On August 20, the "Haitian" super-large-diameter slurry balance shield machine for the Qingdao Jiaozhou Bay Second Tunnel, constructed by China Railway 14th Bureau Group, rolled off the production line. It will soon be deployed in the construction of the south main-line tunnel, embarking on its journey beneath the sea.

The Qingdao Jiaozhou Bay Second Tunnel project has a total length of 17.48 kilometers, with the main-line tunnel totaling 14.37 kilometers. The project adopts a combined construction scheme of open-cut, shield tunneling and drill-and-blast methods, crossing Jiaozhou Bay beneath the seabed.
The shield-tunneled section of the south main-line tunnel built by China Railway 14th Bureau Group is 3,253 meters long, with segment outer diameter of 15 meters. The shield machine will traverse long distances through soft-over-hard strata and full-face hard rock, and cross multiple fault fracture zones. The maximum crown overburden depth reaches 68.6 meters, and the maximum water pressure reaches 9.4 bar, equivalent to a pressure of 9.4 kilograms on an area the size of a fingernail.

The construction team of China Railway 14th Bureau Group, together with experts, conducted thorough research and verification. Drawing on years of large-diameter shield tunneling experience and technical accumulation in crossing "rivers, lakes, seas and cities," they tailored a sea-crossing tool specifically for long-distance hard rock strata.
The "Haitian" shield machine has 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. A number of advanced technologies provide safety assurance, ensuring that the shield equipment completes the construction task safely, quickly and efficiently.

The Jiaozhou Bay Second Tunnel project is the world's largest and longest subsea highway tunnel. Once open to traffic, Qingdao will enter the "dual-tunnel era," building a "Qingdao-Huangdao integrated city," which is of far-reaching significance for enhancing the overall competitiveness of the Jiaodong Peninsula urban agglomeration.