength.The findings of this study provide a scientific basis for the design of soil improvement in disaster mitigation engineering in seasonally frozen soil regions.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
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
Seepage is one of the main causes for the deformation and instability of canal slopes in Xinjiang,China.In this study,centrifugal model tests under wetting-drying(WD)and wetting-drying-freezing-thawing(WDFT)cycles wer...Seepage is one of the main causes for the deformation and instability of canal slopes in Xinjiang,China.In this study,centrifugal model tests under wetting-drying(WD)and wetting-drying-freezing-thawing(WDFT)cycles were performed to investigate the water infiltration characteristics below a canal.The results show that the shallow soil of the canal models was fully saturated in the wetting process.Compared with the canal model under the WD cycles,the canal model under the WDFT cycles had larger saturated areas and a higher degree of saturation below the canal top after each cycle,indicating that the freezing-thawing(FT)process in the WDFT cycles promoted the water infiltration behavior below the canal slope.The cracks on the surface of the canal model under the cyclic action of WDFT developed further and had a higher connectivity,which provided the conditions for slope instability from a transverse tensile crack running through the canal top.On this basis,a field test was conducted to understand the water infiltration distribution below a typical canal in Xinjiang,China,which also verified the accuracy of the centrifugal results.This study provides a preliminary basis for the maintenance and seepage treatment of canals in Xinjiang,China.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
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
基金supported by the National Natural Science Foundation of China(Grant Nos.42525201 and 42230710).
文摘Bio-carbonation of reactive MgO has been regarded as a promising and eco-friendly method for construction and demolition waste(CDW)cementation in various geotechnical engineering applications.However,the beneficial effect of bio-carbonation of reactive MgO cemented CDW(BCM-samples)can be altered when exposed to wetting-drying cycles induced by extreme climate changes or groundwater fluctuations.To better understand the durability of BCM-samples and their underlying deterioration mechanisms,a series of BCM-samples was prepared to investigate their physical-mechanical performance and microstructure evolution subjected to the wetting-drying cycles.The results indicated that the wetting-drying cycles can deteriorate the BCM-samples,and their physical-mechanical behaviors change quickly at the cycle beginning and then smoothly after 2 cycles.With the increase in cycling,the apparent deterioration with efflorescence and microcrack development can be observed.The mass loss and water absorption rates increased while the dry density,compressional wave velocity,and unconfined compression strength decreased.Urea pre-hydrolysis treatment can significantly improve the durability of BCM-samples,as the more hydrated magnesia carbonates(HMCs)enhance the cementing effects.After 10 cycles,the UCS of pre-hydrolyzed samples decreased 25.4%to 4.45 MPa,while that of ordinary samples decreased 50.7%to 1.20 MPa.The deterioration of BCM-samples caused by wetting-drying cycles can be attributed to two factors.One of the main factors is the structural integrity changes caused by the rapid loss of soluble material at the initial cycling stages.Another factor is the decrease in cementation induced by the loss of brucite and HMCs at the following cycle stages.
基金supported by the Chinese National Key R&D Program(No.2022YFC3080200)the Chinese National Natural Science Foundation(No.42090054)。
文摘The rock masses in the hydro-fluctuation zone of reservoir banks sustain wettingdrying cycles(WDC),thereby affecting the stability of the reservoir bank slope.In this paper,rock masses with argillaceous siltstone and silty mudstone interbedded in Badong Formation were taken as the research object to investigate the variation of strength parameters of soft and hard interbedded rock masses with WDC and dip angle through laboratory experiments and numerical experiments.Some attempts were made to reveal the mechanical properties deterioration mechanism of interbedded rock masses by quantitatively analyzing the contribution of strength parameters deterioration of hard rocks,soft rocks,and bedding planes to the strength parameters deterioration of rock masses.The results indicate that the logarithmic function could be used to describe the deterioration of each strength parameter of both argillaceous siltstone and silty mudstone and bedding plane with the number of WDC.The strength parameters of interbedded rock masses decrease as the number of WDC increases,with the largest decrease after the first cycle and then slowing down in the later cycles.The strength parameters initially decrease and then increase as the dip angles increase.The impact of deteriorated strength parameters of bedding planes and rocks on the deterioration of strength parameters of interbedded rock masses differs significantly with the dip angle,which can be divided into four typical ranges of different controlling factors.
