Heat Effect Analysis of Buried Oil Pipeline in the Qinghai-Tibet Plateau

2014 ◽  
Vol 501-504 ◽  
pp. 211-217
Author(s):  
Wei Bo Liu ◽  
Wen Bing Yu ◽  
Xin Yi ◽  
Lin Chen
Keyword(s):  
Temperature Field ◽  
Frozen Soil ◽  
Operating Conditions ◽  
Tibet Plateau ◽  
Soil Mechanic ◽  
Insulation Layer ◽  
Effect Analysis ◽  
Oil Pipeline ◽  
Permafrost Table ◽  
Qinghai Tibet Plateau

The Geermu-Lasa oil pipeline was located in the Qinghai-Tibet Plateau permafrost regions. The building and operating of pipeline will change the temperature field of soil around it, which can lead to changes of frozen soil mechanic properties, and this will induces deformation or even fracture of pipeline. These phenomena will affect the normal transportation of oil. In this paper, temperature field around the pipelines were analyzed due to different pipe diameters and different insulation layer thicknesses in the way of finite element method. The rule of thawing and freezing of soil around the pipeline in an annual cycle was obtained. Artificial permafrost table variations under the pipeline were also obtained due to different operating conditions. For 30cm diameter pipeline with 7cm insulation layer, its artificial permafrost table depth change value is just 0.48m after 30-year running. These analysis results can provide references to the construction of the new Geermu-Lasa oil pipeline.

Geohazards and thermal regime analysis of oil pipeline along the Qinghai–Tibet Plateau Engineering Corridor

2016 ◽  
Vol 83 (1) ◽  
pp. 193-209 ◽  
Author(s):  
Wenbing Yu ◽  
Fenglei Han ◽  
Weibo Liu ◽  
Stuart A. Harris
Keyword(s):  
Thermal Regime ◽  
Tibet Plateau ◽  
Oil Pipeline ◽  
Qinghai Tibet Plateau ◽  
Regime Analysis

scholarly journals PIC v1.3: comprehensive R package for computing permafrost indices with daily weather observations and atmospheric forcing over the Qinghai–Tibet Plateau

2018 ◽  
Vol 11 (6) ◽  
pp. 2475-2491 ◽  
Author(s):  
Lihui Luo ◽  
Zhongqiong Zhang ◽  
Wei Ma ◽  
Shuhua Yi ◽  
Yanli Zhuang
Keyword(s):  
Ground Surface ◽  
R Package ◽  
Frozen Soil ◽  
Tibet Plateau ◽  
Trend Test ◽  
Active Layer Thickness ◽  
Permafrost Degradation ◽  
Spatial Trends ◽  
The Impact ◽  
Qinghai Tibet Plateau

Abstract. An R package was developed for computing permafrost indices (PIC v1.3) that integrates meteorological observations, gridded meteorological datasets, soil databases, and field measurements to compute the factors or indices of permafrost and seasonal frozen soil. At present, 16 temperature- and depth-related indices are integrated into the PIC v1.3 R package to estimate the possible trends of frozen soil in the Qinghai–Tibet Plateau (QTP). These indices include the mean annual air temperature (MAAT), mean annual ground surface temperature (MAGST), mean annual ground temperature (MAGT), seasonal thawing–freezing n factor (nt∕nf), thawing–freezing degree-days for air and the ground surface (DDTa∕DDTs∕DDFa∕DDFs), temperature at the top of the permafrost (TTOP), active layer thickness (ALT), and maximum seasonal freeze depth. PIC v1.3 supports two computational modes, namely the stations and regional calculations that enable statistical analysis and intuitive visualization of the time series and spatial simulations. Datasets of 52 weather stations and a central region of the QTP were prepared and simulated to evaluate the temporal–spatial trends of permafrost with the climate. More than 10 statistical methods and a sequential Mann–Kendall trend test were adopted to evaluate these indices in stations, and spatial methods were adopted to assess the spatial trends. Multiple visual methods were used to display the temporal and spatial variability of the stations and region. Simulation results show extensive permafrost degradation in the QTP, and the temporal–spatial trends of the permafrost conditions in the QTP are close to those of previous studies. The transparency and repeatability of the PIC v1.3 package and its data can be used and extended to assess the impact of climate change on permafrost.

