Volume 6 – Geotechnical Manual, Site Investigation and Engineering ...

Chapter 9 FOUNDATION ENGINEERING
This type of pile is not suitable for driving into ground that contains a significant amount of boulders
or corestones and very hard sand lenses.
i) Precast Prestressed Spun Piles
Precast prestressed spun concrete piles used in Malaysia are closed-ended tubular sections of 400 mm
to 1000 mm diameter with maximum allowable axial loads up to about 3000 kN. Special large diameter
spun piles with diameter greater than 1000mm are also available but the demand is low. Pile sections
are normally 12 m long and are usually welded together using steel end plates.
Precast prestressed spun concrete piles require high-strength concrete and careful tight QA/QC control
during manufacture. Casting is usually carried out in a factory where the curing conditions can be
strictly regulated. Special manufacturing processes such as compaction by spinning or autoclave curing
can be adopted to produce high strength concrete up to about 75 MPa. Such piles may be handled
more easily than precast reinforced concrete piles without damage. Steam curing is usually adopted in
the casting yard to shorten casting time and to ensure the quality of the pile.
ii) Small-Displacement Piles
Small-displacement piles are either solid (e.g. steel H-piles) or hollow (open-ended tubular piles, i.e., GI
pipes) with a relatively low cross-sectional area. This type of pile is usually installed by percussion
method. However, a soil plug may be formed during driving, particularly with tubular piles, and
periodic drilling out may be necessary to reduce the driving resistance. A soil plug can create a greater
driving resistance than a closed end, because of damping on the inner-side of the pile.
Bakau pile is considered to be a small displacement pile. However, due to the conservation of the
mangrove forest and the coastal line of Malaysia. Bakau piles are not allowed to be used special permit
is required if imported bakau pile is used.
iii) Replacement Piles
Replacement or bored piles are mostly formed by machine excavation. When constructed in condition
with high ground water table, the pile bore will need to be supported using steel casings, concrete rings
or drilling fluids such as bentonite slurry, polymer mud, etc to avoid collapsing of drilled hole.
Excavation of the pile bore may also be carried out by hand-digging in the dry; and the technique
developed in Hong Kong involving manual excavation is known locally as hand-dug caissons.
Machine-dug piles are formed by rotary boring, or percussive methods of boring, and subsequently
filling the hole with concrete. Piles with 100 mm or less in diameter are commonly known as smalldiameter
piles. Piles greater than 1000 mm diameter are referred to as large-diameter piles.
a) Machine Bored Piles
The advantages and disadvantages of machine-dug piles are summarized in Table 9.1.
March 2009 9-3