CANADIAN FIRM Urkkada has carried out dynamic testing on piles at JFK Airport's international arrivals terminal, Long Island, New Yo r k .
Using the Pile Driving Analyser program meant experience of testing on one pile type could be transferred to another type and allowed comparison of dynamic test results with static tests.
Two types of tapered piles were installed.
Both were 450mm diameter, tapering to 200mm diameter over the lower 7.6m. Piles 1 and 2 were monotube piles and Piles 3 and 4 were steel taper tube piles.All were driven with a Juntaan HHK-7 hammer to a depth of 18m through a thick deposit of fine to coarse, medium dense to dense glacial sand.
One purpose of the test was to compare the response of the two pile types to the driving and capacity at the end of initial driving.
Dynamic testing of one pile of each type was also performed at beginning of restrike, three weeks after driving. Capacity was determined both by dynamic testing (CAPWAP analysis) and by a static loading test.
Dynamic testing and CAPWAP analyses were performed at the end of initial driving (EIOD) on all four piles and at the beginning of restrike (BOR) on Piles 1 and 3, after 19 days and 35 days respectively. Piles 2 and 4 were not restruck but were filled with concrete and subjected to static loading tests two days after the restrike testing of the other piles.
Urkkada predicted the capacity and pile head movement immediately before the start of the static load tests of Piles 2 and 4.Predictions were based on the similarity between the two pairs of test piles and the assumption that the relative capacity increase from EOID to BOR for Piles 1 and 3 would be the same for Piles 2 and 4, and the movement prediction considered the stiffness change due to concreting of Piles 2 and 4.
Increase of capacity of Piles 1 and 3 between EOID and BOR was 60% for both.Applying the same proportional increase to the EOID of Piles 2 and 4 gave predicted capacities of 3,600kN and 3,780kN and predicted movement of 18mm and 15mm respectively.
The static tests gave capacity of Pile 2 as 3,730kN (within 4% of the dynamic test predictions) and the capacity of Pile 4 as 3,820kN (within 1%). Actual movements were 21mm and 16mm respectively.