CHINA: The Chongtai Tunnel has completed its 11.325 km underwater TBM drive beneath the Yangtze River, clearing the most demanding section of a future 350 km/h high-speed rail crossing.

Chongtai Tunnel Yangtze Drive Reaches 11.3 Km
Photo: China Railway

On July 30, the Linghang tunnel boring machine reached the No. 2 shaft on the river’s southern side. An official project update says the 15-metre-class machine completed a continuous single-heading drive of 11.325 km, establishing a record for a TBM of this diameter.

The milestone does not mean the entire 14.25 km tunnel is finished. The construction team must still excavate the final 1.8 km between the No. 2 and No. 1 shafts, with full tunnel breakthrough expected by the end of 2026.

A 15.4-metre TBM built for high-pressure ground

Linghang has a 15.4-metre cutterhead, measures 148 metres long and weighs about 4,000 tonnes. China Railway Tunnel Group used the machine to excavate the underwater section in one direction while installing the precast segments that form the permanent tunnel lining.

At its deepest point, the alignment lies 89 metres below the Yangtze riverbed, where official Taicang data says water pressure can reach 0.9 MPa. The TBM therefore combines high-pressure seals, a reinforced cutterhead and an intelligent control system designed to keep the alignment within millimetre-level tolerances.

Project chief engineer Li Bin told Xinhua that a large tunnel diameter reduces aerodynamic resistance, while a straight and stable structure is required for trains to maintain their 350 km/h design speed. The tunnel structure was also reinforced to limit movement caused by changes in the riverbed.

The horizontal TBM met a vertical shaft excavated by the Qiming machine. That shaft-boring machine has a 24-metre excavation diameter and completed the 56.08-metre-deep No. 2 shaft before Linghang arrived.

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Two minutes beneath the Yangtze River

The Chongtai Tunnel links Chongming Island in Shanghai with Taicang in neighbouring Jiangsu province. It will bring high-speed rail to Chongming, China’s third-largest island, for the first time.

Once the railway is operational, trains are expected to cover the river crossing in about two minutes. The projected journey from Chongming through Taicang to Shanghai Baoshan station is 17 minutes, although completion of the tunnel is only one stage before the route can open to passengers.

The tunnel forms part of the planned Shanghai–Chongqing–Chengdu high-speed railway, a corridor of roughly 2,000 km passing through three major urban agglomerations. The Chongtai project is valued at more than CNY 7.1 billion, approximately EUR 900 million, while the wider corridor is estimated at over CNY 530 billion, or about EUR 67 billion.

Authorities expect the full corridor to connect areas containing more than a quarter of China’s advanced manufacturing centres and around 40% of its strategic state-run laboratories. For the Chongtai Tunnel itself, the immediate next step is the remaining 1.8 km drive and full breakthrough targeted for the end of 2026.

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