SuperPile 2017 Online Proceedings, (DFI)
Pile Group Effects and Soil Dilatancy at the Fort Lauderdale International Airport
David Rancman, P.E.
The Fort Lauderdale Airport Runway and Taxiway Expansion involved the lengthening of a 5,300-ft long landing strip into a new 8,000 ft-long runway that partially sits on a 50-ft high man-made embankment, and required the construction of two massive bridges for the runway and taxiway to traverse US-1, FEC railway, among other airport roadways. The stringent settlement tolerances coupled with impact loading for the largest commercial aircraft, the Airbus A380, result in a design where the bridge foundations comprise of approximately 2,700 driven 24-inch pre-stressed concrete pilings. The project design had various geotechnical considerations including differential settlement between 50-foot high MSE walls at the bridge abutments, pile group effects, and variable bearing strata. These inherent features were further complicated during construction by the dilation of sands, an uncommon phenomenon for South Florida, which resulted in variable capacity losses. Over 1,000 dynamic pile tests, comprising of over 300 test piles, and nearly 900 set checks and/or redrives were required to ensure the project was completed safely. The presentation will provide an overview of the project and will include specific examples where both refusal conditions and dilative behavior were observed. The marriage of these conditions presented challenges in terms of driving piles to ensure that measured capacities, through dynamic pile testing, would remain higher than the designed capacity over the long term. The technical aspects of dilatancy, its impact on pore water pressure, and in turn effective stress and ultimately pile capacity will be reviewed within the data rich environment. These aspects, among other interesting project features will be presented, with emphasis on the project challenges and how they were overcome.
|article #2670; publication #1031 (SP-2017)|