The thawing of ice-rich permafrost leads to the formation of thermokarst landforms.Precise mapping of retrogressive thaw slumps(RTSs)is imperative for assessing the degradation and carbon exchange of permafrost at bot...The thawing of ice-rich permafrost leads to the formation of thermokarst landforms.Precise mapping of retrogressive thaw slumps(RTSs)is imperative for assessing the degradation and carbon exchange of permafrost at both local and regional scales on the Tibetan Plateau(TP).However,previous methods for RTSs mapping rely on a large number of samples and complex classifiers with low automation level or unnecessary complexity.We propose an automatic mapping network(AmRTSNet)for producing decimeter-level RTSs maps from GaoFen-7 images based on deep learning.Both the quantitative metrics and qualitative evaluations show that AmRTSNet trained in the Beiluhe offers significant advantages over previous methods.Without further fine-tuning,we conducted RTSs automatic mapping based on AmRTSNet in the Wulanwula,Chumarhe,and Gaolinggo.Over 141,312 ha on the TP have been automatically mapped,comprising 926 RTS regions with a total RTS area of 2318.72 ha.The average statistics of the mapped RTSs show low roundness(0.38),moderate rectangularity(0.61),and high convexity(0.79).About 90%of the RTSs are smaller than 6 ha.The average aspect ratio is 2.18.RTSs are unevenly distributed in belt-like aggregations with dominant density peaks.RTSs often concentrate in hillslopes and along lateral streams,with more dense areas more likely to have larger RTSs.展开更多
After the normal operation of the Three Gorges Reservoir,the water level of the reser-voir will fluctuate periodically.Water level fluctuation will soften the rock and soil on the banks,induce underground water fluctu...After the normal operation of the Three Gorges Reservoir,the water level of the reser-voir will fluctuate periodically.Water level fluctuation will soften the rock and soil on the banks,induce underground water fluctuation and decrease the shear strength of rock soil on the banks,and in turn affect the landslide stability.The Huangtupo（黄土坡） landslide is a typical large and complex landslide in the Three Gorges Reservoir region.In particular,the stability of its riverside slumping mass has a great stake.On the basis of the analysis of engineering geological condition and formation mechanism of the Huangtupo landslide,the authors established the 2D finite element model of riverside slumping mass II# and selected proper mechanical parameters of the rock.With the GeoStudio software,ac-cording to the reservoir running curve,the simulation on coupling effect of seepage field and stress field was conducted in 7 different modes in a year.The results showed that：① Huangtupo landslide is a large and complex landslide composed of multiple slumping masses,which occurred at different phases.Before reservoir impoundment,it was stable;② it is quite difficult for riverside slumping mass I# and II# to slide as a whole;③ the stability coefficient of riverside slumping mass II# changes with the res-ervoir water level fluctuations.The minimum stability coefficient occurs 48 days after the water level starts to fall and the moment when the water level falls by 11.9 m.Landslide monitoring result is con-sistent with the numerical simulation result,which shows that although the reservoir water level fluc-tuation will affect the foreside stability of the landslide and induce gradual damage,the riverside slumping mass II# is stable as a whole.展开更多
Transverse cracks and localized slumps frequently occur within loose deposits slopes when the slope base is removed either from natural or manmade processes. Although the contribution of rainfall to the slope failures...Transverse cracks and localized slumps frequently occur within loose deposits slopes when the slope base is removed either from natural or manmade processes. Although the contribution of rainfall to the slope failures was intensely discussed, the influence of localized slumps on hydrogeological conditions has received less attention. Usually, loose deposits slopes are composed of soil layers with different permeability; localized slumps may cause flow paths partly blocked in the permeable layer that is adversely confined between impermeable layers. In this study, a case history of such failure, Xiaodan （/J~ ~__） landslide, is introduced in detail. The localized slump caused the pressure head in the permeable layer to increase substantially, which reduced the stability of the slope. To quantify the influence, Ber- noulli equations are used to analytically study the increase of the pressure head with a hydrogeologicai model simplified from the slope. The factor of safety assessed by limit equilibrium methods may decrease up to 20% when the 80% of flow path is blocked. Thus, we should pay attention not only to changes of stress filed due to localized slumps but also to the influence of seepage variation on the slope stability.展开更多
