Based on the analysis of existing relevant research result, a theoretical basis for the defining freeze- thaw erosion zones of Qinghai-Tibet Plateau was been put forward, and a equation for calculating the altitude of...Based on the analysis of existing relevant research result, a theoretical basis for the defining freeze- thaw erosion zones of Qinghai-Tibet Plateau was been put forward, and a equation for calculating the altitude of the lower bound of the freeze-thaw erosion zones of Qinghai-Tibet Plateau was been established in this paper. Moreover, the freeze-thaw erosion zones in Tibet was been identified by using Geographical Information System (GIS) software. Next, based on the comprehensive analysis of impact factors of freeze-thaw erosion, this paper chooses annul temperature range, slop and vegetation as three indexes, works out the criteria for relative classification of freeze-thaw erosion, and realizes the relative classification of the freeze-thaw erosion in Tibet under the support of GIS software. Then, a synthetic assessment of freeze-thaw erosion in Tibet was been done according to the relative classification result.展开更多
Soil erosion is one of the most serious environmental issues constraining the sustainable development of human society and economies.Soil compound erosion is the result of the alternation or interaction between two or...Soil erosion is one of the most serious environmental issues constraining the sustainable development of human society and economies.Soil compound erosion is the result of the alternation or interaction between two or more erosion forces.In recent years,fluctuations and extreme changes in climatic factors(air temperature,precipitation,wind speed,etc.)have led to an increase in the intensity and extent of compound erosion,which is increasingly considered in soil erosion research.First,depending on the involvement of gravity,compound erosion process can be divided into compound erosion with and without gravity.We systematically summarized the research on the mechanisms and processes of alternating or interacting soil erosion forces(wind,water,and freeze-thaw)considering different combinations,combed the characteristics of compound erosion in three typical regions,namely,high-elevation areas,high-latitude areas,and dry and wet transition regions,and reviewed soil compound erosion research methods,such as station observations,simulation experiments,prediction models,and artificial neural networks.The soil erosion model of wind,water,and freeze-thaw interaction is the most significant method for quantifying and predicting compound erosion.Furthermore,it is proposed that there are several issues such as unclear internal mechanisms,lack of comprehensive prediction models,and insufficient scale conversion methods in soil compound erosion research.It is also suggested that future soil compound erosion mechanism research should prioritize the coupling of compound erosion forces and climate change.展开更多
The three-river source region(TRSR), located in the Qinghai-Tibet Plateau in China, suffers from serious freeze-thaw(FT) erosion in China. Considering the unique eco-environment and the driving factors of the FT proce...The three-river source region(TRSR), located in the Qinghai-Tibet Plateau in China, suffers from serious freeze-thaw(FT) erosion in China. Considering the unique eco-environment and the driving factors of the FT process in the TRSR, we introduce the driving force factors of FT erosion(rainfall erosivity and wind field intensity during FT period) and precipitation during the FT period(indicating the phase-changed water content). The objective was to establish an improved evaluation method of FT erosion in the TRSR. The method has good applicability in the study region with an overall precision of 92%. The spatial and temporal changes of FT erosion from 2000 to 2015 are analyzed. Results show that FT erosion is widely distributed in the TRSR, with slight and mild erosion being the most widely distributed, followed by moderate erosion. Among the three sub-regions, the source region of the Yellow River has the slightest erosion intensity, whereas the erosion intensity of the source region of Yangtze River is the most severe. A slight improvement can be observed in the condition of FTerosion over the whole study region from 2000 to 2015. Vegetation coverage is the dominant factor affecting the intensity of FT erosion in the zones with sparse vegetation or bare land, whereas the climate factors play an important role in high vegetation coverage area. Slopes>28° also have a significant effect on the intensity of FT erosion in the zones. The results can provide a scientific basis for the prevention and management of the soil FT erosion in the TRSR.展开更多
