Water transport at the root/soil interface of 1 year old Pinus sylvestris Linn. var. sylvestriformis (Takenouchi) Cheng et C. D. Chu seedlings under CO 2 doubling was studied by measuring soil electric conductanc...Water transport at the root/soil interface of 1 year old Pinus sylvestris Linn. var. sylvestriformis (Takenouchi) Cheng et C. D. Chu seedlings under CO 2 doubling was studied by measuring soil electric conductance to survey soil water profiles and comparing it with root distribution surveyed by soil coring and root harvesting in Changbai Mountain in 1999. The results were: (1) The profiles of soil water content were adjusted by root activity. The water content of the soil layer with abundant roots was higher. (2) When CO 2 concentration was doubled, water transport was more active at the root/soil interface and the roots were distributed into deeper layer. It was shown in this work that the method of measuring electric conductance is an inexpensive, non_destructive and relatively sensitive way for underground water transport process.展开更多
Soil in a cold region is subject to frequent freezing and thawing cycles.Soil frozen for a prolonged period may cause adverse freeze damage to the plants due to cell dehydration or root cell rupture.It is important to...Soil in a cold region is subject to frequent freezing and thawing cycles.Soil frozen for a prolonged period may cause adverse freeze damage to the plants due to cell dehydration or root cell rupture.It is important to understand the detailed heat transfer behaviors of the freezing and thawing processes to prevent freeze damage,and to devise proper mitigation measures for effective pot planting in cold regions.A theoretical model was developed to analyze the transient moving phase-change interface heat transfer in the freezing and thawing of porous potting soil.The theoretical derivation is based on the assumption that the soil freezes completely at a single temperature.Microscopic poromechanic effects on heat transfer behavior were ignored.The spatial domain of the problem was simplified to a 1D spherical coordinate system with variation in the radial direction.Green's function was applied to solve for the time-dependent body temperature.Experiments were conducted for validation of the theoretical model.Reasonable agreement between the theoretical predictions and experimental measurements was obtained.The theoretical model developed can be easily used to determine the sensitivity of various parameters in the freezing/thawing processes,e.g.,thermal properties of soil,ambient temperature,and planting pot size.展开更多
Blasting has been widely used in mining and construction industries for rock breaking.This paper presents the results of a series of field tests conducted to investigate the ground wave propagation through mixed geolo...Blasting has been widely used in mining and construction industries for rock breaking.This paper presents the results of a series of field tests conducted to investigate the ground wave propagation through mixed geological media.The tests were conducted at a site in the northwestern part of Singapore composed of residual soil and granitic rock.The field test aims to provide measurement data to better understand the stress wave propagation in soil/rock and along their interface.Triaxial accelerometers were used for the free field vibration monitoring.The measured results are presented and discussed,and empirical formulae for predicting peak particle velocity (PPV) attenuation along the ground surface and in soil/rock were derived from the measured data.Also,the ground vibration attenuation across the soil-rock interface was carefully examined,and it was found that the PPV of ground vibration was decreased by 37.2% when it travels from rock to soil in the vertical direction.展开更多
Roots play an important role in stabilizing and strengthening soil. This article aims to study the mechanical properties of the interface between soil and roots with branches, using the pullout test method in the labo...Roots play an important role in stabilizing and strengthening soil. This article aims to study the mechanical properties of the interface between soil and roots with branches, using the pullout test method in the laboratory. The mechanical properties of the soil-root with branches interface is determined through the pullout-force and root-slippage curve （F-S curve）. The results of investigating 24 Pinus tabulaeformis single roots and 55 P. tabulaeformis roots with branches demonstrated three kinds of pullout test failures： breakage failure on branching root, breakage failure on branching node, and pullout failure. The branch angle had a remarkable effect on the failure mode of the roots with branches： the maximum pullout force increased with the sum of the branch diameters and the branch angle. The peak slippage and the initial force had a positive correlation with the sum of the branch diameter. The sig- nificance test of correlation between branch angle and the initial force, however, showed they had no correlation. Branch angle and branch root diameter affect the anchorage properties between root system and soil. Therefore, it is important to investigate the anchorage mechanics of the roots with branches to understand the mechanism of root reinforcement and anchorage.展开更多
Toxicity-data of two carbamate insecticides, carbaryl and carbofuran, and three fungicides, ziram, zineb and mancozeb with rice-field N2-fixing cyanobacterium Cylindrospermum sp., obtained by in vitro growth and at so...Toxicity-data of two carbamate insecticides, carbaryl and carbofuran, and three fungicides, ziram, zineb and mancozeb with rice-field N2-fixing cyanobacterium Cylindrospermum sp., obtained by in vitro growth and at soil-water interface, were analyzed by the probit method. Growth enhancing concentration, no-observed effective concentration, minimum inhibitory concentration, the highest permissive concentration and lethal concentration100 （LCloo） were determined experimentally. The LC^o values of carbaryl, carbofuran, ziram, zineb and mancozeb in N2-fixing liquid medium were 56.2, 588.8, 0.07, 4.2 and 3.4 IJg/mL, respectively, whereas the corresponding LCloo values were 100.0, 1500.0, 0.17, 25.0 and 9.0 IJg/mL, respectively. The LC50 values of these pesticides in succession in N2-fixing agar medium were 44.7, 239.9, 0.07, 1.8 and 2.3 IJg/mL, respectively, whereas the corresponding LC100 values were 100.0, 600.0, 0.17, 10.0 and 7.0 IJg/mL, respectively. Similar results with nitrate supplemented liquid and agar media indicated that nitrate supplementation had toxicity reducing effect. The LCso and LC^oo values of toxicity in the N2-fixing liquid medium at soil-water interface were 91.2 and 200.0 IJg/mL for carbaryl, 2 317 and 6 000 pg/mL for carbofuran, 0.15 and 0.50 pg/mL for ziram, 16.4 and 50.0 pg/mL for zineb, and 7.2 and 25.0 pg/mL for mancozeb, respectively. Each LC^oo value at soil- water interface with a pesticide was significantly higher than its corresponding LCloo value at liquid/agar media. It can be concluded that, under the N2-fixing conditions, the cyanobacterium tolerated higher levels of each pesticide at soil-water interface.展开更多
Using newly developed dynamic shearing devices, the dynamic sheafing strength of frozen soil-conerete interface was studied experimentally. By placing concrete blocks in the lower half of the shear box and frozen soil...Using newly developed dynamic shearing devices, the dynamic sheafing strength of frozen soil-conerete interface was studied experimentally. By placing concrete blocks in the lower half of the shear box and frozen soil sample in the upper part, a series of dynamic shear tests on their interfaces were carried out. The obtained results are summarized and the main influencing factors are revealed.展开更多
