Keller company Case Foundation has completed the foundations for the 60-storey tower in Chicago.
Case Foundations was chosen by contractor Walsh to prepare the foundations for the residential tower.one of three being built in a fork of the Chicago River.
Case Foundation was contracted to construct 50 belled caissons with shafts ranging from 762mm to 2.44m in diameter and bells up to 4.9m in diameter, drilled to a depth of 22.8m.
The work also included 14 rock caissons to support the tower itself, ranging from 2.4m to 3m and drilled to a depth of 35.4m.
Case Foundation’s chief estimator Bill Lederer said: “Constructing such big piles so accurately through a range of conditions, in such a tight timeframe, was very challenging. The project required excellent planning, large-scale equipment and some very highly skilled operators.
Keller Chicago Tower
In addition the site had an abandoned underground freight tunnel running through it, which involved the Case Foundation drilling through the top of the tunnel to enter and seal it at either end with concrete bulkheads, then grouting the whole space solid. This allowed the crew to drill large diameter holes through the solid tunnel and beneath to the design bottom elevation.
“We also had to coordinate a lot of activity on what was a small site footprint of 2972m2, with only one way in and out” adds Lederer.
The tower is due to be completed in 2019.