The glacial history of Pico de Orizaba indicates that during the Last Glacial Maximum,its icecap covered up to~3000 m asl;due to the air temperature increasing,its main glacier has retreated to 5050 m asl.The retracti...The glacial history of Pico de Orizaba indicates that during the Last Glacial Maximum,its icecap covered up to~3000 m asl;due to the air temperature increasing,its main glacier has retreated to 5050 m asl.The retraction of the glacier has left behind an intense climatic instability that causes a high frequency of freeze-thaw cycles of great intensity;the resulting geomorphological processes are represented by the fragmentation of the bedrock that occupies the upper parts of the mountain.There is a notable lack of studies regarding the fragmentation and erosion occurring in tropical high mountains,and the associated geomorphological risks;for this reason,as a first stage of future continuous research,this study analyzes the freezing and thawing cycles that occur above 4000 m asl,through continuous monitoring of surface ground temperature.The results allow us to identify and characterize four zones:glacial,paraglacial,periglacial and proglacial.It was found that the paraglacial zone presents an intense drop of temperature,of up to~9℃ in only sixty minutes.The rock fatigue and intense freeze-thaw cycles that occur in this area are responsible for the high rate of rock disintegration and represent the main factor of the constant slope dynamics that occur at the site.This activity decreases,both in frequency and intensity,according to the distance to the glacier,which is where the temperature presents a certain degree of stability,until reaching the proglacial zone,where cycles are almost non-existent,and therefore there is no gelifraction activity.The geomorphological processes have resulted in significant alterations to the mountain slopes,which can have severe consequences in terms of risk and water.展开更多
The Tibetan Plateau serves an important shelter function for the ecological security of Asia, and especially China. Here, we proposed and improved indicators and methods for assessing the ecological sensitivity and vu...The Tibetan Plateau serves an important shelter function for the ecological security of Asia, and especially China. Here, we proposed and improved indicators and methods for assessing the ecological sensitivity and vulnerability of the terrestrial alpine Plateau ecosystems and assessed the freeze-thaw erosion, land desertification, water-caused soil loss, and land salinization sensitivity, together with ecological vulnerability, from the overall ecological sensitivity, ecological pressure, and elasticity aspects in Tibet. The results indicate that the terrestrial ecosystem of Tibet is quite sensitive to freeze-thaw erosion, land desertification and water-caused soil loss. Extremely and highly sensitive regions account for 9.62% and 83.69%, respectively, of the total area of the Tibet Autonomous Region. Extremely and highly vulnerable areas account for 0.09% and 52.61%, respectively, primarily distributed in the Himalayan and Gangdise mountain regions in west Tibet; the Nyainqentanglha, Tanggula, Hoh Xil, and Kunlun mountain regions; and the northwest and northern regions of the Changtang Plateau. The results will aid the development of customized protection schedules according to different ecological issues in each region.展开更多
In order to effectively assess the mechanical properties of concrete with freeze-thaw and seawater erosion, tests about basic mechanical properties of concrete after freeze-thaw and seawater erosion are conducted base...In order to effectively assess the mechanical properties of concrete with freeze-thaw and seawater erosion, tests about basic mechanical properties of concrete after freeze-thaw and seawater erosion are conducted based on the large-scale static and dynamic stiffness servo test set. 50, 100, 200 and 300 cycles of freeze-thaw cycling are made on normal concrete, and the artificial seawater is produced. The reasonable wet and dry accelerate system is selected. 10, 20, 30, 40, 50 and 60 cycles of wet and dry cycling are made to concrete after freeze-thaw cycling. The degeneration law of the concrete elastic modulus and compressive strength is studied. The Ottosen tri-axial strength criterion considering cycles of freeze-thaw and wet and dry cycling is deduced based on uniaxial mechanical properties of concrete and damage theory. Experimental results show that with the increase in the number of wet and dry cycles and freeze-thaw cycles, the concrete axial compressive strength and the elastic modulus decline gradually. Tensile and compressive meridians of concrete shrink gradually. The research can be referenced for anti-crack design of actual structures eroded by seawater at cold regions.展开更多