Frost heave and thaw settlement in cold regions pose a significant threat to engineering construction.Optical frequency domain reflectometry(OFDR)based on Rayleigh scattering can be applied to monitor ground deformati...Frost heave and thaw settlement in cold regions pose a significant threat to engineering construction.Optical frequency domain reflectometry(OFDR)based on Rayleigh scattering can be applied to monitor ground deformation in frozen soil areas,where the interface behavior of soil-embedded fiber optic sensors governs the monitoring accuracy.In this paper,a series of pullout tests were conducted on fiber optic(FO)cables embedded in the frozen soil to investigate the cable‒soil interface behavior.An experimental study was performed on interaction effects,particularly focused on the water content of unfrozen soil,freezing duration,and differential distribution of water content in frozen soil.The highresolution axial strains of FO cables were obtained using a sensing interrogator,and were used to calculate the interface shear stress.The interfacial mechanical response was analytically modeled using the ideal elasto‒plastic and softening constitutive models.Three freezing periods,correlating with the phase change process between ice and water,were analyzed.The results shows that the freezing effect can amplify the peak shear stress at the cable-soil interface by eight times.A criterion for the interface coupling states was proposed by normalizing the pullout force‒displacement information.Additionally,the applicability of existing theoretical models was discussed by comparing the results of theoretical back‒calculations with experimental measurements.This study provides new insights into the progressive interfacial failure behavior between strain sensing cable and frozen soil,which can be used to assist the interpretation of FO monitoring results of frozen soil deformation.展开更多
Global climate change exerts profound effects on snow cover,with consequential impacts on microbial activities and the stability of soil organic carbon(SOC)within aggregates.Northern peatlands are significant carbon r...Global climate change exerts profound effects on snow cover,with consequential impacts on microbial activities and the stability of soil organic carbon(SOC)within aggregates.Northern peatlands are significant carbon reservoirs,playing a critical role in mitigating climate change.However,the effects of snow variations on microbial-mediated SOC stability within aggregates in peatlands remain inadequately understood.Here,an in-situ field experiment manipulating snow conditions(i.e.,snow removal and snow cover)was conducted to investigate how snow variations affect soil microbial community and the associated SOC stability within soil aggregates(>2,0.25-2,and<0.25 mm)in a peatland of Northeast China.The results showed that snow removal significantly increased the SOC content and stability within aggregates.Compared to the soils with snow cover,snow removal resulted in decreased soil average temperatures in the topsoil(0-30 cm depth)and subsoil(30-60 cm depth)(by 1.48 and 1.34°C,respectively)and increased freeze-thaw cycles(by 11 cycles),consequently decreasing the stability of aggregates in the topsoil and subsoil(by 23.68%and 6.85%,respectively).Furthermore,more recalcitrant carbon and enhanced SOC stability were present in microaggregates(<0.25 mm)at two soil depths.Moreover,reductions in bacterial diversity and network stability were observed in response to snow removal.Structural equation modeling analysis demonstrated that snow removal indirectly promoted(P<0.01)SOC stability by regulating carbon to nitrogen(C:N)ratio within aggregates.Overall,our study suggested that microaggregate protection and an appropriate C:N ratio enhanced carbon sequestration in response to climate change.展开更多
Net primary productivity(NPP)is the net accumulation of organic matter by vegetation through photosynthesis and serves as a key indicator for exploring vegetation responses to climate change.Considering the remote and...Net primary productivity(NPP)is the net accumulation of organic matter by vegetation through photosynthesis and serves as a key indicator for exploring vegetation responses to climate change.Considering the remote and local impacts of soil heat capacities on vegetation growth through pathways of atmospheric circulation and land–atmosphere interaction,this paper develops a statistical prediction model for NPP from April to June(AMJ)across the middle-to-high latitudes of Eurasia.The model introduces two physically meaningful predictors:the snow water equivalent(SWE)from February to March(FM)over central Europe and the FM local soil temperature(ST).The positive phase of FM SWE triggers anomalous eastward-propagating Rossby waves,leading to an anomalous low-pressure system and cooling in the middle-to-high latitudes of Eurasia.This effect persists into spring through snow feedback to the atmosphere and affects subsequent NPP changes.The ST is closely related to the AMJ temperature and precipitation.With positive ST anomalies,the AMJ temperature and precipitation exhibit an east–west dipole anomaly distribution in this region.The single-factor prediction scheme using ST as the predictor is much better than using SWE as the predictor.Independent validation results from 2009 to 2014 demonstrate that the ST scheme alone has good predictive performance for the spatial distribution and interannual variability of NPP.The predictive skills of the multi-factor prediction schemes can be improved by about 13%if the ST predictor is included.The findings confirm that local ST is a predictor that must be included for NPP prediction.展开更多
-In order to analyze the stability of pipelines on the sea bed, the friction characteristics at the pipe-soil interface were examined by means of special direct shear tests. High density polythene was used as the surf...-In order to analyze the stability of pipelines on the sea bed, the friction characteristics at the pipe-soil interface were examined by means of special direct shear tests. High density polythene was used as the surface of the pipe, which is a widely-utilized material for the outer cover of the pipe to prevent sea water corrosion. Sands of different gradings were tested. The reconstituted soft clay taken from the Bohai area was consolidated to different degrees of consolidation by the vacuum preloading technique, and tested.展开更多
The characteristics of a disturbed soil-structure interface were studied based on the variation regularities of the disturbed soil within its mining subsidence area using direct shear tests.The effects of the initial ...The characteristics of a disturbed soil-structure interface were studied based on the variation regularities of the disturbed soil within its mining subsidence area using direct shear tests.The effects of the initial moisture content on the shear strength parameters of the soil-structure interfaces were analyzed.The results indicate that the cohesion of the interface initially increased and then decreased as the initial moisture content increased.In addition,the friction angle of the interface decreased as the initial moisture content increased.A constitutive model of the disturbed soil-structure interface,a rigid-plastic model based on the initial void ratio and saturability(VSRP) model,was established based on the results.In order to validate this model,a finite element analysis of DRS-1 direct shear tests was conducted.The finite element model calculations coincided with the results of the DRS-1 direct shear tests.The proposed model also reflected the nonlinear features of the soil-structure interface.展开更多
