VSM starts operation at Tilbury: shaft sinking safety and design notes for engineers
Reviewed by Tom Sullivan

First reported on Tunnelling Journal – News
30 Second Briefing
Herrenknecht’s “Verena” Vertical Shaft Sinking Machine has begun sinking a 15m internal diameter, >48m deep shaft at National Grid’s Tilbury site for the 2.2km, 400kV Grain–Tilbury cable tunnel under the Thames, replacing the ageing 1960s Thames Cable Tunnel. The remotely operated VSM works in a water-filled shaft, avoiding groundwater lowering and keeping operatives out of the excavation, which is critical for safety in challenging geology. A second shaft at Gravesend and a Mixshield TBM for the tunnel will follow, delivered by Ferrovial BEMO JV.
Technical Brief
- Continuous water-filled operation maintains hydrostatic balance, reducing risk of inflow, instability and sudden ground failure.
- Avoiding groundwater lowering eliminates settlement risks to adjacent assets typically associated with deep dewatering schemes.
- Shaft lining is sunk as excavation progresses, limiting exposure of unsupported ground and reducing fall-of-ground hazards.
- Use of a purpose-built VSM on a UK power tunnel scheme sets a reference for safer deep shafts in soft ground.
Our Take
Herrenknecht AG’s role at National Grid’s Tilbury site adds to its growing UK and European power-tunnel portfolio, and echoes its deployment on the Grand Paris Express Line 15 East TBM drive, signalling that utilities are favouring established metro-scale suppliers for high-risk underground power works.
A 15 m internal diameter, ~48 m deep shaft for the 2.2 km Thames cable tunnel places this Grain to Tilbury electricity upgrade project at the larger end of UK power-tunnel infrastructure in our database, which typically relies on smaller access shafts for 400 kV cable installations.
Within the 141 Infrastructure stories and 334 tag-matched pieces in our coverage, National Grid’s Great Grid Upgrade stands out as one of the few UK projects combining large-diameter deep shafts with long HV cable tunnels, suggesting a template for future river or estuary crossings in constrained corridors.
Prepared by collating external sources, AI-assisted tools, and Geomechanics.io’s proprietary mining database, then reviewed for technical accuracy & edited by our geotechnical team.
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