The construction of the Tianjin-Weifang High-Speed Railway reached a historic milestone on Monday, as the super-large diameter tunnel boring machine Jincheng No.1 broke through beneath the Haihe River, having tunneled over 5,000 meters.

The Jin-Gu Haihe Tunnel, about 6.7 kilometers long, is the only tunnel along the railway and features the largest shield diameter ever constructed beneath the Haihe River.

Tunneling is being carried out using the domestically produced Jincheng No.1 slurry balance TBM, which has a maximum excavation diameter of 13.8 meters.

The participating builder, China Railway 14th Bureau Group Corp Ltd—a unit of the State-owned China Railway Construction Corp—revealed that Jincheng No.1 tunneled beneath a 267-meter-wide section of the river, with a minimal cover of just 17.3 meters below the riverbed and a maximum water depth of 12 meters.

Complex geological conditions, including fractured zones, soft soils and layers prone to liquefaction, posed significant technical challenges. The construction team navigated these conditions while minimizing environmental disruption and maintaining structural integrity near existing infrastructures such as the Central Avenue Haihe Tunnel.

"The TBM began tunneling directly beneath salt fields, where the soil contains corrosive ions at levels about 160 times higher than in typical strata, posing extreme demands on the machine's corrosion resistance and the durability of reinforced concrete," said Liu Zhijian, the project manager from CR14G.

To ensure the safe passage of the TBM under the Haihe River, the construction team adopted innovative techniques such as shield muck treatment technology and a dual-liquid synchronous grouting system. By implementing a differentiated grouting strategy and real-time monitoring, they were able to maintain ground loss at below 0.5 percent.

In response to the challenging fault zone geology, the team customized high-strength tunnel segments and optimized the grouting process to mitigate construction risks.

Additionally, the team upgraded the equipment with anti-corrosion measures, enhanced waterproofing techniques, and high-efficiency construction systems, boosting tunneling efficiency by 40 percent. These measures enabled the TBM to safely traverse the salt fields, water-rich soft soils and complex zones including interchanges and railways.

The Tianjin-Weifang High-Speed Railway runs from Binhai Station in Tianjin to Weifang North Station on the Jinan-Qingdao High-Speed Railway, spanning a total length of 348.9 kilometers. It includes 10 stations and is designed for speeds of up to 350 kilometers per hour.

As a key link in China’s high-speed rail network, the line forms part of both the Beijing-Shanghai and Coastal Corridors. Upon completion, it will significantly enhance connectivity within the Bohai Economic Rim, support the coordinated development of the Beijing-Tianjin-Hebei region, and contribute to the growth of the Shandong Peninsula urban cluster.