In order to explore the spatial variability of soil moisture near the interface of high/low stands, an experiment was conducted at Luancheng Experimental Station, Chinese Academy of Sciences, Hebei, China from May to ...In order to explore the spatial variability of soil moisture near the interface of high/low stands, an experiment was conducted at Luancheng Experimental Station, Chinese Academy of Sciences, Hebei, China from May to June, 1996. By analyzing the observed soil moisture data, it shows that there exists an obvious turning point of soil moisture pattern from one side of the interface to another. The effect of drier soil closer to the interface in winter wheat field is obvious, which is mainly due to the better ventilation condition near the interface in winter wheat filed than in alfalfa field. The irrigation in large scale is one of the most important factors to control the spatial pattern of soil moisture while the small scale human disturbing activity, such as the stealing event occurred during our observation, does not change the spatial pattern of soil moisture obviously. Latent heat, calculated by Bowen ratio method based on our observed micrometeorological data, is shown larger in alfalfa than that in winter wheat both at earring stage from May 8 to 10 and mature stage from June 11 to 14. This fact, together with the larger ground temperature and a little bit larger wind velocity in lower layer, explains that the soil is drier in alfalfa than in winter wheat from May 8 to 10. While for the period from June 11 to 14, irrigation's effect changes the natural interrelationship of soil moisture with meteorology and ground temperature.展开更多
Solution of the practical problems of the ice engineering requires the data about the strength of the ice cover that depends upon its temperature. In most cases, the snow lies on the ice cover and the ice temperature ...Solution of the practical problems of the ice engineering requires the data about the strength of the ice cover that depends upon its temperature. In most cases, the snow lies on the ice cover and the ice temperature differs from the atmospheric air temperature. To reveal the correlation of the air temperature with temperature on interfaces air-snow and snow-ice, the known in the thermophysics solution of the problem of the heat transfer through the multilayer plate was applied. Derived solution connects the temperature of air and temperature on the snow-ice interface and satisfactory correlates with data of the field measurements of the temperature within snow layer and ice cover and ice thickness on the Heilongjiang （Amur） River. Results of investigation are recommended for the ice temperature evaluation in engineering practice.展开更多
The interaction between soil and marine structures like submarine pipeline/pipe pile/suction caisson is a complicated geotechnical mechanism process.In this study,the interface is discretized into multiple mesoscopic ...The interaction between soil and marine structures like submarine pipeline/pipe pile/suction caisson is a complicated geotechnical mechanism process.In this study,the interface is discretized into multiple mesoscopic contact elements that are damaged randomly throughout the shearing process due to the natural heterogeneity.The evolution equation of damage variable is developed based on the Weibull function,which is able to cover a rather wide range of distribution shapes by only two parameters,making it applicable for varying scenarios.Accordingly,a statistical damage model is established by incorporating Mohr–Coulomb strength criterion,in which the interfacial residual strength is considered whereby the strain softening behavior can be described.A concept of“semi-softening”characteristic point on shear stress–displacement curve is proposed for effectively modeling the evolution of strain softening.Finally,a series of ring shear tests of the interfaces between fine sea sand and smooth/rough steel surfaces are conducted.The predicted results using the proposed model are compared with experimental data of this study as well as some results from existing literature,indicating that the model has a good performance in modeling the progressive failure and strain softening behavior for various types of soil–structure interfaces.展开更多
The soil temperature(ST)is closely related to the surface air temperature(AT),but their coupling may be affected by other factors.In this study,significant effects of the AT on the underlying ST were found,and the tim...The soil temperature(ST)is closely related to the surface air temperature(AT),but their coupling may be affected by other factors.In this study,significant effects of the AT on the underlying ST were found,and the time taken to propagate downward to 320 cm can be up to 10 months.Besides the AT,the ST is also affected by memory effects-namely,its prior thermal conditions.At deeper depth(i.e.,320 cm),the effects of the AT from a particular season may be exceeded by the soil memory effects from the last season.At shallower layers(i.e.,<80 cm),the effects of the AT may be blocked by the snow cover,resulting in a poorly synchronous correlation between the AT and the ST.In northeastern China,this snow cover blockage mainly occurs in winter and then vanishes in the subsequent spring.Due to the thermal insulation effect of the snow cover,the winter ST at layers above 80 cm in northeastern China were found to continue to increase even during the recent global warming hiatus period.These findings may be instructive for better understanding ST variations,as well as land−atmosphere interactions.展开更多
Seasonal snow is one of the most important influences on the development and distribution of permafrost and the hydrothermal regime in surface soil. Alpine meadow, which constitutes the main land type in permafrost re...Seasonal snow is one of the most important influences on the development and distribution of permafrost and the hydrothermal regime in surface soil. Alpine meadow, which constitutes the main land type in permafrost regions of the Qinghai-Tibet Plateau, was selected to study the influence of seasonal snow on the temperature and moisture in active soil layers under different vegetation coverage. Monitoring sites for soil moisture and temperature were constructed to observe the hydrothermal processes in active soil layers under different vegetation cover with seasonal snow cover variation for three years from 2010 to 2012. Differences in soil temperature and moisture in areas of diverse vegetation coverage with varying levels of snow cover were analyzed using active soil layer water and temperature indices. The results indicated that snow cover greatly influenced the hydrothermal dynamics of the active soil layer in alpine meadows. In the snow manipulation experiment with a snow depth greater than 15 cm, the snow cover postponed both the freeze-fall and thawrise onset times of soil temperature and moisture in alpine LC(lower vegetation coverage) meadows and of soil moisture in alpine HC(higher vegetation coverage) meadows; however, the opposite response occurred for soil temperatures of alpine HC meadows,where the entire melting period was extended by advancing the thaw-rise and delaying the freeze-fall onset time of the soil temperature. Snow cover resulted in a decreased amplitude and rate of variation in soil temperature, for both alpine HC meadows and alpine LC meadows, whereas the distinct influence of snow cover on the amplitude and rate of soil moisture variation occurred at different soil layers with different vegetation coverages. Snow cover increased the soil moisture of alpine grasslands during thawing periods. The results confirmed that the annual hydrothermal dynamics of active layers in permafrost were subject to the synergistic actions of both snow cover and vegetation coverage.展开更多
