寒区碾压土多周期冻融循环热水力耦合分析

针对冻融循环条件下工程土体内部发生冰水相变、水分迁移以及温度场变化,进而导致土体变形的问题,提出了冻胀及融沉理论,并建立了基于温度场、水分场以及应力场的耦合方程.通过时域差分法建立三场耦合模型对选定碾压土路基工程实例进行计算.结果表明,计算模型能够准确计算土体温度、水分以及变形情况,并对土体变化进行预测.该模型适用于寒区工程建设中土体多场耦合状态分析,为冻融循环诱发的工程安全问题提供了参考.

青藏铁路设计与建设——第六届国际冻土工程会议回顾(英文)

The 6th International Symposium on Permafrost Engineering was successfully held in China in September 2004. About 150 scientists and engineers from 7 countries attended the symposium in Lanzhou on 57 September, and about 35 people from 6 countries participated in the field trip along the Qinghai-Tibet Highway/Railway on 813 September and the seminar in Lhasa on 14 September 2004. During the Symposium, the latest progress on permafrost engineering and the surveys, design and construction of the Qinghai-Tibet Railway were exchanged and inspected. Fifty-eight technical papers in English from the Symposium were published in the first volume of the Proceedings of the Symposium, as a supplement of the Journal of Glaciology and Geocryology, before the symposium. About 6 papers from the symposium are published in the second volume in the volume 27（1） of the Journal of the Glaciology and Geocryology, after the symposium.;The Qinghai-Tibet Railway （QTR） under construction will traverse 632 km of permafrost, and the engineers are facing unprecedented engineering and environmental challenges. With the QTR under construction and to be completed in 2007, permafrost engineering has become the research focus of permafrost scientists and engineers in China. Many encouraging and promising achievements in permafrost engineering have been obtained during the past three years. However, there are still numerous engineering and environmental problems needing to be solved or resolved. ;In the discussions, some experts pointed out that methods, such as removal of snow cover on the embankments and toe areas, light-color embankments and side slope surfaces, awnings for shading the solar radiation, hairpin or tilted thermosyphons, could be applied to actively cool the roadbed of the QTR. Some new ideas on utilization of the natural cold reserves were proposed to protect the QTR permafrost roadbed from thawing. Many questions and answers on the survey, design, construction, operations, maintenance and environmental protection were exchanged in situ and in the Lhasa seminar with participation by some major railway designers, regulators and administrators.

The Impact of Climate Warming on Permafrost and Qinghai-Tibet Railway

Global warming is an inarguable fact. Permafrost is experiencing a change due to climate warming in Qinghai-Tibet Plateau, such as the decreasing of permafrost table, the rising of permafrost temperature, etc. On the basis of analysing the permafrost change under the climate change and engineering action, the thermal regime and spatial distribution of permafrost are predicted for air temperature rising 1℃ and 2.6℃ after 50 years in this paper. The results show that climate change results in the larger change for the thermal regime and spatial distribution of permafrost. Permafrost change will produce the great effect on the Qinghai-Tibet Railway engineering, not only resulting in the decreasing of permafrost table beneath the roadbed, but also resulting in thawing settlement due to the thawing of ground ice near permafrost table. The idea of cooling roadbed and actively protecting permafrost for the Qinghai-Tibet Railway engineering could adjust and control the permafrost thermal state, some better methods are provided to ensure the engineering stability in the areas of warm permafrost and high ice content.

A Roadbed Cooling Approach for the Construction of Qinghai-Tibet Railway

Over one half of the permafrost along the Qinghai-Tibet Railway is “warm" and approximately 40% ice-rich. Under global warming, the construction of the Qinghai-Tibet Railway needs to consider climate changes over the next 50～100 years. Recent estimates indicate that the air temperature on the plateau will increase by 2.2～2.6℃ by 2050. Thus, the key to the success of the railway construction lies in preventing the permafrost underlying roadbeds from thawing. It has been more than 100 years since the first railway was build over permafrost. A frost damage ratio of greater than 30% has been reported for all the railroads built in permafrost regions. Based upon the experience and lessons learned from roadway constructions over permafrost, this paper proposes a more proactive design approach for the construction of the Qinghai-Tibet Railway. This approach focuses on cooling down the roadbed by lowering the ground temperature and is different from the passive method of preventing permafrost from thawing by simply increasing thermal resistance (e.g., increasing embankment height and using insulating materials). This “roadbed cooling" design approach is especially relevant to “warm" and ice-rich permafrost areas. A number of measures can be taken to cool down the roadbed, including proper selection of roadbed material, and configurations to adjust solar radiation, heat convection, and heat conduction patterns in and/or around the roadbed.

