On November 13, as the crawler crane slowly lowered the load, the 600-tonne cutterhead and main drive mated securely, and the cutterhead of the "Haitian" shield machine for the Qingdao Jiaozhou Bay Second Tunnel—the world's largest and longest subsea highway tunnel, constructed by China Railway 14th Bureau Group—was successfully lifted and lowered into the shaft.

The "Haitian" shield machine serves the shield-driven section of the south main line of the Jiaozhou Bay Second Tunnel, with a total excavation length of 3,255 meters. The machine has an excavation diameter of 15.63 meters, an overall length of 142 meters and a total weight of more than 5,000 tonnes, and is equipped with a series of intelligent systems including a telescopic main drive and a telescopic excavation chamber monitoring system.

The cutterhead is the largest single component of the "Haitian" shield machine. In response to the safety and stability requirements for hoisting such an oversized component, the project team carried out multiple rounds of planning and studied the hoisting scheme. The successful lowering of the cutterhead into the shaft lays the foundation for the triumphant launch of the large shield machine for the world's longest subsea highway tunnel.
The "Haitian" shield machine will launch from the shield shaft located within Qingdao Port, bore westward toward the West Coast, and connect undersea with the drill-and-blast tunnel section, passing through various complex geological conditions. The geological conditions along the shield tunneling interval are complex, with long-distance crossing of soft-over-hard strata and full-face hard rock, and passage through multiple fault fracture zones, with a maximum burial depth of 68.5 meters and a maximum water pressure of 9.4 bar, equivalent to a pressure of 9.4 kilograms on an area the size of a fingernail.

The Jiaozhou Bay Second Tunnel project is a provincial-level major construction project in Shandong Province. It adopts a layout of a main tunnel with two bores and two directions of six lanes, plus an intermediate service tunnel. After opening to traffic, Qingdao will break through the boundaries of urban spatial growth, enter the "dual-tunnel era," build "Qingdao-Huangdao urban integration," and promote the coordinated development of the east and west banks of Jiaozhou Bay, which is of far-reaching significance for enhancing the overall competitiveness of the Jiaodong Peninsula urban agglomeration.