The datasets of the five Land-offline Model Intercomparison Project(LMIP)experiments using the Chinese Academy of Sciences Land Surface Model(CAS-LSM)of CAS Flexible Global-Ocean-Atmosphere-Land System Model Grid-poin...The datasets of the five Land-offline Model Intercomparison Project(LMIP)experiments using the Chinese Academy of Sciences Land Surface Model(CAS-LSM)of CAS Flexible Global-Ocean-Atmosphere-Land System Model Grid-point version 3(CAS FGOALS-g3)are presented in this study.These experiments were forced by five global meteorological forcing datasets,which contributed to the framework of the Land Surface Snow and Soil Moisture Model Intercomparison Project(LS3MIP)of CMIP6.These datasets have been released on the Earth System Grid Federation node.In this paper,the basic descriptions of the CAS-LSM and the five LMIP experiments are shown.The performance of the soil moisture,snow,and land-atmosphere energy fluxes was preliminarily validated using satellite-based observations.Results show that their mean states,spatial patterns,and seasonal variations can be reproduced well by the five LMIP simulations.It suggests that these datasets can be used to investigate the evolutionary mechanisms of the global water and energy cycles during the past century.展开更多
This paper presents an analysis of the mechanisms and impacts of snow cover and frozen soil in the Tibetan Plateau on the sum- mer precipitation in China, using RegCM3 version 3.1 model simulations. Comparisons of sim...This paper presents an analysis of the mechanisms and impacts of snow cover and frozen soil in the Tibetan Plateau on the sum- mer precipitation in China, using RegCM3 version 3.1 model simulations. Comparisons of simulations vs. observations show that RegCM3 well captures these impacts. Results indicate that in a more-snow year with deep frozen soil there will be more precipita- tion in the Yangtze River Basin and central Northwest China, western Inner Mongolia, and Xinjiang, but less precipitation in Northeast China, North China, South China, and most of Southwest China. In a less-snow year with deep frozen soil, however, there will be more precipitation in Northeast China, North China, and southern South China, but less precipitation in the Yangtze River Basin and in northern South China. Such differences may be attributed to different combination patterns of melting snow and thawing frozen soil on the Plateau, which may change soil moisture as well as cause differences in energy absorption in the phase change processes of snow cover and frozen soil. These factors may produce more surface sensible heat in more-snow years when the fi＇ozen soil is deep than when the frozen soil is shallow. The higher surface sensible heat may lead to a stronger updraft over the Plateau, eventually contributing to a stronger South Asia High and West Pacific Subtropical High. Due to different values of the wind fields at 850 hPa, a convergence zone will form over the Yangtze River Basin, which may produce more summer pre- cipitation in the basin area but less precipitation in North China and South China. However, because soil moisture depends on ice content, in less-snow years with deep frozen soil, the soil moisture will be higher. The combination of higher frozen soil moisture with latent heat absorption in the phase change process may generate less surface sensible heat and consequently a weaker updraft motion over the Plateau. As a result, both the South Asia High and the West Pacific Subtropical High will be weaker, hence caus- ing more summer precipitation in northern China but less in southem China.展开更多
The shear properties of ice-frozen soil interface are important when studying the constitutive model of frozen soil and slope stability in cold regions.In this research,a series of cryogenic direct shear tests for ice...The shear properties of ice-frozen soil interface are important when studying the constitutive model of frozen soil and slope stability in cold regions.In this research,a series of cryogenic direct shear tests for ice-frozen clay soil interface were conducted.Based on experimental results,a nonlinear interface structural damage model is proposed to describe the shear properties of ice-frozen clay soil interface.Firstly,the cementation and friction structural properties of frozen soil materials were analyzed,and a structural parameter of the ice-frozen clay soil interface is proposed based on the cryogenic direct shear test results.Secondly,a structural coefficient ratio is proposed to describe the structural development degree of ice-frozen clay soil interface under load,which is able to normalize the shear stress of ice-frozen clay soil interface,and the normalized data can be described by the Duncan-Chang model.Finally,the tangent stiffness of ice-frozen clay soil interface is calculated,which can be applied to the mechanics analysis of frozen soil.Also,the shear stress of ice-frozen clay soil interface calculated by the proposed model is compared with test results.展开更多
The presence of a thick snowpack could interfere with forest stability, especially on steep slopes with potential damages for young and old stands. The study of snow gliding in forests is rather complex be- cause this...The presence of a thick snowpack could interfere with forest stability, especially on steep slopes with potential damages for young and old stands. The study of snow gliding in forests is rather complex be- cause this phenomenon could be influenced not only by forest features, but also by snow/soil interface characteristics, site morphology, meteoro- logical conditions and snow physical properties. Our starting hypothesis is that different forest stands have an influence on the snowpack evolu- tion and on the temperature and moisture at the snow/soil interface, which subsequently could affect snow gliding processes and snow forces. The aim of this work is therefore to analyse the snowpack evolution and snow gliding movements under different forest covers, in order to deter- mine the snow forces acting on single trees.展开更多
文摘Water transport at the root/soil interface of 1 year old Pinus sylvestris Linn. var. sylvestriformis (Takenouchi) Cheng et C. D. Chu seedlings under CO 2 doubling was studied by measuring soil electric conductance to survey soil water profiles and comparing it with root distribution surveyed by soil coring and root harvesting in Changbai Mountain in 1999. The results were: (1) The profiles of soil water content were adjusted by root activity. The water content of the soil layer with abundant roots was higher. (2) When CO 2 concentration was doubled, water transport was more active at the root/soil interface and the roots were distributed into deeper layer. It was shown in this work that the method of measuring electric conductance is an inexpensive, non_destructive and relatively sensitive way for underground water transport process.