本世纪甲烷不太可能大量释放

德国科学家在重新研究全球变暖而造成的北极永久冻结带融化状况之后表示：在本世纪不太可能发生甲烷大量释放的现象。

北极气候变暖极有可能改变生态系统

《美国国家地理》消息 由于北极气候变暖，大量永冻土带融化，流人海洋。自2000年以来，数十名科学家便对大约6．2万英里（约合10万km）——占整个北极海岸线的25％左右——北极海岸线进行研究。新研究发现，北极部分地区的永久冻结带每年遭侵蚀的程度最多达到100英尺（约合30m）。拉普帖夫海、东西伯利亚和波弗特海沿岸的永冻土带遭侵蚀情况最为严重。

Investigation and Analysis on New Harmful Features Related to Frozen Ground in Permafrost Regions in Qinghai-Tibet Railway

At first, the forming conditions and developing characteristics of several kinds of typical harmful features related to frozen ground are discussed in the paper, such as flooding ice, icing mound, frost mound, thick ground ice, thaw slumping, thermokarst lake and swampland. Secondly, the investigating results of new harmful permafrost features in winter along Qinghai-Tibet Railway are analysed and summarized. Lastly, some data and suggestions will be provided to designing and construction departments.

Analysis of the Effectiveness of Thermosiphon, Awning and Insulations Board on Permafrost Roadbed

In this paper, the effect of the thermosiphon, insulation board and awning in cooling the permafrost roadbed base was simulated numerically. The computed results were analysed and compared, some practical conclusion were presented.

Application and Study on Dynamic Design in Qinghai-Tibet Railway Construction

The dynamic design method is essentially the evolving processes of various information, it consists of dynamic design and information construction. It is a new technology of increasing popularity. Because of the particularity and complexity of the Qinghai-Tibet Railway construction, the technology of the dynamic design and information constructing was used tentatively. Based on processes of Qinghai-Tibet Railway construction, this paper discussed and analysed the idea of dynamic design and applications. Meanwhile in allusion to arisen problems in design and construction, some principles and suggestions of reinforced measurements were put forward. Though the works of construction and design are being carried through, good results have been obtained.

Discussion on the Designing Difficulties of Fenghoshan Tunnel on Qinghai-Tibet Railway

The major technical difficulties of Fenghuoshan Tunnel were caused by arctic alpine, high altitude and permafrost. Through analysis of the major technical problems of Fenghuoshan Tunnel, this paper explored the designing methods and ways of tunnels in arctic alpine climate, on high altitude and on permafrost regions, to offer reference for the projects of similar nature.

斯瓦尔巴德全球性种子库制冷系统正式启用

全球农作物多样化信托基金挪威朗伊尔城11月16日讯。在斯瓦尔巴德群岛山区永久冻结带建立“斯瓦尔巴德全球性种子库”的目的是为了储存世界各地收藏的不同种子的安全复制品，如果某类种子因为地区性或全球性灾难而消失，我们可以从中复制并重新种植。这些距离北极仅几百英里的储藏室是由总部位于罗马的全球农作物多样化信任基金、挪威政府与北欧基因库联合开凿，最多可容纳450多万种种子，将于明年2月26日正式对外开放。

Blasting Technology Research in Construction of Fenghuoshan Tunnel in Permafrost

The Fenghuoshan Tunnel is an important project in Qinghai-Tibet Railway. How to protect permafrost during tunnelling is one of key technology. There are two kinds of influences on permafrost because of the blasting construction, firstly, blasting results in the damage of the surrounding rock, producing cranny in surrounding rock or making existing cranny spreading even connecting, secondly, the explosion produces gas with high temperature and high pressure, tremendous heat energy influences the heat balance of permafrost. To minimize the effect on permafrost during explosion construction, this paper has done research for relevant explosion scheme based on the theoretic analysis and spot tests. Pre-crack explosion is adopted on the hollow segment, and smooth explosion is adopted on the tunnel body segment, whole section excavation is adopted on the tunnel body segment with grade Ⅳ surrounding rock, and the face steps excavation is adopted on the tunnel body segment with grade Ⅴ surrounding rock. Explosion parameters were optimised finally. The maximal explosion vibration velocity in the surrounding rock is controlled in 5～10 cm/s. To solve the heat disturbance problem, brine mud is adopted to block up explosion holes in order to coll and dustproof. The research result indicated the explosion gaseous cool effect when the brine mud medium as adopted reached 70% compared to 55% when the water mud medium was adopted, so the gaseous cool effect was very distinct.

Discussion on Theoretical Analysis and Calculation of Settlement and Cracking in Subgrade in Permafrost of the Qinghai-Tibet Plateau

This paper carries on the theoretical analysis on characteristic of settlement and cracking in subgrade in permafrost of the Qinghai-Tibet Plateau, proposed mechanism of settlement and cracking in subgrade in permafrost on the Qinghai-Tibet Railway. Based on the slices divide of section of subgrade, proposes that it is rotated according to artificial permafrost table, and then the cracking of thaw settlement is calculated. Based on the theoretical of V.A. Kudriavtsev about permafrost, calculated distance of frost crack in subgrade. Aim at characteristics of settlement and cracking in subgrade in permafrost of the plateau the principle of unequal migration of unfrozen water and deformation caused by thermo sieve effect is firstly used. Considering the relationship between deformation and time, the theoretical mode of calculating cracking is in the paper.

