How China turned a mega-project failure into a defining moment in modern engineering

China has pulled off a daring underground feat, using a multimillion-dollar tunnel boring machine (TBM) to recover its stranded twin beneath the country’s largest river. The rendezvous between the TBMs was achieved with just 2mm (0.078 inch) of vertical error and no horizontal deviation under the Yangtze’s riverbed, setting a benchmark for precision in deep underground engineering, according to state media on Wednesday. The feat saved a megaproject that might otherwise have been scrapped. In...