On May 16th, two large diameter slurry TBMs, developed by China Railway Construction Heavy Industry Corporation Limited (CRCHI), were launched from opposing directions in Ningbo and Zhoushan for the Jintang subsea tunnel on the newly-built Ningbo-Zhoushan Railway. The simultaneous rotation of the cutterheads of the two TBMs marks the start of the TBM boring phase on the world’s longest subsea high-speed railway tunnel.
With a total length of 135m and a maximum excavation diameter of 14.57m, the TBMs named “Dinghai” and “Yongzhou” are adorned with the motifs of the “Divine Dragon.” The Jintang subsea tunnel on the Ningbo-Zhoushan Railway stretches from Yinzhou District in Ningbo City in the west to Jintang Town in Zhoushan City in the east, spanning a total length of 16.18km, of which the TBM section is 11.2km long, with a maximum buried depth of 78m. The tunnel under crosses the 100,000-ton Jintang main navigation channel. The two TBMs will ultimately dock at the bottom of the sea with an accuracy requirement with an error not exceeding 20mm. This marks the world’s first case of the subsea docking and disassembly of super-large diameter shield machines, say CRCHI.
In view of the complex construction characteristics of subsea tunnels, the R&D team at CRCHI has implemented several innovative designs for the shield machine, such as the heavily pressurized cutterhead design, 70 disc cutters, and more than 100 tons of weight added compared to a conventional cutterhead. There is a reduction in cutter spacing, and an increased number of disc cutters. The disc cutters are equipped with an intelligent monitoring system which will enhance the cutterhead’s wear resistance and rock-breaking ability, ensuring complete tunnelling efficiency. The machine also utilises a guidance system with a high control precision, and is also equipped with special features such as advanced geological forecasting and probe grouting reinforcement. These, say CRCHI, will allow for the advanced detection and mitigation of undesirable ground conditions in front of the shield to ensure precision and safety at the point of docking under the sea.
The Ningbo-Zhoushan Railway project spans about 77km and has a design speed of 250km/h. Upon completion, it will effectively promote the development of Yongzhou City and accelerate the construction of the Ningbo metropolitan area.
CRCHI
China Railway Construction Heavy Industry Corporation Limited are manufacturers of Tunnel Boring Machines (TBM’s), Belt Conveyors and Drill & Blast...
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