Permafrost monitoring has been carried out continuously on the Tibetan Plateau since 1988; the year of the establishof the Cryosphere Research Station on the Qinghai- Xizang Plateau. Eleven active-layer monitoring sites, and 18 permafrost-temperature monitoring boreholes along the Qinghai-Xizang Highway (QXHW) cover almost all types of vegetation cover and permafrost found on the plateau.

 

The active layer monitoring sites observe air temperature and humidity at the height of 1.5 m, of soil temperature and moisture at 10 to 15 different depths from the ground surface to the base of active layer, and of soil heat fluxes at 3 depths (2, 5 and 10 cm). The depths of the 18 boreholes range from 20 to 130 m. Starting in 2000, four meteorological stations were established along the QXHW in order to measure air temperature, humidity, wind speed at 2, 5 and 10 m above the ground, solar radiation, net radiation, snow depth, and precipitation. Two fluxes monitoring sites were installed in 2004 in order to monitor the heat, moisture and carbon dioxide fluxes at 3 m above the ground surface.

Five international symposia have been held during the last ten years in order to share and exchange our experience and knowledge in permafrost engineering: in Chita (Russia), 1993; in Harbin (China), 1996; in Chita, 1998; in Lanzhou, 2000, and in Yakutsk (Russia), 2002. Since the first symposium, the participation at these bilateral symposia have increased significantly, evolving into international meetings attended by scholars and engineers from many countries. These symposia have substantially enhanced the development of permafrost science, engineering and technology and the multidisciplinary collaboration within this field. The 6th International Symposium on Permafrost Engineering was held September 5–7, 2004, in Lanzhou, China. The following summary of the symposium was prepared by Huijun Jin and Guodong Cheng.

The 6th International Symposium on Permafrost Engineering was successfully held under the auspices of the Glaciology and Geocryology Branch of the Chinese Geographical Society, the IPA Chinese Adhering Body. It was co-organized by the State Key Laboratory of Frozen Soils Engineering (SKLFSE), the Cold and Arid Regions Environmental and Engineering Research Institute (CAREERI), the Chinese Academy of Sciences (CAS), the Qinghai-Tibet Railway Company (QTRC), the PRC Ministry of Railway, the First Railway Survey and Design Institute (FRSDI), and the United Institute of Permafrost Research and Natural Resources Development, Siberian Branch (Russian Academy of Sciences). Fifty-eight technical papers were published in the Symposium Proceedings, as a supplement of the Journal of Glaciology and Geocryology (Vol. 26).

About 150 scientists and engineers from seven countries attended the symposium. Seventeen Chinese engineers and scientists and 17 scholars from six other countries participated in a field trip along the Qinghai-Tibet Highway/Railway during September 8–13, and in a seminar in Lhasa on September 14. During this seminar, the latest progress on permafrost engineering and the survey, design and construction of the Qinghai-Tibet Railway (QTR) were presented and discussed with some of the major railway designers, regulators and administrators.

Permafrost conditions occupy 22% of China land territory. About 70% of the Qinghai-Tibet Plateau is underlain by high-elevation permafrost. The QTR from Golmud to Lhasa is due for completion in 2007. It will traverse 632 km of the plateau permafrost. The Qinghai- Tibet Highway is generally parallel and about 1 to 2 km away from the railway. Chinese engineers are facing unprecedented engineering and environmental challenges; therefore, permafrost engineering has recently become the main research focus for cold regions scientists and engineers. Moreover, many foreign scientists and engineers have been invited or volunteered to become involved in the resolution of permafrost problems that are developing along the QTR.

Many promising achievements have been obtained during the past three years in the QTR construction practice. These include the adoption of techniques such as rock-stone ventilation roadbeds and side slopes, air-duct ventilated roadbeds, and thermosyphons for cooling the underlying permafrost, and the utilization of insulation boards. The techniques adopted are being tested under real conditions. However, there are still numerous engineering and environmental problems waiting for solutions. In this respect, the Lhasa symposium helped considerably in the development of applications. It aimed at soliciting comments and recommendations for the improvement of the design and construction. During the numerous discussions on design, maintenance and environmental engineering issues, international experts were encouraged to share their experience in order to assure that the QTR utilized the best standards in terms of quality and safety, within limited construction costs. Some experts pointed out that actively cooling the roadbed could be achieved by removing snow from the embankments and toe areas, or using light-coloured embankments and side slope surfaces, awnings for shading the solar radiation, and hairpin or tilted thermosyphons. Some new ideas on using “natural cold reserves” were proposed to protect the QTR permafrost roadbed from thawing.

Some of the major questions from the post-conference field trip that participants were concerned with: field explorations for the design, construction and operations; general understanding of design criteria; construction in building of the QTR; active, passive, reactive and proactive protection of the permafrost foundation underlying the railbed; interactions between the natural and engineering environments; and drainage of excess water. The major concerns from the QTR builders, authorities and administrators dealt with: long-term effects of rock-stone ventilation, convection roadbed and coarse stone protection; applicability of insulation materials; thermosyphons; impacts of climatic warming on the QTR; slope stability and hazards mitigation along railways in permafrost areas; and advice for a long-term QTR monitoring system. The participants were impressed by the innovative designs and quality of workmanship on the QTR.

Professor Valentin Kondratev invited colleagues to join the permafrost engineering conference to be held in Chita in 2005 where emphasis will be on linear infrastructures in permafrost areas. President Guodong Cheng invited participants to join the International Regional Permafrost Conference in 2006 in Lanzhou, China. It is co-sponsored by the IPA and organized jointly by the Chinese Society of Glaciology and Geocryology, the Chinese Academy Sciences, SKLFSE, CAREERI and CAS. A post-conference field excursion to the construction sites in the permafrost areas along the Qinghai-Tibet Railway/Highway will be organized (contact Prof. Lai Yuanming: ymlai@ ns.lzb.ac. cn).

Ma Wei (mawei@ns.lzb.ac.cn)