In Illinois, USA, Kenny Construction is nearing completion on the Chicago Department of Transportation’s Albany Park Stormwater Diversion Tunnel. Plans for the tunnel began in 2013, after flood conditions became so severe that residents had to be evacuated from the area by boat. The tunnel is expected to be functional by April 2018.
A Robbins Main Beam Hard Rock TBM bored the 1.6km long tunnel and broke through at the end of August 2017, bringing the project one step closer to completion. The TBM, also known as “Keri,” has been owned by project contractor Kenny Construction since the 1990s and has been used on several projects prior. “The machine holed through into the inlet shaft,” said Clay Spellman, Project Manager for Kenny Construction. “We excavated the shaft as part of the project. The machine has since been disassembled and removed.”
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For the Albany Park Project, Keri was rebuilt by Kenny Construction with size modifications designed by Robbins. Robbins took an existing cutterhead, repaired it, and then added segments, taking it from 5.2m to 6.2m in diameter. “Extensive modifications were also made underground to the machine to be able to install rock dowels and stand the ring steel under the roof shield,” added Spellman.
Due to the project location in a residential neighborhood, there were restrictions in place as to when the machine could operate and the frequency at which blasting would be allowed per day. Despite these limitations, the TBM achieved a best day of 39.5m and a best week (5 days) of 146.4m. The machine bored through dolomite with an average compressive strength of 64MPa UCS (9,300 psi). “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 Spellman.
The drainage tunnel starts in Eugene Park and extends for under Foster Avenue to the North Shore Channel. When the Chicago River’s water levels reach flood stages—exceeding 2m – the tunnel will divert a flow of 65 cubic meters of water per second, avoiding Albany Park, then deposit it into the Channel. The tunnel will essentially be transferring the water where it would have ended up, without damaging the residential area or adversely affecting the river’s wildlife.