scholarly journals Impacts of changes in vegetation cover on soil water heat coupling in an alpine meadow of the Qinghai-Tibet Plateau, China

2009 ◽  
Vol 13 (3) ◽  
pp. 327-341 ◽  
Author(s):  
W. Genxu ◽  
H. Hongchang ◽  
L. Guangsheng ◽  
L. Na
Keyword(s):  
Heat Flux ◽  
Soil Temperature ◽  
Soil Water ◽  
Vegetation Cover ◽  
Alpine Meadow ◽  
Root Zone ◽  
Frozen Soil ◽  
Tibet Plateau ◽  
Permafrost Region ◽  
Qinghai Tibet Plateau

Abstract. Alpine meadow is one of the most widespread grassland types in the permafrost regions of the Qinghai-Tibet Plateau, and the transmission of coupled soil water heat is one of the most crucial processes influencing cyclic variations in the hydrology of frozen soil regions, especially under different vegetation covers. The present study assesses the impact of changes in vegetation cover on the coupling of soil water and heat in a permafrost region. Soil moisture (θv), soil temperature (Ts), soil heat content, and differences in θv−Ts coupling were monitored on a seasonal and daily basis under three different vegetation covers (30, 65, and 93%) on both thawed and frozen soils. Regression analysis of θv vs. Ts plots under different levels of vegetation cover indicates that soil freeze-thaw processes were significantly affected by the changes in vegetation cover. The decrease in vegetation cover of an alpine meadow reduced the difference between air temperature and ground temperature (ΔTa−s), and it also resulted in a decrease in Ts at which soil froze, and an increase in the temperature at which it thawed. This was reflected in a greater response of soil temperature to changes in air temperature (Ta). For ΔTa−s outside the range of −0.1 to 1.0°C, root zone soil-water temperatures showed a significant increase with increasing ΔTa−s; however, the magnitude of this relationship was dampened with increasing vegetation cover. At the time of maximum water content in the thawing season, the soil temperature decreased with increasing vegetation. Changes in vegetation cover also led to variations in θv−Ts coupling. With the increase in vegetation cover, the surface heat flux decreased. Soil heat storage at 20 cm in depth increased with increasing vegetation cover, and the heat flux that was downwardly transmitted decreased. The soil property varied greatly under different vegetation covers, causing the variation of heat conductivity and water-heat hold capacity in topsoil layer in different vegetation cover. The variation of heat budget and transmitting in soil is the main factor that causes changes in soil thawing and freezing processes, and θv−Ts coupling relationship under different vegetation fractions. In addition to providing insulation against soil warming, vegetation in alpine meadows within the permafrost region also would slow down the response of permafrost to climatic warming via the greater water-holding capacity of its root zone. Such vegetation may therefore play an important role in conserving water in alpine meadows and maintaining the stability of engineering works constructed within frozen soil of the Qinghai-Tibet Plateau.

scholarly journals Study on the Effect of Unilateral Sand Deposition on the Spatial Distribution and Temporal Evolution Pattern of Temperature beneath the Embankment

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Ling Chen ◽  
Hong Yu ◽  
Xiaolin Li ◽  
Zekun Ding
Keyword(s):  
Spatial Distribution ◽  
Temperature Field ◽  
Temporal Evolution ◽  
Operation Time ◽  
Tibet Plateau ◽  
Evolution Pattern ◽  
Permafrost Table ◽  
Soil Temperatures ◽  
Sand Particles ◽  
Sand Deposition

