DHARM654 GEOTECHNICAL ENGINEERING
Laterally loaded piles support horizontal or inclined forces such as the foundations of
retaining walls, bridges, dams, and wharves and as fenders in harbour construction.
In case the lateral loads are of large magnitude they may be more effectively resisted by
batter piles, driven at an inclination. Closely spaced piles or thin sheet piles are used as coffer-
dams, seepage cut-offs and retaining walls. Piles may be used to compact loose granular soils
and also to safeguard foundations against scouring. These are illustrated in Fig. 16.1.
Q(a) Point-bearing pileQ(b) Friction pileQ(c) Tension or anchor pileP(d) Laterally loaded pile
Q(e) Compaction pile (f) Sheet-pile wall (g) Piles to safeguard foundation against scourSoftSoft SoilSoilFig. 16.1 Uses of piles1 6.4 Pile Driving
The operation of forcing a pile into the ground is known as ‘pile driving’. The oldest method
and the most widely used even today is by means of a hammer. The equipment used to lift the
hammer and allow it to fall on to the head of the pile is known as the ‘pile driver’. The Romans
used a stone block hoisted by an A-frame derrick with slave or horse power. While such a
simple pile-driving rig is still in use today with mechanical power, the more common equipment
consists of essentially a crawler-mounted crane, shown schematically in Fig. 16.2. Attached to
the boom are the ‘leads’, which are just two parallel steel channels fastened together by
U-shaped spacers and stiffened by trussing. The leads are braced against the crane with a
stay, which is usually adjustable to permit driving of batter piles. A steam generator or air
compressor is required for steam hammers.
The most important feature of the driving rig, from an engineering point of view, is its
ability to guide the pile accurately. It must be rugged and rigid enough to keep the pile and
hammer in alignment and plumb inspite of wind, underground obstructions and the move-
ment of the pile hammer.