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.The project will allow trains to hurtle through the tunnel at 350km/h (217mph), enabling faster connections between cities on China’s populous eastern coastline and Hefei, the capital of nearby Anhui province, according to state media reports.It is part of a new high-speed railway that will eventually stretch 2,000km westwards to Chengdu – a flagship project in China’s latest five-year plan that will reportedly involve a total investment of more than 500 billion yuan (US$72 billion).A tunnel boring machine emerged from the Yangtze shoreline on Sunday, after spending nearly two years punching a passageway with a 15-metre (49-foot) diameter under the river, according to People’s Daily. The tunnel is the longest of its kind ever constructed in China, it added.