A new kind of nano-rod shaped polycarboxylic acid slump-retaining agent was synthesized.Transmission electron microscope(TEM) experiment showed that the nano-rod was bound together as macromolecular aggregates in solu...A new kind of nano-rod shaped polycarboxylic acid slump-retaining agent was synthesized.Transmission electron microscope(TEM) experiment showed that the nano-rod was bound together as macromolecular aggregates in solution.Application performance studying suggested that this kind nano-sized polymer material had excellently plasticity-retaining performance in cement-based materials and could improve endurance performance of hardened cement-based materials distinctly.The concrete with an initial slump of 2-9 cm could achieve 3 h plasticity-retaining performance with the help of this kind nano-rod.The product had extremely wide application value in the market.展开更多
Under the rapidly warming climate in the Arctic and high mountain areas,permafrost is thawing,leading to various hazards at a global scale.One common permafrost hazard termed retrogressive thaw slump(RTS)occurs extens...Under the rapidly warming climate in the Arctic and high mountain areas,permafrost is thawing,leading to various hazards at a global scale.One common permafrost hazard termed retrogressive thaw slump(RTS)occurs extensively in ice-rich permafrost areas.Understanding the spatial and temporal distributive features of RTSs in a changing climate is crucial to assessing the damage to infrastructure and decision-making.To this end,we used a machine learning-based model to investigate the environmental factors that could lead to RTS occurrence and create a susceptibility map for RTS along the Qinghai-Tibet Engineering Corridor(QTEC)at a local scale.The results indicate that extreme summer climate events(e.g.,maximum air temperature and rainfall)contributes the most to the RTS occurrence over the flat areas with fine-grained soils.The model predicts that 13%(ca.22,948 km^(2))of the QTEC falls into high to very high susceptibility categories under the current climate over the permafrost areas with mean annual ground temperature at 10 m depth ranging from-3 to-1℃.This study provides insights into the impacts of permafrost thaw on the stability of landscape,carbon stock,and infrastructure,and the results are of value for engineering planning and maintenance.展开更多
The loess slumping hazard is a special type of slope failures in the northern area of loess plateau of China. The characteristics of paroxysm and high frequency of the hazard always lead to ruin of cave houses, as we...The loess slumping hazard is a special type of slope failures in the northern area of loess plateau of China. The characteristics of paroxysm and high frequency of the hazard always lead to ruin of cave houses, as well as a high human casualties. The hazard is also seriously harmful to railways, highroads and long transporting pipelines. With the mechanisms of both landslide and falling, as well as the forming process of sliding followed by collapses, loess slumping is used to be treated as landslide or falling. Based on field investigations and lab analyses of the loess between Jingbian County of Shaanxi Province and Puxian County of Shanxi Province along the line of west east gas transportation project which is 300 km long, it is discovered that the hazards of loess slumping are controlled by the content of clay, which lead to their obvious regional properties: the area with a content of clay (<0.005 mm) less than 10 %, called sand loess area, is a seriously developing area of slumping; the area with a content of clay between 10 % and 20 %, called typical loess area, is a medium developing area of slumping; the area with a content of clay more than 20 %, called clay loess area, is a non developing area of slumping. Based on research of the formation mechanism and formation conditions of the loess slumping hazards, some corresponding engineering countermeasures are suggested in this paper.展开更多
A new kind of polycarboxylate superplasticizer with high slump loss resistance was obtained by designing scheduled molecular structure.The number average molecular mass of the polymer was characterized by the gel perm...A new kind of polycarboxylate superplasticizer with high slump loss resistance was obtained by designing scheduled molecular structure.The number average molecular mass of the polymer was characterized by the gel permeation chromatography measurements.And chemical structure of the polymer was observed by the Fourier transform infrared spectroscopy(FT-IR).The results show that the good workable maintaining of self-compacting concrete could be achieved through direct adjustment of number average molecular mass and different unsaturated monomer in synthetic process.The FT-IR analysis illustrated that the high slump loss resistance of polycarboxylate superplasticizers with ester and carboxyl group and expectations of molecular structure were designed.展开更多
