Land cover change along the Qinghai-Tibet Highway and Railway from 1981 to 2001

Based on the NOAA AVHRR-NDVI monthly data from 1981 to 2001, the spatial distribution and dynamic change of land cover along the Qinghai-Tibet Highway and Railway were studied. The results of the analytical data indicate that the NDVI values in July, August and September are rather high during a year, and a linear trend by calculating NDVI of each pixel computed based on the average values of NDVI in July, August and September were obtained. The results are as follows： 1） Land cover of the study area by NDVI displays high at two sides of the area and low in the center, and agriculture area 〉 alpine meadow 〉 alpine grassland 〉 desert grassland. 2） In the study area, the amount ofpixels with high increase, slight increase, no change, slight decrease and high decrease account for 0.29%, 14.86%, 67.61%, 16.7% and 0.57% of the whole area, respectively. The increase of land cover pixels is mainly in the agriculture and alpine meadow and the decrease pixels mainly in the alpine grassland, desert grassland and hungriness. Grassland and hungriness contribute to the decrease mostly and artificial land and meadow contribute to the increase mostly. 3） In the area where human beings live, the changing trend is obvious, such as the valleys of Lhasa River and Huangshui River and area along the Yellow River; in the high altitude area with fewer people living, the changing trend is relatively low, like the area of Hoh Xil. 4） Human being＇s behaviors are a key factor followed by the climate changes affecting land cover.

Influence of Golmud-Lhasa Section of Qinghai-Tibet Railway on Blown Sand Transport

The Qinghai-Tibet Railway(QTR) passes through 281 km of sandy land, 11.07 km of which causes serious sand damage to the railway and thus, the control of blown sand is important for the safe operation of the railway. Construction of the railway and sand prevention system greatly changed the blown sand transport of the primary surface. Effective and feasible sand-control measures include stone checkerboard barriers(SCBs), sand fences(SFs), and gravel coverings. This study simulated the embankments, SCBs and SFs of the QTR in a wind tunnel, and analyzed their respective wind profile, sand deposition, and sand-blocking rate(SBR) in conjunction with field data, aiming at studying the influence of Golmud-Lhasa section of the QTR and sand prevention system on blown sand transport. The results of wind tunnel experiments showed that wind speed increased by 67.7%–77.3% at the upwind shoulder of the embankment and decreased by 50.0%–83.3% at upwind foot of embankment. Wind speed decreased by 50.0%–100.0% after passing through the first SF, and 72.2%–100.0% after the first row of stones within the first SCB grid. In the experiment of sand deposition, the higher the wind speed, the lower the SBR of SCB and SF. From field investigation, the amount of sand blocked by the four SFs decreased exponentially and its SBR was about 50.0%. By contrast, SCB could only block lower amounts of sand, but had a higher SBR(96.7%) than SF. Although, results show that SFs and SCBs along the Golmud-Lhasa section of the QTR provide an obvious sand blocking effect, they lead to the deposition of a large amount of sand, which forms artificial dunes and becomes a new source of sand damage.

Porosity of crushed rock layer and its impact on thermal regime of Qinghai-Tibet Railway embankment

