This paper uses a complete washing and sieving method and accurately determines the clay mass contents in the loess deposits at the eight regions of Xianyang,Ili,Xi'an,Yan'an,Lvliang,Linfen,Xining,and Lanzhou ...This paper uses a complete washing and sieving method and accurately determines the clay mass contents in the loess deposits at the eight regions of Xianyang,Ili,Xi'an,Yan'an,Lvliang,Linfen,Xining,and Lanzhou in China.The method uses nylon cloth sieves with apertures from 0.0008 mm to 0.048 mm and standard steel sieves with apertures from 0.063 mm to 28 mm.It uses a rotary vibration machine to wash and sieve the loess into many clay,silt,sand,and gravel subgroups.The masses of the separated materials construct the complete mass-based particle size distribution(PSD)curves for the tested loesses.The results show that the Xianyang,Ili,Xi'an,Yan'an,Lvliang,Linfen,Xining,and Lanzhou loesses contain 65.28%,56.73%,56.76%,38.7%,31.78%,30.55%,30.1%,and 26.29%clay in mass.These clay contents are 1.3-14.9 times higher than the clay contents from the past publications for the eight types of loess.On the other hand,the plasticity data in past publications show that loess belongs to the clay type of soil.The clay contents in the publications are underestimated,which is caused by the inseparability of fine soils(or clay and silt mixture)from the existing PSD test methods.Macro-photographs,micro-photographs and SEM photographs present the separated materials of individual clay,silt,sand,and gravel particles.Particle sizes measured from the SEM photographs confirm their particle sizes within their size limits.The clay particles exhibit strong internal cohesion,while the silt,sand,and gravel particles are individual and non-cohesive.Atterberg limits test results further demonstrate the clay particles'high plasticity features and the silt particles'non-plasticity features.展开更多
Accurate water budget closure is critical for sustainable water resource management facing increased pressures from climate change and human activities.Although error reduction methods for individual water balance com...Accurate water budget closure is critical for sustainable water resource management facing increased pressures from climate change and human activities.Although error reduction methods for individual water balance components have advanced,persistent biases remain due to the independent development of datasets,impacting basin scale water budget balance.In this research,we analyzed the mathematical origin of the bias between water budget components and developed a new basin-scale water balance calibration method that redistributes errors across components while enforcing water balance constraints.Validation confirms systematic improvements,with reduced RMSE(Precipitation:-2.29 mm/month;ET:-1.34 mm/month)and increased R2 against in situ observations.Applied to the Jinghe River Basin(2000−2019),the calibrated data reveal declining precipitation(-1.70 mm/year)and evapotranspiration(-1.84 mm/year)alongside slightly increasing runoff(0.20 mm/year in basin depth),signaling a drying trend.Land cover changes—marked by cropland loss(-3,497 km^(2))and forest(+720 km^(2))and grassland(+2,776 km^(2))expansion—reflect improved water consumption requirements by ecosystem,raising concerns for water retention and ecosystem stability.The method is particularly effective for ungauged basins with sparse ground data and underscores the need for integrated land-water management to enhance long-term resilience.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
Water infiltration in loess is one of the most significant processes that can lead to geological disasters on the Loess Plateau in China.However,the spatiotemporal characteristics of infiltration in intact loess,parti...Water infiltration in loess is one of the most significant processes that can lead to geological disasters on the Loess Plateau in China.However,the spatiotemporal characteristics of infiltration in intact loess,particularly the heterogeneity of three-dimensional(3D)seepage and its relationship with soil properties,remain poorly understood.This study conducted field infiltration tests on a 3 m×3 m loess column,instrumented with 48 moisture sensors to monitor 3D seepage and infiltration rates.Both horizontal and vertical infiltration behaviors were analyzed,alongside a detailed characterization of soil physical properties.The results demonstrated that the water infiltration process was significantly heterogeneous in intact loess,with wetting front velocities varying considerably across profiles and depths,despite relatively uniform physical properties.The infiltration process also exhibited pronounced anisotropy,with vertical wetting front velocities at least 10 times higher than those of the horizontal velocities.The in situ tests indicated that the physical properties were not the primary factors influencing infiltration.However,the microfeatures that facilitated the formation of preferential pathways exerted the most significant influence on the water infiltration process in thick unsaturated loess.Additionally,prior infiltration events negatively impacted subsequent infiltration in thick unsaturated loess.These findings enhance the understanding of loess infiltration dynamics,providing insights into unsaturated flow processes and their implications for geological stability in loess regions.展开更多
While the Ordos Basin is recognized for its substantial hydrocarbon exploration prospects,its rugged loess tableland terrain has rendered seismic exploration exceptionally challenging[1-3].Persistent obstacles such as...While the Ordos Basin is recognized for its substantial hydrocarbon exploration prospects,its rugged loess tableland terrain has rendered seismic exploration exceptionally challenging[1-3].Persistent obstacles such as complex 3D survey planning,low signal-tonoise ratio raw data,inadequate near-surface velocity modeling,and imaging inaccuracy have long hindered the advancement of seismic exploration across this region.Through a problem-solving approach rooted in geological target analysis,this research systematically investigates the behavioral patterns of nodal seismometer-based high-density seismic acquisition in loess plateau.Tailored advancements in waveform enhancement and depth velocity modelling methodologies have been engineered.Field validations confirm that the optimized workflow demonstrates marked improvements in amplitude preservation and imaging resolution,offering novel insights for future reservoir characterization endeavors.展开更多
Quantifying spatial heterogeneity in soil water retention properties(SWRP)is crucial for enhancing the accuracy of hydrogeological simulations.However,studies on the spatial heterogeneity of SWRP in the Chinese Loess ...Quantifying spatial heterogeneity in soil water retention properties(SWRP)is crucial for enhancing the accuracy of hydrogeological simulations.However,studies on the spatial heterogeneity of SWRP in the Chinese Loess Plateau(CLP)remain scarce,especially at the vertical scale.We conducted laboratory tests on undisturbed loess cores collected from boreholes in CLP to analyze soil physical parameters(SPPs)and SWRP.Measured soil water characteristic curves(SWCCs)were fitted to the Brooks-Corey(BC),Fredlund-Xing(FX),and van Genuchten(vG)models.It was revealed that the FX and vG models outperformed the BC model.The geostatistical analysis identified the Gaussian model as optimal for describing the semivariograms of both SPPs and SWCC fitting parameters(FPs).Strikingly,over 90%of these parameters exhibited strong vertical spatial dependence,with an average autocorrelation length of 213.878 cm for SPPs and 320.678 cm for FPs.Moreover,SWRP was found to be significantly influenced by both SPPs and the vertical position relative to the loess ridge slope surface.Parameters near the ridge slope surface showed significantly degraded spatial dependence.These findings provide valuable insights for parameterizing the spatial heterogeneity of soil water retention properties,which are beneficial for hydrogeological modelling in shallow CLP loess strata.展开更多
