Mammoet Unveils Custom Gantry System to Remove HS2 TBMs in Record Time

Mammoet has successfully removed four Herrenknecht-manufactured Tunnel Boring Machines (TBMs) from the HS2 Northolt Tunnel project on the outskirts of London using a custom-built gantry system. Developed in close collaboration with Skanska Costain STRABAG JV (SCS JV) and Herrenknecht, the bespoke solution allowed the largest TBM components—the cutter head, front, and middle shield—to be lifted as single pieces, dramatically reducing dismantling work inside the shafts.

Traditionally, TBM removal would have required splitting and disassembling components underground, a process fraught with safety risks, ventilation issues, and significant time demands. Instead, Mammoet’s gantry enabled the TBM sections to be extracted to the surface in just one day, compared to several weeks by conventional methods.

Mounted on a hydraulic skidding system, the gantry was designed to lift up to 900 tonnes and move across both vent shafts at Green Park Way. It featured an equalizer beam with an inbuilt swivel, allowing sections to be rotated remotely for precise positioning without manual handling. Once lifted, the TBM sections were placed on 32 axle lines of Self-Propelled Modular Transporters (SPMTs) and moved to a designated disassembly area, where climbing jacks lowered them safely for further dismantling at ground level.

The extraction program demanded meticulous engineering, planning, and coordination, carried out within tight 12-hour weekend railway possessions. In total, it involved four 24-hour lift-and-carry operations, underpinned by months of structural analysis, fabrication, and community engagement.>

By deploying this innovative gantry system, Mammoet and its partners delivered substantial time savings and improved safety outcomes for HS2, providing earlier access for follow-on works across the tunnels. The company now sees opportunities to adapt the system for other projects that require heavy lifting in confined or urban environments.