The Jin-Gu Haihe Tunnel, a key project for the Tianjin–Weifang High-Speed Railway, was completed on Thursday. The final breakthrough was achieved by the domestically produced super-large-diameter tunnel boring machine, Jincheng No 1, which installed the final segment ring.

The Tianjin–Weifang HSR spans 348.9 kilometers, linking Tianjin Binhai Station with Weifang North Station, features 10 stations and has a design speed of 350 km/h. The Jin-Gu Haihe Tunnel is the only tunnel along the entire line and the first high-speed railway tunnel beneath the Haihe River, with its shield-driven section extending about 6.5 km.

Excavation began near the Tianjin Binhai hub using Jincheng No 1, which has a maximum excavation diameter of 13.8 meters.

According to China Railway 14th Bureau Group Corp Ltd, the participating builder and a subsidiary of the State-owned China Railway Construction Corp, the shield machine entered the salt-field strata immediately after launch, where salinity levels were about 160 times higher than in typical layers. This placed stringent demands on corrosion resistance and structural stability.

During tunneling, the shield machine navigated four major curves with a maximum turning radius of 4,000 meters and passed through highly corrosive salt ponds, water-rich soft soil, and several key risk zones, including the Central Avenue Interchange, the Southwest Loop Railway and the Haihe River.

To ensure steady progress, the tunnel boring machine was equipped with a dual-liquid synchronous grouting system, a telescopic main drive, and a synchronized thrust-and-assembly system, boosting efficiency by up to 40 percent compared to conventional methods. The team also applied anti-corrosion coatings to tunnel segments and upgraded waterproofing measures to handle the highly corrosive strata.

While crossing the Haihe River, engineers used high-density slurry, dual-liquid grouting and secondary grouting, forming a reliable external anti-seepage barrier. Ultrafine cement grout was also applied to compensate for soil loss, ensuring safe passage under the river.

The successful breakthrough of the Jin-Gu Haihe Tunnel lays a solid foundation for the Tianjin–Weifang HSR to open as scheduled. Once completed, the line will connect the Beijing–Tianjin intercity railway with the Jinan–Qingdao HSR, greatly enhancing travel convenience for residents along the route, and supporting regional economic and social development.