In the context of climate warming and the frequent wind-sand hazards in the Qinghai-Tibet Engineering Corridor (QTEC), the construction of the embankment will affect the thermal regime of permafrost underground. The influence of embankment construction on the variation of the permafrost table beneath it is different, especially for the regime with different mean annual ground temperatures (MAGTs). In this study, the effects of the unilateral sand particles deposition on the spatial distribution and temporal evolution pattern of temperature beneath the embankment are investigated through the numerical simulations, in which the heat transfer is considered. The model is validated by the field observed data of soil temperatures around an experimental zone built at the sand hazard area in Honglianghe, the interior of Qinghai-Tibet Plateau (QTP). The simulated results indicate that the temperature field beneath the embankment is asymmetrically distributed under the condition of unilateral sand particles deposition. This asymmetry gradually weakened with the increase of operation time and the gradual adjustment of the permafrost temperature field. By comparing the permafrost table beneath the natural surface, the sand deposition center, and the middle of the embankment center, it could be found that the unilateral sand particles deposition has less effect on the degradation of the permafrost table in the center of the embankment. However, for the center of the sand deposition, the change of the permafrost table is larger with the increase of time and the corresponding rate of permafrost table degradation is higher than that without sand particles deposition, especially for the high-temperature permafrost. In addition, with different sand thickness and width conditions, the effect of “narrow-thick” form sand particles deposition on the temperature field beneath embankment is greater than that of “wide-thin” form sand deposition. Hence, in order to reduce its impact on the long-term thermal condition beneath the embankment, it is necessary to clean the thicker deposition sand particles at the toe of the embankment.

scholarly journals Effects of the Freezing–Thawing Cycle Mode on Alpine Vegetation in the Nagqu River Basin of the Qinghai–Tibet Plateau

Water ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 2122 ◽  
Author(s):  
Zihao Man ◽  
Baisha Weng ◽  
Yuheng Yang ◽  
Xiaoyan Gong ◽  
Meng Li ◽  
...  
Keyword(s):  
Climate Change ◽  
River Basin ◽  
Frozen Soil ◽  
Root Cell ◽  
Frequency Mode ◽  
Tibet Plateau ◽  
Alpine Vegetation ◽  
Soil Ecosystem ◽  
Thawing Cycle ◽  
Qinghai Tibet Plateau

The freezing–thawing cycle is a basic feature of a frozen soil ecosystem, and it affects the growth of alpine vegetation both directly and indirectly. As the climate changes, the freezing–thawing mode, along with its impact on frozen soil ecosystems, also changes. In this research, the freezing–thawing cycle of the Nagqu River Basin in the Qinghai–Tibet Plateau was studied. Vegetation growth characteristics and microbial abundance were analyzed under different freezing–thawing modes. The direct and indirect effects of the freezing–thawing cycle mode on alpine vegetation in the Nagqu River Basin are presented, and the changing trends and hazards of the freezing–thawing cycle mode due to climate change are discussed. The results highlight two major findings. First, the freezing–thawing cycle in the Nagqu River Basin has a high-frequency mode (HFM) and a low-frequency mode (LFM). With the influence of climate change, the LFM is gradually shifting to the HFM. Second, the alpine vegetation biomass in the HFM is lower than that in the LFM. Frequent freezing–thawing cycles reduce root cell activity and can even lead to root cell death. On the other hand, frequent freezing–thawing cycles increase microbial (Bradyrhizobium, Mesorhizobium, and Pseudomonas) death, weaken symbiotic nitrogen fixation and the disease resistance of vegetation, accelerate soil nutrient loss, reduce the soil water holding capacity and soil moisture, and hinder root growth. This study provides a complete response mechanism of alpine vegetation to the freezing–thawing cycle frequency while providing a theoretical basis for studying the change direction and impact on the frozen soil ecosystem due to climate change.

scholarly journals Study on the Freeze-Thaw Process of the Lining Structures of a Tunnel on Qinghai-Tibet Plateau with the Consideration of Lining Frost Damage

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Hong Yu ◽  
Kun Zhang ◽  
Xiaoming Zhu ◽  
Zhizhuo Tian ◽  
Qinglong Zhang
Keyword(s):  
Tensile Stress ◽  
Principal Stress ◽  
Tibet Plateau ◽  
Absolute Maximum ◽  
Insulation Layer ◽  
Road Tunnel ◽  
Frozen Ground ◽  
Freeze Thaw ◽  
Lining Structure ◽  
Qinghai Tibet Plateau

