78 Piling equipment and methods
Lifting pointRollersU.B bed frame Tubular raking staysLifting pointsTubular raking strutsTwo channelsRollersPileRollersFigure 3.6Trestle guides for tubular raking pile.
Occasionally, it may be advantageous to use leaders independent of any base machine.
Thus if only two or three piles are to be driven, say as test piles before the main contract, the
leaders can be guyed to ground anchors and operated in conjunction with a separate petrol
or diesel winch. Guyed leaders are slow to erect and move, and they are thus not used where
many piles are to be driven, except perhaps in the confines of a narrow trench bottom where
a normal rig could not operate.
3.1.3 Trestle guides
Another method of supporting a pile during driving is to use guides in the form of a moveable
trestle. The pile is held at two points, known as ‘gates’, and the trestle is designed to be
moved from one pile or pile-group position to the next by crane (Figure 3.6). The hammer
is supported only by the pile and is held in alignment with it by leg guides on the hammer
extending over the upper part of the pile shaft. Because of flexure of the pile during driving