The project consists of a 33-story building with two levels of below-grade parking across the entire building footprint. Timely and cooperative teamwork among the owner/developer, geotechnical engineer, testing agency, structural engineer, construction manager, and pile-driving contractor resulted in an efficient, cost-effective, high-capacity driven-pile foundation on a constrained urban site with significantly variable subsurface conditions. Design objectives included utilizing the highest allowable pile loads reasonably installed from a drivability perspective, using readily available equipment. A pre-production test program was performed on 16-inch-diameter (406-mm-diameter) steel pipe piles, driven closed-ended and subsequently filled with concrete. The test program included dynamic monitoring of 10 piles during installation, and of select piles during long-term restrike testing with a drop hammer, with one instrumented static load test. CAPWAP® analyses were performed on both end-of-initial-drive and beginning-of-restrike dynamic test records. The site exhibited significant soil set-up, even after relatively short wait times. Test-program objectives included characterizing set-up profiles. A design set-up profile was used to develop depth-variable driving criteria for both 500- and 600-kip (2, 224- and 2, 669-kN) allowable load piles. Test program results permitted more-accurate reduced capacities to be assigned to damaged piles, and to piles which experienced practical refusal. These more-accurate assigned reduced capacities decreased the number of replacement piles required by 50 percent, saving both time and cost.
Subjects: deep cutoff wall, QC/QA program, challenges
Author: Van E. Komurka, P.E., D.GE, F.ASCE, William H. Walton, P.E., S.E., F.ASCE, Ryan C. Rusk, P.E., M.ASCE and Patrick J. Hannigan, P.E., M.ASCE
Publisher: DFI