Pile Design and Construction Practice, Fifth edition

Other protective measures in contaminated disturbed ground include jacketting the pile
with concrete or filling the shafts of hollow piles with concrete capable of carrying the
full load.

10.4.2 Steel piles for marine structures

Steel piles supporting jetties, offshore platforms and other river or marine structures must
be considered for protection against corrosion in five separate zones. These are as follows:

(1) Atmospheric zone: exposed to the damp conditions of the atmosphere above highest
water levels or to airborne spray.
(2) Splash zone: above mean high water level and exposed to waves and spray and wash
from ships.
(3) Intertidal zone: between mean high and mean low water levels.
(4) Continuous immersion zone: below lowest water level.
(5) Underground zone: below the soil line.

Morley and Bruce(10.17)made an extensive survey of the extent of corrosion on steel piling
in marine structures at various sites in the UK, Cyprus and the United Arab Emirates.
Average and probable maximum corrosion loss rates for the five zones are shown diagram-
matically in Figure 10.4. The EC3-5 guidance on corrosion rates, which apply to seawater
and fresh water, is not as detailed as these survey values. Design thicknesses to allow for
corrosion loss and methods of protection should take into account the variation in corrosion

494 The durability of piled foundations

Figure 10.4Loss of thickness by corrosion for steel piles in seawater (after Morley and Bruce (10.17)).

HWL

LWL

Steel pile

0.09 mm/year

(0.18)

0.04 mm/year

(0.11)

0.09 mm/year

(0.18)

Abrasion damage may

locally increase losses

to 0.41 mm/year

0.05 mm/year

(0.14)

0.02 mm/year

(0.05)

Average marine corrosion

rates in mm/year (figures in

brackets are 95% maximum

probable rates)

Buried zone

Sea bed

Immersion zone

Low water zone

Inter-tidal zone

Splash zone