基金Project(No.10206014)supported by Research Grant Council Direct Allocation Fund from the University of Hong Kong,China
文摘Soil in a cold region is subject to frequent freezing and thawing cycles.Soil frozen for a prolonged period may cause adverse freeze damage to the plants due to cell dehydration or root cell rupture.It is important to understand the detailed heat transfer behaviors of the freezing and thawing processes to prevent freeze damage,and to devise proper mitigation measures for effective pot planting in cold regions.A theoretical model was developed to analyze the transient moving phase-change interface heat transfer in the freezing and thawing of porous potting soil.The theoretical derivation is based on the assumption that the soil freezes completely at a single temperature.Microscopic poromechanic effects on heat transfer behavior were ignored.The spatial domain of the problem was simplified to a 1D spherical coordinate system with variation in the radial direction.Green's function was applied to solve for the time-dependent body temperature.Experiments were conducted for validation of the theoretical model.Reasonable agreement between the theoretical predictions and experimental measurements was obtained.The theoretical model developed can be easily used to determine the sensitivity of various parameters in the freezing/thawing processes,e.g.,thermal properties of soil,ambient temperature,and planting pot size.
基金supported by the Land and Liveability National Innovation Challenge under L2 NIC Award No. L2NICCFP1-2013-1
文摘Blasting has been widely used in mining and construction industries for rock breaking.This paper presents the results of a series of field tests conducted to investigate the ground wave propagation through mixed geological media.The tests were conducted at a site in the northwestern part of Singapore composed of residual soil and granitic rock.The field test aims to provide measurement data to better understand the stress wave propagation in soil/rock and along their interface.Triaxial accelerometers were used for the free field vibration monitoring.The measured results are presented and discussed,and empirical formulae for predicting peak particle velocity (PPV) attenuation along the ground surface and in soil/rock were derived from the measured data.Also,the ground vibration attenuation across the soil-rock interface was carefully examined,and it was found that the PPV of ground vibration was decreased by 37.2% when it travels from rock to soil in the vertical direction.
基金financially supported by the Fundamental Research Funds for the Central Universities(No.YX2010-20)the National Natural Science Foundation of China(No.31570708,No.30901162)the Open Projects Foundation of Key Laboratory of Soil and Water Conservation&Desertification Combat(Beijing Forestry University),Ministry of Education of China(No.201002)
文摘Roots play an important role in stabilizing and strengthening soil. This article aims to study the mechanical properties of the interface between soil and roots with branches, using the pullout test method in the laboratory. The mechanical properties of the soil-root with branches interface is determined through the pullout-force and root-slippage curve （F-S curve）. The results of investigating 24 Pinus tabulaeformis single roots and 55 P. tabulaeformis roots with branches demonstrated three kinds of pullout test failures： breakage failure on branching root, breakage failure on branching node, and pullout failure. The branch angle had a remarkable effect on the failure mode of the roots with branches： the maximum pullout force increased with the sum of the branch diameters and the branch angle. The peak slippage and the initial force had a positive correlation with the sum of the branch diameter. The sig- nificance test of correlation between branch angle and the initial force, however, showed they had no correlation. Branch angle and branch root diameter affect the anchorage properties between root system and soil. Therefore, it is important to investigate the anchorage mechanics of the roots with branches to understand the mechanism of root reinforcement and anchorage.
基金supported by an ES project on ‘Cyanobacteria’ (Grant No.21 (0859)/11/EMR-II),from Council of Scientific and Industrial Research (CSIR),New Delhi,India
文摘Toxicity-data of two carbamate insecticides, carbaryl and carbofuran, and three fungicides, ziram, zineb and mancozeb with rice-field N2-fixing cyanobacterium Cylindrospermum sp., obtained by in vitro growth and at soil-water interface, were analyzed by the probit method. Growth enhancing concentration, no-observed effective concentration, minimum inhibitory concentration, the highest permissive concentration and lethal concentration100 （LCloo） were determined experimentally. The LC^o values of carbaryl, carbofuran, ziram, zineb and mancozeb in N2-fixing liquid medium were 56.2, 588.8, 0.07, 4.2 and 3.4 IJg/mL, respectively, whereas the corresponding LCloo values were 100.0, 1500.0, 0.17, 25.0 and 9.0 IJg/mL, respectively. The LC50 values of these pesticides in succession in N2-fixing agar medium were 44.7, 239.9, 0.07, 1.8 and 2.3 IJg/mL, respectively, whereas the corresponding LC100 values were 100.0, 600.0, 0.17, 10.0 and 7.0 IJg/mL, respectively. Similar results with nitrate supplemented liquid and agar media indicated that nitrate supplementation had toxicity reducing effect. The LCso and LC^oo values of toxicity in the N2-fixing liquid medium at soil-water interface were 91.2 and 200.0 IJg/mL for carbaryl, 2 317 and 6 000 pg/mL for carbofuran, 0.15 and 0.50 pg/mL for ziram, 16.4 and 50.0 pg/mL for zineb, and 7.2 and 25.0 pg/mL for mancozeb, respectively. Each LC^oo value at soil- water interface with a pesticide was significantly higher than its corresponding LCloo value at liquid/agar media. It can be concluded that, under the N2-fixing conditions, the cyanobacterium tolerated higher levels of each pesticide at soil-water interface.
