scholarly journals Experimental and Numerical Analyses of the Thermal Regime of a Traditional Embankment in Permafrost Regions

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Qihang Mei ◽  
Ji Chen ◽  
Shouhong Zhang ◽  
Xin Hou ◽  
Jingyi Zhao ◽  
...  
Keyword(s):  
Climate Warming ◽  
Thermal Regime ◽  
Thermal Characteristics ◽  
Ground Temperature ◽  
Transfer Model ◽  
Thermal Disturbance ◽  
Undisturbed Site ◽  
Longitudinal Cracks ◽  
Permafrost Regions

Traditional embankment is widely used in the permafrost regions along the Qinghai-Tibet Railway (QTR) because of its simple construction and lower cost. However, this form of embankment has insufficient ability to resist external thermal disturbance. To clarify the thermal characteristics of traditional embankment under climate warming, the ground temperature change process of section K1068 + 750 of the QTR was analysed in this study. Based on the field monitoring data from 2006 to 2019 and the established heat transfer model, the past and future changes of permafrost thermal regime under the embankment were analysed. The results show that the degradation of permafrost under the embankment is faster than that under the undisturbed site due to the combined of embankment construction and climate warming. The sunny-shady slope effect related to embankment orientation makes the distribution of permafrost temperature under embankment asymmetric. In the long term, permafrost degrades both under the undisturbed site and embankment. The continuous degradation of permafrost causes the settlement and deformation of embankment, especially the asymmetric degradation of permafrost on sunny side and shady side will cause longitudinal cracks on the embankment. Therefore, timely application of strengthening measures which can slow down the degradation of permafrost and adjust the uneven ground temperature on the sunny and shady sides under the embankment is of great significance to the safety of the traditional embankment.

scholarly journals A New Mitigation Measure to Counter Thermal Instability of Air-Cooled Embankment in Sandy Permafrost Zones of Tibet Plateau

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Minghao Liu ◽  
Jing Luo ◽  
Liang Zhang ◽  
Xin Ju
Keyword(s):  
Cooling Capacity ◽  
Ground Temperature ◽  
Tibet Plateau ◽  
Crushed Rock ◽  
Transfer Model ◽  
Rock Layer ◽  
Cooling Performance ◽  
Permafrost Warming ◽  
Warm Permafrost

A crushed-rock revetment (CRR) with high permeability that can be paved on embankment slopes is widely used to cool and protect the subgrade permafrost. In this study, a traditional CRR over warm permafrost was selected to investigate its cooling characteristics based on the ground temperature observed from 2003 to 2014. A new mitigation structure (NMS) was designed to improve the cooling capacity of the CRR and to counter the pore-filling of the rock layer. Numerical simulations were conducted to evaluate the cooling performance and reinforcing capacity of the NMS based on a developed heat and mass transfer model. The results indicate that the traditional CRR can improve the symmetry of the permafrost subgrade and decrease the ground temperature of shallow permafrost. However, the CRR cannot generate strong enough cooling to influence the deep (below 10 m depth) and warm permafrost with a mean annual ground temperature above −1.0°C. The wind-blown sand can further weaken the cooling of the CRR and cause significant permafrost warming and thawing beneath the slopes, posing a severe threat to the long-term safe operation of the embankment. The proposed NMS can produce a significantly superior cooling performance to the CRR. If the CRR is reinforced by the new structure, it can not only effectively cool the underlying warm permafrost but also elevate the permafrost table. The new structure can also protect the rock layer on the slopes from sand-filling. The NMS can be used as an effective method for roadbed design or maintenance over warm permafrost.

scholarly journals Long-Term Variability in Ground Thermal State in Central Yakutia’s Tuymaada Valley

Land ◽  
2021 ◽  
Vol 10 (11) ◽  
pp. 1231
Author(s):  
Stepan Prokopievich Varlamov ◽  
Yuri Borisovich Skachkov ◽  
Pavel Nikolaevich Skryabin
Keyword(s):  
Active Layer ◽  
Climate Warming ◽  
Thermal State ◽  
Snow Accumulation ◽  
Ground Temperature ◽  
Active Layer Thickness ◽  
Lena River ◽  
The North ◽  
Term Data

