Pile Design and Construction Practice, Fifth edition

72 Piling equipment and methods
penetrations in difficult environmental conditions where ground investigations have been
limited. This has resulted in on-the-job changes to techniques and equipment requiring a
high degree of geotechnical expertise from the employer and contractor to complete such
projects successfully.
The manufacturers of piling equipment and the range of types they produce are too
numerous for all makes and sizes to be described in this chapter. The principal types of
equipment in each category are described, but the reader should refer to manufacturers’
handbooks for the full details of their dimensions and performance. The various items of
equipment are usually capable of installing more than one of the many piling systems which
are described in Chapter 2. Installation methods of general application are described in the
latter part of this chapter.
All piling equipment should comply with the requirements in BS EN 996: 1996 Piling
equipment – Safety requirements and BS EN 791: 1996 Drill rigs – Safety.
3.1 Equipment for driven piles
3.1.1 Piling frames
The piling frame has the function of guiding the pile at its correct alignment from the stage
of first pitching in position to its final penetration. It also carries the hammer and maintains
it in position co-axially with the pile. The essential parts of a piling frame are the leaders or
leads, which are stiff members of solid, channel, box, or tubular section held by a lattice or
tubular mast that is in turn supported at the base by a moveable carriage and at the upper
level by backstays. The latter can be adjusted in length by a telescopic screw device, or by
hydraulic rams, to permit the leaders to be adjusted to a truly vertical position or to be raked
forwards, backwards, or sideways. Where piling frames are mounted on elevated stagings,
extension leaders can be bolted to the bottom of the main leaders in order to permit piles to
be driven below the level of the base frame.
The piling winch is mounted on the base frame or carriage. This may be a double-drum
winch with one rope for handling the hammer and one for lifting the pile. A three-drum
winch with three sheaves at the head of the piling frame can lift the pile at two points using
the outer sheaves, and the hammer by the central sheave. Some piling frames have multipledrum
winches which, in addition to lifting the pile and hammer, also carry out the duties of
operating the travelling, slewing and raking gear on the rig.
Except in special conditions, say for marine work, stand-alone piling frames have largely
been replaced by the more mobile self-erecting hydraulic leaders on tracked carriages, or by
the crane-mounted fixed or hanging leaders offered by the major piling hammer manufacturers.
In Europe the pile hammer usually rides on the front of the leader, whereas in the
USA the practice is to guide the pile between the leaders. The pile head is guided by a cap
or helmet which has jaws on each side that engage with U-type leaders. The hammer is
similarly provided with jaws. The leaders are capable of adjustment in their relative
positions to accommodate piles and hammers of various widths.
Self-erecting leaders on powerful hydraulic crawler carriages can be configured for a
variety of foundation work. Initial erection and changing from drilling to driving tools can
be rapidly accomplished and with the electronic controls now available the mast can be
automatically aligned for accurate positioning. Some crawlers have expandable tracks to
give added stability and can handle pile hammers with rams up to 12 tonne at 1:1 back rake.