基金supported by the National Natural Science Foundation of China (Grant No. 41171064)the National Basic Research Program of China (973 Program Grant No. 2012CB026104)
文摘Using newly developed dynamic shearing devices, the dynamic sheafing strength of frozen soil-conerete interface was studied experimentally. By placing concrete blocks in the lower half of the shear box and frozen soil sample in the upper part, a series of dynamic shear tests on their interfaces were carried out. The obtained results are summarized and the main influencing factors are revealed.
基金the National Key Research and Development Program of China(Grant No.2023YFF1303501)the National Science Fund for Distinguished Young Scholars of China(Grant No.42225702)the Open Fund of State Key Laboratory of Frozen Soil Engineering(Grant No.SKLFSE201814).
文摘Frost heave and thaw settlement in cold regions pose a significant threat to engineering construction.Optical frequency domain reflectometry(OFDR)based on Rayleigh scattering can be applied to monitor ground deformation in frozen soil areas,where the interface behavior of soil-embedded fiber optic sensors governs the monitoring accuracy.In this paper,a series of pullout tests were conducted on fiber optic(FO)cables embedded in the frozen soil to investigate the cable‒soil interface behavior.An experimental study was performed on interaction effects,particularly focused on the water content of unfrozen soil,freezing duration,and differential distribution of water content in frozen soil.The highresolution axial strains of FO cables were obtained using a sensing interrogator,and were used to calculate the interface shear stress.The interfacial mechanical response was analytically modeled using the ideal elasto‒plastic and softening constitutive models.Three freezing periods,correlating with the phase change process between ice and water,were analyzed.The results shows that the freezing effect can amplify the peak shear stress at the cable-soil interface by eight times.A criterion for the interface coupling states was proposed by normalizing the pullout force‒displacement information.Additionally,the applicability of existing theoretical models was discussed by comparing the results of theoretical back‒calculations with experimental measurements.This study provides new insights into the progressive interfacial failure behavior between strain sensing cable and frozen soil,which can be used to assist the interpretation of FO monitoring results of frozen soil deformation.
基金supported by the National Natural Science Foundation of China(Nos.42222102,41971136,and 42171107)the Jilin Provincial Department of Science and Technology,China(No.20230508089RC)the Professional Association of the Alliance of International Science Organizations(No.ANSO-PA-2020-14).
文摘Global climate change exerts profound effects on snow cover,with consequential impacts on microbial activities and the stability of soil organic carbon(SOC)within aggregates.Northern peatlands are significant carbon reservoirs,playing a critical role in mitigating climate change.However,the effects of snow variations on microbial-mediated SOC stability within aggregates in peatlands remain inadequately understood.Here,an in-situ field experiment manipulating snow conditions(i.e.,snow removal and snow cover)was conducted to investigate how snow variations affect soil microbial community and the associated SOC stability within soil aggregates(>2,0.25-2,and<0.25 mm)in a peatland of Northeast China.The results showed that snow removal significantly increased the SOC content and stability within aggregates.Compared to the soils with snow cover,snow removal resulted in decreased soil average temperatures in the topsoil(0-30 cm depth)and subsoil(30-60 cm depth)(by 1.48 and 1.34°C,respectively)and increased freeze-thaw cycles(by 11 cycles),consequently decreasing the stability of aggregates in the topsoil and subsoil(by 23.68%and 6.85%,respectively).Furthermore,more recalcitrant carbon and enhanced SOC stability were present in microaggregates(<0.25 mm)at two soil depths.Moreover,reductions in bacterial diversity and network stability were observed in response to snow removal.Structural equation modeling analysis demonstrated that snow removal indirectly promoted(P<0.01)SOC stability by regulating carbon to nitrogen(C:N)ratio within aggregates.Overall,our study suggested that microaggregate protection and an appropriate C:N ratio enhanced carbon sequestration in response to climate change.
基金funded by the National Natural Science Foundation of China[grant numbers 42075115 and 41991285]the Joint Open Project of KLME&CIC-FEMD[grant number KLME201901]。
文摘Net primary productivity(NPP)is the net accumulation of organic matter by vegetation through photosynthesis and serves as a key indicator for exploring vegetation responses to climate change.Considering the remote and local impacts of soil heat capacities on vegetation growth through pathways of atmospheric circulation and land–atmosphere interaction,this paper develops a statistical prediction model for NPP from April to June(AMJ)across the middle-to-high latitudes of Eurasia.The model introduces two physically meaningful predictors:the snow water equivalent(SWE)from February to March(FM)over central Europe and the FM local soil temperature(ST).The positive phase of FM SWE triggers anomalous eastward-propagating Rossby waves,leading to an anomalous low-pressure system and cooling in the middle-to-high latitudes of Eurasia.This effect persists into spring through snow feedback to the atmosphere and affects subsequent NPP changes.The ST is closely related to the AMJ temperature and precipitation.With positive ST anomalies,the AMJ temperature and precipitation exhibit an east–west dipole anomaly distribution in this region.The single-factor prediction scheme using ST as the predictor is much better than using SWE as the predictor.Independent validation results from 2009 to 2014 demonstrate that the ST scheme alone has good predictive performance for the spatial distribution and interannual variability of NPP.The predictive skills of the multi-factor prediction schemes can be improved by about 13%if the ST predictor is included.The findings confirm that local ST is a predictor that must be included for NPP prediction.
文摘-In order to analyze the stability of pipelines on the sea bed, the friction characteristics at the pipe-soil interface were examined by means of special direct shear tests. High density polythene was used as the surface of the pipe, which is a widely-utilized material for the outer cover of the pipe to prevent sea water corrosion. Sands of different gradings were tested. The reconstituted soft clay taken from the Bohai area was consolidated to different degrees of consolidation by the vacuum preloading technique, and tested.
