中尼铁路选线研究.doc

Crossing the Himalayas by railZheng Yan Long, TunnelTalk China CorrespondentSerious consideration is being given to the feasibility of a railway link through the Himalayas to connect China with India and via a route that also links Nepal. Zheng Yan Long, TunnelTalks China Correspondent, joined an expedition to Nepal in April this year (2012) that investigated possible routes and alignments of what would be one of the most ambitious mountain barrier crossings. As baseline rail links are being completed through the European Alps at the St. Gotthard, Brenner and Ltschberg Passes, and improved highway links are being considered for highway passes through the Andes in South America, perhaps the most audacious of all mountain links is being investigated for a rail passage through the Himalayas. In April this year (2012) an academic research team from China and Nepal conducted an expedition in Nepal to investigate possible rail alignments between Kathmandu and Zhangmu, a town on the Chinese border. The research team, led by Professor Yun Bai, of Tongji University in Shanghai and also a Vice President of the ITA (International Tunnelling and Underground Space Association), and with his colleague Associate Professor Zhenming Shi, also a member of the International Association for Engineering Geology and the Environment, was accompanied by Professor Dr. Megh Dhital of the Tribhuvan University of Nepal. The investigation was aimed at identifying the topography of the region, the geological conditions likely to be encountered and the main challenges and obstructions of various possible alignments. The expedition received financial support from The Robbins Company and will result in the production of technical papers as well as a working group report. Members of the expedition discuss possible alignmentsNecessity of the linkRecent growth in trade and the movement of people between China and India and Nepal provides sufficient evidence to support the development of a fixed rail link through the mountains. Over the past decade the volume of bilateral trade between China and India has increased fifteenfold, and by sevenfold between China and Nepal (Figs 1 and 2). According to a Joint Communiqu released in December 2010, a target for Sino-Indian trade in 2015 is US$100 billion. Currently most cargo is transported by ship, with land transport through the Nathu La Pass accounting for a small fraction of the volume. Transport has become a bottleneck for growing Sino-Indian bilateral trade. In addition, tourism and business travel between the three countries has grown in the past five years, with most people choosing to travel by air (Figs 3, 4, 5, 6). It is believed by initial supporters of the project that a railway link would, without doubt, attract more people for lower cost and more convenience. What is more, according to Bai Yun of Tonji University in Shanghai, for the purpose of helping the Nepalese, it is vital to include Kathmandu as a transfer station, thus improving its infrastructure, connecting it with the outside world, and stimulating local economic growth while at the same time protecting the vulnerable ecology and environment of the mountains. All these factors support a railway link proposal. Fig 1. Development of Sino-Indian bilateral tradeFig 2. Development of Sino-Nepal bilateral tradePossible alignmentsChina has already established a long term plan for building further railway lines within its borders and began an extension of the Qinghai-Tibetan Railway from Lhasa to Shigatse in September 2010. This is scheduled to be complete and in operation by 2014. According to Chinas medium and long term railway network plan, further extension of the railway will link Shigatse to the counties of Nyalam and Yandong, on its border with Nepal and India (Fig 7). From the Indian side a railway to the Himalayan Mountains across the Gangetic Plain is considered not technically demanding, with only a few short tunnels needed to cross massifs from Kathmandu to the Nepal-India border. Fig 3. Tourists from India to ChinaFig 4. Tourists from Nepal to ChinaFig 5. Tourists from China to NepalFig 6. Tourists from China to IndiaFrom the Chinese side and across Nepal, two possible routes with three main alignment options are suggested (Fig 8). The northern lines will involve several long tunnels at great depth, some reaching more than 20km long and with more than 2,000m cover. Current construction of hydro projects in Nepal has created several access roads along the valleys. At one location a rail tunnel of about 20km length would run parallel with the ongoing Melamchi Water Supply Project to the Kathmandu Valley. The rail project proposal would benefit greatly from the geological and geotechnical data gathered for the water tunnel project and from the valuable experience gained during that excavation. Fig 7. Chinas medium and long term railway planFig 8. Two possible rail route alignmentsThe southern line would follow the alignment of the existing Sino-Nepal Highway, which could involve fewer tunnels but would be more prone to large geological hazards such as landslides and rock falls. Further economic and technical studies of the various alignments is under way. Landslide along the Sino-Nepal HighwayMain challenges and obstacles In total, an international link between China, Nepal and India would require the construction of more than 500km of new rail line through some of the most magnificent mountain topography and most tectonically disturbed geology in the world. The most daunting of many challenges would include the following: Large height drop within a short distanceThe most difficult section would be on the Chinese side of the alignment where the elevation drops by about 2,000m over a distance of 20km between the towns of Nyalam and Zhangmu. A spiral solution could be adopted to stay within the vertical gradient allowance of less than 15% for electric railway operations. Long tunnels under deep overburdenDeep tunnels required on the routes would pass through tectonic faults and shear zones that are usually characterised by high rock stresses and high groundwater pressures, frequently at high temperatures. Special designs would be needed for ventilation, logistics and transportation into the excavation headings of long tunnels. Lack of detailed geological dataLittle geological data and engineering experience is available ahead of excavating long tunnels in the region. Very few tunnels and underground caverns have been excavated in the Himalayan area to data, and current projects are experiencing the conditions for the first time. A great deal of detailed study into the geological, hydro-geological and geo-mechanical conditions of the region would be needed to support the feasibility and proposal of the fixed railway link. West entry to the Kathmandu ValleyEast entry to the Kathmandu ValleyIf