The widely distributed loess deposits in the Yellow River Basin exhibit unique engineering geological characteristics.The variations in their thickness and stratigraphic structure significantly amplify ground motion p...The widely distributed loess deposits in the Yellow River Basin exhibit unique engineering geological characteristics.The variations in their thickness and stratigraphic structure significantly amplify ground motion parameters,directly influencing the regional seismic hazard risk level.This study methodically conducted on-site studies and observations of building collapses and damages resulting from seismic amplification effects,using the Wenchuan M_(S)8.0 earthquake as a case study.Comprehensive experimental and numerical simulation studies were carried out.A large-scale shaking table test was performed,and numerical models for 14 different loess sites types were established.Various types of seismic waves were incorporated into these models for systematic numerical simulation calculations.The research reveals the mechanisms by which loess deposit thickness and stratigraphic structure in the Yellow River Basin affect seismic ground motion amplification.The results indicate that as the epicentral distance increases,the peak ground motion shows a marked attenuation trend,with the horizontal component attenuating substantially faster than the vertical component.As the overlying loess layer thickness increases from 50 to 100 m,the seismic intensity may escalate by 3−4 degrees,and the peak acceleration may amplify by 1.5−2.2 times.With the augmentation of loess deposit thickness and the proliferation of soil layers,both the peak acceleration response spectrum and the characteristic period demonstrate an upward tendency,exhibiting slight fluctuations contingent upon the seismic wave type.展开更多
This study developed a modeling methodology for statistical optimization-based geologic hazard susceptibility assessment,aiming to enhance the comprehensive performance and classification accuracy of the assessment mo...This study developed a modeling methodology for statistical optimization-based geologic hazard susceptibility assessment,aiming to enhance the comprehensive performance and classification accuracy of the assessment models.First,the cumulative probability method revealed that a low probability(15%)of geologic hazards between any two geologic hazard points occurred outside a buffer zone with a radius of 2297 m(i.e.,the distance threshold).The training dataset was established,consisting of negative samples(non-hazard points)randomly generated based on the distance threshold,positive samples(i.e.,historical hazards),and 13 conditioning factors.Then,models were built using five machine learning algorithms,namely random forest(RF),gradient boosting decision tree(GBDT),naive Bayes(NB),logistic regression(LR),and support vector machine(SVM).The comprehensive performance of the models was assessed using the area under the receiver operating characteristic curve(AUC)and overall accuracy(OA)as indicators,revealing that RF exhibited the best performance,with OA and AUC values of 2.7127 and 0.981,respectively.Furthermore,the machine learning models constructed by considering the distance threshold outperformed those built using the unoptimized dataset.The characteristic factors were ranked using the mutual information method,with their scores decreasing in the order of rainfall(0.1616),altitude(0.06),normalized difference vegetation index(NDVI;0.04),and distance from roads(0.03).Finally,the geologic hazard susceptibility classification was assessed using the natural breaks method combined with a clustering algorithm.The results indicate that the clustering algorithm exhibited higher classification accuracy than the natural breaks method.The findings of this study demonstrate that the proposed model optimization scheme can provide a scientific basis for the prevention and control of geologic hazards.展开更多
The shear behavior of intact loess is intricately linked to the spatiotemporal evolution of its mesoscopic characteristics.Understanding this relationship is crucial for comprehending and preventing loess landslides.T...The shear behavior of intact loess is intricately linked to the spatiotemporal evolution of its mesoscopic characteristics.Understanding this relationship is crucial for comprehending and preventing loess landslides.To systematically investigate this connection,our study conducted triaxial shear tests on both Malan loess and Lishi loess,encompassing variations in confining pressures.Additionally,nondestructive,real-time CT observations were employed to track the dynamic evolution of loess mesostructures.The experimental findings illuminate significant insights.The Malan loess exhibits strain hardening during shearing,with the degree of hardening exhibiting an increase in tandem with rising confining pressure.Conversely,the Lishi loess manifests a transition from strain softening to strain hardening as confining pressure increases.Under elevated confining pressure,the specimen undergoes structural damage while concurrently forming a denser configuration through particle friction and rearrangement,leading to strain hardening and volume reduction.In contrast,the central portion of the specimen exhibits heightened sensitivity to deformation under low confining pressures.Gradual crack expansion,emanating from the center and progressing towards the ends,results in progressive specimen destruction and a concomitant reduction in stress.On a macroscopic level,the specimen undergoes expansion at its center while contracting at its ends.The findings of this study unveil the intricate mechanisms governing loess deformation in the presence of varying confining pressures,thereby contributing significantly to our understanding of loess landslide formation and providing a robust theoretical framework for preventive measures.展开更多
In recent years,to better address soil erosion,the Loess Plateau area has seen a surge in the construction of warping dam projects.Warping dams have strong functions in soil and water conservation as well as warping f...In recent years,to better address soil erosion,the Loess Plateau area has seen a surge in the construction of warping dam projects.Warping dams have strong functions in soil and water conservation as well as warping for farmland creation,serving as a key support for ecological restoration and economic development in the Loess Plateau area in the new era.However,in light of practical conditions,there are many problems in their construction process,which have affected their actual operation quality.In this regard,while expounding on the value and significance of warping dam project construction in the Loess Plateau area,this paper discusses the existing problems and effective countermeasures,aiming to provide some references for relevant personnel.展开更多
Tafoni are globally developed on cliffy slopes,and many of them are favorable places for the preservation of stone historical relics.However,the characteristics and formation processes of tafoni in the Loess Plateau a...Tafoni are globally developed on cliffy slopes,and many of them are favorable places for the preservation of stone historical relics.However,the characteristics and formation processes of tafoni in the Loess Plateau are yet to be understood.This paper studied the features of the tafoni on conglomerate slopes in Huoshizhai National Geopark of Ningxia Hui Autonomous Region and discussed its formation processes by field investigation and morphometry,insitu relative humidity(RH)measurement,salt chemistry and X-ray fluorescence spectrometer(XRF)experiments of 24 samples.The bedrock of the tafoni is dominated by reddish fluvial conglomerates of the Lower Cretaceous Heshangpu Formation with abundant chemically unstable components including feldspars,lithic fragments,and calcite cements.The RH values vary from 5%to 100%,but the backwalls of the tafoni have higher RH values than outer surfaces.The more moisture on the backwalls is possibly generated by water influx from the rock interior,resulting in more salt precipitation on the backwalls.As a result,the backwalls have been subject to predominant salt weathering.The dominant salts involved in salt weathering are probably derived from the dissolution of the salt interbeds in the basin,although the chemical dissolution of the unstable components such as feldspars,lithic fragments,and calcite cements might have produced small amounts of salts.The salt types dominantly include nitrates,sulfates,and halite.In the progression of tafoni,the moisture maintenance on the backwalls gives rise to the accretion of salts,which in turn enhance the weathering rates of the backwalls.As a result,the volumes of the tafoni have become enlarged owing to inward growth and coalescence of adjacent smaller ones.展开更多
