A worker inspects the main drive system of a tunnel boring machine on July 23, 2026. On that day, China Railway 11th Bureau Group's world-first "ternary mixed gas" pressure-assisted system completed its first large-scale ultra-high-pressure cutterhead chamber opening and tool replacement operation at the Jintang subsea tunnel of the Ningbo-Zhoushan Railway, the world's longest undersea high-speed railway tunnel, in East China's Zhejiang Province. Photo: VCG