PROJECT OVERVIEW
Phoenix Project #2215
It’s hard to think of anything more quintessential to an urban construction site than a tower crane. In order to build a tall building, you need to move large amounts of heavy material in place up into the sky, and that’s where cranes come into play. What isn’t thought about much is exactly how those skinny little cranes can support very large loads on such a small footprint. That’s where the invisible magic of micropiles comes into play.
Phoenix was asked to return to 100 Hood Park Drive to provide the deep foundation solution for the tower crane needed there. We had already helped Lee Kennedy before with work inside the building and now was the time to help on the outside. We installed 16 drilled micropiles essentially in a 4 x 4 grid to provide for the compressive and tensile loads to be carried to the earth and hold that crane steady. These piles were 9-5/8” diameter and were bonded in the glacial till. To handle the uplift loads, a 3.5 inch diameter (#28) threaded bar was installed along the full depth of each pile with “floating” bearing plates situated atop the piles. Ultimately, these pile tops were incorporated into a crane pad that was over 6 feet thick.
One of the major challenges of this project was that the piles were spaced closely together to fit in the 25-foot square footprint of the pad. It was critical to not install piles too close to ones that were freshly grouted, which made the sequence of installation like an intricate puzzle. Phoenix was able to meet that challenge and finish our scope early to allow for the next phases of work to get ahead.