Although time-dependent deformation of geomaterials underpins slope-failure prediction models,the influence of strain rate on shearing strength and deformation behavior of loess remains unclear.The consolidated undrai...Although time-dependent deformation of geomaterials underpins slope-failure prediction models,the influence of strain rate on shearing strength and deformation behavior of loess remains unclear.The consolidated undrained(CU)and drained(CD)triaxial testing elucidated the impact of strain rate(0.005–0.3 mm/min)on strength envelopes,deformation moduli,pore pressures,and dilatancy characteristics of unsaturated and quasi-saturated loess.Under drained conditions with a controlled matric suction of 50 kPa,increasing strain rates from 0.005 mm/min to 0.011 mm/min induced decreases in failure deviatoric stress(qf),initial deformation modulus(Ei),and cohesion(c),while friction angles remained unaffected.Specimens displayed initial contractive volumetric strains transitioning to dilation across varying confining pressures.Higher rates diminished contractive volumetric strains and drainage volumes,indicating reduced densification and strength in the shear zone.Under undrained conditions,both unsaturated and quasi-saturated(pore pressure coefficient B=0.75)loess exhibited deteriorating mechanical properties with increasing rates from 0.03 mm/min to 0.3 mm/min.For unsaturated loess,reduced contractive volumetric strains at higher rates manifested relatively looser structures in the pre-peak stress phase.The strength decrement in quasi-saturated loess arose from elevated excess porewater pressures diminishing effective stresses.Negative porewater pressures emerged in quasi-saturated loess at lower confining pressures and strain rates.Compared to previous studies,the qf and Ei exhibited rate sensitivity below threshold values before attaining minima with marginal subsequent influence.The underlying mechanism mirrors the transition from creep to accelerated deformation phase of landslides.展开更多
During extensive gully land consolidation projects on China's Loess Plateau,many loess-bedrock fill slopes were formed,which frequently experience shallow landslides induced by rainfall.However,studies on loess-be...During extensive gully land consolidation projects on China's Loess Plateau,many loess-bedrock fill slopes were formed,which frequently experience shallow landslides induced by rainfall.However,studies on loess-bedrock slope failure triggered by continuous heavy rainfall are limited,and the role of the soilerock interface between the original bedrock slope and fill slope in the hydrological and failure process of the slope remains unclear.In this study,we conducted a continuous rainfall model test on a loess-bedrock fill slope.During the test,the responses of volume water content,pore pressure,micro deformation,and movement of the infiltration front were observed.The hydrological process and failure mechanism were then analysed.The findings suggest that the soilerock interface is a predominant infiltration surface within the slope.Rainfall infiltration rates at the interface reach 1.24-2.80 times those of the fill slope,with peak interfacial pore water pressure exceeding that of the loess fill.Furthermore,the infiltration front moves rapidly along the interface toward the bottom of the slope,reducing interfacial cohesion between bedrock and loess.The slope failure modes are summarised into three phases:local failure→flow slide and crack penetration→multistage block retrogressive slides.The cracks generated at the slope surface serve as key determinants of the geometry and scale of shallow landslides.Therefore,we recommend targeted engineering interventions to mitigate the instability and erosion of loessebedrock fill slopes.展开更多
Check dams are widely constructed on China's Loess Plateau,which had a total number of 58,776 by the end of 2019.Great achievements in check dam construction have been gained regarding the economic and environment...Check dams are widely constructed on China's Loess Plateau,which had a total number of 58,776 by the end of 2019.Great achievements in check dam construction have been gained regarding the economic and environmental impacts.This study reviews the remarkable benefits of check dams on the land reclamation and environmental improvement on the Loess Plateau,and sediment reduction entering the Yellow River.However,the flood incidents on check dams have been frequently reported for the past decades,which has attracted more attention in the context of climate change and extreme rainfall events recently.Advances in the flood migration techniques achieved by the research group led by the first author have been highlighted to migrate the breach risk of check dams due to floods.The“family tree method”has been proposed to determine the survival status and critical rainfall threshold of each check dam in the complicated dam system.An updated dam breach flood evaluation framework and the corresponding numerical algorithm(i.e.,DB-IWHR)have been developed.Moreover,innovative types of water-release facilities for check dams,including geobag stepped spillway and prestressed concrete cylinder pipe in the underlying conduit,have been proposed and developed.Finally,the perspectives concerning the check dam construction on the Loess Plateau have been put forward.展开更多
This paper presents a project aimed at developing a trilingual visual dictionary for aircraft maintenance professionals and students.The project addresses the growing demand for accurate communication and technical te...This paper presents a project aimed at developing a trilingual visual dictionary for aircraft maintenance professionals and students.The project addresses the growing demand for accurate communication and technical terminology in the aviation industry,particularly in Brazil and China.The study employs a corpus-driven approach,analyzing a large corpus of aircraft maintenance manuals to extract key technical terms and their collocates.Using specialized subcorpora and a comparative analysis,this paper demonstrates challenges and solutions into the identification of high-frequency keywords and explores their contextual use in aviation documentation,emphasizing the need for clear and accurate technical communication.By incorporating these findings into a trilingual visual dictionary,the project aims to enhance the understanding and usage of aviation terminology.展开更多
