How's Bertha progressing?

Bertha has dug 117 feet with 268 feet to go.

SEATTLE - By mid morning on day five in it's drive below the closed viaduct, Bertha's cutter head has gone 117 feet, or nearly one third of the distance needed to clear the viaduct and reopen it. 

Chris Dixon, head of Seattle Tunnel Partners, on a conference call with media this morning says the goal is to make an average of four rings each day, some days faster than others. Today, the contractor says it will probably set six rings, which are six and one half feet wide.  

At that rate, it would appear the machine could clear the viaduct by Saturday May 14. The Washington State Department of Transportation has not set a specific date for reopening the viaduct. 

Dixon says so far, so good.  The machine is making good time using about half of its thrust, and is running within its acceptable temperature range.  He says there is no shifting of the soil, and no vibration is being detected.  

The critical point comes in another three to four days when Bertha passes under Bent 96 E, for east.  At that point the machine will be just 15 feet away from the pilings that support the column.  To protect the pilings, STP set hundreds of concrete filled steel pipes known as micro-piles.  Other micro-piles are drilled into the ground forming an A -frame type  pattern, providing additional strength for the soil. 

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Copyright 2016 KING


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