On August 6, at the construction site of the shield-driven section of the main line north tube of the Qingdao Jiaozhou Bay Second Tunnel (referred to as Jiaozhou Bay Second Tunnel), machines roared. The cutterhead of the "Deep Blue" shield machine was rotating, advancing at a speed of 8.4 meters per day.

According to reports, the "Deep Blue" shield machine has now excavated 572 meters, successfully completing 542 meters of excavation through upper-soft lower-hard strata, and has completed "standby" adjustments, replacing the cutters with harder and sharper ones, and has entered excavation in full-face hard rock strata.

The Jiaozhou Bay Second Tunnel is invested in and constructed by Qingdao Conson Group. It is a major construction project in Shandong Province, connecting the Qingdao West Coast New Area with the main urban area on the east coast. It has a total length of 17.48 kilometers, with the main tunnel being 14.37 kilometers long, of which the sea section is 9.95 kilometers. It is currently the world's largest and longest subsea highway tunnel under construction, and is also the only project currently under construction in China selected among the "50 Landmark Projects in the Global Tunnel and Underground Engineering Field." Among them, the shield-driven section of the main line north tube of the Jiaozhou Bay Second Tunnel is 3,258 meters long, with a maximum burial depth of 96 meters from sea level. During excavation, it is necessary to overcome a series of construction challenges under extreme conditions, including the complex sea environment, ultra-high water pressure, and the ultra-large-diameter shield passing through large-scale fault fracture zones.

In response to construction difficulties such as complex geological conditions, high water pressure, and long-distance hard rock excavation, the project team, together with authoritative experts in the industry, customized an ultra-large-diameter slurry shield machine adapted for long-distance hard rock strata excavation—the "Deep Blue"; they boldly proposed the application of a "short screw conveyor + rock crusher + rock crushing box" design to cope with the complex subsea geology and effectively reduce the risk of blockage caused by the accumulation of debris in the front chamber, the first such application in China; they created a "smart brain" for the "Deep Blue" shield machine, using a BIM information management platform and equipping it with a series of intelligent systems such as a telescopic main drive and a telescopic excavation chamber monitoring system, giving the shield machine "wings" and greatly improving construction efficiency and safety.

On January 26, 2024, the "Deep Blue" shield machine was officially launched, beginning its "journey across the sea." To ensure the smooth "launch to sea" of "Deep Blue," the project strictly controlled the shield machine assembly and excavation accuracy, set up a video dispatch monitoring room, and through remote video monitoring precisely controlled excavation parameters such as excavation speed, fully and promptly grasping on-site construction safety, quality, progress, and risk conditions. It successfully achieved zero leakage in the portal seal and effectively solved the launch challenge of an ultra-large-diameter shield machine under shallow cover near the sea.

Up to now, the "Deep Blue" shield machine has safely and efficiently excavated more than 570 meters under the sea, with the uplift of the completed tunnel stably controlled within 15 millimeters, meeting design and specification requirements and reaching the industry-leading level.