Floor heave is a common water-induced issue of loess tunnels.However,the mechanism of tunnel floor heave induced by repeated rainfall or irrigation remains poorly understood.This study analyzes moisture variation at t...Floor heave is a common water-induced issue of loess tunnels.However,the mechanism of tunnel floor heave induced by repeated rainfall or irrigation remains poorly understood.This study analyzes moisture variation at the tunnel base and invert deformation through a 15-year survey of an operational loess tunnel.An improved Green-Ampt model was developed to capture the effects of interannual repeated infiltration on water content,permeability,and matric suction at the tunnel base.The model was validated using soil column infiltration tests.The calculated wetting front depth was incorporated into the tunnel numerical simulation to analyze the development of floor heave and assess its several influencing factors.Results show the base average water content at the tunnel base increases exponentially with operational years.After 15 years,over 50%of the monitored sections reach saturation,leading to significant invert uplift.Based on the plastic limit,saturation water content,and liquid limit of loess,floor heave is categorized into four levels with deformation thresholds at 10,25,and 50 mm.The modified Green-Ampt model is suitable for repeated infiltration conditions and offers practical guidance.Neglecting hydraulic deterioration due to repeated infiltration may lead to significant prediction errors.Numerical simulations reveal that the inverted arch uplift height,width,and height-to-width ratio increase linearly with the rise in the number of infiltration events.The uplift deformation follows Gaussian distribution in both cross and longitudinal sections,forming aΛ-shaped floor heave.The influence of infiltration duration,water content,horizontal infiltration,asymmetric infiltration,burial depth,and the number of infiltration events enhanced successively on floor heave.This model facilitates the prediction of floor heave under dynamic hydrological conditions during long-term tunnel operation.展开更多
In this study,compacted loess samples with varying compaction water content but identical dry density were prepared to investigate the evolution of their hydraulic conductivity and compression behavior.Additionally,en...In this study,compacted loess samples with varying compaction water content but identical dry density were prepared to investigate the evolution of their hydraulic conductivity and compression behavior.Additionally,environmental scanning electron microscopy(ESEM)and nuclear magnetic resonance(NMR)analyses were conducted to gain microstructural insights into loess behavior at the laboratory scale.The results indicate that the maximum saturated hydraulic conductivity is observed at the lowest compaction water content,particularly in the early stage of permeability tests.In particular,for loess compacted at water contents below the optimum(as determined by the modified Proctor compaction test),the hydraulic conductivity decreases throughout the permeability tests.Conversely,when the water content exceeds the optimum level,the hydraulic conductivity shows an increasing trend.In terms of compression behavior,when the as-compacted samples are loaded in oedometer conditions,an increase in material compressibility is observed with increasing compaction water content.Again,a different phenomenological behavior was observed when the compaction water content exceeded the optimum,i.e.an abrupt increase in loess compressibility.ESEM tests provide microstructural confirmation of this evidence,as the surface morphology of the compacted loess changes significantly with increasing compaction water content.The microstructural evolution was also quantified in terms of area ratio using image processing software.Finally,NMR was used to quantify the intra-and inter-aggregate water at different compaction water contents,once again highlighting a threshold for the presence or absence of inter-aggregate water similar to the optimum water content.展开更多
Although Vegetation Restoration Programs(VRPs)on the Loess Plateau,China,have significantly improved the region’s ecological condition,their impact on the local economy and agriculture remain unclear.Here we used the...Although Vegetation Restoration Programs(VRPs)on the Loess Plateau,China,have significantly improved the region’s ecological condition,their impact on the local economy and agriculture remain unclear.Here we used the difference-in-differences analysis to quantify the effects of the VRPs on population,economic,and agricultural aspects.Results suggest that the implementation of the VRPs increased mean county-based Gross Domestic Product by 148%and per capita grain production by 30%,but decreased rural labor resources by 11%.VRPs promoted the transfer of population to the secondary industry and increased the income of local farmers.We predict that grain production will likely start to decline when the restoration area exceeds approximately 55%of the total county area in the future.Our study suggests that while VRPs on the Loess Plateau are economically sustainable,their expansion beyond a certain threshold could jeopardize agriculture.展开更多
Loess landforms in the Loess Plateau are typical landforms in arid and semiarid areas and have a significant impact on the environment and soil erosion.Quantitative analyses on loess landform have been employed from v...Loess landforms in the Loess Plateau are typical landforms in arid and semiarid areas and have a significant impact on the environment and soil erosion.Quantitative analyses on loess landform have been employed from various perspectives.Peak intervisibility can provide the potential topographic information implied in the visual connectivity of peaks,however,its application in loess landform analysis remains unexplored.In this study,the interwoven sightlines among peaks,representing peak intervisibility,were extracted from the digital elevation model and simulated into a peak intervisibility network(PIN).Nine indices were proposed to quantify the PIN.Through a case study in Northern Shaanxi,China,three tasks were conducted,including,landform interpretation,spatial pattern mining,and landform classification.The main findings are as follows:(1)PIN responds to terrain morphology and is beneficial for loess landform interpretation.(2)The spatial patterns of PIN indices are heterogeneous and strongly coupled with the terrain morphologies,showing anisotropy and autocorrelation in spatial variations.(3)Using the light gradient boost machine classifier,the PIN index-based classification reaches a mean accuracy of 86.09%,an overall accuracy of 86%and a kappa coefficient of 0.84.These findings shed light on the applicability of PIN in loess landform analysis.Peak intervisibility not only enriches the theories and methodologies of relation-based digital terrain analysis,but also enhances our comprehension of loess landform genesis,morphology,distribution,and evolution.展开更多
Understanding the local ecological security status and its underlying drivers can be used as an effective reference for balancing ecosystem development with societal needs. This study assesses the ecological security ...Understanding the local ecological security status and its underlying drivers can be used as an effective reference for balancing ecosystem development with societal needs. This study assesses the ecological security of the Loess Plateau(LP) by integrating ecosystem health and ecosystem services, explores the varying impacts of ecosystem structure, quality, and services on ecological security index(ESI), and identifies the key driving factors of ESI using the Geodetector model. The results show that:(1) the average ESI indicates a relatively safe ecological status in LP with a significant increase in ESI observed in 50.21% of the region, largely due to the ecological restoration programs.(2) Natural factors predominantly influence ESI, although human factors play a significant role in the earthy-rocky mountain region and plateau wind-sand region.(3) The interactions between driving factors have a much greater impact on ESI than any single factor, with the interactions between precipitation and human factors being the most influential combination. This study provides a novel perspective on assessing ecological security in LP. We recommend that future ecological restoration efforts should consider the varying roles of ecosystem structure, quality, and services in ESI while tailoring strategies to the primary driving factors based on local conditions.展开更多
基金supported by grants from the Research Grant Council of the Hong Kong Special Administra-tive Region,China(Project Nos.HKU 17207518 and R5037-18).