N-2000 is an admixture for concrete,with a low slump loss,high range water-reducing ratio and long-time retarding.The N-2000 is made up of naphthalene-sulfonic-maldehyde polycondensation(NSMP)and ATMP.Its characterist...N-2000 is an admixture for concrete,with a low slump loss,high range water-reducing ratio and long-time retarding.The N-2000 is made up of naphthalene-sulfonic-maldehyde polycondensation(NSMP)and ATMP.Its characteristic results from the synergistic effects of NSMP and ATMP.The results show that when 0.7%-1.2%of N-2000 is added to concrete(by mass of cement),the water reducing ratio is up to 20%-30%,and the slump of fresh concrete can be retained for 2 hours without significant loss.N-2000 can not only improve the workability of fresh concrete but also increase the strength of the hardened concrete,especially early strength.It is also proved to have a good compatibility with various cements.展开更多
In this work, the yield stress evaluation as a function of water content for slip-prone clayey soils is studied in order to understand how yield stress decreases as water content increases, and their relation with the...In this work, the yield stress evaluation as a function of water content for slip-prone clayey soils is studied in order to understand how yield stress decreases as water content increases, and their relation with the chemical properties. The clayey soil samples were taken from the region of Teziutlán-Puebla-Mexico. Yield stress was calculated using the slump test in cylindrical geometry. Results show three zones. The first one shows an exponential decrement on yield stress due to lower water content in accord with clayey soils with high content of illita, followed by a second region where yield stress decreases dramatically at a certain critical water concentration, and the third one where yield stress dependence is not well-defined since the clayey soil flow is seen. Finally, it is discussed how yield stress variation due to the water increment influences the landslide risk increment.展开更多
In recent years, high precision geometric shape, surface roughness, and cost reduction are required for large glass component molding processes. In this research, the polishing process of stainless steel molding dies ...In recent years, high precision geometric shape, surface roughness, and cost reduction are required for large glass component molding processes. In this research, the polishing process of stainless steel molding dies used to form thin glass components is investigated. The surface roughness of the polished stainless steel molding die surface is below Rz = 200 nm （P-V） at 15 h polishing with 0.5 % alumina polishing liquid. In the case of polishing process with only the weight of molding die and a polishing pressure of 0.5 kPa, polishing times are approximately 60 h and 20 h, respectively. Final surface roughness polished stainless steel molding die surface with pressure of 0.5 kPa is Rz = 7 nm （P-V）, rms -- 1.6 nm and Ra = 1.4 nm. In a thin glass component manufacturing method, ＂slumping method＂, surface roughness before glass forming is rms = 0.7 nm and Ra = 0.6 nm, and after is rms = 0.7 nm and Ra = 0.6 nm. Therefore, there were no observable changes their surface roughness.展开更多
China had entered a period of moderate economic growtht one that is moving at an appropriate pace. China＇s economy is bottoming out and seeking a new balance,
Under global warming,permafrost around the world is experiencing degradation which is especially so on the Third Pole,the Qinghai-Tibet Plateau(QTP),China.Retrogressive thaw slump(RTS)is one of the thermokarst feature...Under global warming,permafrost around the world is experiencing degradation which is especially so on the Third Pole,the Qinghai-Tibet Plateau(QTP),China.Retrogressive thaw slump(RTS)is one of the thermokarst features caused by rapid degradation of ice rich permafrost,which transforms landforms and threatens infrastructures,and even affects the terrestrial carbon cycle.In this work,vegetation communities surrounding a RTS in the Fenghuoshan Mountains of the interior portion of the Qinghai-Tibet Plateau have been investigated to examine the impact from RTS.This investigation indicates that the occurrence of RTS influences the vegetation community by altering their habitats,especially the soil water content,which forces the vegetation community to evolve in order to adapt to the alterations.In the interior part of RTS where it has been disturbed tremendously,alterations have produced a wider niche and richer plant species.This favors species of a wet environment in a habitat where it was a relatively dry environment of alpine steppe prior to the occurrence of RTS.This study adds to limited observations regarding the impact of RTS to vegetation community on the QTP and helps us to reach a broader understanding of the effects of permafrost degradation as well as global warming.展开更多
