On October 31st a super-large 16.64m diameter shield machine rolled off the production line in Changsha, Hunan, for use in the construction of the world’s longest underwater shield machine driven highway tunnel – the Haitai Yangtze River Tunnel. The CRCHI shield machine, named Jianghai is 145m long and weighs approximately 5,000 tons.
The Haitai Yangtze River Tunnel is located in the Yangtze River estuary area in Jiangsu Province, starting from the Haimen District in Nantong in the north and ending in Taicang City in Suzhou in the south. The total length of the project line is 39.1km, with the cross-river tunnel being 11.2km long.
It is designed to house a bidirectional six-lane highway, with a design speed of 100km per hour. The central tunnel section is 9,315m long, with a maximum excavation diameter of 16.64m. Along the route, the alignment passes through complex geological belts such as silty clay, silty clay interbedded with silt and fine sand, with a maximum depth of about 75m and a highest water pressure of up to 7.5bars.
Jianghai will undertake the long distance single-heading tunnel bore under the Yangtze River with a settlement control set to within 1cm. Geological exploration of the river is limited, with many uncontrollable and un-mapped areas. The large 16.64m diameter means the cutterhead requires large levels of torque for the excavation, with a significant load on the main drive bearing. The 7.5bar water pressures requires a high pressure-bearing capacity for components such as the main drive seal and the tail seal. Ensuring continuous tunnelling for the 9,315m through the complex environment while maintaining a high-performance load was the main challenge faced by the R&D team.
In response, says CRCHI, the R&D team has made bespoke designs for key machine parts such as the cutterhead and the main drive via innovative research. The TBM is equipped with a soft soil cutterhead that is accessible equipped with alloy cutters that are large, hard, wear resistant, and with extensive face coverage. The main drive has a telescopic function that can sense the overall force of the cutterhead. This will flag up abnormal forces on the cutterhead caused by an overload of the main bearing, facilitating cutter change operations, assisting the cutterhead during break out. It is also equipped with a monitoring system to continuously monitor the operational status of the main drive. The shield body size and structural thickness have been designed according to the local conditions, the oil cylinder specifications have been increased, and the slurry circulation system and grouting system have been optimized to enhance the overall performance of the machine. A smart assembly system for segment connection components has also been configured to meet construction requirements.
The Haitai Yangtze River Tunnel is slated for completion in 2028.
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