基金the financial support by the National Natural Science Foundation of China(Grant No.52108397)“Xiaohe”Science and Technology Talent Special Project(Grant No.2024 TJ-X06)Water Resources Science and Technology Project of Hunan Province(Grant No.XSKJ2023059-41).
文摘Cracking affected by wetting-drying cycles is a major cause of shallow failure of soft rock slopes.Knowledge of rock tensile properties and cracking behaviors helps better assess the stability of soft rock slopes.This study aims to examine the cracking behaviors and tensile strength of silty mudstone under wetting-drying cycles.The wetting-drying cycle and Brazilian splitting tests were performed on silty mudstone considering various cycle number and amplitude.The cracking behaviors of wetting-drying cycles were analyzed by digital image correlation,three-dimensional(3D)scanning technology,and scanning electron microscopy.The results reveal a spiral-like pattern of crack ratio escalation in silty mudstone,with a higher crack ratio observed during drying than wetting.Tensile strength and fracture energy correlate negatively with cycle number or amplitude,with cycle number exerting a more pronounced effect.The variance of the maximum principal strain reflects stages of initial deformation,linear deformation,strain localization,and stable deformation.The formation of strain localization zones reveals the physical process of crack propagation.Crack tip opening displacement progresses through stages of slow growth,exponential growth,and linear growth,delineating the process from crack initiation to stable extension.Failure modes of silty mudstone primarily involve tensile and tensile-shear failure,influenced by the geometric parameters of cracks induced by wetting-drying cycles.Fracture surface roughness and fractal dimension increase with cycle number due to mineral dissolution,physical erosion,and nondirectional crack propagation.Hydration-swelling and dehydration-shrinkage of clay minerals,along with absorption-drying cracking,initiate and merge cracks,leading to degradation of the rock mechanical properties.The findings could provide insights for mitigating shallow cracking of soft rock slopes under wetting-drying cycles.
基金the National Natural Science Foundation of China(Grant Nos.42372333 and 42072318)the China Scholarship Council(CSC)(Grant No.202306370029)。
文摘Compacted clays are widely used as barriers in municipal solid waste(MSW)landfills due to their low permeability,and the hydro-mechanical behaviour of such materials can be greatly affected by environmental conditions.In this study,a series of wetting-drying(W-D)cycle tests and hydraulic conductivity tests were conducted on compacted red clay-bentonite mixtures.Various concentrations of NaCl solution were introduced during wetting to investigate the chemical effects.Scanning electron microscopy(SEM)and mercury intrusion porosimetry(MIP)tests were performed to analyze the evolution of soil microstructure.Results indicate that the compacted mixtures undergo cumulative shrinkage during W-D cycles,reaching an elastic state after three cycles.The hydraulic conductivity decreases as the bentonite content increases,becoming lower than 1×10^(-9)m/s when the bentonite content exceeds 10%,which satisfies the requirement for waste barriers.For a given bentonite content,the relationship between the logarithm of hydraulic conductivity and the void ratio can be well described by a linear regression equation.Additionally,the hydraulic conductivity initially increases and then decreases during the W-D cycles,peaking during the second wetting process.The presence of NaCl solution accelerates microstructural evolution and cumulative shrinkage,particularly in pure red clay.Therefore,adding an appropriate amount of bentonite mitigates the effect of NaCl solution on the volume change.Furthermore,the addition of bentonite exhibits a dual effect:the lubrication effect dominates in the mixtures with low bentonite content,while the filling effect prevails as volume change decreases due to the restriction of aggregates rearrangement when the bentonite content is high enough to fill the macropores.