The Qinghai-Xizang Plateau of China faces challenges like thaw slumping,threatening slope stability and infrastructure.Understanding the mechanical properties of the roots of the dominant herbaceous plant species in t...The Qinghai-Xizang Plateau of China faces challenges like thaw slumping,threatening slope stability and infrastructure.Understanding the mechanical properties of the roots of the dominant herbaceous plant species in the alpine meadow layer of the permafrost regions on the Qinghai-Xizang Plateau is essential for evaluating their role in enhancing soil shear strength and mitigating slope deformation in these fragile environments.In this study,the roots of four dominant herbaceous plant species—Kobresia pygmaea,Kobresia humilis,Carex moorcroftii,and Leontopodium pusillum—that are widely distributed in the permafrost regions of the Qinghai-Xizang Plateau were explored to determine their mechanical properties and effects in enhancing soil shear strength.Through indoor single root tensile and root group tensile tests,we determined the root diameter,tensile force,tensile strength,tensile ratio,and strength frequency distributions.We also evaluated their contributions to inhibiting slope deformation and failure during the formation and development of thermal thaw slumps in the alpine meadow.The results showed that the distribution of the root diameter of the dominant plant species is mostly normal,while the tensile strength tends to be logarithmically normally distributed.The relationship between the root diameter and root tensile strength conforms to a power function.The theoretical tensile strength of the root group was calculated using the Wu-Waldron Model(WWM)and the Fiber Bundle Model(FBM)under the assumption that the cumulative single tensile strength of the root bundle is identical to the tensile strength of the root group in the WWM.The FBM considers three fracture modes:FBM-D(the tensile force on each single root is proportional to its diameter relative to the total sum of all the root diameters),FBM-S(the cross-sectional stress in the root bundle is uniform),and FBM-N(each tensile strength test of individual roots experiences an equal load).It was found that the model-calculated tensile strength of the root group was 162.60%higher than the test value.The model-derived tensile force of the root group from the FBM-D,FBM-S,and FBM-N was 73.10%,28.91%,and 13.47%higher than the test values,respectively.The additional cohesion of the soil provided by the roots was calculated to be 25.90-45.06 kPa using the modified WWM,67.05-38.15 kPa using the FBM-S,and 57.24-32.74 kPa using the FBM-N.These results not only provide a theoretical basis for further quantitative evaluation of the mechanical effects of the root systems of herbaceous plant species in reinforcing the surface soil but also have practical significance for the effective prevention and control of thermal thaw slumping disasters in the permafrost regions containing native alpine meadows on the Qinghai-Xizang Plateau using flexible plant protection measures.展开更多
The soil-bentonite(SB)cut-off wall has been widely considered a vertical barrier to effectively control the migration of pollutants in contaminated sites.Recently,active porous materials have been used as a promising ...The soil-bentonite(SB)cut-off wall has been widely considered a vertical barrier to effectively control the migration of pollutants in contaminated sites.Recently,active porous materials have been used as a promising candidate amendment for mitigating chemical degradation and improving the retardation capacity of the SB cut-off wall.In this study,the silty clay from a typical Cr(VI)contaminated site was selected as the body material of the SB cut-off wall,and zeolite and active carbon were used as the modifiers of the silty clay-bentonite backfills,respectively.The impact of the two modifiers on the engineering properties of the backfills was investigated through a series of slump tests,consolidation tests,hydraulic conductivity tests,and microstructure tests.The experimental results demonstrated that the slump curves closely exhibited a linear relationship between standard slump and moisture content.Meanwhile,bentonite could improve the optimum moisture content of the backfills,while the addition of the two modifiers yielded the opposite outcome.As the bentonite content increased,the compression index of the backfills significantly increased,while the hydraulic conductivity decreased.At a given bentonite content of 5%,the addition of zeolite or active carbon resulted in a reduction in the compression index and initial void ratio,while exhibiting minimal impact on the hydraulic conductivity.Scanning electron microscope(SEM)observations indicated that the silty clay-bentonite backfills became increasingly loose with increasing bentonite content,owing to the filling and expansion of dispersed bentonite layers.The amendment of zeolite or active carbon was able to decrease the backfill volume by promoting the agglomeration of layered bentonite.The findings of this study will be useful for the optimal selection of backfill materials and the performance evaluation of the cut-off wall.展开更多
