HOW THEY DO IT IN THE BIG APPLE
New Junttan PM20UFC ready to drive
its first pile
A fourteen story residential structure has been planned for a site in Battery Park City on the lower Westside of Manhattan.
This man made site extends into the river about one thousand feet (three hundred meters). The upper soils are fill and little resistance is encountered until just above rock.
This site is prime property. The local area is full
of relatively new structures including the nearby World Trade Center.
The Hudson River is a few steps away and a very attractive park area surrounds
Battery Park City.
Throughout the day joggers by the thousands take advantage of this well kept, attractive area of New York City. I thought as I watched them, that they must know something that I don't, since I was working and they were playing.
9 5/8 .545 wall pipe with end plates
On site to drive the test piles was the Underpinning and Foundation Company with their new, all hydraulic, Junttan Pile Driver. This machine was off the carrier and ready to drive piles in less than a half hour. The all hydraulic machine is impressive and fast.
Pipe piles of a larger diameter were originally proposed,
but 9 5/8" X .545 wall pipe with its high strength, availability, and some
cost savings was selected.
The piles were to be test loaded to 320 tons for 96 hours. The design load is 150 tons plus 20 tons down drag. The smaller diameter pipe has an additional advantage in that the reduced surface area is less affected by down drag.
Revitalized downtown area of NYC
with World Trade Center in background
This pipe is a seamless pipe with a 80 ksi or higher yield strength. This is an ideal pipe for sites with obstructions in the soil, or where the driving will be hard. One Contractor I know calls these piles " Cannon Barrel Piles".
The splices used was a DFP Sales S-1800. The splice for 9 5/8" pipe and other casing pipe must be made heavier than conventional splices. The pipe stop or ledge must be at least as wide as the wall thickness of the pipe (in this case .545 inch). The steel also should be of high strength since the pipe can be over 100 ksi yield strength. The splice must be strong and tough enough to reduce the diameter of the pipe slightly because of the tapered (interference) fit. Some commercially available splices have a 3/8" ledge. This would not allow for full load transfer from the pipe to the splice and again to the lower pile section. These units generally are made from a mild steel with lower yield strength.
The Junttan machine was taken from the project that same day and was back in the yard across the East River by 4:00 PM, and it took only one truck to move it.
The pipe was supplied by J. Dougherty Supplies. The pipe splices were supplied by DFP Sales Inc.
Copyright 1997 Pileline Publishing