基金The National Natural Science Foundation of China(No.51578141)the Major State Basic Research Development Program of China(No.2015CB655102)China-Japanese Research Cooperative Program-Ministry of Science and Technology in China(No.2016YFE0118200)
文摘The degradation progress of recycled aggregate concrete(RAC) subjected to sulfate attack under wetting-drying cycles and flexural loading is studied. Three different stress ratios(0, 0.3 and 0.5) were applied in this test. The variations of relative dynamic elastic modulus Erd and water-soluble SO2-4 contents in RAC were used to evaluate degradation progress. The changes in mineral products and microstructures of interior concrete were investigated by means of X-ray diffraction(XRD), the environmental scanning electron microscope(ESEM) and X-ray computed tomography(X-CT). The results indicate that flexural loading accelerates the degradation of RAC under sulfate attack and wetting-drying cycles by expediting the transmission of SO2-4 into interior concrete. Furthermore, the accelerated effect of flexural loading is more obvious with the increase of stress ratio, that is because higher stress ratios can accelerate the extension of microcracks and generate more channels for the transmission of SO2-4. Also, more expansive products(gypsum and ettringite) are generated by the reaction of Ca(OH)2 with SO2-4, which can further accelerate the degradation of RAC.
基金co-funded by the National Natural Science Foundation of China(U204020742277323)+2 种基金the 111 Project of Hubei Province(2021EJD026)the open fund of Key Laboratory of Geological Hazards on Three Gorges Reservoir Area(China Three Gorges University)Ministry of Education(2022KDZ24).
文摘Soil aggregate is the basic structural unit of soil,which is the foundation for supporting ecosystem functions,while its composition and stability is significantly affected by the external environment.This study was conducted to explore the effect of external environment(wetting-drying cycles and acidic conditions)on the soil aggregate distribution and stability and identify the key soil physicochemical factors that affect the soil aggregate stability.The yellow‒brown soil from the Three Gorges Reservoir area(TGRA)was used,and 8 wetting-drying conditions(0,1,2,3,4,5,10 and 15 cycles)were simulated under 4 acidic conditions(pH=3,4,5 and 7).The particle size distribution and soil aggregate stability were determined by wet sieving method,the contribution of environmental factors(acid condition,wetting-drying cycle and their combined action)to the soil aggregate stability was clarified and the key soil physicochemical factors that affect the soil aggregate stability under wetting-drying cycles and acidic conditions were determined by using the Pearson’s correlation analysis,Partial least squares path modeling(PLS‒PM)and multiple linear regression analysis.The results indicate that wetting-drying cycles and acidic conditions have significant effects on the stability of soil aggregates,the soil aggregate stability gradually decreases with increasing number of wetting-drying cycles and it obviously decreases with the increase of acidity.Moreover,the combination of wetting-drying cycles and acidic conditions aggravate the reduction in the soil aggregate stability.The wetting-drying cycles,acidic conditions and their combined effect imposes significant impact on the soil aggregate stability,and the wetting-drying cycles exert the greatest influence.The soil aggregate stability is significantly correlated with the pH,Ca^(2+),Mg^(2+),maximum disintegration index(MDI)and soil bulk density(SBD).The PLS‒PM and multiple linear regression analysis further reveal that the soil aggregate stability is primarily influenced by SBD,Ca^(2+),and MDI.These results offer a scientific basis for understanding the soil aggregate breakdown mechanism and are helpful for clarifying the coupled effect of wetting-drying cycles and acid rain on terrestrial ecosystems in the TGRA.
基金Project(50078054) supported by National Natural Science Foundation of China and Youth Scientific Research Fund of CUMT
文摘Raining and sun-shining processes in natural climate were simulated by water spraying and infrared lightshining alternately as wetting-drying cycles in accelerated durability test. The accelerating effects of the wet-ting-drying cycles and the variation of corrosion current density and corrosion potential of steel bar in concrete undersuch conditions were studied. The result shows that the main reason leading to accelerating corrosion of steel bar inconcrete is the wetting-drying cycles, which can cause the increase of corrosion potential difference between the an-ode and cathode of steel bar corrosion cell and the decrease of concrete resistance. Corrosion rate of the steel bar inconcrete under four typical conditions, including wetting-drying cycle, long time submerging in water, long time ex-posure to indoor and outdoor environment were measured and compared. The test results indicate that the corrosionrates under the four typical conditions are in the order of spraying and infrared light shining cycles, outdoor environ-ment, indoor environment, and submerging in water, respectively.