文摘This paper uses a complete washing and sieving method and accurately determines the clay mass contents in the loess deposits at the eight regions of Xianyang,Ili,Xi'an,Yan'an,Lvliang,Linfen,Xining,and Lanzhou in China.The method uses nylon cloth sieves with apertures from 0.0008 mm to 0.048 mm and standard steel sieves with apertures from 0.063 mm to 28 mm.It uses a rotary vibration machine to wash and sieve the loess into many clay,silt,sand,and gravel subgroups.The masses of the separated materials construct the complete mass-based particle size distribution(PSD)curves for the tested loesses.The results show that the Xianyang,Ili,Xi'an,Yan'an,Lvliang,Linfen,Xining,and Lanzhou loesses contain 65.28%,56.73%,56.76%,38.7%,31.78%,30.55%,30.1%,and 26.29%clay in mass.These clay contents are 1.3-14.9 times higher than the clay contents from the past publications for the eight types of loess.On the other hand,the plasticity data in past publications show that loess belongs to the clay type of soil.The clay contents in the publications are underestimated,which is caused by the inseparability of fine soils(or clay and silt mixture)from the existing PSD test methods.Macro-photographs,micro-photographs and SEM photographs present the separated materials of individual clay,silt,sand,and gravel particles.Particle sizes measured from the SEM photographs confirm their particle sizes within their size limits.The clay particles exhibit strong internal cohesion,while the silt,sand,and gravel particles are individual and non-cohesive.Atterberg limits test results further demonstrate the clay particles'high plasticity features and the silt particles'non-plasticity features.
基金supported by the National Key Research and Development Program of China(Grants No.2024YFF0810500 and 2022YFD1900802)the National Natural Scientific Foundations of China(Grants No.41991232,42301016 and 42571034)the Hainan Provincial Natural Science Foundation of China(Grant No.424QN354).
文摘Accurate water budget closure is critical for sustainable water resource management facing increased pressures from climate change and human activities.Although error reduction methods for individual water balance components have advanced,persistent biases remain due to the independent development of datasets,impacting basin scale water budget balance.In this research,we analyzed the mathematical origin of the bias between water budget components and developed a new basin-scale water balance calibration method that redistributes errors across components while enforcing water balance constraints.Validation confirms systematic improvements,with reduced RMSE(Precipitation:-2.29 mm/month;ET:-1.34 mm/month)and increased R2 against in situ observations.Applied to the Jinghe River Basin(2000−2019),the calibrated data reveal declining precipitation(-1.70 mm/year)and evapotranspiration(-1.84 mm/year)alongside slightly increasing runoff(0.20 mm/year in basin depth),signaling a drying trend.Land cover changes—marked by cropland loss(-3,497 km^(2))and forest(+720 km^(2))and grassland(+2,776 km^(2))expansion—reflect improved water consumption requirements by ecosystem,raising concerns for water retention and ecosystem stability.The method is particularly effective for ungauged basins with sparse ground data and underscores the need for integrated land-water management to enhance long-term resilience.
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 National Natural Science Foundation of China(Grant No.42372307)the Natural Science Basic Research Program of Shaanxi Province(Grant No.2020JC-07)the SCEGC-XJTU Joint Research Center for Future City Construction and Management Innovation,Shaanxi Provincial Land Engineering Construction Group,and Xi’an Jiaotong University(Grant No.20221220).
文摘Water infiltration in loess is one of the most significant processes that can lead to geological disasters on the Loess Plateau in China.However,the spatiotemporal characteristics of infiltration in intact loess,particularly the heterogeneity of three-dimensional(3D)seepage and its relationship with soil properties,remain poorly understood.This study conducted field infiltration tests on a 3 m×3 m loess column,instrumented with 48 moisture sensors to monitor 3D seepage and infiltration rates.Both horizontal and vertical infiltration behaviors were analyzed,alongside a detailed characterization of soil physical properties.The results demonstrated that the water infiltration process was significantly heterogeneous in intact loess,with wetting front velocities varying considerably across profiles and depths,despite relatively uniform physical properties.The infiltration process also exhibited pronounced anisotropy,with vertical wetting front velocities at least 10 times higher than those of the horizontal velocities.The in situ tests indicated that the physical properties were not the primary factors influencing infiltration.However,the microfeatures that facilitated the formation of preferential pathways exerted the most significant influence on the water infiltration process in thick unsaturated loess.Additionally,prior infiltration events negatively impacted subsequent infiltration in thick unsaturated loess.These findings enhance the understanding of loess infiltration dynamics,providing insights into unsaturated flow processes and their implications for geological stability in loess regions.
文摘While the Ordos Basin is recognized for its substantial hydrocarbon exploration prospects,its rugged loess tableland terrain has rendered seismic exploration exceptionally challenging[1-3].Persistent obstacles such as complex 3D survey planning,low signal-tonoise ratio raw data,inadequate near-surface velocity modeling,and imaging inaccuracy have long hindered the advancement of seismic exploration across this region.Through a problem-solving approach rooted in geological target analysis,this research systematically investigates the behavioral patterns of nodal seismometer-based high-density seismic acquisition in loess plateau.Tailored advancements in waveform enhancement and depth velocity modelling methodologies have been engineered.Field validations confirm that the optimized workflow demonstrates marked improvements in amplitude preservation and imaging resolution,offering novel insights for future reservoir characterization endeavors.
基金supported by the National Natural Science Foundation of China(Grant No.52379097)the National Natural Science Foundation of China(No.52509138)+2 种基金the Water Conservancy Science and Technology Project of Jiangxi Province(Grant No.202426ZDKT27)Chongqing Natural Science Foundation Doctoral Program(CSTB2025NSCQ-BSX0020)the Research and Innovation Program for Graduate Students of Chongqing Municipality(Grant No.CYB23251).
文摘Quantifying spatial heterogeneity in soil water retention properties(SWRP)is crucial for enhancing the accuracy of hydrogeological simulations.However,studies on the spatial heterogeneity of SWRP in the Chinese Loess Plateau(CLP)remain scarce,especially at the vertical scale.We conducted laboratory tests on undisturbed loess cores collected from boreholes in CLP to analyze soil physical parameters(SPPs)and SWRP.Measured soil water characteristic curves(SWCCs)were fitted to the Brooks-Corey(BC),Fredlund-Xing(FX),and van Genuchten(vG)models.It was revealed that the FX and vG models outperformed the BC model.The geostatistical analysis identified the Gaussian model as optimal for describing the semivariograms of both SPPs and SWCC fitting parameters(FPs).Strikingly,over 90%of these parameters exhibited strong vertical spatial dependence,with an average autocorrelation length of 213.878 cm for SPPs and 320.678 cm for FPs.Moreover,SWRP was found to be significantly influenced by both SPPs and the vertical position relative to the loess ridge slope surface.Parameters near the ridge slope surface showed significantly degraded spatial dependence.These findings provide valuable insights for parameterizing the spatial heterogeneity of soil water retention properties,which are beneficial for hydrogeological modelling in shallow CLP loess strata.
