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Bertha ready for disassembly and repair 4 March 2015

TunnelTalk reporting

TBM Bertha reached her final resting place in the SR 99 viaduct replacement tunnel recovery shaft on Tuesday night, clearing the way for Seattle Tunnel Partners to begin the disassembly process.

Workers begin disassembly preparations
Video: WSDOT
Bertha in the recovery shaft
Bertha in the recovery shaft

Bertha has moved forward a total of 57ft since resuming her short drive on February 17. In that period the 17.5m diameter machine has completed nine permanent concrete tunnel rings.

With Bertha now in position, crews have begun the challenging task of disassembling the world’s largest tunneling machine. They will move through a number of methodical steps as they prepare to lift four pieces weighing up to 2,000 tonne to the surface for repairs.

According to WSDOT completion of the repair – which involves replacement of the damaged bearing seals and the fitting of a brand new new main bearing as a precautionary measure – will take “weeks”.

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