Permafrost Regions Of Qinghai-Tibet Plateau Research Articles

Methane Emissions From the Qinghai‐Tibet Plateau Ponds and Lakes: Roles of Ice Thaw and Vegetation Zone

AbstractComprehensive seasonal observation is essential for accurately quantifying methane (CH4) emissions from ponds and lakes in permafrost regions. Although CH4 emissions during ice thaw are important and highly variable in high‐latitude freshwater ponds and lakes (north of ∼50°N), their contribution is seldom included in estimates of aquatic‐atmospheric CH4 exchange across different alpine ecosystems. Here, we characterized annual CH4 emissions, including emissions during ice thaw, from ponds and lakes across four alpine vegetation zones in the Qinghai‐Tibet Plateau (QTP) permafrost region. We observed significant spatial variability in annual CH4 emission rates (8.44−421.05 mmol m−2 yr−1), CH4 emission rates during ice thaw (0.26−144.39 mmol m−2 yr−1), and the contribution of CH4 emissions during ice thaw to annual emissions (3−33%) across different vegetation zones. Dissolved oxygen concentration under ice, along with substrate availability and water salinity, played critical roles in influencing CH4 flux during ice thaw. We estimated annual CH4 emissions from ponds and lakes in the QTP permafrost region as 0.04 (0.03−0.05) Tg CH4 yr−1 (median (first quartile−third quartile)), with approximately 20% occurring during ice thaw. Notably, the average areal CH4 emission rate from ponds and lakes in the QTP permafrost region amounts to only 8% of that from high‐latitude waterbodies, primarily due to the dominance of large saline lakes with lower CH4 emission rates in the alpine permafrost region. Our findings emphasize the significance of incorporating comprehensive seasonal observation of CH4 emissions across different vegetation zones in better predicting CH4 emissions from alpine ponds and lakes.

Thermokarst lake changes along the Qinghai-Tibet Highway during 1991–2020

Thermokarst lake development significantly affects hydrologic systems, infrastructure stability and biogeochemical processes, while the spatial and temporal changes in thermokarst lakes remain largely unknown. Here, we created a thermokarst lake dataset on the Qinghai-Tibet Plateau (QTP) using a threshold-based mapping method based on Google Earth Engine (GEE) data associated with visual inspection. The dataset includes a thermokarst lake inventory on the QTP at a 10 m resolution produced from Sentinel-2A images and a multitemporal inventory along the Qinghai-Tibet Highway (QTH) from Landsat and Sentinel-2A images. We analyzed the temporal and spatial changes in thermokarst lake area and their relationships to environmental factors. Our results showed that thermokarst lakes on the QTP permafrost region covered a total area of 1572 ± 184 km2, with most of the thermokarst lakes <10,000 m2 in area. The spatial distributions of thermokarst lakes are affected by the ground thermal stability, active layer thickness, vegetation type, and ground ice content. Over the past 30 years, the number and surface area of thermokarst lakes along the QTH have increased by 58.8 % and 83.1 %, respectively, with the increase in lakes likely caused by climate warming and precipitation increasing. This study provides deep insight in the long-term interannual variations and its driving factors in thermokarst lakes along the QTH.

Root uptake dominates mercury accumulation in permafrost plants of Qinghai-Tibet Plateau

Uptake of atmospheric elemental mercury via foliage is thought to be the dominant pathway of mercury accumulation in terrestrial ecosystems, including those in the Arctic permafrost regions. Whether a similar process operates in alpine permafrost regions remains unknown. Here we report mercury concentrations and stable isotopic signatures in a large cluster alpine permafrost regions of mid-latitude Qinghai-Tibet Plateau. We find a transition from foliage to root uptake of mercury as elevation increases. In alpine permafrost regions, we find that root uptake of mercury from the surrounding soil is the dominant accumulation pathway. We estimate that root uptake accounts for 70 ± 19% of plant mercury in permafrost regions of the Qinghai-Tibet Plateau and propose that this may be related to the harsh climate conditions suppressing foliage growth and promoting lateral root growth.

