19 June 2001
Floating drydocks are ship or U-shaped structures that are sub-
merged by flooding to permit a vessel to enter and then pumped
dry to raise the vessel out of the water.
Marine railways consist of a ramp extending into the water, a
mobile ship cradle on wheels or rollers, groundway ship cradle
tracks, hoisting machinery, and chains or cables for hauling the
ship cradle endwise or sidewise. Figure 2-5 shows a marine
Ship lifts consist of platforms that are lowered into the water to
receive ships. The ship is then lifted out of the water on the platform
by electrical powered hoist equipment. Figure 2-5 shows a vertical
ship lift drydocking system.
More detailed discussions of drydocking and marine railway facilities
can be found in NAVFAC MIL-HDBK-1029, Graving Drydock and MIL-HDBK-
1029/3, Drydocking Facilities Characteristics. Maintenance of drydocking
facilities is not specifically covered in this manual.
Coastal Protection Structures. Structures designed to reduce the
erosive effects of wave action, or to protect harbors from excessive wave action
and the formation of sandbars, are classified as coastal protection structures.
The common coastal protection structures are seawalls, groins, jetties, and
breakwaters. NAVFAC MIL-HDBK-1025/4, Seawalls, Bulkheads, and Quaywalls
and the U. S. Army Corps of Engineers, Shore Protection Manual provide
additional information on the design and configuration of coastal protection
structures. Maintenance of coastal protection structures is not specifically
covered in this handbook. Bulkheads are included, however, because they are
an integral part of solid fill piers.
2-2.5.1 Seawalls. Seawalls are massive coastal structures built along the
shoreline to protect coastal areas from erosion caused by waves and flooding
during heavy seas. Seawalls are constructed of a variety of materials including
rubble-mounds, granite masonry, or reinforced concrete. They are usually
supplemented by steel or concrete sheet pile driven into the soil and are
strengthened by wales and brace-type piles. Figure 2-6 shows three seawall