基金supported by the Earthquake Science and Technology Spark Plan Project(No.XH23041C)The Natural Science Foundation of Gansu Province(No.22JR11RA090)Gansu Lanzhou Geophysics National Observation and Research Station(No.2021Y14).
文摘The widely distributed loess deposits in the Yellow River Basin exhibit unique engineering geological characteristics.The variations in their thickness and stratigraphic structure significantly amplify ground motion parameters,directly influencing the regional seismic hazard risk level.This study methodically conducted on-site studies and observations of building collapses and damages resulting from seismic amplification effects,using the Wenchuan M_(S)8.0 earthquake as a case study.Comprehensive experimental and numerical simulation studies were carried out.A large-scale shaking table test was performed,and numerical models for 14 different loess sites types were established.Various types of seismic waves were incorporated into these models for systematic numerical simulation calculations.The research reveals the mechanisms by which loess deposit thickness and stratigraphic structure in the Yellow River Basin affect seismic ground motion amplification.The results indicate that as the epicentral distance increases,the peak ground motion shows a marked attenuation trend,with the horizontal component attenuating substantially faster than the vertical component.As the overlying loess layer thickness increases from 50 to 100 m,the seismic intensity may escalate by 3−4 degrees,and the peak acceleration may amplify by 1.5−2.2 times.With the augmentation of loess deposit thickness and the proliferation of soil layers,both the peak acceleration response spectrum and the characteristic period demonstrate an upward tendency,exhibiting slight fluctuations contingent upon the seismic wave type.
基金supported by a project entitled Loess Plateau Region-Watershed-Slope Geological Hazard Multi-Scale Collaborative Intelligent Early Warning System of the National Key R&D Program of China(2022YFC3003404)a project of the Shaanxi Youth Science and Technology Star(2021KJXX-87)public welfare geological survey projects of Shaanxi Institute of Geologic Survey(20180301,201918,202103,and 202413)。
文摘This study developed a modeling methodology for statistical optimization-based geologic hazard susceptibility assessment,aiming to enhance the comprehensive performance and classification accuracy of the assessment models.First,the cumulative probability method revealed that a low probability(15%)of geologic hazards between any two geologic hazard points occurred outside a buffer zone with a radius of 2297 m(i.e.,the distance threshold).The training dataset was established,consisting of negative samples(non-hazard points)randomly generated based on the distance threshold,positive samples(i.e.,historical hazards),and 13 conditioning factors.Then,models were built using five machine learning algorithms,namely random forest(RF),gradient boosting decision tree(GBDT),naive Bayes(NB),logistic regression(LR),and support vector machine(SVM).The comprehensive performance of the models was assessed using the area under the receiver operating characteristic curve(AUC)and overall accuracy(OA)as indicators,revealing that RF exhibited the best performance,with OA and AUC values of 2.7127 and 0.981,respectively.Furthermore,the machine learning models constructed by considering the distance threshold outperformed those built using the unoptimized dataset.The characteristic factors were ranked using the mutual information method,with their scores decreasing in the order of rainfall(0.1616),altitude(0.06),normalized difference vegetation index(NDVI;0.04),and distance from roads(0.03).Finally,the geologic hazard susceptibility classification was assessed using the natural breaks method combined with a clustering algorithm.The results indicate that the clustering algorithm exhibited higher classification accuracy than the natural breaks method.The findings of this study demonstrate that the proposed model optimization scheme can provide a scientific basis for the prevention and control of geologic hazards.
基金financially supported by the Second Tibetan Plateau Scientific Expedition and Research Program of China(Grant No.2019QZKK0905)the Youth Fund of Shanxi Provincial Science and Technology Department of China(GrantNo.202103021223200)the Natural Science Foundation of Shaanxi Province,China(Grant No.2024JC-YBMS-314).
文摘The shear behavior of intact loess is intricately linked to the spatiotemporal evolution of its mesoscopic characteristics.Understanding this relationship is crucial for comprehending and preventing loess landslides.To systematically investigate this connection,our study conducted triaxial shear tests on both Malan loess and Lishi loess,encompassing variations in confining pressures.Additionally,nondestructive,real-time CT observations were employed to track the dynamic evolution of loess mesostructures.The experimental findings illuminate significant insights.The Malan loess exhibits strain hardening during shearing,with the degree of hardening exhibiting an increase in tandem with rising confining pressure.Conversely,the Lishi loess manifests a transition from strain softening to strain hardening as confining pressure increases.Under elevated confining pressure,the specimen undergoes structural damage while concurrently forming a denser configuration through particle friction and rearrangement,leading to strain hardening and volume reduction.In contrast,the central portion of the specimen exhibits heightened sensitivity to deformation under low confining pressures.Gradual crack expansion,emanating from the center and progressing towards the ends,results in progressive specimen destruction and a concomitant reduction in stress.On a macroscopic level,the specimen undergoes expansion at its center while contracting at its ends.The findings of this study unveil the intricate mechanisms governing loess deformation in the presence of varying confining pressures,thereby contributing significantly to our understanding of loess landslide formation and providing a robust theoretical framework for preventive measures.
文摘In recent years,to better address soil erosion,the Loess Plateau area has seen a surge in the construction of warping dam projects.Warping dams have strong functions in soil and water conservation as well as warping for farmland creation,serving as a key support for ecological restoration and economic development in the Loess Plateau area in the new era.However,in light of practical conditions,there are many problems in their construction process,which have affected their actual operation quality.In this regard,while expounding on the value and significance of warping dam project construction in the Loess Plateau area,this paper discusses the existing problems and effective countermeasures,aiming to provide some references for relevant personnel.
基金financially supported by the National Natural Science Foundation of China(Grant No.42361002)the Fund of Ningxia Hui Autonomous Region(Grant No.2022AAC03665).
