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Drilling shafts in front of Bertha


It turns out that Bertha, the SR 99 TBM constructing the tunnel to replace the earthquake-damaged Alaskan Way viaduct in Seattle, was stopped by a 20 cm-diameter steel pipe traced to a 2002 groundwater study.

To prepare the ground around Bertha for further investigation, a low-strength blend of cement and sand has been injected into voids in front of the TBM caused by removal of water and soil from the machine’s excavation chamber to facilitate inspection last month.

On 07.01.2014 crews started drilling their own 20 cm-diameter shafts in front of Bertha to check out reports of further metal objects, and to remove them. They are also gathering information about any other factors that might have contributed to the tunnelling holdup last month. For tunnelbuilder archive click here and us/69. Visit www.AlaskanWayViaduct.org and http://www.wsdot.wa.gov/Projects/Viaduct/Contents/Item/Display/1389. 02/14.