Precision Microblasting technology used to dig high speed rail under the Great Wall
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 432 meters 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.
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.
It took Chinese engineers months to "choreograph" the best point for the 174-km Beijing-Zhangjiakou High-Speed Railway Line to intersect the Great Wall.
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".
