Breakwater Structures

hydraulic-engineering works for the protection of water areas in ports and outer harbors from the effect of waves and, in some cases, of ice and debris. Such structures are constructed on open or partially protected shores of seas, lakes, and reservoirs.

In terms of their layout, breakwater structures are classified as moles and jetties. Breakwater structures may consist of one or two moles, a jetty, or a combination of them, depending on local conditions, the shoreline, the direction and type of seas, and the purpose of the port. An open ship channel, the gateway of the port, is left between the mole and the jetty. The gateway is usually situated where the natural depth is adequate for navigation. In this case two requirements are taken into consideration—the ease of entry into and departure from the port in any weather, and provision for minimum penetration of waves through the gateway to the inner water area of the port. In the optimum solution, the axis of the entrance to the port and the direction of the prevailing winds form an angle of about 45°.

Breakwater structures are arranged in such a way as to create water areas that are convenient for the berthing and maneuvering of a specific number of vessels of specific dimensions. The shape and dimensions of the water area should provide for attenuation of waves that penetrate the port’s gateway. Where local conditions are complex, testing of the planned arrangement of the breakwater structures in the laboratory using a three-dimensional model in a tank is advisable.

On the seaward side, each breakwater structure ends in an enlarged head portion, which has a streamlined shape. The heads are usually constructed in water not less than twice as deep as the estimated wave height. The need for stronger construction of the head portions of breakwater structures results from the more intensive wave action on them as compared to the rest of the structure.