China has completed the tunnelling of an 11.3 km section of the Chongtai railway tunnel, built beneath the Yangtze River. The tunnel will be used by high-speed trains travelling at up to 350 km/h, and the journey across the river is expected to take just two minutes.
The work was carried out using ‘Linghang’, the largest TBM ever built in China for a high-speed rail project. The machine, with a diameter of approximately 15 metres, completed the entire underwater section in a single operation.
According to the Chinese news agency Xinhua, this is the longest distance ever tunnelled in a single stage by a TBM of this diameter.
The Chongtai Tunnel will link Chongming Island, which belongs to the municipality of Shanghai, with the city of Taicang in the neighbouring province of Jiangsu. The project will bring high-speed trains to Chongming, China’s third-largest island, for the first time.
Tunnel 89 metres below the Yangtze River
At its deepest point, the tunnel lies 89 metres below the bed of the Yangtze River. The structure has been designed to withstand high water pressure and the risks of ground settlement.
Precision in the construction work is essential, as trains will travel through the tunnel at a design speed of 350 km/h. Once opened, it is set to become the world’s fastest underwater railway tunnel.
“Even minor deviations from the alignment during excavation could affect the safety and comfort of the journey. For a design speed of 350 km/h, the precision requirements for the tunnelling machine have been set at the millimetre level,” explained Wang Yi, deputy project director at China Railway Tunnel Group, the state-owned company specialising in tunnel construction.
TBMs of this size use a rotating head fitted with metal cutting elements, hydraulic cylinders for forward movement and an outer steel casing. As it advances, the machine excavates the ground and allows the segments forming the tunnel structure to be installed.
The river will be crossed in two minutes
China Railway Tunnel Group estimates that trains will take approximately two minutes to cross the Yangtze River via the new tunnel.
The entire Chongtai project is scheduled for completion by the end of 2026. The investment is estimated at over CNY 7.1 billion, equivalent to approximately EUR 900 million.
The tunnel forms a key section of the future Shanghai–Chongqing–Chengdu high-speed railway, which will link China’s coastal regions with major urban centres in the interior of the country.
The line will form a rail corridor approximately 2,000 km long, passing through three major urban agglomerations. The total investment required to complete the project is estimated at over CNY 530 billion, or approximately EUR 67 billion.
A corridor linking industrial and research centres
Once fully operational, the Shanghai–Chongqing–Chengdu line will connect areas home to over a quarter of China’s advanced manufacturing centres and around 40 per cent of its strategic state-run laboratories.
The Chinese authorities believe the project will help strengthen supply chains for technology industries and improve links between the country’s main economic and research centres.
“The Linghang TBM demonstrates that China has mastered the key technologies required for the construction of high-speed railway tunnels under water. The Chongtai Tunnel offers a Chinese solution that can be replicated and scaled up in future infrastructure projects,” said Wang Yi.
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