Freeze-thaw processes can influence hydrology,soil erosion,and morphological development by altering the connectivity between active pathways of water and sediment transport.Concentrated flow experi-ments were conduct...Freeze-thaw processes can influence hydrology,soil erosion,and morphological development by altering the connectivity between active pathways of water and sediment transport.Concentrated flow experi-ments were conducted involving frozen,shallow thawed,and unfrozen soil slopes under 1,2,and 4 L/min runoff rates at a temperature of approximately 5℃.In this study,hydrological connectivity was analysed via the simplified hydrological curve and relative surface connection function.Sediment con-nectivity was analysed via the sediment structure connectivity and sediment functional connectivity.Results indicated that hydrological connectivity was greatest on frozen slopes(FS),followed by shallow thawed slopes(STS),and unfrozen slopes(UFS)given a constant flow rate.Hydrological connectivity increased with increasing runoff rate for each freeze-thaw condition.Freezing condition and runoff rate exhibited a positive response to the hydrological connectivity.Sediment structure connectivity increased with increasing runoff rate for each slope condition.The ordering of sediment structure connectivity across freeze-thaw condition was that FS was greater than STS while STS was greater than UFS inde-pendent of flow rate.Sediment functional connectivity included longitudinal,lateral,and vertical con-nectivity components.Sediment longitudinal and vertical connectivity indicated a trend of first increasing and then decreasing under the different runoff rates and freeze-thaw conditions.For a given runoff rate,the ordering of sediment longitudinal and vertical connectivity across freeze-thaw condition was that FS was greater than STS while STS was greater than UFS.Sediment lateral connectivity exhibited a trend of first decreasing and then stabilizing.The ordering of sediment lateral connectivity across freeze-thaw condition was that UFS was greater than STS while STS was greater than FS.FS could more easily reach longitudinal and vertical penetration.Sediment longitudinal and vertical connectivity rates demonstrated increasing trend展开更多
Freeze-thaw erosion can lead to accelerated soil loss,which is an important factor related to soil erosion in cold regions.Tibet is a typical region that is seriously affected by freeze-thaw erosion.Traditionally,the ...Freeze-thaw erosion can lead to accelerated soil loss,which is an important factor related to soil erosion in cold regions.Tibet is a typical region that is seriously affected by freeze-thaw erosion.Traditionally,the analytic hierarchy process(AHP)method is used to calculate the weight of the factors in evaluations of freeze-thaw erosion,but this method cannot accurately depict the fuzziness and randomness of the problem.To overcome this disadvantage,this study proposed an improved AHP method based on the cloud model for the evaluation of the factors impacting freeze-thaw erosion.To establish an improved evaluation method for freeze-thaw erosion in Tibet,the following six factors were selected:mean annual air temperature,mean annual ground surface temperature,average annual precipitation,aspect,vegetation coverage,and topographic relief.The traditional AHP and the cloud model were combined to assign the weights of the impacting factors,and a consistency check was performed.The comprehensive evaluation index model was used to evaluate the intensity of freeze-thaw erosion in Tibet.The results show that freeze-thaw erosion is extensive,stretching over approximately 66.1%of Tibet.Moreover,mild erosion and moderate erosion are the most widely distributed erosion intensity levels,accounting for 36.4%and 34.4%of the total freeze-thaw erosion,respectively.The intensity of freeze-thaw erosion gradually increased from slight erosion in the northwest to severe erosion in the southeast of the study region.The evaluation results for the intensity and distribution of freeze-thaw erosion in Tibet were confirmed to be consistent with the actual situation.In brief,this study supplies a new approach for quantitatively evaluating the intensity of freeze-thaw erosion in Tibet.展开更多
文摘Based on the analysis of existing relevant research result, a theoretical basis for the defining freeze- thaw erosion zones of Qinghai-Tibet Plateau was been put forward, and a equation for calculating the altitude of the lower bound of the freeze-thaw erosion zones of Qinghai-Tibet Plateau was been established in this paper. Moreover, the freeze-thaw erosion zones in Tibet was been identified by using Geographical Information System (GIS) software. Next, based on the comprehensive analysis of impact factors of freeze-thaw erosion, this paper chooses annul temperature range, slop and vegetation as three indexes, works out the criteria for relative classification of freeze-thaw erosion, and realizes the relative classification of the freeze-thaw erosion in Tibet under the support of GIS software. Then, a synthetic assessment of freeze-thaw erosion in Tibet was been done according to the relative classification result.
