Areas surrounding the access pit being excavated to rescue the stalled Bertha TBM have experienced settlement as much as 1 to almost 1.5 inches according to a draft figure released by WSDOT on December 11, 2014. The aging and seismically deficient Viaduct itself has experienced 1 inch of settlement as well. Structural engineers have inspected it as well as numerous buildings in the area and have not found structural damage. The settlement is thought to be related to the dewatering associated with the access pit construction. The excavation was within 3 feet of the bottom when the settlement issues were first announced on December 5, and WSDOT has since allowed the contractor to complete the excavation. [Source: Read more information in the update provided by the WSDOT Alaskan Way Viaduct Replacement Project team. Image: WSDOT]
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Feb. 7 Bertha update: Two factors contributed to tunnel stoppage
WSDOT released an update on February 7 with some conclusions regarding the blockage that has stopped the Alaska Way Viaduct Tunnel Boring Machine, Bertha’s progress since December 6. Now they don’t think it was necessarily the well casing after all.
They cite two factors that contributed to the blockage. First, the cutterhead was clogged with material. You can see an cool short video of a worker unclogging the cutterhead. Not terribly dramatic, but still cool. The second factor was increased temperatures inside the equipment. STP discovered damage to a seal that protects the machine’s main bearing. They are still determining how the repairs will be done.
If you want to follow the chronology of this issue, read below for summaries and links to previous updates from WSDOT. And Check out the videos too! [Source: WSDOT]
More Trouble for Bertha TBM, Sinkhole, Tunneling Suspended
Seattle tunnel will go under 158 buildings
The tunnel replacing the Alaskan Way Viaduct (SR-99) will pass beneath 158 existing structures requiring an extensive program of vibration and settlement monitoring as well as some remediation. Of the 158 buildings, WSDOT identified 20 […]