SEMINAR ON

MARINE STRUCTURES

Marine structures are either structures built along shoreline or on water. These structures are designed to serve a specific purpose. They may be built to reduce erosion along shoreline or widen the beach or to protect the vessels in the harbor from wind action or wave energy.

A few of the marine structures are

BreakwatersQuaysDocksChannels Jetties,etc

Breakwaters

Quays

Docks

Jetties

The seminar mainly deals on these marine structures:

Mound breakwaters Special breakwaters Docks

Introduction:

Natural harbours

Semi-natural Harbours

Artificial harbour

Breakwaters

• The protective barrier constructed to enclose the harbour and to keep the harbour water undisturbed by the effect of heavy and strong seas are called breakwaters.

Breakwater along Shoreline Breakwater protecting Harbour

Forces acting on breakwaters

Hydrostatic force External forces : Wind and wave actionSolvent action of seawater Sea insects

RUBBLE MOUND TYPE BREAKWATER

Characteristics of mound breakwater:

Dissipation of kinetic energy of incoming waves is done in stages by different layers of mound.

No binding materials are required between layers of stone.

No special bond is required between the layers of construction.

Natural foundation is unprepared.No possibility of overturning and sliding.

Advantages of mound breakwater

• Low in initial cost of materials of construction, equipment for construction and labour required.

• There is no possibility of uplift, since the construction is porous.

• Construction is flexible. Hence, any weak point created at any level is transferred to top, which is above water surface and hence can be repaired easily.

• Dissipates the energy of incoming water wave most efficiently.

DIS-ADVANTAGES OF MOUND TYPE BREAKWATER

• Settlement of mound takes place for first few years by adjustment of voids between adjacent stones and by rolling down of some stones. This requires continuous maintenance for first few years.

• Construction of mound is in the form of pell-mell fashion, hence when projection of stones is chipped by water, the stones role down the slope producing gaps, which makes the mound weak.

• The inner side of mound cannot be used for loading or unloading.

• Huge quantities of materials are required for mound construction.

Special type breakwaters

Floating type breakwater Hydraulic breakwater Pneumatic breakwater

Floating type breakwater

Hydraulic breakwater

Docks

Dry docksWet docks

Dry Docks The arrangement in a

Dry Dock is to take in a vessel, close the door and pump out the water.

The dry docks are used for repairs of vessels

Wet Docks

• The Docks which are used for berthing of vessels to facilitate loading and unloading of passengers and cargo are known as Wet Docks.

Advantages of docks:

• Uniform level of water is maintained which is very convenient for handling cargos. It increases the commercial activities of port.

• It prevents the rubbing of the sides of ships against the quay walls.

• Effects of storms in the outer sea and harbour do not obstruct the dock enclosure

DIS-ADVANTAGES OF DOCKS:

• The main drawback of wet docks is that costly arrangements have to be provided for locks and lock gates and more time will be required for entry and exit.

Conclusion: Marine structures facilitate the ships to

take in and discharge passengers and cargo, provide repair, docking facilities under protected conditions. Marine structures are subjected to destructive forces like wave and wind forces, which carries enormous kinetic energy other than hydrostatic and uplift pressures. Hence careful Analysis and design of marine structures is required.

Thank You