Numerical analysis on hydrothermal process around oil pipeline in permafrost regions of Qinghai-Tibet Plateau

Numerical analysis on hydrothermal process around oil pipeline in permafrost regions of Qinghai-Tibet Plateau

Study on Dynamic Changes of Vegetation in Permafrost Region of Qinghai-Tibet Plateau —— Take the Area along Qinghai-Tibet Highway as an Example

Global warming leads to the degradation of permafrost in the Qinghai-Tibet Plateau, which has an important impact on the growth and distribution of its vegetation. However, the reduction and destruction of vegetation may lead to the degradation or disappearance of frozen soil, which will have a large-scale impact on engineering buildings and frozen soil ecological environment in cold regions. There is serious spatial heterogeneity in vegetation growth and change in permafrost regions of Qinghai-Tibet Plateau, so it is urgent to quantitatively study the process of surface vegetation change along Qinghai-Tibet Highway. In this study, MODIS data was used to study the characteristics of vegetation growth along the Qinghai-Tibet Plateau from 2000 to 2021, and it was found that the vegetation on the east side of the highway was better than that on the west side. On the whole, the vegetation growth from 2000 to 2021 showed a slight upward trend.

A synthesis dataset of permafrost thermal state for the Qinghai–Tibet (Xizang) Plateau, China

Abstract. Permafrost has great influences on the climatic, hydrological, and ecological systems on the Qinghai–Tibet Plateau (QTP). The changing permafrost and its impact have been attracting great attention worldwide like never before. More observational and modeling approaches are needed to promote an understanding of permafrost thermal state and climatic conditions on the QTP. However, limited data on the permafrost thermal state and climate background have been sporadically reported in different pieces of literature due to the difficulties of accessing and working in this region where the weather is severe, environmental conditions are harsh, and the topographic and morphological features are complex. From the 1990s, we began to establish a permafrost monitoring network on the QTP. Meteorological variables were measured by automatic meteorological systems. The soil temperature and moisture data were collected from an integrated observation system in the active layer. Deep ground temperature (GT) was observed from boreholes. In this study, a comprehensive dataset consisting of long-term meteorological, GT, soil moisture, and soil temperature data was compiled after quality control from an integrated, distributed, and multiscale observation network in the permafrost regions of QTP. The dataset is helpful for scientists with multiple study fields (i.e., climate, cryospheric, ecology and hydrology, meteorology science), which will significantly promote the verification, development, and improvement of hydrological models, land surface process models, and climate models on the QTP. The datasets are available from the National Tibetan Plateau/Third Pole Environment Data Center (https://data.tpdc.ac.cn/en/disallow/789e838e-16ac-4539-bb7e-906217305a1d/, last access: 24 August 2021, https://doi.org/10.11888/Geocry.tpdc.271107, Lin et al., 2021).

A first assessment of satellite and reanalysis estimates of surface and root-zone soil moisture over the permafrost region of Qinghai-Tibet Plateau

