J

Closed relieving platform

Open relieving platform

High level platform

Figure 3-7. Types of wharves and quaywalls.

ture is of more serious concern. The main type of fenders and components that are found on older and smaller piers are fender pile systems. For modern larger piers, various types of fenders are attached to the pier, and they include:

• Rubber units in compression or shear (various shapes: cylindrical, rectangular, trapezoidal, wing, etc.).

• Buckling column (various shapes).

• Pneumatic (air filled) shapes.

• Foam filled (typically cylindrical shape).

3.2.1.5 Dolphins. Dolphins (Figure 3-8) are groups of piles placed near piers and wharves or in turning basins and ship channels. These structures are used to guide ves sels into their moorings, to mark underwater structures, to moor vessels to, to berth vessels against, and to support navigational aids.

3.2.1.6 Dry docking Facilities. Drydock-ing facilities are used for construction and maintenance of ships and barges. The different types of drydocks include:

(a) Graving drydocks are fixed basins adjacent to the water's edge and are constructed of stone masonry, concrete, or sheet pile cells. They can be closed off from the waterway by a movable water barrier (usually called a caisson). After closing the caisson, the basin is pumped dry allowing the vessel to settle on the blocking. The caisson and drydock seals and sealing surfaces need to be inspected and serviced (this topic is discussed in Section 3.10).

3.2.2 Coastal Protection Structures

Coastal protection structures are designed to reduce the effects of wave action, so as to protect harbors and reduce the formation of sandbars. They can be fabricated out of a variety of materials including concrete, rock rubble, granite masonry, and reinforced precast concrete armor units as shown in Figure 3-9. Typical coastal structures include seawalls, groins, jetties, and breakwaters. These structures are:

(a) Seawalls are massive coastal structures built along the shoreline. Their primary function is to protect areas from erosion caused by waves or flooding.

(b) Groins (Figure 3-10) are designed to minimize coastal erosion by controlling the rate of shifting sand by influencing offshore currents and waves. Groins project outward, perpendicular to the shoreline.

(c) Jetties extend outward from shore to prevent the formation of sandbars and direct the flow of water from currents, tides, and waves.

(d) Breakwaters are generally located outside the entrance of a harbor, anchorage, or coastline. They are designed primarily to protect the inner waters and shoreline from the effects

(b) Floating drydocks are ship or U-shaped of heavy seas. Breakwaters may be con-structures that are submerged by flooding. Af- nected or detached from the shore, ter flooding, the vessel enters. The dock is then pumped dry which raises the vessel out of the water for maintenance or repair.

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Walkway

Mooring Foro*

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