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Thermal stability of permafrost under U-shaped crushed rock embankment of the Qinghai-Tibet Railway

Advances in Climate Change research 2024年第1期15卷 158-169页

作者： Kun-Ming XU Guan-Li JIANG Ji CHEN Qing-Bai WU State Key Laboratory of frozen soil engineering Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhou 730000China University of Chinese Academy of Sciences Beijing 100049China beiluhe observation station of frozen soil environment and engineering Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhou730000China

The U-shaped crushed rock embankment(UCRE),of which widely utilized in the permafrost regions along the Qinghai-Tibet Railway,has the capability to rapidly reduce the ground temperature of the underlying ***,there remains uncertainty regarding the adaptation of UCRE to climate change and its long-term cooling *** study focuses on nine UCRE monitoring sites along the Qinghai-Tibet Railway to analyze the dynamic variations of the ground temperature underlying permafrost from 2006 to *** efficiency of UCRE in stabilizing permafrost temperature in different permafrost zones is evaluated by considering the permafrost table,ground temperature,and MAGT,as well as the temperature difference between the top and bottom of the crushed rock layer and the ground temperature variation index(GTVI).The results show that UCRE is suitable for application in extremely unstable warm permafrost regions where the MAGT is higher than-0.5℃.Moreover,UCRE effectively diminishes the disparity in permafrost thermal stability between the sunny and shaded shoulders of the *** short-term and long-term effect of cooling permafrost is experiencing a change related with permafrost ***,in stable cold permafrost regions with MAGT lower than-1.5℃,the long-term cooling effect of UCRE on permafrost seems to gradually di-minishes,but UCRE continues to fulfill the role of stabilizing the underlying permafrost thermal state over the *** results show that UCRE can quickly restore and stabilize the thermal state of permafrost in the early stages of construction,and adapt to the influence of future climate *** findings provide important guidance for understanding the variations of permafrost thermal stability beneath the embankment in permafrost regions,as well as for improving the embankment stability and operational safety of the Qinghai-Tibet Railway.

关键词： Qinghai-Tibet Railway U-shaped crushed rock embankment Climate change Permafrost zone Ground temperature variation index Long-term coolingrole

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Degradation of warm permafrost and talik formation on the Qinghai-Tibet Plateau in 2006-2021

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Advances in Climate Change research 2024年第2期15卷 275-284页

作者： Qi-Hang MEI Ji CHEN You-Qian LIU Shou-Hong ZHANG Jing-Yi ZHAO Tian-Chun DONG Jun-Cheng WANG Yao-Jun ZHAO beiluhe observation and research station of frozen soil engineering and environment Key Laboratory of Cryospheric Science and Frozen Soil EngineeringNorthwest Institute of Eco-Environmental and ResourcesChinese Academy of SciencesLanzhou 730000China China Railway Qinghai-Tibet Group Co.Ltd Xining 810007China University of Chinese Academy of Sciences Beijing 100049China

Permafrost is degrading globally,particularly those with low thermal stability on the Qinghai-Tibet Plateau,owing to climate ***,the inadequacy of direct research on permafrost degradation based on in-situ monitoring limits the prediction of permafrost degradation and engineering *** study explored the processes and modes of permafrost degradation into talik by analyzing ground temperature data from five points in the hinterland of the Qinghai-Tibet Plateau from 2006 to *** results showed that the degradation of the warm permafrost layer with a geothermal gradient of zero occurred simultaneously in the top and bottom *** rate of permafrost degradation from the top down and bottom up increase during the degradation process,but the increase of the former is more drastic after the formation of thawed ***,the construction of the Qinghai-Tibet Railway changed the degradation modes of the permafrost in adjacent natural sites through horizontal heat transfer,particularly after through talik formation under the *** findings suggest that taking countermeasures before or immediately after forming thawed interlayer is more *** evaluating the thermal impact of projects in warm permafrost regions,special attention should be given to the horizontal heat transfer process that may result from the formation of a through talik.

