Constructing the Qinghai-Tibet Railroad: New Challenges to Chinese Permafrost Scientists

Constructing the Qinghai-Tibet Railroad: new challenges to Chinese permafrost scientists

G-D. Cheng & X. Li State Key Laboratory of Frozen Soil Engineering, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou, China

ABSTRACT: The new Qinghai-Tibet railroad will run across the world’s highest permafrost region for 632 km, of which about half is high-temperature and ice-rich permafrost. Therefore, an important and challenging engineering problem is the possible instability and sensitivity of permafrost. Chinese permafrost scientists are now making efforts to solve the problem by carrying out numerous field and laboratory experiments. A GIS-based modeling platform is also being developed. In the paper, we first present the permafrost related problems in the Qinghai-Tibet railroad project, and then introduce some countermeasures for protecting the permafrost.

1 INTRODUCTION 4 What will happen in permafrost when climatic warming is superimposed on the effects of the rail- 1.1 Background road project? 5 How about the engineering stability with changed Running from Golmud in the Qinghai Province to permafrost? Lhasa in the Xizang Autonomous Region, 1118 kilo- To answer these questions, the Chinese Academy of meters of steel track is being built on the planet’s high- Science granted a key project named “the interaction est plateau. Aside from the extreme altitude, engineers between the Qinghai-Tibet railroad and permafrost are facing the challenges of permafrost. The new rail- and its environmental effects”, in which numerous road runs across the permafrost region for 632 km, of field and laboratory experiments should be carried which more than half is high-temperature and ice-rich out. Another objective is to develop a modeling plat- permafrost. Therefore, a formidable engineering prob- form based on the (Geographic Information System) lem, that constructors must acknowledge, is the insta- GIS technique. bility of permafrost. Scientists and engineers must In this paper, we first present the permafrost related develop techniques that will eliminate the danger of problems in the project of Qinghai-Tibet railroad, and land heating up, which results from both the climatic then introduce some countermeasures for protecting warming and railroad construction. Otherwise, there permafrost. could be frost heave or thaw settlement. The track could be destroyed or sink into distressed permafrost.

2 SCIENTIFIC PROBLEMS 1.2 Scientific issues 2.1 Climatic change in the region No doubt, studies on the interaction between the climate system, permafrost, and the railroad project itself Climatic warming is a big challenge for constructing are very important for the megaproject. Chinese perma- the railroad, but how the climate changes in the region frost scientists, collaborating with engineers are keen of Tibetan Plateau is still uncertain. According to the on contributing their knowledge and experience to the IPCC reports (IPCC 1992, 2001), the air temperature crucial nation-building infrastructure. Scientists believe rise is about 1.4–5.8°C from 1990 to 2100 – this is a that the research results from many years of studies and global mean value. As the Tibetan Plateau is consid- engineering practices (Cheng 1998, Cheng & He 2001, ered to be an amplifier and trigger of climatic warming, Ma et al. 1999, Ma 2001), especially those with the it is believed that the climatic warming in the region is Qinghai-Tibet Highway (Tong & Wu 1996, Wu & even higher (Cheng 1996). Some investigations also Cheng 1988) can be very useful for the project. But, showed that, in the last two decades, the temperature still many questions need to be answered and clarified: increased notably along the Qinghai-Tibet Highway 1 How does the climate change on the Tibetan plateau? (Cheng et al. 1993, Wang & Zhao 1999) and the low 2 How will climatic warming impact the permafrost? altitude-limit of alpine permafrost rises (Xie 1996). 3 What changes will occur in the permafrost when Obviously, forecasting climatic change and its the railroad is built? variability is very important. This needs very fine

