Mammoet has utilised its Move3D software to create a detailed visualisation of a TBM disassembly saving both time and money.
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Working on the UK’s flagship transportation project, High Speed Two, Mammoet was contracted by the Align JV to disassemble the TBMs. Mammoet contacted the assembly team and, upon finding out that a 600-tonne crawler was needed to assemble the machine, created the project in Move3D to prove that a 400-tonne crane could do the job due to changed conditions.
“We determined that the equipment used to build the boring machines wasn’t necessarily the equipment needed for their dismantling,” said Simon Crawley, Senior Commercial Manager at Mammoet. “There were different limitations at the two sites. Because there were obstructions in the way, a 600-tonne crawler crane was needed at the construction stage. We believed that a 400-tonne crawler crane would be adequate to perform the dismantling.”
Seeing how the job would be carried out using the smaller crane, the client was satisfied with the recommendations that Mammoet put forward and was able to use a more cost-effective solution. The 400-tonne capacity crawler crane, a CC2400, was used to remove the biggest components from the TBMs. For the heaviest component, the cutter head, an LR1300SX crawler crane was also used to perform a tandem lift.
The components were lowered onto Mammoet Self-Propelled Modular Transporters (SPMTs) before being taken to one of two laydown areas.
Additional crawler cranes, including the LR1300SX and an LR1250 support crane, offloaded the components onto the ground or supports for further dismantling.
As the cutter head was too heavy for the smaller cranes to lift, climbing jacks were used to offload it from SPMTs to the ground. A challenging aspect of the project was the fact that the cutter head’s center of gravity (COG) could not be fully known.
The lifts also needed to be performed on a slight incline because the TBMs exited the tunnel at an angle. Typically, challenges such as this this would result in having to create additional drawings and manage changes before performing the lift, according to Mammoet, that would add unnecessary delays depending on how pronounced the differences were with respect to the original project planning.
The team instead came up with an engineering solution that would avoid unnecessary changes, and days or even weeks of potential downtime.
“We used air hoists to make pneumatic length changes and keep the components level,” said Mammoet Project Manager, Rhys Burley. “It took away that manual element of hoisting chain blocks. It was done on a compressor rather than using manual labor, which was safer and more efficient.”