Keller protected existing adjacent structures' foundations while drilling at several locations containing existing timber piles.
The project
An existing six-story office building supported on timber piles was demolished to make way for a new 41-story luxury apartment building. The new high rise would be supported on a drilled shaft (aka caisson) foundation system.
The challenge
Logistics accessing the site presented challenges since it was a corner lot on the Millennium Mile, a highly populated urban area with heavy vehicular and pedestrian traffic. The existing timber piles in place from the previous structure also presented a challenge for drilling the foundation elements. Care was also required while drilling the shafts adjacent to the foundations of existing adjacent buildings to avoid potentially damaging movement of the buildings.
The solution
Careful coordination and planning with the main contractor resulted in safe access from the busy intersection. Extra care to maintain the accurate location of the shafts was taken while drilling through the existing timber piles. To protect the foundations of the adjacent existing buildings, a permanent steel casing was installed when constructing the adjacent shafts. Each of the fifty-two belled caissons was founded on hardpan approximately 85 feet below grade.