131 resolution, maybe just 1 or 2 km(s) to fit the engineering human activities. Permafrost monitoring is a prerequi- problems. However, no credible regional-scale predic- site for this kind of work. tion of climate change in the Tibetan Plateau has been achieved so far. A new generation Regional Climate 2.4 Engineering stability of permafrost when Model (RCM) is therefore proposed to be developed, the railroad is built with the coupling of a land surface model. Downscaling methods of climatic scenarios are also in top priorities. Permafrost is very sensitive to climatic warming. When phase transition (frozen to unfrozen) occurs, it 2.2 Impact of the climatic warming becomes very unstable and many unfavorable conse- on the permafrost quences will emerge. In general, frost heave and thaw settlement are main engineering hazards when the There are a total of 416 km of high-temperature perma- railroad is built. Particularly, according to the scenario frost areas distributed along the Qinghai-Tibet rail- of a warming climate, thaw settlement is a more dan- road. Among them, 150 km is with the MAGT (Mean gerous threat to the Qinghai-Tibet railroad. Previous Annual Ground Temperature) of 0.5 to 0°C; 125 km investigations showed that for the Qinghai-Tibet high- is with the MAGT of 1.0 to 0.5°C; 141 km is with way, the settlement of the roadbed is about 15cm with the MAGT of 1.5 to 1.0°C. When air temperature the maximum value of 50 cm (Liu et al. 2002, Wu & increases, much of the permafrost, especially those Cheng 1988, Wu et al. 2002b). This is obviously unac- with very high ground temperature (0.5 to 0°C) ceptable for a railroad because even a few centi- could melt. Some research results show that climatic meters’ subsidence could destroy the track. warming will significantly impact the permafrost on Different engineering measures can be used to pre- the Tibetan Plateau (Li et al. 1996, Li & Cheng 1999, vent thaw settlement. The best way of testing these Wu et al. 2000a). Based on the report from Wu et al. measures is by doing field experiments. Numerical (2001), if the air temperature increases by about 3°C, modeling is also necessary although it is difficult to the permafrost along the Qinghai-Tibet highway will develop models for predicting thaw settlement, which change drastically, e.g. 50% of transitional permafrost needs the coupling of heat, water, and force fields. will evolve to high-temperature permafrost and 70–80% of stable permafrost will evolve to the transi- 2.5 Environmental change tional type. Since the Qinghai-Tibet railroad is parallel to the highway, it is expected that there could be a very How will the railroad construction affect the fragile significant permafrost change there as well. environment of Tibetan Plateau? This is not only a sci- Since the permafrost along Qinghai-Tibet railroad entific question that environmentalists must answer, has the properties of high temperature and is ice rich, but also a big concern for decision makers, environ- more accurate physical-based models need to be devel- mental protectors, and the public. In some regions oped by taking the phase transition into account for along the Qinghai-Tibet highway, desertification and simulating dynamic change of permafrost conditions. land degradation has been getting more and more seri- ous (Huang et al. 1993, Wang 1996, Wang & Cheng 2001, Wu et al. 2000b). Human activity is absolutely 2.3 Impact of railroad project on the permafrost one of the main factors. Fortunately, constructors have realized this. They promised to construct the Qinghai- Human activities have a great influence on perma- Tibet railroad as an environment-protected railroad and frost. Permafrost degradation is more dominant under build it as a green corridor; they will even build pas- engineering conditions than in its natural condition. sageways for wildlife to cross the tracks. It is believed For example, the continuous permafrost along the that the railroad project impact on the environment Qinghai-Tibet highway degraded over about 28 km will be minimized. from 1979 to 1991, but in its natural condition the per- These promises on environmental protection need mafrost boundary only retreated 1–2 km at the same scientific support. Prediction of environmental change time (Wu et al. 2000a). is a precondition. Moreover, detailed investigation into However, no modeling work has ever been per- the ecotypes and their distribution along the railroad formed on permafrost’s response to human projects and study of ecological restoration are very important. until now. Since this is very important for understand- ing the interaction between permafrost and the railroad project, some models should be developed. 3 COUNTERMEASURES The models include the evaluation model of the permafrost environment under railroad engineering, and In the research project on “the interaction between the prediction model of permafrost’s response to the Qinghai-Tibet railroad and permafrost and its

