18 Types of pile
Heads of timber piles should be protected against splitting during driving by means of a
mild steel hoop slipped over the pile head or screwed to it (Figure 2.2a and b). A squared pile
toe can be provided where piles are terminated in soft to moderately stiff clays (Figure 2.2a).
Where it is necessary to drive them into dense or hard materials a cast steel point should be
provided (Figure 2.2b). As an alternative to a hoop, a cast steel helmet can be fitted to the pile
head during driving. The helmet must be deeply recessed and tapered to permit it to fit well
down over the pile head, allowing space for the insertion of hardwood packing.
Commercially available timbers are imported in lengths of up to 18 m. If longer piles are
required they may be spliced as shown in Figure 2.3. A splice near the centre of the length
of a pile should be avoided since this is the point of maximum bending moment when the
pile is lifted from a horizontal position by attachments to one end or at the centre. Timber
piles can be driven in very long lengths in soft to firm clays by splicing them in the leaders
of the piling frame as shown in Figure 2.4. The abutting surfaces of the timber should be cut
truly square at the splice positions in order to distribute the stresses caused by driving and
loading evenly over the full cross-section.
2.2.2 Precast concrete piles
Precast concrete piles have their principal use in marine and river structures, i.e. in situations
where the use of driven and cast-in-place piles is impracticable or uneconomical. For land
Corners of pile
chamfered to
receive circular
hoopScrewCast steel point60 × 20 mm
M.S. hoop45 × 7 mm M.S. straph20:1 Screws
taperdd(a) (b)Figure 2.2Protecting timber piles from splitting during driving (a) Protecting head by mild steel hoop
(b) Protecting toe by cast steel point.