Figure 8-33. - Steel sheet-pile bulkhead.

A BULKHEAD serves the same general purpose as a seawall, namely, to establish and maintain a stable shoreline. However, while a seawall is self-contained, relatively thick, and is supported by its own weight, the bulkhead is a relatively thin wall. Bulkheads are classified according to types of construction, such as the following:

1. Pile-and-sheathing bulkhead

2. Wood sheet-pile bulkhead

3. Steel sheet-pile bulkhead

4. Concrete sheet-pile bulkhead

Most bulkheads are made of steel sheet piles, as shown in figure 8-33, and are supported by a series of tie wires or tie rods that are run back to a buried anchorage (or deadman). The outer ends of the tie rods are anchored to a steel wale that runs horizontally along the outer or inner face of the bulkhead. The wale is usually made up of pairs of structural steel channels that are bolted together back to back.

In stable soil above the groundwater level, the anchorage for a bulkhead may consist simply of a buried timber, a concrete deadman, or a row of driven and buried sheet piles. A more substantial anchorage for each tie rod is used below the groundwater level. Two common types of anchorages are shown in figure 8-34. In view A, the anchorage for each tie rod consists of a timber cap, supported by a batter pile, which is bolted to a bearing pile. In view B, the anchorage consists of a reinforced concrete cap, supported by a pair of batter piles. As shown in the figure, tie rods are supported by piles located midway between the anchorage and the bulkhead.

Bulkheads are constructed from working drawings like those shown in figure 8-35. The detail plan for the bulkhead shows that the anchorage consists of a row of sheet piles to which the inner ends of the tie rods are anchored by means of a channel wale.

The section view shows that the anchorage will lie 58 feet behind the bulkhead. This view also suggests the order of construction sequence. First, the shore and bottom will be excavated to the level of the long, sloping dotted line. The sheet piles for the bulkhead and anchorage will then be driven. The intervening dotted lines, at intervals of 19 feet 4 inches, represent supporting piles, which will be driven to hold up the tie rods. The piles will be driven next, and the tie rods then set in place. The wales will be bolted on, and the tie rods will be tightened moderately (they are equipped with turnbuckles for this purpose).

Figure 8-34. - Two types of tie-rod anchorages for bulkheads.