Advantages:
- Material
of pile can be inspected before it goes into the ground.
- Stable
in "squeezing" ground
- Not damaged
by ground heave when driving adjacent piles
- Construction
procedure unaffected by ground water
- Can be
readily carried above ground level, especially in marine structures
- Can be
driven in very long lengths
Disadvantages:
- May break
during hard driving causing delays and replacement charges, or worse
still may suffer major unseen damage in hard driving conditions
- Uneconomical
if amount of material in pile is governed by handling and driving stresses
rather than by stresses from permanent loading
- Noise
and vibration during driving may cause nuisance or damage
- Displacement
of soil during driving piles in groups may damage adjacent structures
or cause lifting by ground heave of adjacent piles
- Cannot
be driven in very large diameters
- End enlargements
not always advantages
- Cannot
be driven in conditions of low headroom
Choice between
different types of driven preformed piles:
Timber
Suitable
for light loads or temporary works. Unsuitable for heavy loads. Subject
to decay due to fluctuating water table. Liable to unseen splitting or
brooming if driven too heavily.
Concrete
Suitable
for all ranges of loading. Concrete can be designed to suit corrosive
soil conditions. Readily adaptable to various sizes and shapes. Disadvantages:
additional reinforcement must be provided for handling and driving stresses;
liable to unseen damage under heavy driving; delay between casting and
driving.
Steel
Suitable
for all ranges of loading. Can be readily cut down or extended. Cut off
portions have scrap value and they can be used for extending other piles.
Can be driven hard without damage. Can be driven in very long lengths
by welding on additional lengths. Some types have small ground displacement.
Structural steel bracing can be readily welded or bolted on. Resilience
makes it suitable for jetty or dolphin structures. Disadvantages: subject
to corrosion in marine structures and requires elaborate paint treatment
and/or cathodic protection; long and slender piles liable to go off line
during driving.