In seasonally frozen ground, there are many frost problems in highway road tunnel after its excavation due to the heat exchange between the cold air and lining structure inside the tunnel. To mitigate these frost-related damages, thermal insulation layer is widely used at entrance and exit sections of the tunnel. In this study, a coupled mathematical model of heat, moisture, and stress was built for tunnels in seasonally permafrost regions. Then, based on the field-observed air temperature inside a roadway tunnel at Altun Mountain on the Qinghai-Tibet Plateau (QTP), seasonal freeze-thaw process of the surrounding rocks (SR) and lining structures were numerically investigated with the consideration of insulation methods: without insulation (WTIL) and laying the insulation layer on the inner surface of the second lining structure (STIL). Combined with the principle of Miner damage accumulation, the stress regimes of the lining structures of tunnel were investigated in WTIL and STIL. The results show that there was a significantly thermal disturbance of the SR after the tunnel excavation. In the 5th year of the operation period, the maximum seasonal freeze depth (MSFD) of the SR can reach 1.6 m at the vault of the arch and that at the inverted arch was only 1.0 m due to the pavement inside the tunnel. Then, both the absolute maximum value of the maximum principal stress (MAPS) and minimum principal stress (MIPS) in cold season were bigger than those in warm season comparing the value of the stress filed of the lining structure. In the same way, both the MAPS and MIPS of the lining structure in WTIL are bigger than those in STIL in numerical simulation. The positions of the maximum tensile stress of the primary lining structure in STIL and WTIL were inverted arch. For the lining structures, the greater tensile stress was generally harmful. Thus, the inverted arch of the tunnel should be laid on the insulation layer.

scholarly journals Impacts of changes in vegetation cover on soil water heat coupling in an alpine meadow, Qinghai-Tibet Plateau, China

2008 ◽  
Vol 5 (4) ◽  
pp. 2543-2579
Author(s):  
W. Genxu ◽  
H. Hongchang ◽  
L. Yuanshou ◽  
W. Yibo
Keyword(s):  
Heat Flux ◽  
Soil Temperature ◽  
Soil Water ◽  
Vegetation Cover ◽  
Alpine Meadow ◽  
Root Zone ◽  
Frozen Soil ◽  
Tibet Plateau ◽  
Permafrost Region ◽  
Qinghai Tibet Plateau

Abstract. Alpine meadow is one of the most widespread grassland types in the permafrost regions of the Qinghai-Tibet Plateau. The transmission of coupled soil water heat is one of the most important processes influencing cyclic variations in the hydrology of frozen soil regions, especially under conditions of changing vegetation cover. The present study assesses the impact of changes in vegetation cover on the coupling of soil water and heat in a permafrost region. Soil moisture (θv), soil temperature (Ts), soil heat content, and differences in θv−Ts coupling were monitored on a seasonal and daily basis under three different densities of vegetation cover (30, 65, and 93%) upon both thawed and frozen soils. Regression analysis of θv vs. Ts plots under different levels of vegetation cover indicates that soil freeze-thaw processes were significantly affected by changes in vegetation cover. With decreasing vegetation cover upon an alpine meadow, the difference between air temperature and ground temperature (ΔTa−s) also decreased. A decrease in vegetation cover also resulted in a decrease in the Ts at which soil froze and an increase in the temperature at which it thawed; this was reflected in a greater response of soil temperature to changes in air temperature (Ta). For ΔTa−s outside the range of −0.1 to 1.0°C, root zone soil-water temperatures showed a significant increase with increasing ΔTa−s; however, the magnitude of this relationship was dampened with increasing vegetation cover. At the time of maximum water content in the thawing season, the soil temperature decreased with increasing vegetation. Changes in vegetation cover also led to variations in θv−Ts coupling. With increasing vegetation cover, the surface heat flux increased, along with the amplitude of its variations. Soil heat storage at 20 cm depth also increased with increasing vegetation cover, and the downward transmitted of heat flux decreased. In addition to providing insulation against soil warming, vegetation in alpine meadows within the permafrost region also slows down the response of permafrost to climatic warming via the greater water-holding capacity of its root zone. Such vegetation may therefore play an important role in conserving water in alpine meadows and maintaining the stability of engineering works constructed within frozen soil of the Qinghai-Tibet Plateau.

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