Constructors make a safety inspection at the construction site of Qingdao Jiaozhou Bay Second Tunnel in Qingdao, east China"s Shandong Province, Oct. 2, 2026. (Xinhua/Li Ziheng)

　　BEIJING, Oct. 2 (Xinhua) -- China"s longest undersea highway tunnel completed all shield-driven excavation work on Friday as a shield machine reached its designated position at a depth of 105 meters beneath the sea surface in Jiaozhou Bay, eastern China"s Shandong Province, according to China Railway Construction Corporation Limited.

　　The Qingdao Jiaozhou Bay Second Tunnel will connect Qingdao"s main urban area with the Qingdao West Coast New Area. The latter is a national-level new area. The 17.48-km project includes a 14.37-km main tunnel section, featuring two main tunnels and a middle service tunnel, with three lanes in each direction and a design speed of 80 km per hour.

　　According to Wang Junping with the China Railway 14th Bureau Group Corporation Limited, the project used a combination of drill-and-blast and shield tunneling methods, advancing from both the east and west shores of Jiaozhou Bay and meeting under the sea.

　　The main shield section has a maximum depth of 95 meters below the sea surface, and the service tunnel reaches 105 meters, creating high water pressure and requiring stringent sealing and waterproofing.

　　The team, for the first time, adopted a new muck discharge system, integrating a screw conveyor, rock crusher box and rock crusher, to improve efficiency and reduce blockage risks, Wang said, adding that innovative anti-vibration technology was developed for the shield body to improve stability.

　　Once completed, the new tunnel will help Qingdao form a multi-level cross-bay transport network together with the existing Jiaozhou Bay Tunnel, Jiaozhou Bay Bridge and Jiaozhou Bay Highway.