It has been proven that crushed rock layers used in roadbed construction in permafrost regions have a cooling effect. The main reason is the existence of large porosity of the rock layers. However, due to the strong winds, cold and high radiation conditions on the Qinghai-Tibet Plateau(QTP), both wind-blown sand and/or weathered rock debris blockage might reduce the porosity of the rock layers, resulting in weakening the cooling effect of the crushed rock layer(CRL) in the crushed rock embankment(CRE) of the Qinghai-Tibet Railway(QTR) in the permafrost regions. Such a process might warm the underlying permafrost, and further lead to potential threat to the QTR's integrity and stability. The different porosities corresponding to the different equivalent rock diameters were measured in the laboratory using water saturation method, and an empirical exponential equation between porosity and equivalent rock diameter was proposed based on the measured experimental data and an important finding is observed in our and other experiments that the larger size crushed rock tends to lead to the larger porosity when arbitrarily packing. Numerical tests were carried out to study impacts of porosity on permafrost degradation and differential thaw depths between the sunny and shady shoulders. The results show that the decrease in porosity due to wind-blown sand or weathered rock debris clogging can worsen the permafrost degradation and lead to the asymmetric thermal regime. In the traditional embankment(without the CRL within it), the largest differential thaw depth can reach up to 3.1 m. The optimized porosity appears in a range from 34% to 42% corresponding to equivalent rock diameter from 10 to 20.5 cm. The CRE with the optimized porosities can make underlying permafrost stable and 0 ℃ isotherms symmetric in the coming 50 years, even under the condition that the climate warming can lead to permafrost degradation under the CRE and the traditional embankment. Some practical implications were proposed to benefit the future design, construction and maintenance of CRE in permafrost regions.

Influence of proximity to the Qinghai-Tibet highway and railway on variations of soil heavy metal concentrations and bacterial community diversity on the Tibetan Plateau

An understanding of soil microbial communities is crucial in roadside soil environmental assessments.The 16S rRNA se quencing of a stressed microbial community in soil adjacent to the Qinghai-Tibet Highway(QTH)revealed that the accu mulation of heavy metals(over about 10 years)has affected the diversity of bacterial abundance and microbial community structure.The proximity of a sampling site to the QTH/Qinghai-Tibet Railway(QTR),which is effectively a measure of the density of human engineering,was the dominant factor influencing bacterial community diversity.The diversity of bacterial communities shows that 16S rRNA gene abundance decreased in relation to proximity to the QTH and QTR in both alpine wetland and meadow areas.The dominant phyla across all samples were Actinobacteria and Proteobacteria.The concentration of Cr and Cd in the soil were positively correlated with proximity to the QTH and QTR(MC/WC sam pling sites),and Ni,Co,and V were positively correlated with proximity to the QTH and QTR(MA/WA sampling sites).The results presented in this study provide an insight into the relationships among heavy metals and soil microbial commu nities,and have important implications for assessing and predicting the impacts of human-induced activities from the QTH and QTR in such an extreme and fragile environment.

A system for automated monitoring of embankment deformation along the Qinghai-Tibet Railway in permafrost regions

At present, the monitoring of embankment deformation in permafrost regions along the Qinghai-Tibet Railway is mainly done manually. However, the harsh climate on the plateau affects the results greatly by lowering the observation frequency, so the manual monitoring can barely meet the observational demand. This research develops a system of automated monitoring of embankment deformation, and aims to address the problems caused by the plateau climate and the perma- frost conditions in the region. The equipment consists of a monitoring module, a data collection module, a transmission module, and a data processing module. The field experiments during this program indicate that （1） the combined auto- mated monitoring device overcame the problems associated with the complicated and tough plateau environment by means of wireless transmission and automatic analysis of the embankment settlement data; （2） the calibration of the combined settlement gauge at -20 ℃ was highly accurate, with an error rate always 〈0.5%; （3） the gauge calibration at high-temperature conditions was also highly accurate, with an error rate 〈0.5% even though the surface of the instrument reached more than 50 ℃; and （4） compared with the data manually taken, the data automatically acquired during field monitoring experiments demonstrated that the combined settlement gauge and the automated monitoring system could meet the requirements of the monitoring mission in permafrost regions along the Qinghai-Tibet Railway.

Permafrost Characteristics of the Qinghai-Tibet Plateau and Methods of Roadbed Construction of Railway

Permafrost along the Qinghai-Tibet railway is featured by abundant ground ice and high ground temperature. Under the influence of climate warming and engineering activities, the permafrost is under degradation process. The main difficulty in railway roadbed construction is how to prevent thawing settlement caused by degradation of permafrost. Therefore the proactively cooling methods based on controlling solar radiation, heat conductivity and heat convection were adopted instead of the traditional passive methods, which is simply increasing thermal resistance. The cooling methods used in the Qinghai-Tibet railway construction include sunshine-shielding roadbeds, crushed rock based roadbeds, roadbeds with rock revetments, duct-ventilated roadbeds, thermosyphon installed roadbeds and land bridges. The field monitored data show that the cooling methods are effective in protecting the underlying permafrost, the permafrost table was uplifted under the embankments and therefore the roadbed stability was guaranteed.