基金The Second Tibetan Plateau Scientific Expedition and Research,No.2022QZKK0101National Natural Science Foundation of China,No.42271427。
文摘The thawing of ice-rich permafrost leads to the formation of thermokarst landforms.Precise mapping of retrogressive thaw slumps(RTSs)is imperative for assessing the degradation and carbon exchange of permafrost at both local and regional scales on the Tibetan Plateau(TP).However,previous methods for RTSs mapping rely on a large number of samples and complex classifiers with low automation level or unnecessary complexity.We propose an automatic mapping network(AmRTSNet)for producing decimeter-level RTSs maps from GaoFen-7 images based on deep learning.Both the quantitative metrics and qualitative evaluations show that AmRTSNet trained in the Beiluhe offers significant advantages over previous methods.Without further fine-tuning,we conducted RTSs automatic mapping based on AmRTSNet in the Wulanwula,Chumarhe,and Gaolinggo.Over 141,312 ha on the TP have been automatically mapped,comprising 926 RTS regions with a total RTS area of 2318.72 ha.The average statistics of the mapped RTSs show low roundness(0.38),moderate rectangularity(0.61),and high convexity(0.79).About 90%of the RTSs are smaller than 6 ha.The average aspect ratio is 2.18.RTSs are unevenly distributed in belt-like aggregations with dominant density peaks.RTSs often concentrate in hillslopes and along lateral streams,with more dense areas more likely to have larger RTSs.
基金supported by the National Natural Science Fundation of China (No. 40872175)the National Basic Research Program of China (973 Program) (No. 2011CB710604)
文摘After the normal operation of the Three Gorges Reservoir,the water level of the reser-voir will fluctuate periodically.Water level fluctuation will soften the rock and soil on the banks,induce underground water fluctuation and decrease the shear strength of rock soil on the banks,and in turn affect the landslide stability.The Huangtupo（黄土坡） landslide is a typical large and complex landslide in the Three Gorges Reservoir region.In particular,the stability of its riverside slumping mass has a great stake.On the basis of the analysis of engineering geological condition and formation mechanism of the Huangtupo landslide,the authors established the 2D finite element model of riverside slumping mass II# and selected proper mechanical parameters of the rock.With the GeoStudio software,ac-cording to the reservoir running curve,the simulation on coupling effect of seepage field and stress field was conducted in 7 different modes in a year.The results showed that：① Huangtupo landslide is a large and complex landslide composed of multiple slumping masses,which occurred at different phases.Before reservoir impoundment,it was stable;② it is quite difficult for riverside slumping mass I# and II# to slide as a whole;③ the stability coefficient of riverside slumping mass II# changes with the res-ervoir water level fluctuations.The minimum stability coefficient occurs 48 days after the water level starts to fall and the moment when the water level falls by 11.9 m.Landslide monitoring result is con-sistent with the numerical simulation result,which shows that although the reservoir water level fluc-tuation will affect the foreside stability of the landslide and induce gradual damage,the riverside slumping mass II# is stable as a whole.
基金supported by the National Natural Science Foundation of China(No.40972187)the Key Innovation Team Support Project of ZhejiangProvince(No.2009R50050)
文摘Transverse cracks and localized slumps frequently occur within loose deposits slopes when the slope base is removed either from natural or manmade processes. Although the contribution of rainfall to the slope failures was intensely discussed, the influence of localized slumps on hydrogeological conditions has received less attention. Usually, loose deposits slopes are composed of soil layers with different permeability; localized slumps may cause flow paths partly blocked in the permeable layer that is adversely confined between impermeable layers. In this study, a case history of such failure, Xiaodan （/J~ ~__） landslide, is introduced in detail. The localized slump caused the pressure head in the permeable layer to increase substantially, which reduced the stability of the slope. To quantify the influence, Ber- noulli equations are used to analytically study the increase of the pressure head with a hydrogeologicai model simplified from the slope. The factor of safety assessed by limit equilibrium methods may decrease up to 20% when the 80% of flow path is blocked. Thus, we should pay attention not only to changes of stress filed due to localized slumps but also to the influence of seepage variation on the slope stability.
