“China is constructing a 2,000-kilometre high-speed railway from Shanghai to Chengdu under the Yangtze River as part of its 15th Five-Year Plan.”
“The project, costing over 500 billion yuan ($72 billion), aims to promote regional coordinated development and boost industrial value added by nearly 1.5 trillion yuan. The rail line passes under the busy Yangtze River, where cargo ships operate constantly, with the Chongming-Taicang tunnel currently under construction.”
See also: How China is building faster high-speed railways using vast underwater tunnels
“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.”
https://www.scmp.com/economy/china-economy/article/3348533/how-china-building-faster-high-speed-railways-using-vast-underwater-tunnels