WATER FRONT STRUCTURES.

Structures constructed along the shore line of water bodies e.g. oceans, lakes, rivers etc.

1 Sea Walls.

They are constructed to resist encroachment by the sea. They are constructed of various
materials ranging from masonry blocks, and precast concrete to insitu concrete. The design of
the wall should minimize the effect of wave action and prevent under scouring of the
foundation concrete block with projecting reinforcement may be used inconjuction with insitu
backing.

2 Docks.

A dock is a place in a harbor, river etc. with gates through which water may be let in and out
where ships unload, load, or repaired. There are two main types of docks that is;

(i) Wet docks

(ii) Dry docks.

Dry docks.
A dry dock consists of a floor, walls, and entrance. The walls are usually in cooperate with floor
to form a rigid structure in order to reduce the uplift which is caused by hydrostatic pressure.
By nature of its location, adjacent to deep waters, dry dock excavation is certain to extend much
below the ground water level and the dock shall consequently displace far more water than the
ship accommodates. Insufficient dead weight cannot be introduced into construction to prevent
buoyancy, a venting system must be provided to release the hydrostatic pressure. The walls are
usually cast insitu. In deep trench excavation at stages of 2m with stepped construction joints.
Longitudinal joints may be constructed at intervals of 15m. They are essentially construction
joints with water bars and should be filled with bitumen or other ceiling compound (to make
them leak proof). The floor to resist uplift forces it should be strong enough to distribute the
ships loads without settlement or undue deflection. Lock gates which are provided are steel and
may be pivoted or of sliding type.

A floating dry dock is a steel floating structure with sides and can be floated and sunk at will.
When a vessel at sea needs under water repair, the floating dock partially sinks by itself beneath
the vessel and makes its self boyard again by pumping out its water and raising the vessel out of
the water with it. The vessel can then be repaired in dry state. It is mobile.

Wet Docks.

A large area of water bounded by vertical solid walls against which vessels tie up. The walls must
be impermeable to retain the water at high tide levels. Locks are provided if entry to the dock is
desired. The walls may be formed by sinking monoliths to suitable depths and joining together
with insitu concrete. A space of (2-3)m is left between the monoliths to facilitate jointing and
finishing.

3 Wharves.

Wharves are berths for shipping which may retain the surrounding wall or provide mooring
facilities at both sides can constructed of piles with concrete decking. Precast concrete block
which may be dove tailed keyed weighing between 10-30 tons are used as an alternative to
insitu concrete. In general a wharf consist of concrete supported on piles which are driven into
the sea bed. Forces acting on the piles include, the wharf itself, and the hydrostatic pressure.
4 Jetties.

It provides a berth some distance from the shore. It usually consists of a deck carried on piles
which jet out into the sea usually at right angles to the shore lines. It may be built in sheltered
harbor waters to provide a relatively cheap berth for specialized cargo vessels. In such cases a
short approach structure is all that is usually needed. Alternatively a jetty may be built off shore
in open sea with the long approach structure to reach adequate depths. For tankers and bulk
carriers a jetty can be an economical means of providing facility but the hostile construction
environment and the periods when the berth is suitable because of weather becomes its draw
back. It can be L or T shaped and they are usually of steel or concrete, hexagonal, piling with
heavy concrete decks or timber supported decks. The decks may require bracing to piles if it is
to be used to off load heavy cargo.
5 Fenders.

A Fender system is to ensure safe berthing without drainage to the vessel or wall to absorb
forces which may occur while the vessel is moored and the quay wall. Only part of the forces
between the vessel and the wall is absorbed by the fenders. The forces in the mooring systems
are supposed to take care of most of the forces working parallel to the wall but are un able to
handle the forces that are perpendicular to end against the wall.

Types of fenders.

(i) Protective fenders: They function as energy absorbing protective pad between the vessel and
the wall available at all times.

(ii) Impact fenders: They absorb impact forces particularly during the berth maneuvers.
6 Break Waters.

Break water is a structure used as a first defense line for protecting a harbor, anchorage or
basing from attacking waves from open seas so that calm condition are created for port area in
an open coast. They cause waves to break upon, and then to reflect the waves through friction
and turbulence. They can either be detached from or linked to the shore. They may also be
totally submerged or may emerge above steel water level for all or part of the tidal cycle. They
may vary in profile from steep to the gentle sloping and can be constructed from relatively
cheap dumping materials in the sea or formed from insitu or precast concrete, natural stones,
asphalt materials etc. They can also be constructed from large blocks of rocks or armor units
placed randomly over suitable filler layers. The armor blocks are made of concrete blocks. Break
water for beach protection may have both beneficial and detrimental effects. The reduction or
elimination of wave action reduces along shore transport, and helps the formation of deposition
barrier which builts out towards the break waters.
7 Moles.

A mole is a fill of rock extending out from the shore, the side slopes of the fill are protected from
erosion by armour rocks. The upper surface of the rock is made wide enough and graded to
accommodate the required facilities to serve the pier such as roadways, sidewalks, rail roads,
pipelines, conveyors etc. Moles are usually constructed in areas in which the greater depth is
3000mm (3m) but the maximum height above the water should not exceed 7.5m side slopes
which are constructed of armour rocks depends on the degree of exposure and the interior fill
of core should be made off, kept off, or run off quarry rocks.

8. Dolphins.

These are individual mooring points to which vessels maybe tied while waiting to enter a wharf
or dock. They are also used as guides to ships entering narrow harbors. There construction is
similar to that of jetties.

9. Groynes.

Are small section sea walls of concrete or other suitable material which are built to protect or to
retain beach material. Steel sheet piling maybe used suitably kept and backed with concrete.