132 environmental effect”, some countermeasures for 3.1.3 Control of conduction “protecting” permafrost were proposed. There are usu- 1 Insulation: Turf, moss, polystyrene, and other insu- ally three principles in permafrost engineering, i.e. pro- lation materials can be used to backfill roadbed (Li tecting permafrost, allowing permafrost to melt, and 2000, Liu et al. 2000). This is an economical way thawing permafrost in advance. Since climatic warm- for protecting permafrost. ing will be significant, the best way to keep permafrost 2 Change of the roadbed height: It is a traditional way stable is to protect permafrost actively, namely, to cool to keep permafrost frozen. The objective of the off the roadbed. In this section, some countermeasures experiment is to find the optimized height. for cooling permafrost are introduced. 3 Thermal semiconductor: It is this kind of an ideal material that in summer is an insulator of heat but 3.1 Experiments in winter can release heat to air freely. Researchers can find the material by utilizing the principles of The effectiveness of these countermeasures must be phase transition or convection in porous material validated by engineering practice. To do this, numer- (Sheng, pers. comm.). ous engineering experiments are being implemented in the Beiluhe area where high-temperate and ice-rich 3.2 Long-term monitoring permafrost is widely distributed. Along the four kilo- meters of roadbed in the area, we plan to set up 37 sec- Lots of equipment has been installed along the tions in order to test different kinds of engineering Qinghai-Tibet roadbed. These monitoring sites are countermeasures for cooling off permafrost, which distributed on both the roadbed and the natural surface include those described in the following sections. for comparison. Monitoring of freeze/thaw processes, the active layer, permafrost thickness, ground ice, soil 3.1.1 Control of radiation moisture and soil temperature profile, heat fluxes and Solar radiation is the source of heat to the soil. By water fluxes is being carried out. In addition, a high- changing the surface color (black to white), the accuracy GPS (Global Positioning System) network is absorbed radiation can be reduced. By obstructing the going to be established in the Beiluhe area for moni- sunshine, the incident solar radiation can be hindered. toring the deformation of roadbed, frost heave and Sunshade awning has been tested as an effective frost settlement. method to protect permafrost for the Russian Siberian The data obtained from the monitoring systems will railroads. be put into a common database, which is shared among collaborating research projects. Other institutions that 3.1.2 Control of convection are involved in the construction of the Qinghai-Tibet 1 Dry bridge: Though an expensive way, using a con- railroad might also have the right to access the data- tinuous dry bridge can ensure the safety of tracks base. Data exchange among international research in the permafrost region. It will be extensively used projects (such as GAME-Tibet) is suggested and would in the high-risk (with very high temperature and be strongly supported. rich ice) sections of the Qinghai-Tibet railroad. Through experiments we can obtain the rational buried depth of bridge piles and find out ways to 3.3 Modeling platform keep the ground stable. 2 Ventiduct roadbed: A lot of heat can be released by Numerical modeling is another important way of using ventiducts in the roadbed and thus forcing investigating interactions between the climatic sys- the soil to freeze. tem, permafrost, and the railroad project. Besides 3 Air convection embankments: Rock fill embank- the individual models introduced in section 2 of this ment and rock fill cover on slopes are tested on the paper, a common modeling platform is proposed to be plateau. In addition to normal conductive heat developed. The platform will be GIS based, focused on removal from the embankment and foundation, this digital emulation and three-dimensional visualization kind of embankment can enhance ground cooling technologies. in winter by convective air circulation and shading The objective of the platform, which is also called in the summer within the open voids of the rock fill. the “digital roadbed”, is to simulate the heat, water, 4 Thermal-pile: It is a self-adaptive convection system stress, and deformation fields according to different (Cheng & He 2001). In winter the heat is trans- permafrost conditions, roadbed structures, and climatic ferred to upper layers of soil, driven by temperature scenarios. Obviously, this needs the coupling of heat difference. Therefore, the temperature of roadbed and water budget models, a permafrost model, and is reduced. It is reported that the thermal pile can climatic model as well as the integration of a multi- reduce soil temperature by four degrees in winter. resource database.

