HR: 13:40h
AN: C23B-01 INVITED     [Abstracts]
TI: Design and Build of the Qinghai-Tibet Railway considering the Impacts of Warming Climate and Permafrost
AU: * Ma, W
EM: mawei@lzb.ac.cn
AF: PO Box FM05BW, State Key Laboratory of Frozen Soils Engineering, CAREERI, CAS, 326 West Donggang Road, Lanzhou, GS 730000 China
AU: Jin, H
EM: hjjin@lzb.ac.cn
AF: PO Box FM05BW, State Key Laboratory of Frozen Soils Engineering, CAREERI, CAS, 326 West Donggang Road, Lanzhou, GS 730000 China
AU: Cheng, G
EM: gdcheng@lzb.ac.cn
AF: PO Box FM05BW, State Key Laboratory of Frozen Soils Engineering, CAREERI, CAS, 326 West Donggang Road, Lanzhou, GS 730000 China
AU: Wu, Q
EM: qbwu@lzb.ac.cn
AF: PO Box FM05BW, State Key Laboratory of Frozen Soils Engineering, CAREERI, CAS, 326 West Donggang Road, Lanzhou, GS 730000 China
AU: Lai, Y
EM: ymlai@lzb.ac.cn
AF: PO Box FM05BW, State Key Laboratory of Frozen Soils Engineering, CAREERI, CAS, 326 West Donggang Road, Lanzhou, GS 730000 China
AB: During the period from 1960 to 2000, an 1°C increase of air temperature has been observed along the Qinghai-Tibet Railway (QTR) traversing 632 km of warm and ice-rich permafrost through the interior of the Qinghai-Tibet Plateau. Correspondingly, mean annual ground temperatures (MAGTs) of warm (>-1 °C) permafrost on average increased about 0.3 to 0.5°C during 1970s-1990, while that of colder permafrost had increased by 0.1 to 0.3°C. During 1996-2004, ground temperatures at the permafrost table were increasing at the rates of 0.01-0.08°C a-1, and the permafrost table was lowering at the rates of 2.6 to 6.6 cm a-1; and the ground temperatures at depths of 6 to 8 m were warming at the rates of 0.02 to 0.05°C a-1. Consequently, the strengths of permafrost as the foundation of the QTR would be weakened if proper engineering measures were not taken. Based on the experiences and lessons learned from the road construction in permafrost regions from Alaska, Canada and Russia, and northeastern China, and taking into consideration of possible climatic warming along the QTR during the next 100 years, the design and construction of the QTR adopted the principle of``cooling the roadbed'' because most of the permafrost along the route is too deep to be thawed, too thermally sensitive to climatic warming and too critical to have appreciable thaw settlements. About 550 km of QTR is in continuous permafrost zone, 82 km is in discontinuous permafrost zone; 275 km is in warm permafrost areas, and 110 km of permafrost is ice-rich. The QTR is designed for safe operations during the next 100 years during which a warming of 2.2 to 2.6°C by 2050 is projected. Without engineering measures to keep ground frozen or maintain the settlement within the acceptable limits, thaw settlement in the foundation soils, and induced environmental instability would threaten the integrity and safety of QTR operation. However, only increasing therma resistance, such as increasing fill thickness or using insulation materials is a passive method of permafrost protection and inadequate to ensure the engineering reliability and long-term stability of foundation soils under a persistent warming climate. Therefore, the design of the QTR has to adopt the principle of active cooling by controlling radiation, convection and conduction through modifying road structures. The measures for controlling radiation include the applications of ligh-color fill materials and side-slope materials, and awnings. The measures fo controlling the convection include air ducts, coarse rock roadbed and sideslope structures, and thermosyphons. The methods for controlling the conduction include insulation materials with strong thermal offsets and sufficient strength and durability, grassing of side slopes. Some of the abovementioned methods are combined to enhance the cooling effect in critical sections with warm and ice rich permafrost. These engineering measures based on extensive field and laboratory scientific experimental and simulation research have been adopted by the design and construction of the QTR. The preliminary results indicate that they have been quite effective in maintaining permafrost table positions and the strength of frozen soils at desired levels and thaw settlements at acceptable limits.
UR: http://www.casnet.ac.cn
DE: 0700 CRYOSPHERE (4540)
DE: 0702 Permafrost (0475)
DE: 0704 Seasonally frozen ground
DE: 0706 Active layer
DE: 0760 Engineering
SC: Cryosphere [C]
MN: Fall Meeting 2005