To systematically investigate the short-term consequences of sudden temperature fluctuations and address the challenges of frost damage in extreme environments,this study examined tunnel entrances in the Northeast Chi...To systematically investigate the short-term consequences of sudden temperature fluctuations and address the challenges of frost damage in extreme environments,this study examined tunnel entrances in the Northeast China.Laboratory freeze-thaw/freezing tests and multi-field coupling simulations were conducted to assess the response of tunnel linings and adjacent rock in cold regions.This study reveals,for the first time,the spatial and temporal migration pattern of'low temperature at the foot of the arch–high temperature at the arch',providing a reference for the anti-freezing design of tunnels in cold regions.The main conclusions are as follows:(1)High water content and repeated freeze-thaw cycles significantly affect the soil's stress-strain curves,hardening them under increasing confining pressure while accelerating soil strength degradation.Before the freeze-thaw cycle,a 3%increase in water content reduces the modulus of elasticity by approximately 40%.After 10 freeze-thaw cycles,the modulus reduction escalates to 33%–63%,with soil specimens exhibiting the most significant degradation at the optimal water content.(2)During the freezing process,the soil's stress-strain curves exhibit softening features,with failure strength and cohesion increasing nonlinearly as temperature decreases.The internal friction angle reveals no clear pattern,and the failure mode tends toward brittleness.(3)A sudden temperature decrease results in the lowest temperature at the arch foot of the secondary lining,while the highest is at the primary support's vault.After a sudden temperature increase,the lowest temperature shifts to the primary support's arch foot,while the highest shifts to the secondary lining's vault.Temperature changes in the surrounding rock are most pronounced within 0.5 m outside the lining.(4)Sudden temperature fluctuations induce short-term irreversible vertical displacement at the ground surface,expansion of horizontal clearance after temperature decrease,and convergence after the temperature increase.The vault and invert undergo cyclical uplift and settlement due to freezing and thawing.A temperature decrease of 20◦C leads to the maximum freeze-heave stress.Stress distribution in the lining shows tensile stress at the sidewalls(473 kPa)and compressive stress at the arch foot(1,005 kPa).Both values are below the material's strength limits,indicating structural safety under freeze-heave stress alone.展开更多
Rapid urbanization has accelerated biodiversity loss and ecosystem instability,particularly in ecologically fragile cold-region cities.As a critical node along the East Asian–Australasian Flyway,Harbin provides essen...Rapid urbanization has accelerated biodiversity loss and ecosystem instability,particularly in ecologically fragile cold-region cities.As a critical node along the East Asian–Australasian Flyway,Harbin provides essential habitats for migratory birds but faces increasing ecological fragmentation.To better understand how urban ecological networks(ENs)respond to disturbances in cold-region environments,this study proposes an integrated framework that explicitly incorporates resilience simulation into EN analysis.Understory insectivorous birds,characterized by high ecological sensitivity and recognized as“urban avoiders”,were selected as indicator species to identify key habitats and ecological corridors.ENs were constructed based on species habitat suitability and landscape connectivity analyses,while resilience was evaluated through disturbance-based simulations that examined network responses under targeted and random node removal scenarios.The results indicate that most of the 120 identified ecological sources are distributed along both banks of the Songhua River,Northeast China,and are connected by 280 ecological corridors,including 39 key corridors.A total of 12 key nodes and 25 barrier points were detected,primarily concentrated in the old urban areas in the southern part of the city.Resilience simulations show that targeted disturbances lead to a substantially faster decline in both structural and functional resilience compared with random disturbances.The key nodes located along the Songhua River corridor and in southern Harbin play a critical role in maintaining overall network stability.By linking species-based habitat modeling with disturbance-driven resilience assessment,this study advances the understanding of EN stability in cold-region urban ecosystems and provides practical guidance for biodiversity conservation and sustainable urban planning in cold-region and other ecologically vulnerable cities.展开更多
The cold-region eco-environments along the China-Russia Crude Oil Pipeline (CRCOP) in northern Northeast China are in disequilibrium due to the combined influences of pronounced climate warming and intensive anthropog...The cold-region eco-environments along the China-Russia Crude Oil Pipeline (CRCOP) in northern Northeast China are in disequilibrium due to the combined influences of pronounced climate warming and intensive anthropogenic activities.This is evidenced by the sharp areal reduction and northward shifting of the boreal forests,shrinking of wetlands,enhancing of soil erosion,accelerating degradation of permafrost and deteriorating of cold-region eco-environments.The degradation of permafrost plays an important role as an internal drive in the eco-environmental changes.Many components of the cold-region eco-environments,including frozen ground,forests,wetlands and peatlands,forest fires and 'heating island effect' of rapid urbanization,are interdependent,interactive,and integrated in the boreal ecosystems.The construction and long-term operation of the CRCOP system will inevitably disturb the cold-region environments along the pipeline.Therefore,a mandatory and carefully-elaborated environ-mental impact statement is indispensable for the proper mitigation of the ensued adverse impacts.Proper management,effective protection and practical rehabilitation of the damaged cold-region environments are a daunting,costly and long-term commitment.The recommended measures for protection and restoration of permafrost eco-environments along the pipeline route include adequate investigation,assessment and monitoring of permafrost and cold-region environments,compliance of pipeline construction and operation codes for environmental management,proper and timely re-vegetation,returning the cultivated lands to forests and grasslands,and effective mitigation of forest fire hazards.展开更多
基金supported by the National Key R&D Program of China(No.2024YFF0507901)the National Natural Science Foundation of China(Nos.U2468217 and U2034205).
