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
Fig. Typical details of marine piles
5. What is the mechanism of formation of soil plugs in marine driven
steel piles with reinforced concrete infill? (MP2)
During initial driving process, open-ended steel piles are driven through the
soils at their bases. However, shaft friction will gradually develop between
the steel piles and soils inside piles at some time after pile driving. The
hitting action of driving hammers induces forces to the soil and later it
comes to a stage when the inertial forces of inside soils, together with the
internal frictional forces exceeding the bearing capacity of soils at pile toes.
Consequently, the soil plug formed is brought down by the piles. Reference
is made to M. J. Tomlinson (1977).
Note: A soil plug is a column of soil formed at the bottom portion of marine pile type of
steel tubular piles with reinforced concrete infill.
6. How does soil plug in open-ended tubular piles affect its loading
carrying capacity? (MP2)
In marine piles, the tubular piles are sometimes purposely designed to be
open-ended to facilitate deeper penetration. In this mode of pile formation,
soil plug is formed inside the piles.
The plugging ratio (the ratio of length of soil plug to the length of pile
penetration) affects the load carrying capacity of piles. It was demonstrated
by experiments that the end bearing capacity decreases with an increase
in the plugging ratio. Moreover, close-ended piles display a higher end
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