Long-term and high-quality surface soil moisture (SSM) and root-zone soil moisture (RZSM) data is crucial for understanding the land-atmosphere interactions of the Qinghai-Tibet Plateau (QTP). More than 40% of QTP is covered by permafrost, yet few studies have evaluated the accuracy of SSM and RZSM products derived from microwave satellite, land surface models (LSMs) and reanalysis over that region. This study tries to address this gap by evaluating a range of satellite and reanalysis estimates of SSM and RZSM in the thawed soil overlaying permafrost in the QTP, using in-situ measurements from sixteen stations. Here, seven SSM products were evaluated: Soil Moisture Active Passive L3 (SMAP-L3) and L4 (SMAP-L4), Soil Moisture and Ocean Salinity in version IC (SMOS-IC), Land Parameter Retrieval Model (LPRM) Advanced Microwave Scanning Radiometer 2 (AMSR2), European Space Agency Climate Change Initiative (ESA CCI), Advanced Scatterometer (ASCAT), and the fifth generation of the land component of the European Centre for Medium-Range Weather Forecasts atmospheric reanalysis (ERA5-Land). We also evaluated three RZSM products from SMAP-L4, ERA5-Land, and the Noah land surface model driven by Global Land Data Assimilation System (GLDAS-Noah). The assessment was conducted using five statistical metrics, i.e. Pearson correlation coefficient (R), bias, slope, Root Mean Square Error (RMSE), and unbiased RMSE (ubRMSE) between SSM or RZSM products and in-situ measurements. Our results showed that the ESA CCI, SMAP-L4 and SMOS-IC SSM products outperformed the other SSM products, indicated by higher correlation coefficients (R) (with a median R value of 0.63, 0.44 and 0.57, respectively) and lower ubRMSE (with a median ubRMSE value of 0.05, 0.04 and 0.07 m3/m3, respectively). Yet, SSM overestimation was found for all SSM products. This could be partly attributed to ancillary data used in the retrieval (e.g. overestimation of land surface temperature for SMAP-L3) and to the fact that the products (e.g. LPRM) more easily overestimate the in-situ SSM when the soil is very dry. As expected, SMAP-L3 SSM performed better in areas with sparse vegetation than with dense vegetation covers. For RZSM products, SMAP-L4 and GLDAS-Noah (R = 0.66 and 0.44, ubRMSE = 0.03 and 0.02 m3/m3, respectively) performed better than ERA5-Land (R = 0.46; ubRMSE = 0.03 m3/m3). It is also found that all RZSM products were unable to capture the variations of in-situ RZSM during the freezing/thawing period over the permafrost regions of QTP, due to large deviation for the ice-water phase change simulation and the lack of consideration for unfrozen-water migration during freezing processes in the LSMs.

ACTIVE LAYER THICKNESS RETRIEVAL OVER THE QINGHAI-TIBET PLATEAU FROM 2000 TO 2020 BASED ON INSAR-MEASURED SUBSIDENCE AND MULTI-LAYER SOIL MOISTURE

Abstract. Active layer thickness (ALT) is an important index to reflect the stability of permafrost. The retrieval of ALT based on Interferometric Synthetic Aperture Radar (InSAR) technology has been investigated recently in permafrost research. However, most of such studies are carried out in a limited extend and relatively short temporal coverage. The combination of temporal-spatial multi-layer soil moisture data and multi-temporal InSAR is a promising approach for the large-scale characterization of ALT. In this study, we employed Small Baseline Subset Interferometry (SBAS-InSAR) technology to obtain the seasonal surface deformation from radar images of Envisat and Sentinel-1 in a permafrost region of Qinghai-Tibet Plateau (QTP). We attempt to verify and calibrate the temporal-spatial multi-layer soil moisture product in combination with the in-situ data. Based on the land subsidence data and the temporal-spatial multi-layer soil moisture data, we further improve method to retrieve the ALT information. This paper describes the progress so far and point out the future work.

Risk assessment of potential thaw settlement hazard in the permafrost regions of Qinghai-Tibet Plateau

Climate warming could exacerbate the occurrence of thaw settlement hazard in the permafrost regions of the Qinghai-Tibet Plateau (QTP), which would threaten the stability of engineering infrastructure in cold regions. The risk associated with permafrost settlement, valuable for the regional sustainable development, remains poorly assessed or understood on the QTP. In this study, three common Geo-hazard indices were used to assess the settlement risks in the permafrost regions of the QTP, including the settlement index, the risk zonation index, and the allowable bearing capacity index. However, large spatial differences existed in simulating the risk maps by using the abovementioned Geo-hazard indices. Hence, we developed a combined index (Ic) by integrating the three indices to reduce the uncertainty of the simulations. The results indicated that the ground ice is a critical factor for assessing the settlement risk in permafrost regions. We also applied the Ic to assess the settlement risk along the Qinghai-Tibet Railway (QTR). The proportion of low-risk area along the QTR would be the highest (45.38%) for the future periods 2061–2080 under Representative Concentration Pathway 4.5. The medium-risk area combined with the high-risk area would be accounted for more than 40%, which were located at the boundary of the present permafrost regions. Therefore, the corresponding adaptation measures should be taken to reduce the potential economic losses caused by the high-risk regions to the infrastructure. Overall, the results would present valuable references for engineering design, construction and maintenance, and provide insights for early warning and prevention of permafrost thaw settlement hazard on the QTP.