Analysis of the Cooling Mechanism of a Crushed Rock Embankment in Warm and Lower Temperature Permafrost Regions along the Qinghai-Tibet Railway

Based on data monitored in situ and theoretical analysis,the characteristics of the temperature field and mechanism of thermal conduction of a crushed rock embankment were studied along the Qinghai-Tibet Railway.The results of experi-ments in the field revealed that the cooling effect of a crushed rock embankment is influenced mainly by the natural con-vection in winter and shield effect in summer,the ventilation of crushed rocks,and the ground temperature regime be-neath the embankment.Consequently,these three factors should be taken into account in numerical simulations,but it is as a result of natural convection only.

Impact of the Qinghai-Tibet Railway on Population Genetic Structure of the Toad-Headed Lizard,Phrynocephalus vlangalii

Using data from nine microsatellite DNA loci and a population genetic approach,we evaluate the barrier effect of the Qinghai-Tibet Railway on toad-headed lizard,Phrynocephalus vlangalii. The study area is along a 20 km stretch of the railway on northern Qinghai-Tibet Plateau,and this section of the railway was constructed between 1958–1979. Both assignment tests and analysis of molecular variance(AMOVA) were used for data analysis. We found significant genetic differentiation between the populations from the study area and those from a further southeastern area,which are separated by a 20 km gap. This suggests the existence of population substructure at a fine-scale. However,we did not detect any difference between samples from the western and eastern sides of the railway within the study area,and concluded that the railway may not impose a significant barrier effect on these lizard populations at the present time. Available suitable habitat alongside the railway and bridge underpasses may have facilitated the gene exchange between the sides. The relatively short time since the completion of the railway may not allow the differentiation to accumulate to a detectable level. Since the Qinghai-Tibet Plateau maintains a unique and fragile ecosystem,long-term monitoring of such man-made landscape features is imperative for protecting this ecosystem.

Analyses on the Types,Distributions and Characteristics of Vegetation and Soil along Qinghai-Tibet Railway

[Objeective] The research aimed to study the types, distributions and characteristics of vegetation and soil along Qinghai -Tibet Rail- way. [ Method]Types, distributions and characteristics of vegetation and soil along Qinghai -Tibet Railway were studied by field investigation meth- od. [Result] The vegetation along Qinghai -Tibet Railway was dominated by alpine grassland and meadow, while the soil was dominated by alpine steppe soil and meadow soil corresponding along the railway. They both concentrated distnbutions at the section from Kunlun Mountain to Nyainqen- tanglha Mountain. [ Conclusion] The research could provide the basis for disaster control and resource development of Qinghai-Tibet Railway.

Thermal Characteristics of the Embankment with Crushed Rock Side Slope to Mitigate Thaw Settlement Hazards of the Qinghai-Tibet Railway

Permafrost （perennially frozen ground） appears widely in the Golmud-Lhasa section of the Qinghai-Tibet railway and is characterized by high ground temperature （≥1℃） and massive ground ice. Under the scenarios of global warming and human activity, the permafrost under the railway will gradually thaw and the massive ground ice will slowly melt, resulting in some thaw settlement hazards, which mainly include longitudinal and lateral cracks, and slope failure. The crushed rock layer has a thermal semiconductor effect under the periodic fluctuation of natural air. It can be used to lower the temperature of the underlying permafrost along the Qinghai-Tibet railway, and mitigate the thaw settlement hazards of the subgrade. In the present paper, the daily and annual changes in the thermal characteristics of the embankment with crushed rock side slope （ECRSS） were quantitatively simulated using the numerical method to study the cooling effect of the crushed rock layer and its mitigative ability. The results showed that the ECRSS absorbed some heat in the daytime in summer, but part of it was released at night, which accounted for approximately 20% of that absorbed. Within a year, it removed more heat from the railway subgrade in winter than that absorbed in summer. It can store approximately 20% of the ＂cold＂ energy in subgrade. Therefore, ECRSS is a better measure to mitigate thaw settlement hazards to the railway.

