(TibetanReview.net, Aug01’22) – The Yunnan-Tibet Railway when completed and beginning operation by the end of this year will connect Tibet to Southeast Asia, stimulating economic development on the world’s highest plateau with faster and cheaper cargo transport to ports in the South China Sea, reported the scmp.com Jul 29, citing the Chinese government. A big possible snag to achieving this target is the 9km (5.6-mile) Haba Snow Mountain Tunnel in the Deqen (Tibetan: Dechen) Tibetan autonomous prefecture in what is now part of China’s Yunnan Province.
The report cited the team of engineers building the railway as saying some completed sections of this tunnel were hit by a crushing force caused by the collision of the Indian and Eurasian plates.
In less than a month, the tunnel had got squeezed from a diameter of 12 metres to less than 3 metres – barely enough for a car to pass, the project engineers were reported to have told the Science and Technology Daily in a report published on Jul 27.
Instrument readings were reported to have suggested that the rocks around the tunnel had come under pressure as great as 30 megapascals, equal to the combined weight of 75 elephants standing on a single foot.
The tunnel’s rocks were stated to be mostly formed by lava, making them too soft to bear the burden.
Noting that the Haba tunnel had completely surpassed his understanding of tunnel construction, Tian Weiquan, project manager with the China Railway Sixth Group Corporation, has told the state-owned newspaper, “It is the most challenging tunnel in China at present … with the deformation rate, duration and damage all breaking previous records.”
The project team was reported to have tried to support the tunnel with ultra-strong reinforced concrete structures built to meet high safety standards. But the enormous force turned the cement to dust and ripped apart the strongest steel rods.
But now Tian and his colleagues have said they have a solution to help them meet the deadline by drilling a hole smaller than designed through the mountain, which would help release most of the pressure that had built up in the rocks. When the condition stabilises, they will expand the size of the tunnel to meet the design requirement.
The report said more than 1,200 people were working at the tunnel site day and night, four times as many as previously planned.
Noting that they were making history, Wei Peng, a lead engineer of the project, has said, “We are strengthening the work organisation on the expansion and excavation of the main hole to strive for the early completion of the tunnel.”
The Yunnan-Tibet Railway, when completed, will go through 20 tunnels, and the Haba tunnel is the last and the only one not completed, the report said.
Upon completion, the Haba tunnel will form part of a 139km-long tourist line in Yunnan linking Lijian with Shangri La (Tibetan: Gyalthang) in Tibet, the report added.