Analysis on Ground Temperature Changes and Thermal Effects of Duct-Ventilated Embankment of the Qinghai-Tibet Railway

Cooling principle is adopted in roadbed constructions in permafrost regions on the Qinghai-Tibet Plateau for protecting the underlying permafrost. One way is to use duct-ventilated emban kment. Based on ground temperature data collected along experimental emban kments in Beiluhe section of the Qinghai-Tibet Railway, engineering effects of duct-ventilation for protection of the permafrost beneath the emban kment were studied. Analyses of ground temperature changes and heat inlux indicate that ventilation ducts effectively cool the soils surrounding the ducts in the emban kment and that yearly heat collection of the ambient soils appears as heat release. Permafrost behaviour beneath conventional emban kment and test emban kments with ducts installed at a high and low positions were studied to determine temperature-changing tendency during three years. Where the permafrost under the conventional emban kment and the duct high-positioned emban kment decreasingly absorbs heat during the period. The ground temperature of the permafrost under the conventional emban kment rises and that under the high-positioned emban kment decreases slightly. The temperature of the permafrost under the duct low-positioned emban kment decreased remarkable due to release of heat. These findings demonstrate that ventilated emban kments with low-positioned ducts produce beneficial temperature-controlling effects that actively cool the roadbed soils and keep the roadbed thermally stable. Accordingly, they were strongly recommended for use in the construction of emban kments in the permafrost regions on the plateau.

The Informatization Construction of Fenghuoshan Tunnel in Permafrost

Based on the characteristics of tunnels in permafrost, we established an integrated infromatization management system for the construction of the Fenghuoshan Tunnel Qinghai-Tibet Railway. In addition to information collection items of generic tunnels, our emphases were placed on the monitoring of the work face temperature, environment temperature, surrounding rock temperature, frost heave force on lining, water pressure on lining and rock bolt force. According to the work face and environment temperatures during construction, we regulated and controlled the ventilation temperature in fime to guarantee the stabilization of the work face and the construction quality of concrete. According to the changes in surrounding rock temperatures, water pressure and frost heave force on the lining, we could estimate the effectiveness of waterproof and temperature preservation systems. According to the changes in frost heave force on lining and rock bolt force, we could estimate the mechanical effectiveness of support system.

埋藏在西伯利亚的“定时炸弹”

由于全球气候变暖等因素，位于西伯利亚西部永久冻结带上全球最大的冻泥炭沼泽开始融化，这片在距今11000年前形成的冻土正在逐渐变成一个个浅湖。而这一过程释放出的甲烷气体。（温室气体的一种）也将会加速全球变暖的进程。

全球变暖威胁粮食安全，联合国报告“求变”

8月8日,联合国政府间气候变化专门委员会在瑞士日内瓦召开的联合国会议上获得各国代表批准,发布一则报告。报告显示,自从工业化以来,全球地表气温上升1.53℃,使全球平均气温上升幅度将近两倍;全球平均气温这一时期上升0.87℃。地表温度升高加剧土地退化,增加沙漠面积,缩小永久冻结带,使森林更易发生干旱、火灾、虫害。

Symbiosis of Marshes and Permafrost in Da and Xiao Hinggan Mountains in Northeastern China

Recently, the degradation of permafrost and marsh environments in the Da and Xiao Hinggan Mountains has become a great concern as more human activities and pronounced climate warming were observed during the past 30 years and projected for the near future. The distr/bution patterns and development mechanisms of the permafrost and marshes have been examined both in theories and in field observations, in order to better understand the symbiosis of permafrost and marshes. The permafrost and marshes in the Da and Xiao Hinggan Mountains display discernible zonations in latitude and elevation. The marsh vegetation canopy, litter and peat soil have good thermal insulation properties for the underlying permafrost, resulting in a thermal offset of 3 ℃ to 4℃ and subsequently suppressing soil temperature. In addition, the much higher thermal conductivity of frozen and ice-rich peat in the active layer is conducive to the development or in favor of the protection of permafrost due to the semi-conductor properties of the soils overlying the permafrost. On the other hand, because permafrost is almost impervious, the osmosis of water in marsh soils can be effectively reduced, timely providing water supplies for helophytes growth or germination in spring. In the Da and Xiao Hinggan Mountains, the permafrost degradation has been accelerating due to the marked climate warming, ever increasing human activities, and the resultant eco-environmental changes. Since the permafrost and marsh environments are symbiotic and interdependent, they need to be managed or protected in a well-coordinated and integrated way.

Studies on frozen ground of China

Permafrost in China includes high latitude permafrost in northeastern China, alpine permafrost in northwestern China and high plateau permafrost on the Tibetan Plateau. The high altitude permafrost is about 92% of the total permafrost area in China. The south boundary or lower limit of the seasonally frozen ground is defined in accordance with the 0 ℃ isothermal line of mean air temperature in January, which is roughly corresponding to the line extending from the Qinling Mountains to the Huaihe River in the east and to the southeast boundary of the Tibetan Plateau in the west. Seasonal frozen ground occurs in large parts of the territory in northern China, including Northeast, North, Northwest China and the Tibetan Plateau except for permafrost regions, and accounting for about 55% of the land area of China. The southern limit of short-term frozen ground generally swings south and north along the 25° northern latitude line, occurring in the wet and warm subtropic monsoon climatic zone. Its area is less than 20% of the land area of China.