Construction of a railway in southwestern China from Sichuan province to Tibet is still on track despite having to navigate areas where extreme heat from the Earth’s crust has made working close to impossible.
A significant proportion of its route involves tunnelling through rock too hot for humans or machines to bear, with ground temperatures of up to 89 degrees Celsius (192 degrees Fahrenheit) – the highest on record for a transport infrastructure project, according to geologists.
When the Tibetan plateau was created by a collision between the Eurasian plate and the Indian subcontinent, with the tectonic force giving rise to the Himalayas, an enormous amount of heat was trapped inside the elevated crust.
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The 1,543km (959-mile) Sichuan-Tibet railway has to cross more than 40 major fault lines, more than attempted by any previous rail project.
“The underground heat sources spread upwards along the fault zone and generate random local heat spots, causing frequent geothermal disasters,” said geophysics professor Lan Hengxing and his colleagues with the Institute of Geographic Sciences and Natural Resources Research, in a paper published last week in the domestic peer-reviewed publication Journal of Engineering Geology.
Scientists and engineers have come up with some ways to reduce the heat while workers struggle to push the project forward to meet their 2024 completion deadline.
The railway is to link Chengdu, the economic powerhouse of the densely populated southwest, to the Tibetan capital, Lhasa. A third of the line is complete, with trains running.
Their speed of up to 200km/h (124mph) could cut the journey time to Tibet from a week to 12 hours, although that is slower than the 350km/h China’s high-speed rail is capable of because the trains will need to climb more than 3,000 metres (9,840 feet) through some of the world’s most remote and hostile terrain, shaped by earthquakes, landslides, flooding and glaciers – now melting.
The idea of building a railway from the fertile Sichuan basin to Tibet was proposed about a century ago, when the journey would take traders nearly a year on horseback.
In the 1950s, to strengthen control over Tibet, Beijing built a motorway there from Sichuan. The 2,000km road was completed in four years at a cost of more than 3,000 lives.
A railway is more difficult to build than a road. In 2014, the Chinese government launched the Sichuan-Tibet project with a 10-year deadline. Almost the entire route is being built on bridges or through tunnels. With eight mountains more than 4,000 metres high in the way, civil engineers have rated it the most challenging rail project in history.
More than 70 per cent of its workers have suffered physically – most frequently with chest pain, vomiting and loss of consciousness – because of the high temperatures in the tunnels, 2019 research led by professor He Chuan of Southwest Jiaotong University found.
Workers have been able to stand the conditions for only a couple of hours at a time, according to He and colleagues.
The temperatures overheated the engines of heavy-duty machinery including trucks and bulldozers, while tyres and brakes ceased to function.
But the most deadly threat was rock bursting under enormous heat and pressure, which threatened everyone on site.
There are more than 70 tunnels on the route, the longest stretching more than 40km. To reduce the temperature, engineers set up huge fans to blast cool air into the tunnel at over 300 cubic metres per second – the volume of air being equivalent to recycling the air of the Empire State Building every half an hour.
Cold water was also constantly splashed on the rocks to absorb heat. In the drilling sections, ice blocks – at times more than 200 tonnes per day – were stacked along tunnel walls, He said.
“These methods have been used and proven effective,” professor Lan and colleagues said in their latest study. “The high risk of geothermal threat to the Sichuan-Tibet railway is therefore generally under control.”
Remaining sections must still be built through dangerous areas with less geographical knowledge available, but the railway is progressing and could further expand China’s influence in South Asia.
There is already the Qinghai-Tibet railway connecting Lhasa to western and northern China, but the lengthy route takes in cities far from China’s more economically influential and highly populated areas.
Sichuan, a province of 80 million people with a GDP equivalent to Saudi Arabia’s, is home to the military theatre command that has confronted Indian troops in an ongoing border dispute. With a rail route into the Himalayas, they could mobilise troops in mere hours, some Chinese military experts have said.
The new railway could also boost investment, tourism and other commercial activities that could strengthen ties with South Asian countries, while President Xi Jinping even said at the launch of construction of a 1,000km section last year that the project was important for “maintaining national unity, promoting ethnic harmony [and] consolidating border stability”.
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