关键词： Warm permafrost Degradation Talik Qinghai-Tibet Plateau Climate change

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Climate warming is likely to weaken the performance of two-phase closed thermosyphon on the Qinghai-Tibet Plateau

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Advances in Climate Change research 2024年第1期15卷 90-100页

作者： Guan-Li JIANG Zi-Teng FU Xin-Yu MEN Hong-Ting ZHAO Si-Ru GAO Yong-Zhi LI Qing-Bai WU State Key Laboratory of frozen soil engineering Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhou 730000China beiluhe observation and research station on frozen soil engineering and environment in the Qinghai-Tibet Plateau Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhou 730000China Muli Field Scientific observation and research station for Gas Hydrate China Geological SurveyBeijing 100083China University of Chinese Academy of Sciences Beijing 100049China School of Civil engineering and Architecture Jiaxing Nanhu UniversityJiaxing 314001China

Over the years,numerous geotechnical approaches have been implemented to mitigate the adverse effects of climate warming on various infrastructures in the permafrost region of the Qinghai-Tibet Plateau(QTP),such as the Qinghai-Tibet Highway and Railway,and achieved the expected engineering ***,little attention has been given to whether the performance of these geotechnical approaches has changed during the ongoing process of climate *** investigate the performance variation of one of these geotechnical approaches,which is two-phase closed thermosyphon(TPCT),during sustained climate warming,we conducted a statistical analysis of soil temperature monitoring data in 2003-2020 from eight regular embankments and six TPCT embankments in our permafrost monitoring *** results indicate that TPCT undeniably has a cooling effect on the permafrost beneath embankments,even rapidly eliminated previously formed taliks beneath ***,further analysis reveals that the performance of TPCT has been weakening during sustained climate warming,which has confirmed by the re-forming of the taliks beneath embankment where they had been previously *** on the current understanding,we attributed the weakening of thermosyphon performance to a significant reduction in the air temperature freezing index caused by ongoing climate *** this study,we aimed to draw attention to the evolving performance of geotechnical approaches in permafrost regions amid climate warming,prompting necessary engineering innovations to address this situation and ensure the sustainable development of the permafrost region on the QTP.

关键词： Two-phase closed thermosyphon Climate warming Supra-permafrost talik Permafrost degradation Qinghai-Tibet Highway

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Application of a concrete thermal pile in cooling the warming permafrost under climate change

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Advances in Climate Change research 2024年第1期15卷 170-183页

作者： Yun-Hu SHANG Fu-Jun NIU Guo-Yu LI Jian-Hong FANG Ze-Yong GAO State Key Laboratory of frozen soil engineering Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhou 730000China Da Xing'anling observation and research station of frozen-Ground engineering and environment Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesJagdaqi 165000China Qinghai research Institute of Transportation Xining 810008China

Permafrost degradation caused by climate warming is posing a serious threat to the stability of cast-in-place pile foundations in warm permafrost *** cold energy can be effectively utilized by two-phase closed thermosyphons(TPCTs)to cool the ***,we installed TPCTs in a cast-in-place pile foundation to create a unique structure called a thermal pile,which effectively utilizes the TPCTs to regulate ground *** we conducted a case study and numerical simulation to exhibit the cooling performance,and optimize the structure of the thermal *** purpose of this study is to promote the application of thermal piles in unstable permafrost *** on the findings,the thermal pile operated for approximately 53%of the entire year and effectively reduced the deep ground temperature at a rate of at least-0.1℃per ***,it successfully raised the permafrost table that is 0.35 m shallower than the natural ground *** characteristics prove highly beneficial in mitigating the adverse effects of permafrost degradation and enhancing infrastructure *** the length of the condenser section and the diameter of the TPCT in a suitable manner can effectively enhance the cooling capability of the thermal pile and ensure the long-term mechanical stability of the pile foundation even under climate warming.