文摘Tafoni are globally developed on cliffy slopes,and many of them are favorable places for the preservation of stone historical relics.However,the characteristics and formation processes of tafoni in the Loess Plateau are yet to be understood.This paper studied the features of the tafoni on conglomerate slopes in Huoshizhai National Geopark of Ningxia Hui Autonomous Region and discussed its formation processes by field investigation and morphometry,insitu relative humidity(RH)measurement,salt chemistry and X-ray fluorescence spectrometer(XRF)experiments of 24 samples.The bedrock of the tafoni is dominated by reddish fluvial conglomerates of the Lower Cretaceous Heshangpu Formation with abundant chemically unstable components including feldspars,lithic fragments,and calcite cements.The RH values vary from 5%to 100%,but the backwalls of the tafoni have higher RH values than outer surfaces.The more moisture on the backwalls is possibly generated by water influx from the rock interior,resulting in more salt precipitation on the backwalls.As a result,the backwalls have been subject to predominant salt weathering.The dominant salts involved in salt weathering are probably derived from the dissolution of the salt interbeds in the basin,although the chemical dissolution of the unstable components such as feldspars,lithic fragments,and calcite cements might have produced small amounts of salts.The salt types dominantly include nitrates,sulfates,and halite.In the progression of tafoni,the moisture maintenance on the backwalls gives rise to the accretion of salts,which in turn enhance the weathering rates of the backwalls.As a result,the volumes of the tafoni have become enlarged owing to inward growth and coalescence of adjacent smaller ones.
文摘Although time-dependent deformation of geomaterials underpins slope-failure prediction models,the influence of strain rate on shearing strength and deformation behavior of loess remains unclear.The consolidated undrained(CU)and drained(CD)triaxial testing elucidated the impact of strain rate(0.005–0.3 mm/min)on strength envelopes,deformation moduli,pore pressures,and dilatancy characteristics of unsaturated and quasi-saturated loess.Under drained conditions with a controlled matric suction of 50 kPa,increasing strain rates from 0.005 mm/min to 0.011 mm/min induced decreases in failure deviatoric stress(qf),initial deformation modulus(Ei),and cohesion(c),while friction angles remained unaffected.Specimens displayed initial contractive volumetric strains transitioning to dilation across varying confining pressures.Higher rates diminished contractive volumetric strains and drainage volumes,indicating reduced densification and strength in the shear zone.Under undrained conditions,both unsaturated and quasi-saturated(pore pressure coefficient B=0.75)loess exhibited deteriorating mechanical properties with increasing rates from 0.03 mm/min to 0.3 mm/min.For unsaturated loess,reduced contractive volumetric strains at higher rates manifested relatively looser structures in the pre-peak stress phase.The strength decrement in quasi-saturated loess arose from elevated excess porewater pressures diminishing effective stresses.Negative porewater pressures emerged in quasi-saturated loess at lower confining pressures and strain rates.Compared to previous studies,the qf and Ei exhibited rate sensitivity below threshold values before attaining minima with marginal subsequent influence.The underlying mechanism mirrors the transition from creep to accelerated deformation phase of landslides.
基金supported by the National Key R&D Program of China(Grant No.2023YFC3008404)the National Key Research and Development Program,China(Grant No.2017YFD0800501)the National Natural Science Foundation of China(No.41790443).
文摘During extensive gully land consolidation projects on China's Loess Plateau,many loess-bedrock fill slopes were formed,which frequently experience shallow landslides induced by rainfall.However,studies on loess-bedrock slope failure triggered by continuous heavy rainfall are limited,and the role of the soilerock interface between the original bedrock slope and fill slope in the hydrological and failure process of the slope remains unclear.In this study,we conducted a continuous rainfall model test on a loess-bedrock fill slope.During the test,the responses of volume water content,pore pressure,micro deformation,and movement of the infiltration front were observed.The hydrological process and failure mechanism were then analysed.The findings suggest that the soilerock interface is a predominant infiltration surface within the slope.Rainfall infiltration rates at the interface reach 1.24-2.80 times those of the fill slope,with peak interfacial pore water pressure exceeding that of the loess fill.Furthermore,the infiltration front moves rapidly along the interface toward the bottom of the slope,reducing interfacial cohesion between bedrock and loess.The slope failure modes are summarised into three phases:local failure→flow slide and crack penetration→multistage block retrogressive slides.The cracks generated at the slope surface serve as key determinants of the geometry and scale of shallow landslides.Therefore,we recommend targeted engineering interventions to mitigate the instability and erosion of loessebedrock fill slopes.
基金National Natural Science Foundation of China,Grant/Award Number:42330719National Natural Science Foundation of China,Grant/Award Number:U2443228+1 种基金Power Construction Corporation of China,Grant/Award Number:DJ-ZDXM-2021-51China Institute of Water Resources and Hydropower Research,Grant/Award Number:GE121003A0042022。
文摘Check dams are widely constructed on China's Loess Plateau,which had a total number of 58,776 by the end of 2019.Great achievements in check dam construction have been gained regarding the economic and environmental impacts.This study reviews the remarkable benefits of check dams on the land reclamation and environmental improvement on the Loess Plateau,and sediment reduction entering the Yellow River.However,the flood incidents on check dams have been frequently reported for the past decades,which has attracted more attention in the context of climate change and extreme rainfall events recently.Advances in the flood migration techniques achieved by the research group led by the first author have been highlighted to migrate the breach risk of check dams due to floods.The“family tree method”has been proposed to determine the survival status and critical rainfall threshold of each check dam in the complicated dam system.An updated dam breach flood evaluation framework and the corresponding numerical algorithm(i.e.,DB-IWHR)have been developed.Moreover,innovative types of water-release facilities for check dams,including geobag stepped spillway and prestressed concrete cylinder pipe in the underlying conduit,have been proposed and developed.Finally,the perspectives concerning the check dam construction on the Loess Plateau have been put forward.
文摘This paper presents a project aimed at developing a trilingual visual dictionary for aircraft maintenance professionals and students.The project addresses the growing demand for accurate communication and technical terminology in the aviation industry,particularly in Brazil and China.The study employs a corpus-driven approach,analyzing a large corpus of aircraft maintenance manuals to extract key technical terms and their collocates.Using specialized subcorpora and a comparative analysis,this paper demonstrates challenges and solutions into the identification of high-frequency keywords and explores their contextual use in aviation documentation,emphasizing the need for clear and accurate technical communication.By incorporating these findings into a trilingual visual dictionary,the project aims to enhance the understanding and usage of aviation terminology.