This paper presents the results of long-term temperature monitoring at the Yakutsk and Zeleny Lug stations, which are experimental sites, for the thermal state of valley permafrost landscapes under the conditions of modern climate warming. An analysis of the long-term data from meteorological stations in the region clearly showed one of the highest trends of increase in the mean annual air temperature in the north of Russia. Here, we established quantitative regularities in the long-term variability of the ground temperature at the bottom of the active layer and at zero amplitude. The dynamics of the ground temperature of the layer of zero amplitude during climate warming indicate the thermal stability of permafrost. The main regulating factor of the thermal state of grounds in permafrost landscapes is short-term fluctuations in the regime of snow accumulation. Active layer thickness is characterized by low interannual variability, weak climate warming responses, and insignificant trends. The results of studies of the thermal regime of soils can be extended to the same types of valley landscapes in the Lena River, and are a reliable basis for predicting heat transfer in natural and disturbed landscapes.

scholarly journals Thermal regime of a highly regulated Italian river (Ticino River) and implications for aquatic communities

2016 ◽  
Author(s):  
Francesca Salmaso ◽  
Silvia Quadroni ◽  
Gaetano Gentili ◽  
Giuseppe Crosa
Keyword(s):  
Fish Species ◽  
Climate Warming ◽  
Thermal Regime ◽  
Thermal Characteristics ◽  
Climatic Conditions ◽  
Regulated River ◽  
Low Flow ◽  
Aquatic Communities ◽  
Thermal Alteration ◽  
River Temperature

<p>Thermal alteration is one of the adverse effects of flow regulation sharpened in recent years due to climate changes. In this work, we characterize the thermal regime of a highly regulated river located in Northern Italy, which is the emissary of Lake Maggiore. The thermal characteristics of the study reach are influenced by the presence of two dams and by climate warming. In the 15-year monitored period (1999-2013) a significant increase of the mean annual river temperature (i.e., +1.8°C) was indeed recorded. Minimum and maximum water temperatures were detected in correspondence of low-flow periods in February and August, respectively. During August the temperature reached a maximum of 27°C, that is a value below the upper thermal limit of tolerance for most of the aquatic taxa collected in the study area. Moreover, the local presence of seeps and the interaction with groundwater play an important ecological role by guaranteeing patches of cool water to the aquatic communities. Nevertheless, the sensitive early life stages of fish species that spawn in spring/summer may be affected by the high summer temperatures and the expected future climate warming. The wider range of temperatures preferred by alien fish species could result into a competitive disadvantage for autochthonous species. The current minimum flows established by local laws as environmental flows appeared to be able to guarantee an acceptable thermal alteration in morphologically heterogeneous reaches where river/groundwater interaction occurred, at least within the current climatic conditions.</p>

The Application of Crushed Rock Materials upon Railway Embankments in Permafrost Regions

2011 ◽  
Vol 255-260 ◽  
pp. 4027-4033 ◽  
Author(s):  
Yan Hu Mu ◽  
Wei Ma ◽  
Zhi Zhong Sun ◽  
Yong Zhi Liu
Keyword(s):  
Thermal Stability ◽  
Warming Trend ◽  
Ground Temperature ◽  
Crushed Rock ◽  
Rock Materials ◽  
Ground Temperatures ◽  
Permafrost Table ◽  
Thermal Stability Of ◽  
Permafrost Regions

Crushed rock materials had been utilized extensively upon embankments, termed as crushed rock embankment (CRE), along the Qinghai-Tibet Railway in permafrost regions. Based on a long-term monitoring system along the railway, thermal stability and deformation characteristics and mechanisms of CRE were analyzed by field monitoring datasets from 2005 to 2009. The thermal stability analyses indicated that permafrost tables beneath CRE all had upwards movements but to varying degrees. For U-shaped crushed rock embankment (UCRE), the thermal stability of underlying permafrost kept well; along with permafrost table moving upwards, the shallow ground temperatures beneath the embankment decreased obviously while deep ground temperatures kept almost constant. For crushed rock revetment embankment (CCRE), the cooling effect was effective in cold permafrost regions. But in warm permafrost regions, the shallow permafrost beneath the embankment had no obvious cooling trend while the deep permafrost had a slight warming trend. The deformation analyses indicated that CREs experienced frost heave in permafrost regions with mean annual ground temperature (MAGT) < -1.5 °C but settlement in permafrost regions with mean annual ground temperature > -1.5 °C. The magnitudes of both heave and settlement were not significant. Since the better thermal stability of underlying permafrost, it was inferred that the settlement of CRE mainly originated from compression of warm and ice-rich permafrost layer near permafrost table.