关键词： Heat transfer Cold energy Warm permafrost Two-phase closed thermosyphons Cast-in-place pile foundation

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Experimental and numerical interpretation on composite foundation consisting of soil-cement column within warm and ice-rich frozen soil

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Journal of Mountain Science 2024年第1期21卷 313-321页

作者： WANG Honglei ZHANG Jianming WEI Shoucai SUN Zhizhong ZHANG Hu School of Civil engineering Hebei University of EngineeringHandan 056038China State Key Laboratory of frozen soil engineering Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhou 730000China Second Geological Brigade Bureau of Geology and Mineral Resources Exploration and DevelopmentLhasa 850000China Da Xing’anling observation and research station of frozen Ground engineering and environment Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesJiagedaqi 165100China School of Civil engineering Northeast Forestry UniversityHarbin 150040China

Affected by climate warming and anthropogenic disturbances, the thermo-mechanical stability of warm and ice-rich frozen ground along the Qinghai-Tibet engineering corridor(QTEC) is continuously decreased, which may delay the construction of major projects in the future. In this study, based on chemical stabilization of warm and icerich frozen ground, the soil-cement column(SCC) for ground improvement was recommended to reinforce the foundations in warm and ice-rich permafrost regions. To explore the validity of countermeasures mentioned above, both the original foundation and the composite foundation consisting of SCC with soil temperature of -1.0℃ were prepared in the laboratory, and then the plate loading tests were carried out. The laboratory investigations indicated that the bearing capacity of composite foundation consisting of SCC was higher than that of original foundation, and the total deformation of original foundation was greater than that of composite foundation, meaning that overall stability of foundation with warm and ice-rich frozen soil can be improved by SCC installation. Meanwhile, a numerical model considering the interface interaction between frozen soil and SCC was established for interpretating the bearing mechanism of composite foundation. The numerical investigations revealed that the SCC within composite foundation was responsible for the more applied load, and the applied load can be delivered to deeper zone in depth due to the SCC installation, which was favorable for improving the bearing characteristic of composite foundation. The investigations provide the valuable guideline for the choice of engineering supporting techniques to major projects within the QTEC.

关键词： Chemical stabilization Ground improvement Composite foundation frozen soil engineering Qinghai-Tibet engineering corridor

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Thermal performance of cast-in-place piles with artificial ground freezing in permafrost regions

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Journal of Mountain Science 2024年第4期21卷 1307-1328页

作者： WANG Xinbin CHEN Kun YU Qihao GUO Lei YOU Yanhui JIN Mingyang State Key Laboratory of frozen soil engineering Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhou 730000China University of Chinese Academy of Sciences Beijing 100049China

During the construction of cast-in-place piles in warm permafrost,the heat carried by concrete and the cement hydration reaction can cause strong thermal disturbance to the surrounding *** the bearing capacity of the pile is quite small before the full freeze-back,the quick refreezing of the native soils surrounding the cast-in-place pile has become the focus of the infrastructure construction in *** solve this problem,this paper innovatively puts forward the application of the artificial ground freezing(AGF)method at the end of the curing period of cast-in-place piles in permafrost.A field test on the AGF was conducted at the beiluhe observation and research station of frozen soil engineering and environment(34°51.2'N,92°56.4'E)in the Qinghai Tibet Plateau(QTP),and then a 3-D numerical model was established to investigate the thermal performance of piles using AGF under different engineering ***,the long-term thermal performance of piles after the completion of AGF under different conditions was *** experiment results demonstrate that AGF is an effective method to reduce the refreezing time of the soil surrounding the piles constructed in permafrost terrain,with the ability to reduce the pile-soil interface temperatures to below the natural ground temperature within 3 *** results further prove that AGF still has a good cooling effect even under unfavorable engineering conditions such as high pouring temperature,large pile diameter,and large pile ***,the application of this method is meaningful to save the subsequent latency time and solve the problem of thermal disturbance in pile construction in *** research results are highly relevant for the spread of AGF technology and the rapid building of pile foundations in permafrost.

