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1.
As an effective solution for protecting the underlying permafrost and preventing roadway damages, the block-rock embankment(BRE) has been widely used on the Qinghai–Tibet Railway, Qinghai–Tibet Highway, and Ching–Hong Road;and it will be promoted for other roadways in the future. To evaluate the adaptability of BRE, the catastrophe-progression method was adopted for the evaluation. By analyzing the factors affecting the stability of BRE and utilizing engineering experience, we were able to establish the mathematical model and divide the adaptability of BRE into five grades. After the verifying analysis of 28 practical engineering examples, the evaluation results are broadly in line with practical application effects. Therefore, the adaptability of BRE can be evaluated and predicted more accurately with this evaluation model. 相似文献
2.
One of the main construction problems in permafrost regions is protecting permafrost thermal stability. Although ventilating ducts and crushed-rock layers were successfully used in railway embankment construction, their effects might not meet large-width expressway requirements. The convection-intensifying composite embankment composed of perforated ventilation ducts and crushed-rock layers was numerically studied to investigate its cooling effects. Adopting a numerical model, the temperature fields for two kinds of composite embankment with and without air doors were analyzed considering air flow and heat transfer characteristics in porous media. The results show that wind velocity in the crushed-rock zone is intensified by the perforated ventilation duct. The underlying permafrost temperature obviously decreases, and the 0 °C isotherm position rises significantly due to composite embankment. The composite embankment with air doors is more effective than that without air doors. Therefore, the new convection-intensifying composite embankment is potentially a highly efficient cooling measure for construction in permafrost regions. 相似文献
3.
Rudolf V. Zhang 《寒旱区科学》2014,6(4):0340-0347
This article discusses the current concepts of dam design and construction in permafrost regions. It is demonstrated that embankment dams often change their state from frozen to thawed and back during the operation period. It is shown that these transitions are not always attributable to observed climate warming. Where geotechnical, hydrogeological, and permafrost conditions are complicated, proper performance of embankment dams can only be provided by adhering to a selected thermal design for, as an example, a frozen state. 相似文献
4.
The unfrozen water content and ice content of frozen soil change continuously with varying temperatures, resulting in the temperature dependence of mechanical properties of frozen soil. Thus the dynamic behavior of embankment in permafrost regions under train loading also alters with seasons. Based on a series of strong-motion tests that were carried out on the traditional embankment of Qinghai-Tibet Railway(QTR) in permafrost regions, the acceleration waveforms recorded at the embankment shoulder and slope toes were obtained. Testing results show an obvious attenuation effect on the vertical train loading from road shoulder to slope toes. Furthermore, numerical simulations of a traditional embankment under vertical train loading in different seasons were conducted, and the dynamic behavior of the embankment was described. The results show that the vibration attenuation in the cold season is greater than that in the warm season. The maximum acceleration of vibration drops to about 5% when the train vibration load is transferred through the embankment into the permafrost, and the high-frequency components are absorbed when the vibration transmits downward. Moreover, the dynamic stress under the dynamic train loading decreases exponentially with an increasing depth in different seasons. The results can be a reference for design and maintenance of embankments in permafrost regions. 相似文献
5.
Rudolf V. Zhang 《寒旱区科学》2014,6(4):0348-0355
Global climate warming which began in the second half of the twentieth century is continuing. It is associated with increased risks for ecological management, especially in permafrost areas comprising over 65% of Russia. Of special concern are dams constructed on permafrost. They are subject not only to climatic impacts, but also to additional hydrothermal loads from water reservoirs. This paper presents the concept of geocryological monitoring of dams and other water resource projects and substantiates its necessity in view of climatic change. It also presents methods, scope and implementation of geocryological monitoring at medium and small dams, considering the specific nature of Far Northern areas, as well as the complicated geotechnical, hydrogeological and permafrost conditions. 相似文献
6.
Railroad operating experience in permafrost conditions has shown that deformations of embankments on thawing foun-dations last for a long time. After an initial period of heat settlement due to permafr... 相似文献
7.
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 permafrost 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 automated 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 °C 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 °C; 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. 相似文献
8.
Sergei Kudriavtcev Tatiana Valtsev Alexei Kazharskyi Elena Goncharov Iurii Berestianyi 《寒旱区科学》2013,5(4):0404-0407
The goal of a predictive thermotechnical calculation is to model the behavior of the top permafrost boundary under current
operational conditions as well as increasing average annual air temperatures that results in degradation of the permafrost
layer. Numerical modeling was used to assess the efficient application of construction measures to create sustainable operation
of the railroad. The numerical modeling was carried out in the programming complex FEM-models developed by
geotechnical engineers of St. Petersburg, Russia under Prof. V. M. Ulitsky’s guidance. The Termoground Program as a part
of the FEM-models enables the research of freezing, heaving and thawing in different design solutions. Research was
carried out in space resolution for a year cycle. The performed model has shown that the designing measures accepted for
permafrost protection from retreat in the subgrade support were generally effective. 相似文献
9.