基金the Jiangsu Province Natural Science Foundation(No.BK2008520)the Jiangsu Postdoctoral Research Funds(No.0901008C)the China Postdoctoral Science Foundation(No.20090461120)
文摘A new kind of nano-rod shaped polycarboxylic acid slump-retaining agent was synthesized.Transmission electron microscope(TEM) experiment showed that the nano-rod was bound together as macromolecular aggregates in solution.Application performance studying suggested that this kind nano-sized polymer material had excellently plasticity-retaining performance in cement-based materials and could improve endurance performance of hardened cement-based materials distinctly.The concrete with an initial slump of 2-9 cm could achieve 3 h plasticity-retaining performance with the help of this kind nano-rod.The product had extremely wide application value in the market.
基金funded by the National Natural Science Foundation of China(42372334)the Science and Technology Research and Development Program of the Qinghai-Tibet Group Corporation(Grant No.QZ2022-G05)。
文摘Under the rapidly warming climate in the Arctic and high mountain areas,permafrost is thawing,leading to various hazards at a global scale.One common permafrost hazard termed retrogressive thaw slump(RTS)occurs extensively in ice-rich permafrost areas.Understanding the spatial and temporal distributive features of RTSs in a changing climate is crucial to assessing the damage to infrastructure and decision-making.To this end,we used a machine learning-based model to investigate the environmental factors that could lead to RTS occurrence and create a susceptibility map for RTS along the Qinghai-Tibet Engineering Corridor(QTEC)at a local scale.The results indicate that extreme summer climate events(e.g.,maximum air temperature and rainfall)contributes the most to the RTS occurrence over the flat areas with fine-grained soils.The model predicts that 13%(ca.22,948 km^(2))of the QTEC falls into high to very high susceptibility categories under the current climate over the permafrost areas with mean annual ground temperature at 10 m depth ranging from-3 to-1℃.This study provides insights into the impacts of permafrost thaw on the stability of landscape,carbon stock,and infrastructure,and the results are of value for engineering planning and maintenance.
文摘The loess slumping hazard is a special type of slope failures in the northern area of loess plateau of China. The characteristics of paroxysm and high frequency of the hazard always lead to ruin of cave houses, as well as a high human casualties. The hazard is also seriously harmful to railways, highroads and long transporting pipelines. With the mechanisms of both landslide and falling, as well as the forming process of sliding followed by collapses, loess slumping is used to be treated as landslide or falling. Based on field investigations and lab analyses of the loess between Jingbian County of Shaanxi Province and Puxian County of Shanxi Province along the line of west east gas transportation project which is 300 km long, it is discovered that the hazards of loess slumping are controlled by the content of clay, which lead to their obvious regional properties: the area with a content of clay (<0.005 mm) less than 10 %, called sand loess area, is a seriously developing area of slumping; the area with a content of clay between 10 % and 20 %, called typical loess area, is a medium developing area of slumping; the area with a content of clay more than 20 %, called clay loess area, is a non developing area of slumping. Based on research of the formation mechanism and formation conditions of the loess slumping hazards, some corresponding engineering countermeasures are suggested in this paper.
文摘A new kind of polycarboxylate superplasticizer with high slump loss resistance was obtained by designing scheduled molecular structure.The number average molecular mass of the polymer was characterized by the gel permeation chromatography measurements.And chemical structure of the polymer was observed by the Fourier transform infrared spectroscopy(FT-IR).The results show that the good workable maintaining of self-compacting concrete could be achieved through direct adjustment of number average molecular mass and different unsaturated monomer in synthetic process.The FT-IR analysis illustrated that the high slump loss resistance of polycarboxylate superplasticizers with ester and carboxyl group and expectations of molecular structure were designed.
