2.2
EQUIPMENT
2.2.1
Pile Hammers
The hammer used shall have a delivered energy suitable for the total weight
of the pile, the character of subsurface material to be encountered, and
the pile capacity to be developed. The driving energy of the hammer shall
be not less than 20,350 J (15,000 foot-pounds) 15,000 foot-pounds.
2.2.2
Driving Helmets and Pile Cushions
A driving helmet or cap, including a pile cushion, shall be used between
the top of the pile and the ram to prevent impact damage to the pile. The
driving helmet, or cap and pile cushion combination, shall be capable of
protecting the head of the pile, minimizing energy absorption and
dissipation, and transmitting hammer energy uniformly over the top of the
pile. The driving helmet or cap shall fit loosely around the top of the
pile so that the pile is not restrained by the driving cap if the pile
tends to rotate during driving. The pile cushion may be made of solid wood
or of laminated construction using plywood, softwood, or hardwood boards or
other cushion material as approved by the Contracting Officer. The pile
cushion shall completely cover the top surface of the pile and shall be
retained by the driving helmet. The minimum thickness of the pile cushion
shall be 75 mm 3 inches and the thickness shall be increased so as to be
suitable for the size and length of pile, character of subsurface material
encountered, hammer characteristics, and required driving resistance.
PART 3
EXECUTION
3.1
INSTALLATION
3.1.1
Pile Driving
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NOTE: The last sentence, concerning tip elevation
and driving resistance, should be edited to conform
to subsurface conditions and type of pile (friction
or end bearing).
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Excavation shall be stopped at 305 mm 1 foot above foundation grade before
piles are driven. When pile driving is completed, excavation shall be
completed to lines and grades shown. Piles shall be driven to or below the
"calculated" tip elevation to reach a driving resistance in accordance with
the schedule which the Contracting Officer will prepare from the load test
results. The pile hammer used for driving shall be the same type, operated
at the same rate and in the same manner, as that used for driving the test
piles. Diesel-powered hammers shall be operated at the rate recommended by
the manufacturer throughout the entire driving period. Sufficient pressure
shall be maintained at the steam hammer so that: for a [double-acting
hammer, the number of blows per minute during and at the completion of
driving of a pile is equal approximately to that at which the hammer is
rated;] [single-acting hammer, there is full upward stroke of the ram;]
[differential type hammer, there is a slight rise of the hammer base during
each upward stroke.] A new pile cushion shall be used at the start of
driving for each pile and the cushion shall be replaced whenever it has
become highly compressed, charred, burned, or deteriorated in any manner
during driving. Each pile shall be driven continuously and without
interruption until the required depth of penetration and penetration rate
SECTION 02456A
Page 9
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