August 16, 2017

Bridging the Sichuan-Tibet gap

Written by  Yu Fei
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China is embarking on a hugely ambitious project to build a new railway between Chengdu and Lhasa in Tibet. Xinhua’s Yu Fei outlines the project and the environmental challenges facing its contractors and engineers.

BREATHTAKING scenery and breathtaking dangers - both will face Chinese engineers as they embark on building the Sichuan-Tibet Railway, which will pass through the southeast of the Qinghai-Tibet Plateau, one of the world’s most geologically active areas.

China Railway Eryuan Engineering Group, which is designing the line, says it will run from Chengdu, capital of southwest China’s Sichuan Province, through Ya’an and Kangding, and enter Tibet via Qamdo. It will then run through Nyingchi and Shannan prefectures before arriving in Lhasa, capital of Tibet. The total construction length will be about 1700km and it will cost Yuan 250bn ($US 36.87bn)

The Sichuan-Tibet Railway is a key project in China’s 13th Five-Year Plan from 2016 to 2020. It the second railway into southwest China’s Tibet Autonomous Region after the Qinghai-Tibet Railway, described as the world’s highest, which opened in 2008. The new line will reach similar heights, climbing from the Sichuan Basin several hundred meters above sea level to the “Roof of the World,” at an altitude of more than 4400m.

Mr Xia Lie, a senior engineer at China Railway Eryuan Engineering Group, described the line as a huge “roller coaster” through risky terrain of mountains and canyons. It will pass through eight ascents and descents, and more than 80% of the line will run in tunnels or on bridges. “The cumulative ascent of the Sichuan-Tibet Railway will exceed 16,000m, which is equivalent to double the height of Everest, the world’s highest mountain,” Xia says.

Construction has begun at both ends of the railway - from Nyingchi to Lhasa, and between Chengdu and Ya’an, which are expected to open in June 2018. The feasibility study for the section between Ya’an and Kangding has been completed. However, the section from Kangding to Nyingchi - the longest and most difficult - is still at the design stage. Xia says construction is expected to begin in 2019 and could take about seven years to complete.

The line will be designed for maximum speeds of 160-200km/h. On completion, the journey time by train between Chengdu and Lhasa will be cut from 48 hours to about 13 hours.

Xia says experts conducted a scientific study of the key technologies needed for construction in May 2016. When the team arrived at a town in Tibet’s Markam County, all the people turned out to present them with hada, pieces of silk given as greetings, and butter tea, and expressed a desire to see the railway built as early as possible.

Mountain hazards

Mr You Yong, chief engineer of the Institute of Mountain Hazards and Environment of the Chinese Academy of Sciences (CAS), who is leading a scientific and technological support team to avoid disasters in the mountains, and who has spent almost 30 years studying mountain hazards, says the line will traverse the eastern Qinghai-Tibet Plateau, which has sharp changes in terrain.

It will pass over 21 mountains of more than 4000m and cross 14 major rivers. The active geological structure of the region causes intense earthquakes. For example, the magnitude-8 earthquake that devastated Sichuan’s Wenchuan County in 2008 caused great environmental changes and destroyed countless roads. The quake caused hazards such as landslides and debris flows.

The railway will pass through earthquake zones such as the Longmen Mountain and Yarlung Zangbo River seismic belts, with scientists indicating that prospective dangers along the alignment include landslides, debris flows, and snow and ice damage. Landslides occur primarily in the alpine gorges of the Hengduan Mountains and southeastern Tibet.

“Constructing a railway in such a complicated geological environment will face a lot of scientific and technological difficulties. And the prevention and control of mountain hazards will be key to its success,” You says.

On the other hand, a large construction project traversing the region might aggravate the risks of mountain disasters and endanger the project itself. “We must urgently master the distribution pattern of landslides, debris flows and other mountain hazards, and their influence on the railway project. We need to demarcate safe and dangerous areas, and study how to forecast and prevent disasters,” You adds.

CAS began to analyse the mountain hazard distribution patterns and risks, and experiment on disaster prevention along the route in 2014. To date, scientists have identified the basic distribution and activities of mountain hazards, and set up a data bank for the hazards along the route.

Based on analysis of the risks, researchers offered their advice on the route selection and technologies to prevent and control the landslides and debris flows. The Chinese government is also planning to build a highway connecting Sichuan and Tibet, with the scientific findings also set to be applied in that construction.

If successful, the railway will overcome some of the biggest risks a construction project will ever face. It will also provide a vital economic link to Tibet and the communities along the route.

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