Soil Moisture Estimation based on the Distributed Scatterers Adaptive Filter over the QTP Permafrost Region using Sentinel-1 and High-resolution TerraSAR-X Data

ABSTRACT Synthetic aperture radar (SAR) data have been widely and primarily used for soil-moisture estimation. The original radar backscattering coefficients show great noise and temporal-spatial decorrelation due to complex surface features and seasonal vegetation changes, which increase the difficulty of soil-moisture estimation over the Qinghai-Tibet Plateau (QTP). To overcome these limitations, a soil-moisture retrieval method based on the Distributed Scatterers Adaptive Filter (DSAF) is proposed and applied in this paper. First, the statistically homogeneous pixels (SHP) with similar scatter behaviour are identified using the Anderson-Darling (AD) test method. Then, the Distributed Scatterers (DSs) are selected according to the SHPs threshold, and the backscattering coefficients of DSs are filtered using the SHPs distribution and coherences. In order to eliminate the negative influence of vegetation and roughness, the filtered backscattering coefficients are further processed by coupling the Water Cloud Model (WCM) and the images acquired in the winter season. The response of soil moisture to backscattering coefficients is greatly improved. Finally, the backscatter coefficients () are transformed into soil-moisture units by using the Least Square Regression (LSR) model and multi-temporal Change Detection (CD) method, respectively. The 15 scenes of TerraSAR-X images and 18 scenes of Sentinel-1 images in Northern Piedmont river, Northern Tibet, were used for experimental study. The results reveal that the response of the filtered backscattering coefficients to in-situ soil moisture is greatly improved. The soil-moisture content estimated by LSR and CD model using TerraSAR-X data is consistent with in-situ measurements, with coefficient of determination (R 2) of 0.52 and 0.56, Root Mean Square Error (RMSE) of 0.08 and 0.06, respectively. The results show that the proposed method can improve the accuracy of soil-moisture estimation, especially over the complex surface features of the QTP permafrost region.

Warming and monsoonal climate lead to large export of millennial-aged carbon from permafrost catchments of the Qinghai-Tibet Plateau

Permafrost carbon pool destabilization causes substantial fluvial export of soil carbon, yet the export patterns and magnitudes are not well understood. Here we investigated the radiocarbon (14C) in dissolved organic and inorganic carbon (DOC and DIC, respectively) exported from a mid-sized river in the central Qinghai-Tibet Plateau (QTP) permafrost region. We utilized the radiocarbon dating technique to reveal the ages of riverine dissolved carbon and a statistical model to partition the riverine carbon from different age categories. DOC and DIC showed bomb-depleted 14C signatures corresponding to millennial ages. Seasonally, 14C-depleted DOC and DIC ages were associated with active layer thaw and flow path deepening. Spatially, older DOC and DIC were found in the valley sites correlated with warmer permafrost and higher groundwater flow. Further, isotopic mixing models suggested that 83 ± 27% of riverine DOC was derived from active layer and permafrost layer aged carbon. DIC export was comprised of a smaller portion of aged carbon (47.3 ± 2.6%) but a much larger flux of aged carbon due to higher annual DIC export. Interestingly, approximately 56% of annual aged DOC and DIC were exported in the short summer season (July to September). The monsoon climate-induced overlap of high discharge and maximum active layer thaw depth in summer enhanced the remarkably rapid fluvial export of millennial-aged carbon. Annual aged carbon yields in YRSR (275 ± 90 and 1661 ± 91 kg km−2 yr−1 for DOC and DIC, respectively) are much larger than those of Kolyma River (160 ± 89 and 234 ± 105 kg km−2 yr−1 for DOC and DIC, respectively). These results suggest a unique old carbon loss pattern in the QTP permafrost region compared to higher latitude permafrost regions with a non-monsoonal climate. As climate warms, more old carbon export is expected, which may affect the permafrost carbon pool and the river biogeochemical processes.