基金provided by the National Natural Science Foundation of China(Grant No.51169005)
文摘Alternating rainfall and evaporation in nature severely impact the shear strength of expansive soils.This study presents an instrument for simulating the effect of wetting–drying cycles on the strength of expansive soils under different loads,and its testing error is verified.With this instrument,direct shear tests were performed on samples experiencing 0-6 cycles under vertical loads of 0 kPa,5 kPa,15 kPa,and 30 k Pa.The results found that this instrument provides a new method for evaluating the effects of wetting–drying cycles on soils,and this method represents actual engineering conditions more accurately than do preexisting methods.It accurately controls the water content within 1%while simulating the specified loads at different soil depths.Cohesion is significantly affected by wetting–drying cycles,while the friction angle is not as sensitive to these cycles.Decrease in shear strength can be attributed to the fissures in soils caused by wetting–drying cycles.The existence of vertical loads effectively restricts shrinkage fissuring and cohesion attenuation,consequently inhibiting the attenuation of shear strength.
文摘Piliostigma reticulatum is a native woody shrub found in cropped fields in the Sahel and has been shown to increase crop productivity and soil quality. Frequently occurring drying and rewetting cycles (DRW) may alter the soil quality beneath these shrubs. We investigated the effect of DRW cycles on microbial community in soil beneath and outside the P. reticulatum canopy and the roles of this shrub in the adaptation of the microbial community to abiotic stress. Soils were incubated in a climate controlled chamber for 45 days, after exposure to 10 consecutive days of DRW cycles at 75% of water holding capacity (WHC). Basal respiration, β-glucosidase activity, microbial biomass carbon (MBC), and available nitrogen (;) were measured at 2, 30, and 45 days after soil exposed to the DRW cycles. MBC increased significantly two days after the DRW cycles and was greater for soil beneath the shrub canopy compared with soil outside the shrub canopy. PCA analysis based on basal respiration, microbial biomass carbon, available nitrogen, and β-Glucosidase activity resulted in a tight clustering in the beneath shrub soil samples. Soils incubated for more than 30 days after DRW cycles had higher available nitrogen content than soils incubated for less than 30 days. Soil from beneath the shrub canopy significantly improved soil resilience based on β-glucosidase activity. Soil from beneath the shrub canopy also had higher nutrient levels and greater microbial activity even when subjected to DRW cycles, potentially improving the ability of crops to withstand in-season drought when they are adjacent to shrubs. The work should bring our scientific community into a more comprehensive assessment of potential effects of a crop-shrub intercropping that may allow for increased crop yields in semi-arid ecosystems under drought conditions.
基金We thank the Agriculture,Fisheries and Conservation Department of the Hong Kong SAR Government(China)for the permission of field sampling.
文摘Effects of earthworm casts on soil nutrient dynamics and their responses to changing moisture availability in subtropical ecosystems remain poorly understood.This study aimed to examine short-term carbon(C)and nitrogen(N)dynamics and their interactions with wetting-drying cycles in three different structural forms(i.e.,granular,globular,and heap-like)of Amynthas earthworm casts.The rates of C and N mineralization in the earthworm casts were examined under two different wetting-drying cycles(i.e.,2-d and 4-d wetting intervals)using a rainfall simulation experiment.After three simulated rainfall events,subsamples of the earthworm casts were further incubated for 4 d for the determination of CO2 and N2O fluxes.The results of this study indicated that the impacts of wetting-drying cycles on the short-term C and N dynamics were highly variable among the three cast forms,but wetting-drying cycles significantly reduced the cumulative CO2 and N2O fluxes by 62%-83%and 57%-85%,respectively,when compared to the control without being subjected to any rainfall events.The C mineralization rates in different cast forms were affected by the amount of organic substrates and N content in casts,which were associated with the food preference and selection of earthworms.Meanwhile,the cumulative N2O fluxes did not differ among the three cast forms.Repeated wetting and drying of casts not only enhanced aggregate stability by promoting bonds between the cast particles,but also inhibited microbial survival and growth during the prolonged drying period,which together hindered decomposition and denitrification.Our findings demonstrated that the interactions between the structural forms,aggregate dynamics,and C and N cycling in the earthworm casts were highly complex.
基金supported by the National Natural Science Foundation of China(Grant Nos.42177138 and 41907239)the Central Guidance Funds for Local Science and Technology Development of China(Grant No.YDZJSX2025D031).
