An EPB TBM manufactured by China Railway Construction Heavy Industry Corporation Ltd (CRCHI) has completed an integral jacking and bridge-crossing without disassembly of the shield.
The achievement with the 9.36m-diameter machine was made on April 16 on the Messina-Catania railway project in Sicily.
CRCHI says the process saves labour, material resources and costs required for the disassembly, transport and reassembly of large-diameter TBMs.
Section 2 of the Messina-Catania project consists of two sections with twin-tube and double-track layout, and a total tunnel length of approximately 12.54km.
Under the original plan, after the breakthrough of the right tunnel in the first section, the TBM main body was to be disassembled, transported to the opposite valley and reassembled. However, restricted by rugged and narrow mountain roads and limited portal working space in Sicily, large cranes could not be deployed for disassembly and reassembly.
To overcome these challenges, the client proposed integral bridge-crossing for the whole equipment.
However, the weight of the load – 1,200 tonnes for the shield, and 1,500 tonnes including transport tooling and haulage vehicles – exceeded the load-bearing capacity of a single bridge. CRCHI and the client set up a dedicated service team and developed a technical solution of spanning two bridges with a centre distance of 30m between them.
Drawing on successful domestic engineering practices for the launching and stepping of large-diameter TBMs in railway and water diversion tunnel projects, the team conducted finite element analysis to verify the positioning, stiffness and strength of right-angle support bases, optimised welding procedures and control measures. They also completed a comprehensive risk assessment and a detailed safety technical disclosure.
In addition, multiple online and offline meetings were held to confirm the overall scheme, refine technical details and finalise the plan.
CRCHI’s service technical team provided on-site follow-up and guidance throughout the process.
After two months of planning, the operation to transport the equipment across the bridges to reach the receiving site was completed in a day.
The dismantling of transfer tooling for the equipment is under way to prepare for the TBM launch and excavation of the next tunnel section.