Importance of active layer freeze-thaw cycles on the riverine dissolved carbon export on the Qinghai-Tibet Plateau permafrost region.

The Qinghai-Tibet Plateau (QTP) is experiencing severe permafrost degradation, which can affect the hydrological and biogeochemical processes. Yet how the permafrost change affects riverine carbon export remains uncertain. Here, we investigated the seasonal variations of dissolved inorganic and organic carbon (DIC and DOC) during flow seasons in a watershed located in the central QTP permafrost region. The results showed that riverine DIC concentrations (27.81 ± 9.75 mg L−1) were much higher than DOC concentrations (6.57 ± 2.24 mg L−1). DIC and DOC fluxes were 3.95 and 0.94 g C m−2 year−1, respectively. DIC concentrations increased from initial thaw (May) to freeze period (October), while DOC concentrations remained relatively steady. Daily dissolved carbon concentrations were more closely correlated with baseflow than that with total runoff. Spatially, average DIC and DOC concentrations were positively correlated with vegetation coverage but negatively correlated with bare land coverage. DIC concentrations increased with the thawed and frozen depths due to increased soil interflow, more thaw-released carbon, more groundwater contribution, and possibly more carbonate weathering by soil CO2 formed carbonic acid. The DIC and DOC fluxes increased with thawed depth and decreased with frozen layer thickness. The seasonality of riverine dissolved carbon export was highly dependent on active layer thawing and freezing processes, which highlights the importance of changing permafrost for riverine carbon export. Future warming in the QTP permafrost region may alter the quantity and mechanisms of riverine carbon export.

Consumption of atmospheric methane by the Qinghai–Tibet Plateau alpine steppe ecosystem

Abstract. The methane (CH4) cycle on the Qinghai–Tibet Plateau (QTP), the world's largest high-elevation permafrost region, is sensitive to climate change and subsequent freezing and thawing dynamics. Yet, its magnitudes, patterns, and environmental controls are still poorly understood. Here, we report results from five continuous year-round CH4 observations from a typical alpine steppe ecosystem in the QTP permafrost region. Our results suggest that the QTP permafrost region was a CH4 sink of -0.86±0.23 g CH4-C m−2 yr−1 over 2012–2016, a rate higher than that of many other permafrost areas, such as the Arctic tundra in northern Greenland, Alaska, and western Siberia. Soil temperature and soil water content were dominant factors controlling CH4 fluxes; however, their correlations changed with soil depths due to freezing and thawing dynamics. This region was a net CH4 sink in autumn, but a net source in spring, despite both seasons experiencing similar top soil thawing and freezing dynamics. The opposite CH4 source–sink function in spring versus in autumn was likely caused by the respective seasons' specialized freezing and thawing processes, which modified the vertical distribution of soil layers that are highly mixed in autumn, but not in spring. Furthermore, the traditional definition of four seasons failed to capture the pattern of the annual CH4 cycle. We developed a new seasonal division method based on soil temperature, bacterial activity, and permafrost active layer thickness, which significantly improved the modeling of the annual CH4 cycle. Collectively, our findings highlight the critical role of fine-scale climate freezing and thawing dynamics in driving permafrost CH4 dynamics, which needs to be better monitored and modeled in Earth system models.