V. G. Kondratiev 《寒旱区科学》2013,5(4):0377-0386
The history of railway and highway construction in permafrost zones in Russia, the United States, Canada, and China spans more
than 110 years. Nonetheless, no railway track or highway has yet been built in such area that is impervious to deformation caused
by subsidence resulting from the thawing of ice-rich subgrade soils. This paper presents data on the roadbed states of the Transbaikalian
and the Baikal-Amur Railways as well as the Russian "AMUR" Chita-Khabarovsk Highway. It also discusses the feasibility
of roadbed stability maintenance using methods based on the reduction of the mean annual ground temperature and roadbed
preservation in a permafrost state by means of the natural cooling and heating factors ratio regulation resulting in a reduction of the
heat generation in the roadbed and the adjoining area accompanied by an increase of heat consumption with help of the
sun-precipitation protective sheds (awnings), rock covers, dolomite powder (reflective paint), cooling tube and thermosyphons as
well as tower supports and corrugated pipe culverts stability. 相似文献
10.
For the purpose of enhancing air convection and controlling solar radiation, a new crushed-rock slope embankment design combined with a sun-shade measure is proposed. A newly designed embankment was constructed in the Tuotuohe section of the Qinghai-Tibet Railway and a field-testing experiment was carried out to determine its convection and temperature characteristics. The results show that distinct air convection occurred in the crushed-rock layer of the new embankment, especially in cold seasons, which was enhanced when it flowed upwards along the slope. This preliminarily indicated that the new design of the embankment slope was good for reinforcing air convection in the crushed-rock layer. The frequent fluctuations of the convection speed and the environmental wind speed were in good agreement, suggesting that the convection in the crushed rock primarily came from the ambient wind. It was also preliminarily determined that the new embankment had a better cooling effect and sun-shade effect for decreasing the temperature of the embankment slope compared with a traditional crushed-rock slope embankment, and the mean temperature difference between them was up to 1.7 °C. The mean annual temperature at the bottom boundary of the crushed-rock layer was obviously lower than that at the top boundary, and heat flux calculation showed that the shallow soil beneath the embankment slope was weakly releasing heat, all of which indicated that the new embankment slope design was beneficial to the thermal stability of the embankment. This study is helpful in providing some references for improved engineering design and maintenance of roadbeds in permafrost regions. 相似文献
11.
Based on ground temperatures and deformations monitored at the Xieshuihe site along the Qinghai-Tibet Highway(QTH)in permafrost regions from 2004 to 2015,variation of artificial permafrost table(APT),maximum frozen depth(MFD),thawed interlayer thickness(TIT)and ground temperature beneath embankment is analyzed,respectively.The results indicate that under the embankment,the change of APT occurred from October to December of that year and presented a deepening trend.The change of MFD occurred from April to June of that year with no obvious change trend,and TIT had an increasing trend year by year,which mainly resulted from the deepening artificial permafrost table.Mean annual ground temperature at 0.5 m depth was 3.91°C higher beneath the embankment center than that under the natural field.The rising ground temperature at shallow layer of embankment resulted in the development of thawed interlayer beneath the embankment and warming of underlying permafrost.Embankment settlement is closely associated with TIT.Greater settlement easily occurs when permafrost with higher ice content exists under the thawed interlayer,and in turn the settlement is smaller when permafrost with lower ice content exists under the thawed interlayer. 相似文献
12.
In order to maintain the thermal stability of very wide highway embankments in permafrost regions, the thermal isolation
material EPS is often utilized. To examine the effects of this insulation on the China National Highway (G214),
two-dimensional finite element analysis of temperature fields was conducted for varying widths of highway embankments
with and without EPS insulation. The numerical results show that in permafrost regions the effect of thermal aggregation on
asphalt pavement is more obvious when highway embankments are wider, and, specifically for the G214 highway, the insulation
should be more than 25 cm thick for 24-m-wide embankments. However, considering other factors such as the structural
rationality of the embankments and high engineering costs, it might not be feasible to install EPS insulation in
24-m-wide embankments of the G214 highway when the height of the embankments is less than 3.65 m. 相似文献
13.
