How China is building faster high-speed railways using vast underwater tunnels

China has finished digging the underwater section of a high-speed rail tunnel stretching more than 14km (9 miles) under a busy segment of the Yangtze River, as the country increasingly turns to vast subterranean passages to expand its railway network. The tunnel beneath China’s longest waterway, which will link Shanghai’s Chongming Island with Taicang city in neighbouring Jiangsu province, is on track to be completed by the end of the year, state broadcaster CCTV reported.