Investigation of Thermal Cooling Effectiveness of RRVCS for Permafrost Protection under Wide Expressway Embankment

In order to improve the thermal stability of wide embankment for the Qinghai-Tibet Expressway (QTE) to be constructed in permafrost zones on Qinghai-Tibet plateau, a new kind of reflective-resistant-ventilated coupling structure (RRVCS) was proposed and designed. A numerical model was then developed through ABAQUS to investigate the influences of RRVCS on the thermal regime of wide embankment. The temperature field and thawing depth of normal wide embankment without protective measures, wide embankment with crushed stone layer, and wide embankment with RRVCS were compared to verify the cooling effectiveness of RRVCS based on numerical analysis. Vermiculite powder has great influences on the thermal property of asphalt mixture, and it can be reduced by 22.8%, 29.5%, 37.3%, and 50.6% after the addition of 4%, 6%, 8%, and 10% vermiculite powder, respectively. Under the same condition, the temperature of RRVCS embankment is the lowest and its thermal stability is the best. Setting crushed stone layer can improve the thermal stability of embankment. However, the improvement is limited for wide embankment with width exceeding 26 m. RRVCS has the best protective effects on the thermal stability of wide embankment and is recommended as a protective measure for wide embankment of expressway in permafrost regions of Qinghai-Tibet Plateau.

A Combinational Prediction Model for Transverse Crack of Asphalt Pavement

Reliable transverse crack prediction can benefit the design and maintenance and improve the reliability of field investigation for asphalt pavement in permafrost regions of Qinghai-Tibet plateau. This study adopted the crack prediction model in the newly developed pavement design method named Pavement ME Design (PMED) and the modified grey predictive model (GM (1, 1)) to predict the transverse crack of asphalt pavement in permafrost regions. The complementary advantages for the two models based on the weight distribution theory were discussed, and a combined prediction model (PME-DGM combination model) taking account into region characteristics was developed. Finally, the applicability of combined prediction model was analyzed. The result showed that, the predictive accuracy of PME-DGM combination model established by the error sum of squares reciprocal method was the highest, the best weight allocations for each sub-model were LNCH = 0.601 and LDGM = 0.399, and the combination model can be applied in the permafrost region involved in this paper; The combination model is more appropriate in predicting the development trend of transverse crack of project-level asphalt pavement in permafrost regions; For PMED predictive model, this study raised a modified method base on a third-party model (DGM (1,1), and the result showed that the method worked well in the permafrost region of Qinghai-Tibet plateau.

Air quality assessment during indoor use of the tobacco heating system THS2.2

The wastes placed at a sanitary landfill contain biodegradable, nondegradable, and semidegradable matters. The biodegradable matters will be rapidly decomposed chemically and biologically into stabilized substances such as humus and inorganic fractions, which is referred to as aged refuse in this book. For the organic wastes, most organic carbon are converted into gases, few into leachate, and others remained as aged refuse. Higher temperature will lead to more rapid degradation and result to higher conversion of the organic carbon to biogas and lower to both solid residues and leachate. The refuse at landfill might be fully mineralized and the accumulative settlement might be over 30% of the initial height after around 22–30 years closure, and postclosure care may be stopped after 22 years, while chemical oxygen demand concentrations in leachate would be reduced naturally to 300 mg/L after over 15 years. A similarity and disparity comparison for different-scale lysimeters with a refuse weight from several hundred kilograms to 10,800 tons, is made, and find that a similarity exists from viewpoint of refuse degradation mechanism and declination tendency of leachate quality and refuse composition among these varied scale lysimeter. An enough weight of waste, such as over 200 kg, should be used at lab when the landfill stabilization process is simulated. The relationships between the refuse components and composition with refuse age are explored in detail and found that the wastes can be considered to be stabilized and become recyclable aged refuse after 8–10 years of placement in China. The air quality at the aged refuse mining point is acceptable and only total bacteria and PM10 may be over the control values. Microbial communities in aged refuse are much more complex than expected. Most of the predominant bacteria in aged refuse exhibit high identity to some extremophiles found in extreme conditions such as highly alkaline and/or saline environments, rocks of an ancient gold mine, old sediments, hypertolerant to arsenic, cold sulfur-rich spring, and the Qinghai-Tibet Plateau permafrost region. The predominated bacilli-like bacteria coexisted with methanogenic archaea, with a rich source of extremophiles, especially alkaliphilic and/or halophilic microbes.

