China's largest tunnel boring machine enters testing phase for world's longest underwater highway tunnel construction

China's largest tunnel boring machine (TBM) cutter head, with a record-breaking diameter of 16.64 meters, descended at the construction site of the Haitai Yangtze River Tunnel in East China's Jiangsu Province on Wednesday, signaling the start of its initial testing phase. 

The TBM, named "Jianghai," was independently designed and developed by China Railway Construction Heavy Industry Corp in collaboration with China Railway 14th Bureau Group Corp. Measuring 145 meters in length and weighing about 5,000 tons, the TBM represents a significant engineering achievement. 

The cutter head, measuring 16.64 meters in diameter and weighing 460 tons, was precisely lowered into place at the site, highlighting one of the most intricate and challenging stages of the TBM's assembly, according to a CCTV report.

The Haitai Yangtze River Tunnel, a key component of the world's longest underwater highway tunnel, will stretch 39.07 kilometers, including an 11.185-kilometer underwater section. The tunnel will feature a six-lane design, utilizing the TBM to navigate challenging geological conditions, including high water pressure and intricate operational demands.

The project is expected to progress rapidly, as more than 200 workers remain on-site during the coming Spring Festival holidays to assemble TBM components and finalize adjustments. By the end of March, the machine is slated to begin tunneling work, setting the stage for the tunnel's eventual groundbreaking excavation.