The results of the subsurface exploration programs performed at
the site indicated that approximately two-thirds of the new bridge
would be able to be supported on driven, open-end pipe piles deriving
their support primarily in end-bearing in glacial till or bedrock.
bearing piles, drilled shafts and rammed aggregate piers were
designed to support the new bridges. The main span towers and
anchor piers of the bridge were designed to be supported on six-foot
diameter, open-end steel pipe piles bearing on either glacial till or
sedimentary or metamorphic bedrock at depths of up to 270 feet.
The nominal resistance of these piles is up to 7,000 kips.
The bridge approaches were designed to be supported on
three- and four-foot diameter, open-end steel pipe piles with nominal
resistances of up to 6,300 kips. About half of the approach piles
are friction piles in the deep glacial lake varved clays with nominal
resistances of up to 4,300 kips. The friction piles were up to 340
feet long.
The four- and six-foot diameter piles were designed with a
wall thickness of only one inch, which resulted in a savings of about
20,000 tons of steel, as compared to a 1.25-inch wall.
Due to relatively shallow bedrock conditions, drilled shafts
were used for support of the eastern bridge abutment. Drilled
shafts were designed to be 48-inch diameter with a minimum rock
socket length of 10 feet. The western bridge abutment was designed
to be supported on shallow foundations following ground improvement
consisting of rammed aggregate piers.
This design was used as a basis for preparing the bid price for
the project.
Pile load testing
In order to confirm the foundation design developed prior to bidding,
an extensive load testing program consisting of both static
axial and lateral load tests and dynamic testing was implemented.
Members of the project team worked around the clock to set up,
coordinate and oversee the testing. Data analysis and recommendations
for production pile installation requirements were typically
turned around within one week following the completion of each
test. In order to meet the project requirements, the project team
POY WINNER – ASSOCIATE/ENGINEERING AFFILIATE
Photo by Chris Martinez
Pile driving at the main span of the New N.Y. Bridge
Subsurface profile along the alignment of the bridge
President Obama during his site visit in May 2014
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