关键词： Permafrost engineering Cast-in-place pile Artificial ground freezing Thermal performance.

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Permafrost degradation along the Qinghai-Tibet Highway from 1995 to 2020

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Advances in Climate Change research 2023年第2期14卷 248-254页

作者： Zhi-Zhong SUN Wei MA Gui-Long WU Yong-Zhi LIU Guo-Yu LI State Key Laboratory of frozen soil engineering Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhou 730000China Da Xing'anling observation and research station of frozen Ground engineering and environment Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesJagdaqi 165000China beiluhe observation and research station on frozen soil engineering and environment in QinghaieTibet Plateau Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesGeermu 816000China

Permafrost degradation significantly affects engineering infrastructure,hydrologic processes,landscape and geomorphic processes,ecosystems and carbon cycling in cold *** permafrost degradation along the Qinghai–Tibet Highway(QTH)on the Qinghai–Tibet Plateau,China,introduces an adverse effect on the deformation of the highway *** present,observation of a long series of ground temperatures is *** 1995 to 2020,a monitoring system of ground temperature in 10 natural sites along QTH was built and *** temperatures at different depths were continuously observed *** this study,permafrost changes along QTH were quantitatively investigated based on these *** main results showed that both the permafrost table depth(PTD)and ground temperature at different depths exhibited an increasing trend from 1995 to 2020 with widespread spatiotemporal *** higher the annual mean and range of PTD were,the higher the increase rate in *** increase rates in PTDs in the warm permafrost regions were 6.18 cm per year larger than those in the cold ***,the increase rates in ground temperature decreased with the increase in depth at each *** different depths,the smaller the mean annual ground temperature(MAGT)was,the larger the increase rate in the permafrost *** larger the range of ground temperatures was,the bigger the increase rate in the permafrost *** a depth of 6.0 m,the increase rate in the ground temperature in cold permafrost regions was twice that in warm permafrost *** on the magnitudes and differences in permafrost degradation along QTH is necessary for the design of effective adaption strategies for engineering construction and environment protection in permafrost regions under climatic warming.

关键词： Permafrost table depth Permafrost temperature Permafrost degradation Qinghai-Tibet Highway Qinghai-Tibet Plateau

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Discussion on pile axial load test methods and their applicability in cold regions

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research in Cold and Arid Regions 2022年第4期14卷 239-249页

作者： JiaWei Gao Ji Chen Xin Hou QiHang Mei YongHeng Liu beiluhe observation and research station on frozen soil engineering and environment in Qinghai-Tibet Plateau State Key Laboratory of Frozen Soil EngineeringLanzhouGansu730000China University of Chinese Academy of Sciences Beijing100049China

The measurement of pile axial load is of great significance to determining pile foundation design parameters such as skin friction and end bearing capacity and analyzing load transfer *** by the temperature and ice content of frozen ground,the interface contact relationship between pile foundation and frozen soil is complicated,making pile axial load measurements more uncertain than that in non-frozen ***,it is necessary to gain an in-depth understanding of the current pile axial load test *** methods are systematically reviewed:vibrating wire sensors,strain gauges,sliding micrometers,and optical fiber strain *** the same time,the applicability of the four test methods in frozen soil regions is discussed in *** first two methods are mature and commonly *** sliding micrometer is only suitable for short-term *** the Fiber Bragg grating(FBG)strain gauge meets the monitoring requirements,the Brillouin optical time-domain reflectometer(BOTDR)needs further *** paper aims to provide a technical reference for selecting and applying different methods in the pile axial load test for the stability study and bearing capacity assessment of pile foundations in cold regions.

