Rebuilt main beam for water diversion in Chicago 01 Mar 2018

Robbins News Release

A rebuilt Robbins main beam hard rock TBM has achieved a best day of 39.5m and a best five day week of 146.4m during excavation for the Albany Park stormwater diversion tunnel in Chicago, USA. The TBM, owned by project contractor Kenny Construction since the 1990s and used on several projects before, was rebuilt and modified for the Albany Park project with help from Robbins, who repaired an existing cutterhead and added segments to increase the machine from 5.2m to 6.2m diameter.

The 6.2m diameter Robbins main beam used at Albany Park
The 6.2m diameter Robbins main beam used at Albany Park

“Rebuilding TBMs has always been a core part of the Robbins business,” said Steve Smading, Robbins Engineering Manager. "A rebuilt machine with updated systems offers value without increasing risk, and a rebuilt machine can usually be delivered faster."

“The financial and schedule advantages are obvious, and boring diameters can be increased or decreased and machine configurations changed. A single shield can be reconfigured as a double shield, or vice versa, and a main beam TBM can be reconfigured as a shielded machine. Soft ground machines can be configured for different geologies and can be set up as either slurry or EPB.”

More than 50% of Robbins main beam gripper TBMs have been used on three or more projects and many are reaching more than 50km of use. The TBM used for the Albany Park project was previously for tunnel drives in the Dominican Republic, Saudi Arabia, New York and Chicago, completing a total of at least 19.5km.

Rebuilt by Kenny Construction with modifications from Robbins
Rebuilt by Kenny Construction with modifications from Robbins

For the project in Chicago, extensive modifications were made underground to the machine. "During boring we encountered approximately 30.4m of fractured ground that had to be supported with rolled channels, straps, and 19 full circle steel rings,” said Clay Spellman, Project Manager for contractor Kenny Construction. The drive was through dolomite with an average compressive strength of 64MPa UCS.

The drainage tunnel for the Chicago Department of Transportation starts in Eugene Park and extends about one mile under Foster Avenue to the North Shore Channel. When the Chicago River water levels reach more than 2m, the tunnel will divert a flow of 65m3/sec. The tunnel transfers water directly to the Channel without damaging the residential area or adversely affecting the river wildlife.

The tunnel was planned in 2013 to divert water from the area after flood conditions were severe enough to warrant evacuation by boat. Excavation was completed in August 2017 and it is expected to be functional by April 2018.


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