The world's largest undersea highway tunnel under construction—the Second Jiaozhou Bay Tunnel in Qingdao—has officially begun shield tunneling beneath the sea, and the tunnel is expected to be completed and opened to traffic in December 2027.

According to reports, the shield tunneling distance is 3,255 meters, driving westward from within the Qingdao Port wharf toward the West Coast, where it will connect with the drill-and-blast tunnel section, and the shield machine will be received and dismantled in an undersea chamber. The geological conditions beneath Jiaozhou Bay are complex; the shield machine enters the sea immediately after launch and must traverse long distances through complex, variable, soft-hard uneven strata and fault zones. The "Haitian" shield machine used in the project has a total length of 142 meters, a total weight of 4,275 tons, and an excavation diameter of 15.63 meters, and is equipped with a series of intelligent systems including a telescopic main drive and a telescopic excavation chamber monitoring system. The integration of multiple advanced technologies and targeted design greatly enhance the construction safety assurance of the shield machine, ensuring that the shield equipment completes construction tasks safely, quickly and efficiently. After the Jiaozhou Bay project opens to traffic, Qingdao will break through the boundaries of urban spatial growth, which is of far-reaching significance for promoting the coordinated development of the east and west banks of Jiaozhou Bay and enhancing the overall competitiveness of the Jiaodong Peninsula city cluster.

It is understood that the Second Jiaozhou Bay Tunnel project starts in the West Coast New Area of Qingdao in the west, crosses Jiaozhou Bay eastward, and lands near Qingdao Port, connecting to the eastern urban area of Qingdao via an elevated bridge. The main line has a total length of 17.48 kilometers, of which the tunnel is 14.37 kilometers long, including a 9.95-kilometer undersea section. The main-line tunnel has a shield machine excavation diameter of 15.63 meters and its deepest point is 115 meters below sea level. The tunnel is constructed with a layout of two main tunnels plus an intermediate service tunnel, built to the standard of a dual six-lane urban expressway with a design speed of 80 kilometers per hour.