基金supported by the key research and development and transformation project of Qinghai Province,China(2022-SF-173)the Second Tibetan Plateau Scientific Expedition and Research Program,China(2019QZKK0606)the National Natural Science Foundation of China(42101027).
文摘Soil erosion is one of the most serious environmental issues constraining the sustainable development of human society and economies.Soil compound erosion is the result of the alternation or interaction between two or more erosion forces.In recent years,fluctuations and extreme changes in climatic factors(air temperature,precipitation,wind speed,etc.)have led to an increase in the intensity and extent of compound erosion,which is increasingly considered in soil erosion research.First,depending on the involvement of gravity,compound erosion process can be divided into compound erosion with and without gravity.We systematically summarized the research on the mechanisms and processes of alternating or interacting soil erosion forces(wind,water,and freeze-thaw)considering different combinations,combed the characteristics of compound erosion in three typical regions,namely,high-elevation areas,high-latitude areas,and dry and wet transition regions,and reviewed soil compound erosion research methods,such as station observations,simulation experiments,prediction models,and artificial neural networks.The soil erosion model of wind,water,and freeze-thaw interaction is the most significant method for quantifying and predicting compound erosion.Furthermore,it is proposed that there are several issues such as unclear internal mechanisms,lack of comprehensive prediction models,and insufficient scale conversion methods in soil compound erosion research.It is also suggested that future soil compound erosion mechanism research should prioritize the coupling of compound erosion forces and climate change.
基金funded by the Open fund of Key Laboratory for Digital Land and Resources of Jiangxi Province, East China University of Technology (Grant No. DLLJ201709)Open fund of Key Laboratory for National Geographic Census and Monitoring, National Administration of Surveying, Mapping and Geoinformation (Grant No. 2016NGCM02)+2 种基金Open fund of Key Laboratory of Precise Engineering and Industry Surveying (Grant No. PF2015-17)National Administration of Surveying, Mapping and Geoinformation, National Natural Science Foundation of China (Grant Nos. 41501416, 40775019)the Natural Science Foundation of Shandong Province (Grant Nos. ZR2014DL001, ZR2015DL005)
文摘The three-river source region(TRSR), located in the Qinghai-Tibet Plateau in China, suffers from serious freeze-thaw(FT) erosion in China. Considering the unique eco-environment and the driving factors of the FT process in the TRSR, we introduce the driving force factors of FT erosion(rainfall erosivity and wind field intensity during FT period) and precipitation during the FT period(indicating the phase-changed water content). The objective was to establish an improved evaluation method of FT erosion in the TRSR. The method has good applicability in the study region with an overall precision of 92%. The spatial and temporal changes of FT erosion from 2000 to 2015 are analyzed. Results show that FT erosion is widely distributed in the TRSR, with slight and mild erosion being the most widely distributed, followed by moderate erosion. Among the three sub-regions, the source region of the Yellow River has the slightest erosion intensity, whereas the erosion intensity of the source region of Yangtze River is the most severe. A slight improvement can be observed in the condition of FTerosion over the whole study region from 2000 to 2015. Vegetation coverage is the dominant factor affecting the intensity of FT erosion in the zones with sparse vegetation or bare land, whereas the climate factors play an important role in high vegetation coverage area. Slopes>28° also have a significant effect on the intensity of FT erosion in the zones. The results can provide a scientific basis for the prevention and management of the soil FT erosion in the TRSR.