摘要To systematically investigate the short-term consequences of sudden temperature fluctuations and address the challenges of frost damage in extreme environments,this study examined tunnel entrances in the Northeast China.Laboratory freeze-thaw/freezing tests and multi-field coupling simulations were conducted to assess the response of tunnel linings and adjacent rock in cold regions.This study reveals,for the first time,the spatial and temporal migration pattern of'low temperature at the foot of the arch–high temperature at the arch',providing a reference for the anti-freezing design of tunnels in cold regions.The main conclusions are as follows:(1)High water content and repeated freeze-thaw cycles significantly affect the soil's stress-strain curves,hardening them under increasing confining pressure while accelerating soil strength degradation.Before the freeze-thaw cycle,a 3%increase in water content reduces the modulus of elasticity by approximately 40%.After 10 freeze-thaw cycles,the modulus reduction escalates to 33%–63%,with soil specimens exhibiting the most significant degradation at the optimal water content.(2)During the freezing process,the soil's stress-strain curves exhibit softening features,with failure strength and cohesion increasing nonlinearly as temperature decreases.The internal friction angle reveals no clear pattern,and the failure mode tends toward brittleness.(3)A sudden temperature decrease results in the lowest temperature at the arch foot of the secondary lining,while the highest is at the primary support's vault.After a sudden temperature increase,the lowest temperature shifts to the primary support's arch foot,while the highest shifts to the secondary lining's vault.Temperature changes in the surrounding rock are most pronounced within 0.5 m outside the lining.(4)Sudden temperature fluctuations induce short-term irreversible vertical displacement at the ground surface,expansion of horizontal clearance after temperature decrease,and convergence after the temperature increase.The vault and invert undergo cyclical uplift and settlement due to freezing and thawing.A temperature decrease of 20◦C leads to the maximum freeze-heave stress.Stress distribution in the lining shows tensile stress at the sidewalls(473 kPa)and compressive stress at the arch foot(1,005 kPa).Both values are below the material's strength limits,indicating structural safety under freeze-heave stress alone.
基金supported by the Heilongjiang Provincial Atlas of Key Protected Wild Fauna and Flora,commissioned by the Heilongjiang Provincial Forestry and Grassland Administration(No.[230001]GFCG[CS]20250022)。
摘要Rapid urbanization has accelerated biodiversity loss and ecosystem instability,particularly in ecologically fragile cold-region cities.As a critical node along the East Asian–Australasian Flyway,Harbin provides essential habitats for migratory birds but faces increasing ecological fragmentation.To better understand how urban ecological networks(ENs)respond to disturbances in cold-region environments,this study proposes an integrated framework that explicitly incorporates resilience simulation into EN analysis.Understory insectivorous birds,characterized by high ecological sensitivity and recognized as“urban avoiders”,were selected as indicator species to identify key habitats and ecological corridors.ENs were constructed based on species habitat suitability and landscape connectivity analyses,while resilience was evaluated through disturbance-based simulations that examined network responses under targeted and random node removal scenarios.The results indicate that most of the 120 identified ecological sources are distributed along both banks of the Songhua River,Northeast China,and are connected by 280 ecological corridors,including 39 key corridors.A total of 12 key nodes and 25 barrier points were detected,primarily concentrated in the old urban areas in the southern part of the city.Resilience simulations show that targeted disturbances lead to a substantially faster decline in both structural and functional resilience compared with random disturbances.The key nodes located along the Songhua River corridor and in southern Harbin play a critical role in maintaining overall network stability.By linking species-based habitat modeling with disturbance-driven resilience assessment,this study advances the understanding of EN stability in cold-region urban ecosystems and provides practical guidance for biodiversity conservation and sustainable urban planning in cold-region and other ecologically vulnerable cities.
基金funding from the Chinese Academy of Sciences Knowledge Innovation Program (Grant No. KZCX2-YW-311)the Chinese Academy of Sciences 100-Talents Program (HuiJun Jin)
摘要The cold-region eco-environments along the China-Russia Crude Oil Pipeline (CRCOP) in northern Northeast China are in disequilibrium due to the combined influences of pronounced climate warming and intensive anthropogenic activities.This is evidenced by the sharp areal reduction and northward shifting of the boreal forests,shrinking of wetlands,enhancing of soil erosion,accelerating degradation of permafrost and deteriorating of cold-region eco-environments.The degradation of permafrost plays an important role as an internal drive in the eco-environmental changes.Many components of the cold-region eco-environments,including frozen ground,forests,wetlands and peatlands,forest fires and 'heating island effect' of rapid urbanization,are interdependent,interactive,and integrated in the boreal ecosystems.The construction and long-term operation of the CRCOP system will inevitably disturb the cold-region environments along the pipeline.Therefore,a mandatory and carefully-elaborated environ-mental impact statement is indispensable for the proper mitigation of the ensued adverse impacts.Proper management,effective protection and practical rehabilitation of the damaged cold-region environments are a daunting,costly and long-term commitment.The recommended measures for protection and restoration of permafrost eco-environments along the pipeline route include adequate investigation,assessment and monitoring of permafrost and cold-region environments,compliance of pipeline construction and operation codes for environmental management,proper and timely re-vegetation,returning the cultivated lands to forests and grasslands,and effective mitigation of forest fire hazards.