SURFACE DEFORMATION MONITORING IN PERMAFROST REGIONS OF TIBETAN PLATEAU BASED ON ALOS PALSAR DATA

Abstract. The permafrost region of Qinghai-Tibet Plateau is widely distributed with the freeze/thaw processes that cause surface structural damage. The differential interferometry synthetic aperture radar (DInSAR) can detect large scale surface deformation with high precision, thus can be used to monitor the freeze/thaw processes of frozen soil area. In this paper, the surface deformation pattern of Qinghai-Tibet railway was analyzed by using the PALSAR 1.0 raw data of the ALOS satellite (L band) and 90m resolution SRTM DEM data, with the help of two-pass DInSAR method in GAMMA software, and the differential interferograms and deformation maps were obtained accordingly. Besides, the influence of temperature, topography and other factors on deformation of frozen soil were also studied. The following conclusions were obtained: there is a negative correlation between deformation and temperature, and there is a delay between the deformation change and that of temperature; deformation and elevation are positively correlated; the permafrost deformation is also affected by solar radiation that could form variable amplitude variation.

Selective Preference Method of Highway Route Scheme in Permafrost Regions of Qinghai-Tibet Plateau Based on AHP and Fuzzy Comprehensive Evaluation

To solve the problem that traditional highway route selection method cannot fully consider the complex geographical environment in the permafrost region of Qinghai-Tibet Plateau, AHP (Analytic Hierarchy Process) and fuzzy comprehensive evaluation were introduced into the highway route comparison and selection in permafrost region. Influence degrees of various factors on different route schemes in permafrost regions of the Qinghai-Tibet Plateau were analyzed by the AHP. The annual average temperature, engineering reliability and engineering capacity were selected as the characteristic parameters and their weights were determined. Variation range of the various influencing factors in permafrost regions of the Qinghai-Tibet Plateau were analyzed by the fuzzy comprehensive evaluation, 5 evaluation grades of highway route scheme in permafrost regions were established, and the actual highway route schemes between Xiushui River and Yamarle River were compared and selected. The results show that the temperature and frozen soil diseases are the main factors affecting the highway route plan in the permafrost regions of the Tibetan plateau, outstanding route plan needs comprehensive consideration of stability of highway engineering and environmental protection.

Thermal Regime Analysis and Protective Measure Evaluation for Wide Embankment in Permafrost Regions of Qinghai-Tibet Plateau

This study analyzed the effects of a wide embankment on the thermal regime of permafrost and evaluated the feasibility of different measures to protect the permafrost underlying the wide embankment. Based on a specific embankment section of the Qinghai-Tibet highway and field observed data, a finite-element model was built and verified to conduct thermal analysis. Based on numerical analysis, the temperature fields and thawing depths of embankments with different widths were analyzed. The influences of different protective measures on the thermal stability of embankments were evaluated. The findings indicate that, after embankment construction, the annual ground temperature and maximum thawing depth increase with time. Thus, the embankment construction causes serious disturbance of the thermal stability of permafrost. An embankment with a larger width has a lower thermal stability. The results also show that raising the embankment height, setting a crushed stone layer, or setting an expanded polystyrene (EPS) layer can improve the thermal stability of an embankment. However, the improving effect of a single protective measure is not obvious for wide embankments with widths larger than 26 m. A combination of a crushed stone layer and an EPS layer provides the best protective effect on the thermal stability of a wide embankment. Thus, it is recommended as a protective measure for wide embankments of expressways in permafrost regions of the Qinghai-Tibet Plateau.

The Gas-Source Study of Gas Hydrates in Wuli and Muli Permafrost Region of Qinghai-Tibet Plateau

The Gas-Source Study of Gas Hydrates in Wuli and Muli Permafrost Region of Qinghai-Tibet Plateau