Jan. 14 Bertha Update: Going Hyperbaric – Source: WSDOT This press release by WSDOT is fascinating, you should definitely check it out. It describes the hyperbaric intervention that deep see divers performed to try and determine what has impeded the progress of the Bertha TBM on the Alaska Way Viaduct Tunnel project. They describe how a bentonite mud is injected in front of the cutterhead to create a "membrane" so they could pump air into the excavation chamber to create an air bubble that the hyperbaric divers could work in. The air pushes the bentonite membrane into the soil face and holds back the soil and water. They use the screw conveyor to remove sufficient material from the excavation chamber so that the divers can work in the top half of the excavation chamber.
Jan. 21 Bertha Update: Initial Results of Hyperbaric Inspections – Source: WSDOT In this press release, WSDOT reported that as of January 21, STP divers had spent more than 35 hours under hyperbaric conditions inspecting the TBM cutterhead from inside the excavation chamber. They removed a piece of bent well casing, pieces of PVC pipe, and found a large boulder or piece of concrete in a cutterhead opening.
Jan. 23 Bertha Update: More Hyperbaric Work, No New Findings – Source: WSDOT In this press release, WSDOT mainly just updated the total tally of hours worked by the deep see divers in the TBM intervention at the cutterhead. As of January 23, they were up to 68 hours of work performed during 17 sessions.
Jan. 31 Bertha Update: Further evaluation required before tunneling can resume – Source: WSDOT Bertha moved forward about 2 feet on January 28 to test the cutterhead and build the next tunnel liner ring. STP crews observed abnormally high temperatures in some components, similar to what was observed during the original stoppage on December 6. The made adjustments, moved forward another 2 feet but the temperatures persisted. The analysis will continue.
The $14.8 billion project that has constructed a dizzying array of underground highways, bridges, ramps and tunnels in the middle of Boston has finally ended. The end of 2007 apparently was also the end of the Bechtel/Parsons Brinkerhoff joint venture that designed and built the project. More… (Photo by brewrat)
The “breakthrough” media event for CALTRANS’ Devil’s Slide Tunnel project was this past Friday. A large crowd of politicians, news crews and locals were on hand as a road-header broke through a shotcrete face in a ceremony to mark the completion of the excavation portion of the first of two tunnels. It will still be over a year until the tunnels are opened to traffic. The second tunnel is expected to breakthrough as early as this week. (Photo by SFGate.com)