基金Project(51274192)supported by National Natural Science Foundation of China
文摘The characteristics of a disturbed soil-structure interface were studied based on the variation regularities of the disturbed soil within its mining subsidence area using direct shear tests.The effects of the initial moisture content on the shear strength parameters of the soil-structure interfaces were analyzed.The results indicate that the cohesion of the interface initially increased and then decreased as the initial moisture content increased.In addition,the friction angle of the interface decreased as the initial moisture content increased.A constitutive model of the disturbed soil-structure interface,a rigid-plastic model based on the initial void ratio and saturability(VSRP) model,was established based on the results.In order to validate this model,a finite element analysis of DRS-1 direct shear tests was conducted.The finite element model calculations coincided with the results of the DRS-1 direct shear tests.The proposed model also reflected the nonlinear features of the soil-structure interface.
基金Projects supported by the National Natural Science Foundation of China (Nos. 49471016, 49771019 and 49890330)
文摘In order to explore the spatial variability of soil moisture near the interface of high/low stands, an experiment was conducted at Luancheng Experimental Station, Chinese Academy of Sciences, Hebei, China from May to June, 1996. By analyzing the observed soil moisture data, it shows that there exists an obvious turning point of soil moisture pattern from one side of the interface to another. The effect of drier soil closer to the interface in winter wheat field is obvious, which is mainly due to the better ventilation condition near the interface in winter wheat filed than in alfalfa field. The irrigation in large scale is one of the most important factors to control the spatial pattern of soil moisture while the small scale human disturbing activity, such as the stealing event occurred during our observation, does not change the spatial pattern of soil moisture obviously. Latent heat, calculated by Bowen ratio method based on our observed micrometeorological data, is shown larger in alfalfa than that in winter wheat both at earring stage from May 8 to 10 and mature stage from June 11 to 14. This fact, together with the larger ground temperature and a little bit larger wind velocity in lower layer, explains that the soil is drier in alfalfa than in winter wheat from May 8 to 10. While for the period from June 11 to 14, irrigation's effect changes the natural interrelationship of soil moisture with meteorology and ground temperature.
基金Reported investigations were partially supported by the Russian Foundation for Basic researches project No. 15-58-53013 FФEH a and the National Natural Science Foundation of China under contracts No. 51279122 and No. 51511130042.
文摘Solution of the practical problems of the ice engineering requires the data about the strength of the ice cover that depends upon its temperature. In most cases, the snow lies on the ice cover and the ice temperature differs from the atmospheric air temperature. To reveal the correlation of the air temperature with temperature on interfaces air-snow and snow-ice, the known in the thermophysics solution of the problem of the heat transfer through the multilayer plate was applied. Derived solution connects the temperature of air and temperature on the snow-ice interface and satisfactory correlates with data of the field measurements of the temperature within snow layer and ice cover and ice thickness on the Heilongjiang （Amur） River. Results of investigation are recommended for the ice temperature evaluation in engineering practice.
基金financially supported by the China Postdoctoral Science Foundation(Grant No.2023M732997)the National Natural Science Foundation of China(Grant Nos.51890912,52008268)Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering,Hohai University(Grant No.2023007)。
文摘The interaction between soil and marine structures like submarine pipeline/pipe pile/suction caisson is a complicated geotechnical mechanism process.In this study,the interface is discretized into multiple mesoscopic contact elements that are damaged randomly throughout the shearing process due to the natural heterogeneity.The evolution equation of damage variable is developed based on the Weibull function,which is able to cover a rather wide range of distribution shapes by only two parameters,making it applicable for varying scenarios.Accordingly,a statistical damage model is established by incorporating Mohr–Coulomb strength criterion,in which the interfacial residual strength is considered whereby the strain softening behavior can be described.A concept of“semi-softening”characteristic point on shear stress–displacement curve is proposed for effectively modeling the evolution of strain softening.Finally,a series of ring shear tests of the interfaces between fine sea sand and smooth/rough steel surfaces are conducted.The predicted results using the proposed model are compared with experimental data of this study as well as some results from existing literature,indicating that the model has a good performance in modeling the progressive failure and strain softening behavior for various types of soil–structure interfaces.
基金This work was sponsored by the National Key R&D Program of China(Grant No.2016YFA0600404)the National Natural Science Foundation of China(Grant Nos.41530532 and 41675088)N.Y.also thanks the support from the Chinese Academy of Sciences Pioneer Hundred Talents Program.
文摘The soil temperature(ST)is closely related to the surface air temperature(AT),but their coupling may be affected by other factors.In this study,significant effects of the AT on the underlying ST were found,and the time taken to propagate downward to 320 cm can be up to 10 months.Besides the AT,the ST is also affected by memory effects-namely,its prior thermal conditions.At deeper depth(i.e.,320 cm),the effects of the AT from a particular season may be exceeded by the soil memory effects from the last season.At shallower layers(i.e.,<80 cm),the effects of the AT may be blocked by the snow cover,resulting in a poorly synchronous correlation between the AT and the ST.In northeastern China,this snow cover blockage mainly occurs in winter and then vanishes in the subsequent spring.Due to the thermal insulation effect of the snow cover,the winter ST at layers above 80 cm in northeastern China were found to continue to increase even during the recent global warming hiatus period.These findings may be instructive for better understanding ST variations,as well as land−atmosphere interactions.