基金Key Science and Technology Development Fund Project of Hubei Province.China(No.941PO106).
文摘N-2000 is an admixture for concrete,with a low slump loss,high range water-reducing ratio and long-time retarding.The N-2000 is made up of naphthalene-sulfonic-maldehyde polycondensation(NSMP)and ATMP.Its characteristic results from the synergistic effects of NSMP and ATMP.The results show that when 0.7%-1.2%of N-2000 is added to concrete(by mass of cement),the water reducing ratio is up to 20%-30%,and the slump of fresh concrete can be retained for 2 hours without significant loss.N-2000 can not only improve the workability of fresh concrete but also increase the strength of the hardened concrete,especially early strength.It is also proved to have a good compatibility with various cements.
文摘In this work, the yield stress evaluation as a function of water content for slip-prone clayey soils is studied in order to understand how yield stress decreases as water content increases, and their relation with the chemical properties. The clayey soil samples were taken from the region of Teziutlán-Puebla-Mexico. Yield stress was calculated using the slump test in cylindrical geometry. Results show three zones. The first one shows an exponential decrement on yield stress due to lower water content in accord with clayey soils with high content of illita, followed by a second region where yield stress decreases dramatically at a certain critical water concentration, and the third one where yield stress dependence is not well-defined since the clayey soil flow is seen. Finally, it is discussed how yield stress variation due to the water increment influences the landslide risk increment.
文摘In recent years, high precision geometric shape, surface roughness, and cost reduction are required for large glass component molding processes. In this research, the polishing process of stainless steel molding dies used to form thin glass components is investigated. The surface roughness of the polished stainless steel molding die surface is below Rz = 200 nm （P-V） at 15 h polishing with 0.5 % alumina polishing liquid. In the case of polishing process with only the weight of molding die and a polishing pressure of 0.5 kPa, polishing times are approximately 60 h and 20 h, respectively. Final surface roughness polished stainless steel molding die surface with pressure of 0.5 kPa is Rz = 7 nm （P-V）, rms -- 1.6 nm and Ra = 1.4 nm. In a thin glass component manufacturing method, ＂slumping method＂, surface roughness before glass forming is rms = 0.7 nm and Ra = 0.6 nm, and after is rms = 0.7 nm and Ra = 0.6 nm. Therefore, there were no observable changes their surface roughness.
文摘China had entered a period of moderate economic growtht one that is moving at an appropriate pace. China＇s economy is bottoming out and seeking a new balance,
基金funded by the Second Tibetan Plateau Scientific Expedition and Research Program(STEP)(Grant No.2021QZKK0201)the State Key Laboratory of Frozen Soil Engineering Funds(SKLFSE-ZT-202109)the fund of Qinghai Provincial Investigation Project“Study on permafrost degradation and its geological hazard effect”(E1490604).
文摘Under global warming,permafrost around the world is experiencing degradation which is especially so on the Third Pole,the Qinghai-Tibet Plateau(QTP),China.Retrogressive thaw slump(RTS)is one of the thermokarst features caused by rapid degradation of ice rich permafrost,which transforms landforms and threatens infrastructures,and even affects the terrestrial carbon cycle.In this work,vegetation communities surrounding a RTS in the Fenghuoshan Mountains of the interior portion of the Qinghai-Tibet Plateau have been investigated to examine the impact from RTS.This investigation indicates that the occurrence of RTS influences the vegetation community by altering their habitats,especially the soil water content,which forces the vegetation community to evolve in order to adapt to the alterations.In the interior part of RTS where it has been disturbed tremendously,alterations have produced a wider niche and richer plant species.This favors species of a wet environment in a habitat where it was a relatively dry environment of alpine steppe prior to the occurrence of RTS.This study adds to limited observations regarding the impact of RTS to vegetation community on the QTP and helps us to reach a broader understanding of the effects of permafrost degradation as well as global warming.
基金supported by the Qinghai Science and Technology Department Project(2025-QY-225)the National Natural Science Foundation of China(42267024)the Second Comprehensive Scientific Investigation and Research Project of the Qinghai-Xizang Plateau(2019QZKK0905).