基金financially supported by the National Natural Science Foundation of China(grant numbers:42077265,41927806)the Science and Technology Project of Gansu Provincial Department of Transportation(grant number:2023-12)the Gansu Science and Technology Department of Key Projects(grant number:21YF5FA002)。
文摘Floor heave is a common water-induced issue of loess tunnels.However,the mechanism of tunnel floor heave induced by repeated rainfall or irrigation remains poorly understood.This study analyzes moisture variation at the tunnel base and invert deformation through a 15-year survey of an operational loess tunnel.An improved Green-Ampt model was developed to capture the effects of interannual repeated infiltration on water content,permeability,and matric suction at the tunnel base.The model was validated using soil column infiltration tests.The calculated wetting front depth was incorporated into the tunnel numerical simulation to analyze the development of floor heave and assess its several influencing factors.Results show the base average water content at the tunnel base increases exponentially with operational years.After 15 years,over 50%of the monitored sections reach saturation,leading to significant invert uplift.Based on the plastic limit,saturation water content,and liquid limit of loess,floor heave is categorized into four levels with deformation thresholds at 10,25,and 50 mm.The modified Green-Ampt model is suitable for repeated infiltration conditions and offers practical guidance.Neglecting hydraulic deterioration due to repeated infiltration may lead to significant prediction errors.Numerical simulations reveal that the inverted arch uplift height,width,and height-to-width ratio increase linearly with the rise in the number of infiltration events.The uplift deformation follows Gaussian distribution in both cross and longitudinal sections,forming aΛ-shaped floor heave.The influence of infiltration duration,water content,horizontal infiltration,asymmetric infiltration,burial depth,and the number of infiltration events enhanced successively on floor heave.This model facilitates the prediction of floor heave under dynamic hydrological conditions during long-term tunnel operation.
基金the China Postdoctoral Science Foundation(Grant No.2024MD753992)Shaanxi Geotechnical Mechanics and Engineering Young Talent Support Program Project(Grant No.YESS2024005)the National Natural Science Foundation of China(Grant No.41931285).
文摘In this study,compacted loess samples with varying compaction water content but identical dry density were prepared to investigate the evolution of their hydraulic conductivity and compression behavior.Additionally,environmental scanning electron microscopy(ESEM)and nuclear magnetic resonance(NMR)analyses were conducted to gain microstructural insights into loess behavior at the laboratory scale.The results indicate that the maximum saturated hydraulic conductivity is observed at the lowest compaction water content,particularly in the early stage of permeability tests.In particular,for loess compacted at water contents below the optimum(as determined by the modified Proctor compaction test),the hydraulic conductivity decreases throughout the permeability tests.Conversely,when the water content exceeds the optimum level,the hydraulic conductivity shows an increasing trend.In terms of compression behavior,when the as-compacted samples are loaded in oedometer conditions,an increase in material compressibility is observed with increasing compaction water content.Again,a different phenomenological behavior was observed when the compaction water content exceeded the optimum,i.e.an abrupt increase in loess compressibility.ESEM tests provide microstructural confirmation of this evidence,as the surface morphology of the compacted loess changes significantly with increasing compaction water content.The microstructural evolution was also quantified in terms of area ratio using image processing software.Finally,NMR was used to quantify the intra-and inter-aggregate water at different compaction water contents,once again highlighting a threshold for the presence or absence of inter-aggregate water similar to the optimum water content.
基金financially supported by the National Natural Science Foundation of China(Grants No.42325101,42401060,42301052)the Science and Technology Development Plan Project of Jilin Province,China(Grant No.20250601010RC)+3 种基金the Postdoctoral Fellowship Program of CPSF(Grant No.GZB20230127)the Fundamental Research Funds for the Central Universities(Grant No.2412024QD025)the China Postdoctoral Science Foundation(Grant No.2024M760407)the Youth Growth Science and Technology Program of Jilin Province(Grant No.20230508119RC).
文摘Although Vegetation Restoration Programs(VRPs)on the Loess Plateau,China,have significantly improved the region’s ecological condition,their impact on the local economy and agriculture remain unclear.Here we used the difference-in-differences analysis to quantify the effects of the VRPs on population,economic,and agricultural aspects.Results suggest that the implementation of the VRPs increased mean county-based Gross Domestic Product by 148%and per capita grain production by 30%,but decreased rural labor resources by 11%.VRPs promoted the transfer of population to the secondary industry and increased the income of local farmers.We predict that grain production will likely start to decline when the restoration area exceeds approximately 55%of the total county area in the future.Our study suggests that while VRPs on the Loess Plateau are economically sustainable,their expansion beyond a certain threshold could jeopardize agriculture.
基金supported by the National Natural Science Foundation of China(Grant No.41771423)the Natural Science Foundation of Fujian Province(Grant No.2023J01421).
文摘Loess landforms in the Loess Plateau are typical landforms in arid and semiarid areas and have a significant impact on the environment and soil erosion.Quantitative analyses on loess landform have been employed from various perspectives.Peak intervisibility can provide the potential topographic information implied in the visual connectivity of peaks,however,its application in loess landform analysis remains unexplored.In this study,the interwoven sightlines among peaks,representing peak intervisibility,were extracted from the digital elevation model and simulated into a peak intervisibility network(PIN).Nine indices were proposed to quantify the PIN.Through a case study in Northern Shaanxi,China,three tasks were conducted,including,landform interpretation,spatial pattern mining,and landform classification.The main findings are as follows:(1)PIN responds to terrain morphology and is beneficial for loess landform interpretation.(2)The spatial patterns of PIN indices are heterogeneous and strongly coupled with the terrain morphologies,showing anisotropy and autocorrelation in spatial variations.(3)Using the light gradient boost machine classifier,the PIN index-based classification reaches a mean accuracy of 86.09%,an overall accuracy of 86%and a kappa coefficient of 0.84.These findings shed light on the applicability of PIN in loess landform analysis.Peak intervisibility not only enriches the theories and methodologies of relation-based digital terrain analysis,but also enhances our comprehension of loess landform genesis,morphology,distribution,and evolution.
基金National Natural Science Foundation of China,No.42371103Natural Science Basic Research Plan in Shaanxi Province of China,No.2023-JC-YB-229。
文摘Understanding the local ecological security status and its underlying drivers can be used as an effective reference for balancing ecosystem development with societal needs. This study assesses the ecological security of the Loess Plateau(LP) by integrating ecosystem health and ecosystem services, explores the varying impacts of ecosystem structure, quality, and services on ecological security index(ESI), and identifies the key driving factors of ESI using the Geodetector model. The results show that:(1) the average ESI indicates a relatively safe ecological status in LP with a significant increase in ESI observed in 50.21% of the region, largely due to the ecological restoration programs.(2) Natural factors predominantly influence ESI, although human factors play a significant role in the earthy-rocky mountain region and plateau wind-sand region.(3) The interactions between driving factors have a much greater impact on ESI than any single factor, with the interactions between precipitation and human factors being the most influential combination. This study provides a novel perspective on assessing ecological security in LP. We recommend that future ecological restoration efforts should consider the varying roles of ecosystem structure, quality, and services in ESI while tailoring strategies to the primary driving factors based on local conditions.