文摘Loess landslides are major hazards in the Chinese Loess Plateau(CLP).The loess in this region is frequently subjected to repeated wetting–drying(W-D)cycles due to climatic factors,which significantly increases the likelihood of landslides.Therefore,investigating the shear behavior and microstructural evolution of loess under climate-induced W-D cycles is crucial to understanding the mechanisms of loess landslides.In this study,Malan loess is analyzed using unsaturated triaxial tests,resistivity tests,scanning electron microscopy,and mercury intrusion porosimetry.The test results show that shear strength decreases with increased W-D cycles,and the degradation effect is more pronounced under lower confining pressure.The variations in conductive pathways indicate that electrical resistivity can effectively reflect the structural damage of loess during W-D cycles,which is associated with increased direct point contacts and spaced pores.Aggregation of clay particles and growth of cracks during the W-D cycles can further destabilize the loess microstructure.As the confining pressure increases,crushed particles rearrange and convert spaced pores into intergranular pores.The number and peak intensity of dominant spaced pores decrease,resulting in a more stable structure.This study clarifies the mechanisms of loess landslides under W-D cycles and provides theoretical support for landslide prevention and control in the CLP.
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 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 the Jilin Science and Technology Program(20230203130SF)。
文摘Freeze–thaw(F–T)cycle-induced cracking in silty clays poses a significant risk to engineering stability.Although the individual addition of fly ash(FA)or sisal fiber(SF)provides partial solutions,their simultaneous application may result in a synergistic effect to compensate for their respective shortcomings.In this study,the effects of SF and FA on the mechanical properties,crack resistance,water retention,and erosion resistance of improved soil were systematically investigated through unconfined compressive strength(UCS)tests,crack evolution analysis,simulated rainfall erosion tests,and microscopic characterization(laser particle size analysis and nitrogen adsorption).The results reveal that the volumetric stability of FA particles significantly inhibits cracking in soil after F–T cycles.However,FA contributes only slightly to soil strength and erosion resistance.SF,on the other hand,plays a substantial role in increasing both soil strength and erosion resistance.The synergy between FA and SF results in the simultaneous increase in crack resistance,erosion resistance,and strength.FA improves the aggregate stability during F–T cycles,whereas SF reinforces the bonds between these aggregates.A comprehensive evaluation of the improved soil during F–T cycles using the entropy weight-TOPSIS method reveal that the combination of 10%FA+18 mm SF performed the best,achieving a 246%higher composite score than the unmodified soil did.With respect to this optimal combination,compared with the unmodified soil,the SF–FA-improved soil exhibits a 30%reduction in the average crack width,a 30%reduction in the erosion rate,and a 46%increase in strength.The findings of this study provide a scientific basis for the design of soil improvement in disaster mitigation engineering in seasonally frozen soil regions.
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Project(2017YFC0405100)supported by the National Key Research and Development Program of ChinaProjects(51879166,51709185,51909170)supported by the National Natural Science Foundation of China+1 种基金Project(SKLFSE201909)supported by the Open Research Fund Program of State Key Laboratory of Permafrost Engineering,ChinaProject(2018M640500)supported by Postdoctoral Science Foundation of China。
文摘Seepage is one of the main causes for the deformation and instability of canal slopes in Xinjiang,China.In this study,centrifugal model tests under wetting-drying(WD)and wetting-drying-freezing-thawing(WDFT)cycles were performed to investigate the water infiltration characteristics below a canal.The results show that the shallow soil of the canal models was fully saturated in the wetting process.Compared with the canal model under the WD cycles,the canal model under the WDFT cycles had larger saturated areas and a higher degree of saturation below the canal top after each cycle,indicating that the freezing-thawing(FT)process in the WDFT cycles promoted the water infiltration behavior below the canal slope.The cracks on the surface of the canal model under the cyclic action of WDFT developed further and had a higher connectivity,which provided the conditions for slope instability from a transverse tensile crack running through the canal top.On this basis,a field test was conducted to understand the water infiltration distribution below a typical canal in Xinjiang,China,which also verified the accuracy of the centrifugal results.This study provides a preliminary basis for the maintenance and seepage treatment of canals in Xinjiang,China.
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.