关键词： Pile axial load Test methods Pile shaft resistance Sensors Cold regions

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Thermal effect of the accumulated water with different depths on permafrost subgrade in cold regions

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Advances in Climate Change research 2023年第2期14卷 179-189页

作者： Er-Xing PENG Xiao-Ying HU Yu SHENG Ji-Chun WU Wei CAO Qi-Fan YANG Xiang-Bin ZHAO Ji CHEN State Key Laboratory of frozen soil engineering Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhou 730000China School of Civil engineering Lanzhou University of TechnologyLanzhou 730050China beiluhe observation and research station on frozen soil engineering and environment in Qinghai‒Tibet Plateau State Key Laboratory of Frozen Soil EngineeringNorthwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhou 730000China

In cold regions,the thermal effect of accumulated water on underlying permafrost and permafrost subgrade remains a significant hazard causing engineering *** depth of accumulated water may be an important influence factor of permafrost thermal stability,but there is lack of qualitative and quantitative research about *** this study,equivalent thermal conductivity theory and solid heat transfer theory have been used to establish the calculation model for simulating heat transfer in water and ***,the accuracy and reliability of the calculation model are checked by monitored data and subsequently used to analyze the thermal erosion of water on underlying permafrost and permafrost under the *** simulation results show that shallow water can protect permafrost and deeper water disrupts the thermal stability of underlying *** thermal effect extent of water is primarily determined by its depth,and the concept of critical depth and stable depth of accumulated water has been ***,the temperature field of permafrost under embankment can be changed by the slope toe *** addition,the thermal effect range of the slope toe water is limited by the thermal influence radius,which increases with the depth of standing *** findings provide support as well as a fundamental base for environmental issues arising from the accumulated *** observations will,thus,also be valuable to further engineering environment studies in cold regions.

关键词： Accumulated water Water depth Permafrost Embankment Thermal effect

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Response of soil hydrothermal processes within the active layer to variable alpine vegetation conditions on the Qinghai‒Tibet Plateau

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Advances in Climate Change research 2023年第2期14卷 200-212页

作者： Zi-Teng FU Qing-Bai WU Lu-Yang WANG Ya-Li LIU State Key Laboratory of frozen soil engineering Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhou 730000China University of Chinese Academy of Sciences Beijing 100049China beiluhe observation station of frozen soil environment and engineering Northwest Institute of Eco-environment and ResourcesChinese Academy of SciencesLanzhou 730000China

Alpine vegetation plays an important role in the thermal stability of the permafrost under a warming climate,as it affects ground hydrothermal *** response of soil hydrothermal dynamics in the active layer to permafrost degradation under different alpine grassland types is unclear on the Qinghai‒Tibet *** this study,long-term soil temperature and soil water content in the active layer were monitored in situ from October 2010 to December 2018 at five sites in the Kaixinling permafrost region on the interior Qinghai‒Tibet Plateau along the QinghaieTibet *** sites included an alpine steppe(AS),three alpine meadows(AM)with different degrees of degraded vegetation,and an alpine swamp meadow(ASM).Based on field-monitored data,the variations in soil temperature,soil water content,and freezeethaw processes were examined in the active *** response characteristics of the soil hydrothermal processes to climate change were analysed under the different alpine *** results showed that the duration of the thawing and freezing stages of the active layer of the AMs was shorter than that of the ASM and the *** average mean annual soil temperature(MAST)in the active layer of the AM((-1.25±0.50)℃)was lower than those in the AS((-0.71±0.39)℃)and ASM((-0.45±0.57)℃),while the AM had the highest rate of soil temperature increase((0.2±0.06)℃ per year).The annual amplitude of ground temperature in the active layer increased with the transition direction of the alpine vegetation type from ASM to AM to *** small surface offset(SO)and thermal offset(TO)(absolute values)indicated that the ground thermal state of the AM was more unstable,as it was more sensitive to the increase in air temperature than the ASM or the *** properties controlled the distribution of soil water content within the active layer,but vegetation improved the shallow soil structure by producing more belowground phytomass,thus,enhancing soil water content in the 0-30 cm layer.

关键词： Alpine ecosystem soil temperature soil water dynamics Climate warming Permafrost degradation

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