Because of the global warming and the increasing human activity, the air temperature and the precipitation along the Qinghai-Tibet Railway increased gradually in recent years, which endanger the permafrost table, the embankment of the railway. The statistics of the air temperature, the precipitation and the geothermal temperature in recent 50 years in this dissertation come from the four weather station along the railway, that are Wudaoliang Station, Fenghuo Mountains Station, Tuotuo River Station and Ando Station. This dissertation analyzes the change of climate along the railway and then develops a research on the effect of the changing geothermal temperature on permafrost table and its countermeasures. The experiment result shows that the air temperature of the permafrost region rise steadily in about 50 years, especially in this century, the tendency of rising temperature is more obvious. The precipitation fluctuates but it is also rising rapidly, for the largest precipitation reached 492.6 mm. For 30 years now, the Qinghai-Tibet Plateau has been in the megathermal period, which also affects the permafrost region along the railway. The condition of permafrost is degrading greatly. 相似文献
14.
Based on the analysis and comparison of soil temperature, thermal regime and permafrost table under the experimental embankment of crushed rock structures in Beiluhe, results show that crushed rock structures provide an extensive cooling effect, which produces a rising permafrost table and decreasing soil temperatures. The rise of the permafrost table under the embankment ranges from an increase of 1.08 m to 1.67 m, with an average of 1.27 m from 2004 to 2007. Mean annual soil temperatures under the crushed rock layer embankment decreased significantly from 2005 to 2007, with average decreases of ?1.03 °C at the depth of 0.5 m, ?1.14 °C at the depth of 1.5 m, and ?0.5 °C at the depth of 5 m. During this period, mean annual soil temperatures under the crushed rock cover embankment showed a slight decrease at shallow depths, with an average decrease of ?0.2 °C at the depth of 0.5 m and 1.5 m, but a slight rise at the depth of 5 m. After the crushed rock structures were closed or crammed with sand, the cooling effect of the crushed rock layer embankment was greatly reduced and that of the crushed rock cover embankment was just slightly reduced. 相似文献
15.
At present, embankment longitudinal cracks are a major problem in highways through permafrost regions, and seriously affect traffic safety and the normal operations of the highway. In the past, roadbed height in permafrost regions was relatively low, and embankment cracks were rare and did not affect traffic safety. Thus, highway designers and researchers paid little attention to this problem, and they knew very little about distribution laws and mechanism of embankment longitudinal cracks. Due to this lack of knowledge, there is no uniform opinion on this problem, making it difficult to find measures that will mediate the impact of longitudinal cracks. Temperature is a major factor that affects and controls embankment stability in permafrost regions, especially in ice-rich and high-temperature regions, and solar radiation is the principal factor that determines surface temperatures. Under higher embankment, the difference of temperature will be larger between a sunny slope and a shady slope. Hence, the probability for longitudinal cracks generation is higher. In this paper, a survey and analysis of longitudinal cracks along the Qinghai-Tibet Highway were carried out. The longitudinal cracks are found to be related to the road strikes. Solar radiation is considered to play an important role in the generation of longitudinal cracks. 相似文献
16.
Permafrost thickness under identical climates in cold regions can vary significantly because it is severely affected by climate change, topography, soil physical and thermal properties, and geothermal conditions. This study numerically in- vestigates the response of ground thermal regime and talik development processes to permafrost with different thicknesses under a thermokarst lake on the Qinghai-Tibet Plateau. On the basis of observed data and information from a representative monitored lake in the Beiluhe Basin, we used a heat transfer model with phase change under a cylindrical coordinate system to conduct three simulation cases with permafrost thicknesses of 45 m, 60 m, and 75 m, respectively. The simulated results indicate that increases in permafrost thickness not only strongly retarded the open talik formation time, but also delayed the permafrost lateral thaw process after the formation of open talik. Increasing the permafrost thickness by 33.3% and 66.7% led to open talik formation time increases of 83.66% and 207.43%, respectively, and resulted in increases in the lateral thaw duration of permafrost under the modeled thermokarst lake by 28.86% and 46.54%, respectively, after the formation of the open taliks. 相似文献
17.
As one of the widely used upgrading way in road engineering, the widening embankment(WE) has suffered evident differential deformation, which is even severer for highway in permafrost regions due to the temperature sensitivity of frozen soil and the heat absorption effect of the asphalt pavement. Given this issue, a full-scale experimental highway of WE was performed along the Qinghai-Tibet Highway(QTH) to investigate the differential deformation features and its developing law. The continuous three years' monitoring data taken from the experimental site, including the ground temperature and the layered deformation of WE and original embankment(OE), were used to analyze the thermal-deformation process. The results indicate that the widening part presented the remarkable thermal disturbance to the existing embankment(EE). The underlying permafrost was in a noteworthy degradation state, embodying the apparent decrease of the permafrost table and the increase of the ground temperature. Correspondingly, the heat disruption induced by widening led to a much higher deformation at the widening side compared to the original embankment, showing a periodic stepwise curve. Specifically, the deformation mainly occurred in the junction of the EE and the widening part, most of which was caused by the thawing consolidation near the original permafrost table. In contrast, the deformation of EE mainly attributed to the compression of the active layer. Furthermore, it was the deformation origination differences that resulted in the differential deformation of WE developed gradually during the monitoring period, the maximum of which reached up to 64 mm. 相似文献
18.
