Pile Design and Construction Practice, Fifth edition

conditions where a sufficient period of time is available for the concrete to set before the
bottom of the box is submerged. Arrangements should be made to flood the box to equalize
pressures above and below the seal until the concrete has hardened (Figure 9.28b).
Where piers are located in deep water and there is a risk of ship collision it is desirable to
construct the pile cap at bed level in order to eliminate any unsupported length of piling.
This arrangement is also desirable if lateral forces from earthquakes are transmitted from
the bridge superstructure and piers on to the piles. The pier and pile cap can be constructed

470 Miscellaneous piling problems

Figure 9.28Construction of submerged pile caps (a) In cofferdam (b) In open-topped box.

Pier

Pile cap

Sheet piles

High water

Low water

River bed

Impervious

stratum forming

cut-off for sheet piles

Precast concrete box

Pier

Concrete infill

High water

Low water

Collar

River bed

Rubber seal

to opening

(a) (b)

Figure 9.27Fender beam and piles protecting the river piers of the Sungei Perak Bridge, Malaysia
(after Stanley(9.36)).

1 800 mm OD tubular

steel piles supporting

fender beam

1 500 mm OD

tubular steel

piles

Trough-section

RC fender beam

Pile cap supporting

bridge pier

Riverflow (tidal)