Panama Canal Mixshield undercrossing: design and tunnelling lessons for engineers
Reviewed by Joe Ashwell

First reported on Tunnelling Journal – News
30 Second Briefing
A 13.46m diameter Herrenknecht Mixshield TBM has broken through into the future Balboa station on Panama Metro Line 3 after completing the first-ever TBM undercrossing of the Panama Canal at depths exceeding 60m below sea level. The 5,600kW, 26,616kNm machine, fitted with an accessible cutterhead and more than 4,500 sensors linked via the Herrenknecht.Connected platform, has achieved peak advance of 150 segment rings (about 300m) per month through mixed sandstone, tuff, breccias and basalt. Around 1.5km of the 4.5km twin-track tunnel remains to final breakthrough.
Technical Brief
- Project specifications mandated zero impact on Panama Canal operations, driving strict settlement and hydraulic control.
- Drive launched September 2024 from the canal’s western shore, reaching Balboa station on 2 February 2026.
- Tunnel length is ~4.5km for twin-track metro operation, with ~1.5km still to excavate.
- At 13.5m diameter, the Mixshield is reported as Latin America’s largest TBM of this type.
- Accessible cutterhead allows tool changes from the rear under atmospheric pressure, reducing hyperbaric interventions.
- Support package includes segment formwork, a separation plant for spoil, three multi-service vehicles and navigation systems.
Our Take
Herrenknecht’s 13.5m Mixshield on Panama Metro Line 3 now sits at the upper end of its global fleet in our database, comparable in strategic complexity to its large slurry and single-shield machines on the Brenner Base Tunnel and HS2 Euston drives, which signals strong positioning for future deep, long urban transit bores.
With more than 4.5km of drive beneath and adjacent to the Panama Canal, Metro Panama’s risk profile is closer to major rail base tunnels than to typical metro works in our Infrastructure coverage, implying that lessons on face pressure control, segment design and settlement management here will be closely watched by other coastal and port-city projects.
Hyundai Engineering & Construction and Posco E&C’s role in this Panama project extends the pattern seen in our database of Korean contractors taking technically demanding underground works in overseas markets, which may give them an edge in bidding for future large-diameter urban tunnels where Herrenknecht equipment is specified.
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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