By Rose Bell
Being manufactured by China Railway Construction Heavy Industry Corporation Limited (CRCHI), two super-large diameter slurry TBMs were launched from opposite directions in Ningbo and Zhoushan for the Jintang subsea tunnel of the newly-built Ningbo-Zhoushan Railway on May 16th. Following simultaneous rotation of the cutterheads of the two TBMs, commencement of the TBM advance phase for the world’s longest subsea high-speed railway tunnel was marked.
TBMs Dinghai and Yongzhou, which have a total length of 135 meters and a maximum excavation diameter of 14.57 meters, are adorned with the motifs of the Divine Dragon. Running from Yinzhou District in Ningbo City in the west to Jintang Town in Zhoushan City in the east, the Jintang subsea tunnel of the Ningbo-Zhoushan Railway is spanning a total length of 16.18 kilometers, whereas the TBM section is 11.2 kilometers long, with a maximum buried depth of 78 meters.
Beneath the 100,000-ton Jintang main navigation channel, is the passing route of this TBM and it is using two TBMs that start digging towards each other from Ningbo and Zhoushan respectively, finally docking at the bottom of the sea with an accuracy requirement of an error not exceeding 20 millimeters. This marks the world’s first case of subsea docking and disassembly of super-large diameter shield machines.
Considering that the conditions for construction of subsea tunnels are complex, the R&D team of CRCHI has implemented several innovative designs for the shield machine. While the heavy pressurized cutterhead design, 70 disc cutters, and more than 100 tons of weight added compared to the conventional cutterhead, there is a reduction in cutter spacing, and an increased number of disc cutters.
In order to enhancing the cutterhead’s wear resistance and rock-breaking ability and ensuring complete tunneling efficiency, the disc cutters wear an intelligent monitoring system which has been developed and applied.
Additionally, a guidance system with high control precision and advanced technology is used by the shield machine for acting as the eyes for the tunneling equipment, that is equipped with special features such as advanced geological forecasting and probe grouting reinforcement. These allow for advanced detection and reinforcement of undesirable geology in front of the shield machine to ensure the precision and safety at the point of the docking under the sea.
With a design speed of 250 km/h, the Ningbo-Zhoushan Railway Railway project stretches almost 77 kilometers. Once completed, it is slated to effectively promote the development of Yongzhou City and accelerate the construction of the Ningbo metropolitan area.