With globe warming, road safety will change dramatically, especially within the Qinghai-Tibet Plateau permafrost regions. Because
of higher elevation and better atmospheric transparency, the Qinghai-Tibet Plateau has stronger radiation than other regions,
which can change the daily variation of ground surface temperature on the Plateau. The awning measure (shading board) is one of
the actively protected permafrost measures, which was adopted along the Qinghai-Tibet railway and highway and the Qing-Kang
Highway in China. Field test results show that embankment surface month mean net radiation is 60–130 W/m2, but the value is
below 20 W/m2 under the shading board, and the reducing level of natural net radiation is 80%–90%. The shading board reduced
the heat flow entering into the embankment by 80%–90% or more, with heat entering into the soil on the common embankment,
but emitting from the embankment under the shading board. At the same time, ground surface temperature under the shading
board is 6–8 °C lower than the exposed embankment. Test results show that the shading board measure can rapidly and effectively
reduce net radiation and heat flow into the embankment, decrease embankment surface and interior temperature, effectively delay
increase rate of soil temperature under globe warming, ensure stability and safety of the embankment, and guarantee unblocked
road projects in cold and permafrost regions. 相似文献
19.
黄河源区多年冻土空间分布变化特征数值模拟 总被引:2,自引:1,他引:2
基于IPCC第五次评估报告预估的气温变化情景,采用数值模拟的方法对黄河源区典型冻土类型开展模拟,推算过去及预测未来黄河源区冻土分布空间变化过程和发展趋势。结果表明:1972-2012年源区多年冻土只有少部分发生退化,退化的冻土面积为833 km2,季节冻土主要集中在源区东南部的热曲谷地、小野马岭以及两湖流域南部的汤岔玛地带;RCP 2.6、RCP 6.0、RCP 8.5情景下,2050年多年冻土退化为季节冻土的面积差别不大,分别为2224 km2、2347 km2、2559 km2,占源区面积的7.5%、7.9%、8.6%;勒那曲、多曲、白马曲零星出现季节冻土,野牛沟、野马滩以及鄂陵湖东部的玛多四湖所在黄河低谷大片为季节冻土;2100年多年冻土退化为季节冻土的面积分别为5636 km2、9769 km2、15548 km2,占源区面积的19%、32.9%、52.3%;星宿海、尕玛勒滩、多格茸的多年冻土发生退化,低温冻土变为高温冻土,各类年平均地温出现了不同程度的升高。到2100年,RCP 2.6情景下源区多年冻土全部退化为季节冻土主要发生在目前年平均地温高于-0.15 oC的区域,而-0.15~-0.44 oC的区域部分发生退化;RCP 6.0、RCP 8.5情景下目前年平均地温分别为高于-0.21 oC以及-0.38o C的区域多年冻土全部发生退化,而-0.21~-0.69 oC以及-0.38~-0.88 oC的区域部分发生退化。 相似文献
20.
In the last several decades, the underlying surface conditions on the Qinghai-Tibet Plateau have changed dramatically, causing permafrost degradation due to climate change and human activities. This change severely influenced the cold regions environment and engineering infrastructure built above permafrost. Permafrost is a product of the interaction between the atmosphere and the ground. The formation and change of permafrost are determined by the energy exchange between earth and atmosphere system. Fieldwork was performed in order to learn how land surface change influenced the thermal regime in permafrost regions. In this article, the field data observed in the Fenghuo Mountain regions was used to analyze the thermal conditions under different underlying surfaces on the Qinghai-Tibet Plateau. Results show that underlying surface change may alter the primary energy balance and the thermal conditions of permafrost. The thermal flux in the permafrost regions is also changed, resulting in rising upper soil temperature and thickening active layer. Vegetation could prevent solar radiation from entering the ground, cooling the ground in the warm season. Also, vegetation has heat insulation and heat preservation functions related to the ground surface and may keep the permafrost stable. Plots covered with black plastic film have higher temperatures compared with plots covered by natural vegetation. The reason is that black plastic film has a low albedo, which could increase the absorbed solar radiation, and also decrease evapotranspiration. The "greenhouse effect" of transparent plastic film might effectively reduce the emission of long-wave radiation from the surface, decreasing heat loss from the earth's surface, and prominently increasing ground surface temperature. 相似文献