(photo: courtesy of China Railway Kunming Group Co)

The digging of China's deepest rail tunnel shaft - a 764.74-meter-deep shaft in a railway project in the border region of South China's Yunnan Province - was completed on Friday, Chinese media reported.

The record-breaking shaft is a ventilation shaft of the Gaoligong Mountain Rail Tunnel in the under-construction 330-meter-long Dali-Ruili railway, a key railway project of the Belt and Road Initiative (BRI) that is expected to link Yunnan's renowned tourist city Dali and China-Myanmar border city Ruili, reported Xinhua News Agency on Friday.

The 34.538-kilometer-long Gaoligong Mountain Rail Tunnel, having been drilled for 11 kilometers, will be China's longest rail tunnel, said China Railway Kunming Group Co. This project is highly difficult due to complicated geological conditions, the group said, according to Xinhua.

Problems and emergencies including water inrush and collapse have frequently occurred since the construction of the 764.74-memter-deep shaft started, with the largest amount of water inflow reaching 300 cubic meters per hour, the group introduced.

To get over the problems, constructers invited related experts to the site more than 20 times to continuously improve the water-control technologies and water-plugging materials, and eventually successfully completed the construction, said the group.

Global Times