基金support from the Programa de Apoyos para la Superación del Personal Académico (DGAPA)the support by the Alexander von Humboldt Foundationpart of the SIREI project num 531062023178 developed at CCT-UV
文摘The glacial history of Pico de Orizaba indicates that during the Last Glacial Maximum,its icecap covered up to~3000 m asl;due to the air temperature increasing,its main glacier has retreated to 5050 m asl.The retraction of the glacier has left behind an intense climatic instability that causes a high frequency of freeze-thaw cycles of great intensity;the resulting geomorphological processes are represented by the fragmentation of the bedrock that occupies the upper parts of the mountain.There is a notable lack of studies regarding the fragmentation and erosion occurring in tropical high mountains,and the associated geomorphological risks;for this reason,as a first stage of future continuous research,this study analyzes the freezing and thawing cycles that occur above 4000 m asl,through continuous monitoring of surface ground temperature.The results allow us to identify and characterize four zones:glacial,paraglacial,periglacial and proglacial.It was found that the paraglacial zone presents an intense drop of temperature,of up to~9℃ in only sixty minutes.The rock fatigue and intense freeze-thaw cycles that occur in this area are responsible for the high rate of rock disintegration and represent the main factor of the constant slope dynamics that occur at the site.This activity decreases,both in frequency and intensity,according to the distance to the glacier,which is where the temperature presents a certain degree of stability,until reaching the proglacial zone,where cycles are almost non-existent,and therefore there is no gelifraction activity.The geomorphological processes have resulted in significant alterations to the mountain slopes,which can have severe consequences in terms of risk and water.
基金National Natural Science Foundation of China(41601458,41771141)Natural Science Foundation of Jiangsu Province of China(BK 20170272)
文摘The Tibetan Plateau serves an important shelter function for the ecological security of Asia, and especially China. Here, we proposed and improved indicators and methods for assessing the ecological sensitivity and vulnerability of the terrestrial alpine Plateau ecosystems and assessed the freeze-thaw erosion, land desertification, water-caused soil loss, and land salinization sensitivity, together with ecological vulnerability, from the overall ecological sensitivity, ecological pressure, and elasticity aspects in Tibet. The results indicate that the terrestrial ecosystem of Tibet is quite sensitive to freeze-thaw erosion, land desertification and water-caused soil loss. Extremely and highly sensitive regions account for 9.62% and 83.69%, respectively, of the total area of the Tibet Autonomous Region. Extremely and highly vulnerable areas account for 0.09% and 52.61%, respectively, primarily distributed in the Himalayan and Gangdise mountain regions in west Tibet; the Nyainqentanglha, Tanggula, Hoh Xil, and Kunlun mountain regions; and the northwest and northern regions of the Changtang Plateau. The results will aid the development of customized protection schedules according to different ecological issues in each region.
基金The Natural Science Foundation of Shandong Province(No.ZR2009FQ020)the Ph.D.Programs Foundation of Ministry of Education of China(No.20100131120042)
文摘In order to effectively assess the mechanical properties of concrete with freeze-thaw and seawater erosion, tests about basic mechanical properties of concrete after freeze-thaw and seawater erosion are conducted based on the large-scale static and dynamic stiffness servo test set. 50, 100, 200 and 300 cycles of freeze-thaw cycling are made on normal concrete, and the artificial seawater is produced. The reasonable wet and dry accelerate system is selected. 10, 20, 30, 40, 50 and 60 cycles of wet and dry cycling are made to concrete after freeze-thaw cycling. The degeneration law of the concrete elastic modulus and compressive strength is studied. The Ottosen tri-axial strength criterion considering cycles of freeze-thaw and wet and dry cycling is deduced based on uniaxial mechanical properties of concrete and damage theory. Experimental results show that with the increase in the number of wet and dry cycles and freeze-thaw cycles, the concrete axial compressive strength and the elastic modulus decline gradually. Tensile and compressive meridians of concrete shrink gradually. The research can be referenced for anti-crack design of actual structures eroded by seawater at cold regions.