133 4 SUMMARY Li, X. & Cheng, G-D. 1999. A GIS aided response model of high altitude permafrost to global change. Science in Permafrost is a major challenge for the construction of China, Series D. 42(1): 72–79. the Qinghai-Tibet railroad. The safety of the Qinghai- Li, Y-Q. 2000. Stability of cut slope covered with heat- Tibet railroad is based upon its roadbed; the success insulating material in thick ice section of permafrost region on the Qinghai-Tibet Plateau. Journal of of this roadbed construction is determined by the sta- Glaciology and Geocryology 22 (Suppl.): 6–11. bility of the permafrost; the key problem of the stability Liu, Y-F., Ding, J-K., He, G-S. et al. 2000. Application of of permafrost is thaw settlement. Therefore, it is very expandable polystyrene insulation layer to roadbed important to study the interaction between permafrost engineering over permafrost region. Journal of Glaci- and the railroad project. Additionally, a warming cli- ology and Geocryology 22 (Suppl.): 26–32. matic scenario must be considered. Chinese permafrost Liu, Y-Z., Wu, Q-B., Zhang, J-M. & Sheng, Y. 2002. scientists, facing these challenges, are now making Deformation of highway roadbed in permafrost efforts to resolve them by implementing systematic regions of the Tibetan Plateau. Journal of Glaciology experiments, setting up long-term monitoring equip- and Geocryology 24(1): 10–15. Ma, W. 2001. Review and prospect of the studies of ground ments, and doing numerical calculations. We believe freezing technology in China. Journal of Glaciology that the research results achieved from the studies can and Geocryology 23(3): 218–224. benefit the building of the Qinghai-Tibet railroad and Ma, W., Cheng, G-D., Zhu, Y-L. & Xu, X-Z. 1999. The enrich the knowledge base of permafrost science and State Key Laboratory of Frozen Soil Engineering, engineering. review and prospect. Journal of Glaciology and Geo- cryology 21(4): 317–325. Tong, C-J. & Wu, Q-B. 1996. The effect of climate warm- ACKNOWLEDGMENT ing on the Qinghai-Tibet Highway, China. Cold Regions Science and Technology 24: 101–106. This work is supported by the Innovation project of Wang, G-X. & Cheng, G-D. 2001. Characteristics of grass- land and ecological changes of vegetation in the CAS (KZCX1-SW-04). source regions of Yangtze and Yellow rivers. Journal of Desert Research 21(2): 101–107. Wang, S-L. 1996. An approach on permafrost degradation REFERENCES and environmental problems in the Tibetan Plateau. In Proceedings of the Fifth Chinese Conference on Cheng, G-D. 1996. The role of cryosphere in climate Glaciology and Geocryology 1: 11–17. Lanzhou: change. In: Proceedings of the Fifth National Con- Gansu Culture Press. ference on Glaciology and Geocryology: 807–817. Wang, S-L. & Zhao, X-M. 1999. Analysis of the ground Lanzhou: Gansu Culture Press. temperature monitored in permafrost regions on the Cheng, G-D. 1998. Glaciology and Geocryology of China Tibetan Plateau. Journal of Glaciology and in the past 40 years, Progress and prospects. Journal of Geocryology 21(2): 159–163. Glaciology and Geocryology 20(3): 213–226. Wu, Q-B., Li, X. & Li, W-J. 2000a. The prediction of per- Cheng, G-D. & He, P. 2001. Linearity engineering in permafrost change along the Qinghai-Tibet highway, mafrost areas. Journal of Glaciology and Geocryology China. Permafrost and Periglacial Processes 11(4): 23(3): 213–217. 371–376. Cheng, G-D., Huang, X-M. & Kang, X-C. 1993. Recent Wu, Q-B., Li, X. & Li, W-J. 2001. The response model of permafrost degradation along the Qinghai-Tibet high- permafrost along the Qinghai-Tibet highway under way. In Proceedings of the Sixth International Con- climatic change. Journal of Glaciology and Geo- ference on Permafrost: 1010–1013. cryology 23(1): 1–6. Huang, Y-Z., Guo, D-X. & Zhao, X-F. 1993. The desertifi- Wu, Q-B., Liu, Y-Z., Tong, C-J. et al. 2000b. Interaction cation in the permafrost region of Tibetan Plateau and between frozen soil and engineering in cold regions. its environmental influence. Journal of Glaciology Journal of Engineering Geology 8(3): 281–287. and Geocryology 15(1): 52–57. Wu, Q-B., Shi, B. & Liu, Y-Z. 2002. Interaction study of IPCC, 1992. Climate change 1992. The supplementary permafrost and highway along Qinghai-Xiang high- report to the IPCC Scientific Assessment. Cambridge, way. Science in China, Series D., in press. UK: Cambridge Univ. Press. Wu, Z-W. & Cheng, G-D. 1988. Roadbed Engineering in IPCC, 2001. Technical summary, a report accepted by Permafrost Regions. Lanzhou: Lanzhou University Working Group I (Climate Change 2001: the Scientific Press. Basis) of the IPCC. http://www.ipcc.ch/. Xie, Y-Y. 1996. Effects of Climate Change on Permafrost in Li, S-X., Cheng, G-D. & Guo, D-X. 1996. The future ther- China. Global Change Study No. 2, Series publication. mal regime of numerical simulating permafrost on Institute of Geography, Chinese Academy of Sciences. Qinghai-Xizang (Tribet) plateau, China under climate warming. Sciences in China, Series D-Earth Sciences 39(4): 434–441.

134