scholarly journals Modelling of the thermal regime of permafrost during 1990–2014 in Hornsund, Svalbard

2016 ◽  
Vol 37 (2) ◽  
pp. 219-242 ◽  
Author(s):  
Tomasz Wawrzyniak ◽  
Marzena Osuch ◽  
Jarosław Napiórkowski ◽  
Sebastian Westermann
Keyword(s):  
Thermal Regime ◽  
Environmental Changes ◽  
Thermal State ◽  
Ground Surface ◽  
Temperature Data ◽  
Ground Temperature ◽  
The Arctic ◽  
Transfer Model ◽  
Numerical Heat Transfer ◽  
Air Temperatures

AbstractThe thermal state of permafrost is a crucial indicator of environmental changes occurring in the Arctic. The monitoring of ground temperatures in Svalbard has been carried out in instrumented boreholes, although only few are deeper than 10 m and none are located in southern part of Spitsbergen. Only one of them, Janssonhaugen, located in central part of the island, provides the ground temperature data down to 100 m. Recent studies have proved that significant warming of the ground surface temperatures, observed especially in the last three decades, can be detected not only just few meters below the surface, but reaches much deeper layers. The aim of this paper is evaluation of the permafrost state in the vicinity of the Polish Polar Station in Hornsund using the numerical heat transfer model CryoGrid 2. The model is calibrated with ground temperature data collected from a 2 m deep borehole established in 2013 and then validated with data from the period 1990–2014 from five depths up to 1 m, measured routinely at the Hornsund meteorological station. The study estimates modelled ground thermal profile down to 100 m in depth and presents the evolution of the ground thermal regime in the last 25 years. The simulated subsurface temperature trumpet shows that multiannual variability in that period can reach 25 m in depth. The changes of the ground thermal regime correspond to an increasing trend of air temperatures observed in Hornsund and general warming across Svalbard.

scholarly journals Intelligent long-term performance analysis in power electronics systems

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Saeed Peyghami ◽  
Tomislav Dragicevic ◽  
Frede Blaabjerg
Keyword(s):  
Performance Indicator ◽  
Thermal Characteristics ◽  
Operating Conditions ◽  
System Level ◽  
Power Electronic ◽  
Reliability Modeling ◽  
Artificial Neural Network Ann ◽  
Long Term Performance ◽  
Term Performance

AbstractThis paper proposes a long-term performance indicator for power electronic converters based on their reliability. The converter reliability is represented by the proposed constant lifetime curves, which have been developed using Artificial Neural Network (ANN) under different operating conditions. Unlike the state-of-the-art theoretical reliability modeling approaches, which employ detailed electro-thermal characteristics and lifetime models of converter components, the proposed method provides a nonparametric surrogate model of the converter based on limited non-linear data from theoretical reliability analysis. The proposed approach can quickly predict the converter lifetime under given operating conditions without a further need for extended, time-consuming electro-thermal analysis. Moreover, the proposed lifetime curves can present the long-term performance of converters facilitating optimal system-level design for reliability, reliable operation and maintenance planning in power electronic systems. Numerical case studies evaluate the effectiveness of the proposed reliability modeling approach.

Land conversion regulates the effects of long-term climate warming on soil micro-food web communities

2021 ◽  
Vol 314 ◽  
pp. 107426
Author(s):  
Pingting Guan ◽  
Mohammad Mahamood ◽  
Yurong Yang ◽  
Donghui Wu
Keyword(s):  
Food Web ◽  
Climate Warming ◽  
Land Conversion ◽  
Web Communities
Sign in / Sign up

Export Citation Format

Share Document