Mumbai University > Civil Engineering > Sem 6 > Transportation Engineering 2

Topic : Water Transport

Difficulty : Medium

Docks arc enclosed areas for berthing ships,to keep them afloat at a uniform level, to facilitate loading and unloading cargo.Wet Docks are enclosed and are shut off by entrances or locks to maintain a fairly uniform level of water, and basins are partially enclosed areas of water, which are approached by open entrances and are subject to fluctuations of levels, due to tidal variations.

Advantages of wet docks: (1) Uniform level of water is maintained which is very convenient for handling cargo. (2) Prevents the rubbing of the ships sides against the quay walls. (3) Effect of storms in the outer sea and harbour do not obstruct the dock enclosure.

Repair docks are necessary for the execution of repairs, cleaning and painting of ships bottom. Hence these docks and docking arrangements should be such as to expose, the ship's exterior fully and keep it out of water during the progress of repairs or renovation . There are generally four classes of such docks viz:

1. Graving or dry dock. 2. Floating dock. 3. Marine railway. 4. Lift docks.

1.Graving or Dry Dock: The graving dock, also known as a dry dock is a long, excavated chamber, having side walls, a semicircular end wall and a floor. The open end of the chamber is provided with a gate and acts as the entrance to the dock. The below figure show the plan and an enlarged cross-section of a typical graving dock.

The side walls are formed with a series of steps known as altar courses to receive the ends of the shores which support the vessel in a vertical position while being docked. The dock is constructed of concrete or masonry and the altar courses and steps

A floating dock, floating pier or floating jetty is a platform or ramp supported by pontoons. It is usually joined to the shore with a gangway. The pier is usually held in place by vertical poles referred to as pilings, which are embedded in the seafloor or by anchored cables. In shipbuilding and ship operations the term floating dock refers to a floating dry dock. Frequently used in marinas, this type of pier maintains a fixed vertical relationship to watercraft secured to it, independent of tidal, river or lake elevation