Nerves are taut in China over the structural integrity of the Great Wall at Badaling as engineers blast a tunnel deep underneath for a record-breaking high-speed railway, and a cavernous station.
The 12-km-long tunnel will sink to a maximum depth of 432m under the most visited section of China’s Great Wall, completed in 1504, to carry a trains running at 350km/h between Beijing and the city of Zhangjiakou ahead of the 2022 Winter Olympics, which the two cities are co-hosting.
Engineers are using "precision micro-blasting" technology to dig the tunnel so as not to damage the world-famous monument above, reports state-owned newspaper, Global Times.
The project’s chief engineer Luo Duhao said precision micro-blasting has a velocity of 0.2cm per second and generates a weaker tremor than traditional blasting.
Since February there have been 4,500 blasts.
"I myself once stood on the Great Wall and I could not feel the blast at all," Dai Longzhen, deputy manager of the Beijing-Zhangjiakou High-Speed Railway Line, told the Global Times.
It took Chinese engineers months to "choreograph" the best point for the 174-km railway to intersect the Great Wall, Global Times reported.
When complete in 2019, the railway is expected to cut the journey time between the two cities from more than 3 hours to around 1 hour.
As well as the tunnel, engineers are building a large station 102m underneath the Great Wall. The station is reported to be 36,000 sq m in area.
Dai Longzhen said the construction area and the depth of the station is "record-breaking".
With the Great Wall at Badaling surrounded by parks and scenic areas, the station is being built underground to avoid damaging the environment, Dai said, and to showcase China’s rail construction capabilities.
Image: Great Wall of China at Badaling (CEphoto, Uwe Aranas / CC-BY-SA-3.0)