基金supported by the National Key Research and Development Program of China(No.2022YFF1300801)the National Natural Science Foundation of China(Nos.52009104,U2040208,42107087)+3 种基金the Sin0-German Mobility Programme(No.M-0427)the Shaanxi Province Innovation Talent Promotion Plan Project Technology Innovation Team(No.2020TD-023)the Natural Science Foundations of Shaanxi Province(No.2022JQ-509)Shaanxi Province Water Conservancy Science and Technology Project(2022slkj-04).
文摘Freeze-thaw processes can influence hydrology,soil erosion,and morphological development by altering the connectivity between active pathways of water and sediment transport.Concentrated flow experi-ments were conducted involving frozen,shallow thawed,and unfrozen soil slopes under 1,2,and 4 L/min runoff rates at a temperature of approximately 5℃.In this study,hydrological connectivity was analysed via the simplified hydrological curve and relative surface connection function.Sediment con-nectivity was analysed via the sediment structure connectivity and sediment functional connectivity.Results indicated that hydrological connectivity was greatest on frozen slopes(FS),followed by shallow thawed slopes(STS),and unfrozen slopes(UFS)given a constant flow rate.Hydrological connectivity increased with increasing runoff rate for each freeze-thaw condition.Freezing condition and runoff rate exhibited a positive response to the hydrological connectivity.Sediment structure connectivity increased with increasing runoff rate for each slope condition.The ordering of sediment structure connectivity across freeze-thaw condition was that FS was greater than STS while STS was greater than UFS inde-pendent of flow rate.Sediment functional connectivity included longitudinal,lateral,and vertical con-nectivity components.Sediment longitudinal and vertical connectivity indicated a trend of first increasing and then decreasing under the different runoff rates and freeze-thaw conditions.For a given runoff rate,the ordering of sediment longitudinal and vertical connectivity across freeze-thaw condition was that FS was greater than STS while STS was greater than UFS.Sediment lateral connectivity exhibited a trend of first decreasing and then stabilizing.The ordering of sediment lateral connectivity across freeze-thaw condition was that UFS was greater than STS while STS was greater than FS.FS could more easily reach longitudinal and vertical penetration.Sediment longitudinal and vertical connectivity rates demonstrated increasing trend
基金funded by the National Key Research and Development Program of China(No.2017YFB0503500)the Shandong Provincial Natural Science Foundation(Nos.ZR2020MD015 and ZR2020MD018)+1 种基金the Guangdong Academy of Sciences to build First-rate Research Institution Special Fund for Action Project(No.2019GDASYL-0103003)the Young Teacher Development Support Program of Shandong University of Technology(No.4072-115016).
文摘Freeze-thaw erosion can lead to accelerated soil loss,which is an important factor related to soil erosion in cold regions.Tibet is a typical region that is seriously affected by freeze-thaw erosion.Traditionally,the analytic hierarchy process(AHP)method is used to calculate the weight of the factors in evaluations of freeze-thaw erosion,but this method cannot accurately depict the fuzziness and randomness of the problem.To overcome this disadvantage,this study proposed an improved AHP method based on the cloud model for the evaluation of the factors impacting freeze-thaw erosion.To establish an improved evaluation method for freeze-thaw erosion in Tibet,the following six factors were selected:mean annual air temperature,mean annual ground surface temperature,average annual precipitation,aspect,vegetation coverage,and topographic relief.The traditional AHP and the cloud model were combined to assign the weights of the impacting factors,and a consistency check was performed.The comprehensive evaluation index model was used to evaluate the intensity of freeze-thaw erosion in Tibet.The results show that freeze-thaw erosion is extensive,stretching over approximately 66.1%of Tibet.Moreover,mild erosion and moderate erosion are the most widely distributed erosion intensity levels,accounting for 36.4%and 34.4%of the total freeze-thaw erosion,respectively.The intensity of freeze-thaw erosion gradually increased from slight erosion in the northwest to severe erosion in the southeast of the study region.The evaluation results for the intensity and distribution of freeze-thaw erosion in Tibet were confirmed to be consistent with the actual situation.In brief,this study supplies a new approach for quantitatively evaluating the intensity of freeze-thaw erosion in Tibet.