基金funded the Natural Science Foundation of China (Grant No. 41301024 and No. 40925002) the National Basic Research Program of China (973 Program, Grant No. 2013CBA01807)
文摘Seasonal snow is one of the most important influences on the development and distribution of permafrost and the hydrothermal regime in surface soil. Alpine meadow, which constitutes the main land type in permafrost regions of the Qinghai-Tibet Plateau, was selected to study the influence of seasonal snow on the temperature and moisture in active soil layers under different vegetation coverage. Monitoring sites for soil moisture and temperature were constructed to observe the hydrothermal processes in active soil layers under different vegetation cover with seasonal snow cover variation for three years from 2010 to 2012. Differences in soil temperature and moisture in areas of diverse vegetation coverage with varying levels of snow cover were analyzed using active soil layer water and temperature indices. The results indicated that snow cover greatly influenced the hydrothermal dynamics of the active soil layer in alpine meadows. In the snow manipulation experiment with a snow depth greater than 15 cm, the snow cover postponed both the freeze-fall and thawrise onset times of soil temperature and moisture in alpine LC(lower vegetation coverage) meadows and of soil moisture in alpine HC(higher vegetation coverage) meadows; however, the opposite response occurred for soil temperatures of alpine HC meadows,where the entire melting period was extended by advancing the thaw-rise and delaying the freeze-fall onset time of the soil temperature. Snow cover resulted in a decreased amplitude and rate of variation in soil temperature, for both alpine HC meadows and alpine LC meadows, whereas the distinct influence of snow cover on the amplitude and rate of soil moisture variation occurred at different soil layers with different vegetation coverages. Snow cover increased the soil moisture of alpine grasslands during thawing periods. The results confirmed that the annual hydrothermal dynamics of active layers in permafrost were subject to the synergistic actions of both snow cover and vegetation coverage.
文摘The datasets of the five Land-offline Model Intercomparison Project(LMIP)experiments using the Chinese Academy of Sciences Land Surface Model(CAS-LSM)of CAS Flexible Global-Ocean-Atmosphere-Land System Model Grid-point version 3(CAS FGOALS-g3)are presented in this study.These experiments were forced by five global meteorological forcing datasets,which contributed to the framework of the Land Surface Snow and Soil Moisture Model Intercomparison Project(LS3MIP)of CMIP6.These datasets have been released on the Earth System Grid Federation node.In this paper,the basic descriptions of the CAS-LSM and the five LMIP experiments are shown.The performance of the soil moisture,snow,and land-atmosphere energy fluxes was preliminarily validated using satellite-based observations.Results show that their mean states,spatial patterns,and seasonal variations can be reproduced well by the five LMIP simulations.It suggests that these datasets can be used to investigate the evolutionary mechanisms of the global water and energy cycles during the past century.
基金supported by the National Key Basic Research Program (No. 2007CB411505)the National Natural Science Foundation (No. 40705031)
文摘This paper presents an analysis of the mechanisms and impacts of snow cover and frozen soil in the Tibetan Plateau on the sum- mer precipitation in China, using RegCM3 version 3.1 model simulations. Comparisons of simulations vs. observations show that RegCM3 well captures these impacts. Results indicate that in a more-snow year with deep frozen soil there will be more precipita- tion in the Yangtze River Basin and central Northwest China, western Inner Mongolia, and Xinjiang, but less precipitation in Northeast China, North China, South China, and most of Southwest China. In a less-snow year with deep frozen soil, however, there will be more precipitation in Northeast China, North China, and southern South China, but less precipitation in the Yangtze River Basin and in northern South China. Such differences may be attributed to different combination patterns of melting snow and thawing frozen soil on the Plateau, which may change soil moisture as well as cause differences in energy absorption in the phase change processes of snow cover and frozen soil. These factors may produce more surface sensible heat in more-snow years when the fi＇ozen soil is deep than when the frozen soil is shallow. The higher surface sensible heat may lead to a stronger updraft over the Plateau, eventually contributing to a stronger South Asia High and West Pacific Subtropical High. Due to different values of the wind fields at 850 hPa, a convergence zone will form over the Yangtze River Basin, which may produce more summer pre- cipitation in the basin area but less precipitation in North China and South China. However, because soil moisture depends on ice content, in less-snow years with deep frozen soil, the soil moisture will be higher. The combination of higher frozen soil moisture with latent heat absorption in the phase change process may generate less surface sensible heat and consequently a weaker updraft motion over the Plateau. As a result, both the South Asia High and the West Pacific Subtropical High will be weaker, hence caus- ing more summer precipitation in northern China but less in southem China.
基金supported the National Key Research and Development Program of China(Nos.2016YFE0202400,2018YFC1505306)the National Natural Science Foundation of China(No.41971076)the State Key Laboratory of Road Engineering Safety and Health in Cold and High-altitude Regions(No.YGY2017KYPT-04)。
文摘The shear properties of ice-frozen soil interface are important when studying the constitutive model of frozen soil and slope stability in cold regions.In this research,a series of cryogenic direct shear tests for ice-frozen clay soil interface were conducted.Based on experimental results,a nonlinear interface structural damage model is proposed to describe the shear properties of ice-frozen clay soil interface.Firstly,the cementation and friction structural properties of frozen soil materials were analyzed,and a structural parameter of the ice-frozen clay soil interface is proposed based on the cryogenic direct shear test results.Secondly,a structural coefficient ratio is proposed to describe the structural development degree of ice-frozen clay soil interface under load,which is able to normalize the shear stress of ice-frozen clay soil interface,and the normalized data can be described by the Duncan-Chang model.Finally,the tangent stiffness of ice-frozen clay soil interface is calculated,which can be applied to the mechanics analysis of frozen soil.Also,the shear stress of ice-frozen clay soil interface calculated by the proposed model is compared with test results.
基金supported by the Project"Forêts de protection:techniques de gestion et innovation dans les Alpes occidentals" within the Operational Program ALCOTRA Italy-France 2009-2012)"
文摘The presence of a thick snowpack could interfere with forest stability, especially on steep slopes with potential damages for young and old stands. The study of snow gliding in forests is rather complex be- cause this phenomenon could be influenced not only by forest features, but also by snow/soil interface characteristics, site morphology, meteoro- logical conditions and snow physical properties. Our starting hypothesis is that different forest stands have an influence on the snowpack evolu- tion and on the temperature and moisture at the snow/soil interface, which subsequently could affect snow gliding processes and snow forces. The aim of this work is therefore to analyse the snowpack evolution and snow gliding movements under different forest covers, in order to deter- mine the snow forces acting on single trees.