Prevention and management of wind-blown sand damage along Qinghai-Tibet Railway in Cuonahu Lake area

This paper analyzes the characteristics of climate, geology and geomorphology, vegetation, and sand dune distribution in the Cuonahu Lake area beside the Qinghai-Tibet Railway. The types and causes of railway blown-sand hazards are discussed, and the effectiveness of various sand-controlling measures is assessed. From the perspective of integrated management, a sand-controlling system that combines several engineering measures, including nylon net sand barriers, concrete sand barriers, movable-board sand barriers, sand interception ditches, gravel/rock cover, film sandbags, and permanent vegetation is most beneficial.

Characteristics of sand damages and dynamic environment along the Tuotuohe section of the Qinghai-Tibet Railway

Sand damages along the Qinghai-Tibet Railway occur frequently and have spread rapidly since it was completely opened to traffic in 2006. The goal of this study was to understand the effects of sand damages on the railway via meteorological data and in situ observation of wind-blown sand. We selected the Tuotuohe section of this railway as a typical research object, and we systematically investigated its characteristics of sand damages, drift potential, sand-driving wind rose, and their time variation. The direction of sand-drifting wind clearly varies with the season. In winter, the predominant wind blows from the west and lasts for three months, while in summer the frequency of northeasterly wind begins to increase and multi-directional winds also occurs in July. The drift potential in this area is 705.81 VU, which makes this a high-energy wind environment according to Fryberger＇s definition. The directional variability （RDP/DP） is 0.84 and the resultant drift potential is 590.42 VU with a resultant direction of 89.1°.

Applying the AHP-FUZZY method to evaluate the measure effect of rubble roadbed engineering in permafrost regions of Qinghai-Tibet Plateau: a case study of Chaidaer-Muli Railway

This article attempts to investigate the measure effect of rubble roadbed engineering in permafrost regions of Qinghai-Tibet Plateau. As a case study, Chaidaer-Muli Railway is used to evaluate the measure effect of rubble roadbed engineering in permafrost regions. The AHP(Analytic Hierarchy Process) method is thus employed to establish the evaluation indicator system. The evaluation factor is selected by analyzing the mutual relation between the permafrost environment and roadbed engineering. Thus, a hierarchical structure model is established based on the selected evaluation indices. Each factor is weighted to determine the status in the evaluation system, and grading standards are built for providing a basis for the evaluation. Then, the fuzzy mathematical method is introduced to evaluate the measure effect of rubble roadbed engineering in permafrost regions along the Chadaer-Muli Railway. Results show that most of the permafrost roadbed is in a preferable condition(b) along the Chaidaer-Muli Railway due to rubble engineering measures. This proportion reaches to 86.1%. The proportion in good(a), general(c) and poor states(d) are 0.0%, 7.5% and 6.4%, respectively, in all the evaluation sections along the Chaidaer-Muli Railway. Ground-temperature monitoring results are generally consistent with AHP-FUZZY evaluation results. This means that the AHP-FUZZY method can be applied to evaluate the effect of rubble roadbed engineering measures in permafrost regions. The effect evaluation of engineering measures will provide timely and effective feedback information for further engineering design. The series of engineering measures will more effectively protect permafrost stability.

