A Self-Learning Manual - Institution of Engineers Mauritius

A Self-Learning Manual
Mastering Different Fields of Civil Engineering Works (VC-Q&A Method) Vincent T. H. CHU
3. What is the problem in traditional marine piling system of steel
tubular pile with concrete infill and what are the possible remedial
measures? (MP1)
In the design of marine piles of steel tubular piles with concrete infill, loads
from pier deck are taken up by steel tubular piles before the occurrence of
corrosion of steel piles above seabed. In fact, it is assumed that steel piles
above seabed level will all be corroded after a certain year. The load
transfer mechanism after complete corrosion of steel pile above seabed is
as follows: loads from pier deck are taken up by concrete infill above the
seabed level. Below the seabed level, loads would be transferred to steel
piles through frictional forces between concrete infill and steel casings.
However, substantial radial shrinkage and contraction occurs after
concreting of concrete infill and this will hinder the load transfer from the
concrete infill to steel piles because the bond may be ruptured by radial
shrinkage. It is in doubt if frictional forces can be properly developed in this
situation. To solve this problem, shear keys could be installed at regular
spacing inside steel piles to ensure their rigid connection with concrete infill.
Alternatively, expanding agents may be adopted in concrete mixes to
ensure that there is no shrinkage after the concreting process.
4. Why are steel tubular marine piles often driven open-ended? (MP4)
In marine structures where piles are constantly subject to significant lateral
and uplift forces induced by berthing operation and wave action, it is
necessary to drive the piles to much greater depth. To avoid premature
refusal so that insufficient soil cover may develop which is incapable of
providing the required lateral and uplift resistance, tubular piles are
normally driven open-ended so that they are driving to greater depths than
piles with closed ends.
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