Sheet Pile Breakwater

These structures are built with objectives similar to solid vertical barriers. They are usually used where design wave parameters allow for construction of light type structures to dissipate wave energy, or substantially quail the waves.

Sheet pile type breakwaters may be constructed in the form of free-standing walls, or walls supported by battered piles. In the former case the reinforced concrete sheets, or reinforced concrete tubular piles of miscellaneous constructions(steel sheet piling included), are propped either on one side or on both by pile (usually by concrete piles). Unsupported walls are used where foundation soils are competent enough to provide reliable lateral support for sheet piling.

Depending on bottom soil geotechnical conditions, wave parameters, and sheet pile construction, for example, flat planks or tubular piles, the height of the unsupported breakwater may be up to 6 to 8m. The height of the propped sheet pile wall may be much higher.

An example of a propped sheet pile breakwater constructed at the Fisherman’s Wharf on San Francisco Bay is discussed by Thuet(1987). There the interlocking precast pre-stressed concrete sheet pile were used for construction of the 460m long breakwater. Sheeting was supported by precast pre-stressed batter piles and capped with cast in place reinforced concrete cope. Batter piles were used on both sides of this breakwater, except for a 130m long section which bad batter piles on the harbor side only. Two types of sheet pile 76 × 76 cm and 62 cm thick and 102m wide were used. The batter piles 61 × 61 cm were driven into the bottom at a slope 5 (horizontal) on 12(vertical). The size, spacing, and length of both sheet piles and batter piles were designed to resist action of the design wave 1.8m high, and seismic and other horizontal loads. A differential head of about 3.0m was assumed across the breakwater to account for possible scour and liquefaction on the “sea” side and a trough on the “lee” side.

Sheet piles and batter piles were brought together by a cast in place 3.05 m wide and 1.22 m high concrete cap.