Automatic testing system design and data analysis of permafrost temperature in Qinghai-Tibet Railway

Aimed at the characteristics of permafrost temperature influencing the safety of Qinghai-Tibet Railway and its on-line testing system, comparing the achievement of permafrost study nationwide with those worldwide, an automatic testing system of permafrost temperature, containing a master computer and some slave computers, was designed. By choosing high-precise thermistors as temperature sensor, designing and positioning the depth and interval of testing sections, testing, keeping and sending permafrost temperature data at time over slave computers, and receiving, processing and analyzing the data of collecting permafrost temperature over master computer, the change of the permafrost temperature can be described and analyzed, which can provide information for permafrost railway engineering design. Moreover, by taking permafrost temperature testing in a certain section of Qinghai-Tibet Railway as an instance, the collected data of permafrost temperature were analyzed, and the effect of permafrost behavior was depicted under the railway, as well as, a BP model was set up to predict the permafrost characteristics. This testing system will provide information timely about the change of the permafrost to support the safety operation in Qinghai-Tibet Railway.

Thermal features of Qinghai-Tibet Railway Embankment with Crushed-stone Slope Protection in Permafrost Regions

The Embankment with Crushed-Stone Slope Protection(ECSSP) in permafrost regions is an effective measure to cool subgrade and protect permafrost.It can mitigate the engineering hazards of the Qinghai-Tibet railway in the permafrost regions. Considering the influence of the noctumal cold air during summer months in Qinghai-Tibet Plateau。

The Qinghai-Tibet Railway:An Engineering Miracle

WHEN railway constructionworkers first came to theQinghai-Tibet Plateau, they were amazed at the majesty ofits snowfield scenery. Cut off from theoutside world, everything on the plateau- its snow-capped mountains, grassland,lamas, prayer banners, the Potala Palace,and the Tibetan people living 4,000 metersor more above sea level, has an aura ofmystery.Beautiful it may be, but Tibet lags behind other areas of China. Inadequate transportation facilities restrict its economic development, as it is only accessible by highway or air transportation.

Analysis of the Theoretical Foundation and Engineering Effect for Air-duct Embankment on the Qinghai-Tibet Railway

Based on the corresponding theories of engineering thermodynamics and hydro-dynamics, a careful study is made of the characteristics of air flow in different duct-embedded ways. According to critical Reynolds number, the atmospheric critical velocity of the duct with different diameters, which makes laminar flow different from turbulent flow, is calculated. Given the condition in which a forced flow occurs and the wind strength is larger than the atmospheric pressure gradient along the air-duct, a rational ratio of the length to the diameter is presented. Based on the above theory and field test data on soil temperature and embankment settlement, the advantages and disadvantages are discussed in details of all duct-embedded ways that might affect the stability of embankment.

Golmud,the Kunlun Mountains and the Qinghai-Tibet Railway

QINGHAI Province, on the Qinghai-Tibet Plateau, is to many people a remote and mysterious place. This reporter recently traveled with the 2002 Qinghai in Focus Photographers Group on their trip from the Qinghai hinterland on the northern part of the plateau to Golmud, the Kunlun Mountains, and the Qinghai-Tibet Railway construction site.Golmud, Born with the HighwayIt took us 2 hours and 10 minutes to fly the 1,150 kilometer distance from Beijing to Xining, capital city of Qinghai Province. From there we boarded a train that went directly west to Golmud.

“Golden Bridge”for Tibetan People——How the Qinghai-Tibet Railway is Being Built

Aplateau railway, the Qinghai-Tibet Railway, will run across the "roof of the world" with an average elevation of more than 4,000 meters. The railway, the highest in altitude in the world, will terminate in Lhasa, capital of Tibet Autonomous Region. This steel artery is likened to a "golden bridge" on the great plateau. For the Tibetan people, the "golden bridge" leads to Beijing and to a better life.

QINGHAI-TIBET RAILWAY:FROM DREAM TO REALITY

On July 1,2006, the Qinghai-Tibet Railway will go into service on a trial basis, taking people in Beijing, Shanghai, Guangzhou and Chengdu to Lhasa and back.