Onshore Sections Complete for World's Longest Undersea Rail Tunnel

Construction teams have fully excavated the onshore segments of the 16.18-kilometer Jintang Undersea Tunnel, marking a key milestone for the Ningbo-Zhoushan Railway in eastern China's Zhejiang province. With the breakthrough of a 3,617-meter rock tunnel section in Ningbo, the onshore sections totaling 7.83 kilometers are now finished, according to state media. Overall construction on the 76.4-kilometer high-speed rail project has reached 77 percent, shifting primary operations to complex undersea shield tunneling that will eventually link the island archipelago of Zhoushan to the national rail network.

Completing the land-based excavation removes major onshore geological risks, allowing engineers to concentrate resources on the technical challenges of undersea shield tunneling. When operational, the rail line will eliminate Zhoushan's status as an island without passenger rail, cutting travel time between Ningbo and Zhoushan to roughly 26 minutes and linking Zhoushan to provincial capital Hangzhou in about 90 minutes.

Excavation crews have completed the onshore sections of the Jintang Undersea Tunnel, a critical engineering component of the Ningbo-Zhoushan high-speed rail line in eastern China's Zhejiang province, state media reported on September 4. The final onshore breakthrough occurred at the western entrance in Ningbo's Beilun district, clearing the remaining rock barrier along a 3,617-meter section built by China Railway 14th Bureau Group. The Jintang tunnel spans 16.18 kilometers in total, connecting Beilun on the mainland with Jintang Island in Zhoushan. Designed for train speeds of up to 250 kilometers per hour in a single-tube, double-track configuration, the project is recognized as the world's longest undersea high-speed railway tunnel. The tunnel is divided into onshore and offshore segments. With the latest excavation complete, the entire 7.83 kilometers of onshore tunneling is now finished. According to Qiu Lixu, a site manager for China Railway 14th Bureau, crews contended with multiple fault lines and dense joint zones in Ningbo. Engineers utilized smooth-wall and micro-delay blasting techniques to minimize seismic disruption, supported by advanced geological forecasting and real-time rock monitoring to maintain structural stability throughout excavation. With onshore excavation complete, construction priorities have pivoted fully toward undersea shield tunneling. The Ningbo-Zhoushan Railway covers a total mainline length of 76.4 kilometers, and overall construction progress has reached 77 percent, according to project updates released via Xinhua. Once shield operations complete the subsea crossing, subsequent phases will involve laying ballastless tracks and installing power and signaling equipment. Upon completion, high-speed rail travel between Ningbo and Zhoushan will take approximately 26 minutes, while the journey between Hangzhou and Zhoushan will be shortened to about 90 minutes, ending Zhoushan's historic reliance on marine and highway transit.