文摘The Qinghai-Xizang Plateau of China faces challenges like thaw slumping,threatening slope stability and infrastructure.Understanding the mechanical properties of the roots of the dominant herbaceous plant species in the alpine meadow layer of the permafrost regions on the Qinghai-Xizang Plateau is essential for evaluating their role in enhancing soil shear strength and mitigating slope deformation in these fragile environments.In this study,the roots of four dominant herbaceous plant species—Kobresia pygmaea,Kobresia humilis,Carex moorcroftii,and Leontopodium pusillum—that are widely distributed in the permafrost regions of the Qinghai-Xizang Plateau were explored to determine their mechanical properties and effects in enhancing soil shear strength.Through indoor single root tensile and root group tensile tests,we determined the root diameter,tensile force,tensile strength,tensile ratio,and strength frequency distributions.We also evaluated their contributions to inhibiting slope deformation and failure during the formation and development of thermal thaw slumps in the alpine meadow.The results showed that the distribution of the root diameter of the dominant plant species is mostly normal,while the tensile strength tends to be logarithmically normally distributed.The relationship between the root diameter and root tensile strength conforms to a power function.The theoretical tensile strength of the root group was calculated using the Wu-Waldron Model(WWM)and the Fiber Bundle Model(FBM)under the assumption that the cumulative single tensile strength of the root bundle is identical to the tensile strength of the root group in the WWM.The FBM considers three fracture modes:FBM-D(the tensile force on each single root is proportional to its diameter relative to the total sum of all the root diameters),FBM-S(the cross-sectional stress in the root bundle is uniform),and FBM-N(each tensile strength test of individual roots experiences an equal load).It was found that the model-calculated tensile strength of the root group was 162.60%higher than the test value.The model-derived tensile force of the root group from the FBM-D,FBM-S,and FBM-N was 73.10%,28.91%,and 13.47%higher than the test values,respectively.The additional cohesion of the soil provided by the roots was calculated to be 25.90-45.06 kPa using the modified WWM,67.05-38.15 kPa using the FBM-S,and 57.24-32.74 kPa using the FBM-N.These results not only provide a theoretical basis for further quantitative evaluation of the mechanical effects of the root systems of herbaceous plant species in reinforcing the surface soil but also have practical significance for the effective prevention and control of thermal thaw slumping disasters in the permafrost regions containing native alpine meadows on the Qinghai-Xizang Plateau using flexible plant protection measures.
基金the National Natural Science Foundation of China (Grant Nos.42072318 and 42207227)Central South University Innovation-Driven Research Program (Grant No.2023CXQD044).
文摘The soil-bentonite(SB)cut-off wall has been widely considered a vertical barrier to effectively control the migration of pollutants in contaminated sites.Recently,active porous materials have been used as a promising candidate amendment for mitigating chemical degradation and improving the retardation capacity of the SB cut-off wall.In this study,the silty clay from a typical Cr(VI)contaminated site was selected as the body material of the SB cut-off wall,and zeolite and active carbon were used as the modifiers of the silty clay-bentonite backfills,respectively.The impact of the two modifiers on the engineering properties of the backfills was investigated through a series of slump tests,consolidation tests,hydraulic conductivity tests,and microstructure tests.The experimental results demonstrated that the slump curves closely exhibited a linear relationship between standard slump and moisture content.Meanwhile,bentonite could improve the optimum moisture content of the backfills,while the addition of the two modifiers yielded the opposite outcome.As the bentonite content increased,the compression index of the backfills significantly increased,while the hydraulic conductivity decreased.At a given bentonite content of 5%,the addition of zeolite or active carbon resulted in a reduction in the compression index and initial void ratio,while exhibiting minimal impact on the hydraulic conductivity.Scanning electron microscope(SEM)observations indicated that the silty clay-bentonite backfills became increasingly loose with increasing bentonite content,owing to the filling and expansion of dispersed bentonite layers.The amendment of zeolite or active carbon was able to decrease the backfill volume by promoting the agglomeration of layered bentonite.The findings of this study will be useful for the optimal selection of backfill materials and the performance evaluation of the cut-off wall.
