cofferdam

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cofferdam,

temporary barrier for excluding water from an area that is normally submerged. Made commonly of wood, steel, or concrete sheet piling (see pilepile,
post of timber, steel, or concrete used to support a structure. Vertical piles, or bearing piles, the most common form, are generally needed for the foundations of bridges, docks, piers, and buildings. Slender tree trunks, roughly trimmed and about 10 in. (25.
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), cofferdams are used in constructing the foundations of dams, bridges, and similar subaqueous structures and for temporary drydocks. If double sheeting is utilized, the space between the sheets is usually filled with clay and gravel. When great strain or pressure is likely to be encountered, as in deep water, the pneumatic caissoncaisson
[Fr.,=big box], in engineering, a chamber, usually of steel but sometimes of wood or reinforced concrete, used in the construction of foundations or piers in or near a body of water. There are several types.
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 is preferred to the cofferdam.

Bibliography

See L. White and E. A. Prentis, Cofferdams (2d ed. 1956).

Cofferdam

 

a narrow airtight compartment separating neighboring units on a ship. It prevents the penetration from one compartment to another of gases given off by petroleum products. Cofferdams, for example, isolate living quarters from tanks of liquid fuel. Freight tanks on tanker ships are separated by cofferdams from bow compartments and machine rooms. Cofferdams are filled with water during the transporting of cargoes with low flash points. Gases accumulating in cofferdams are removed by means of ventilation systems. Many obsolete war-ships had cofferdams, called waterproof compartments, situated along the sides of the ship not protected by armor; they protected against the penetration of water through underwater punctures.


Cofferdam

 

a watertight barrier for protecting hydraulic engineering structures or work sites from flooding during construction or repair. Cofferdams are built of earth (either dry fill or alluvial deposits), rock fill, or wood; more rarely, they are built of concrete and metal.

cofferdam

[′kȯ·fər‚dam]
(civil engineering)
A temporary damlike structure constructed around an excavation to exclude water.
(naval architecture)
A void between two bulkheads designed to separate two adjacent liquid-containing compartments.

Cofferdam

A temporary, wall-like structure to permit dewatering an area and constructing foundations, bridge piers, dams, dry docks, and like structures in the open air. A dewatered area can be completely surrounded by a cofferdam structure or by a combination of natural earth slopes and cofferdam structure. The type of construction is dependent upon the depth, soil conditions, fluctuations in the water level, availability of materials, working conditions desired inside the cofferdam, and whether the structure is located on land or in water (see illustration). An important consideration in the design of cofferdams is the hydraulic analysis of seepage conditions, and erosion of the bottom when in streams or rivers.

Types of cofferdams for use on land: ( a ) cross-braced sheet piles, ( b ) cast-in-place concrete cylinder; and in water: ( c ) cross-braced sheet piles, ( d ) earth damenlarge picture
Types of cofferdams for use on land: (a) cross-braced sheet piles, (b) cast-in-place concrete cylinder; and in water: (c) cross-braced sheet piles, (d) earth dam

Where the cofferdam structure can be built on a layer of impervious soil (which prevents the passage of water), the area within the cofferdam can be completely sealed off. Where the soils are pervious, the flow of water into the cofferdam cannot be completely stopped economically, and the water must be pumped out periodically and sometimes continuously.

A nautical application of the term cofferdam is a watertight structure used for making repairs below the waterline of a vessel. The name also is applied to void tanks which protect the buoyancy of a vessel.

cofferdam

A temporary watertight enclosure around an area of water or water-bearing soil, in which construction is to take place, bearing on a stable stratum at or above the foundation level of new construction. The water is pumped from within to permit free access to the area.

cofferdam

1. a watertight structure, usually of sheet piling, that encloses an area under water, pumped dry to enable construction work to be carried out. Below a certain depth a caisson is required
2. (on a ship) a compartment separating two bulkheads or floors, as for insulation or to serve as a barrier against the escape of gas or oil
References in periodicals archive ?
The entire work area was thoroughly cleaned of any debris or foreign material related to the work, and the lines were re-bedded and buried, using the clean fill previously used for cofferdams.
At one site, the divers relied on underwater sliplining to repair two 42-inch diameter siphon pipes, while at the second site specially constructed cofferdams provided a solution to allow repairs to be made in the dry to a 60-diameter siphon pipe.
Construction of the foundations involves making a concrete base layer inside the cofferdams and assembling a steel cage made out of 190 tonnes of steel reinforcing bars.
Investigations have placed the blame for the accident on the inadequate and unstable structure of steel cofferdams at the construction site, severe defects in the project procedures and regulation violations during the project supervision process, according to sources with the work safety committee under the Chongqing Municipal government.
Abuse of the streams (2 cofferdams, temporary bUsage and sink)
On June 20, DWR personnel, a crew from the California Conservation Corps, and crane operators from Teichert rescued 193 fish before completely draining the aqueduct section between temporary cofferdams.
The project includes - All earthworks for the derivation of the bed of the Giffre and working platforms for carrying out four piers and abutments,- The construction of access tracks,- And rockfill embankments adjacent to the supports of the structure,- The restoration of the initial state Giffre bed after work,- The viaduct on the Giffre (4 batteries, length: 300 ml) - Abutments with deep foundations (piles)- Cofferdams, with deep foundation piles (piles)- Composite deck,- Sealing,- Coated on deck,- Equipment and superstructures- Networks- 20 ml portion of pavement side of the structure.
The Portadam system creates temporary, portable cofferdams for use in construction and above-ground impoundments for natural gas fracking water storage and retention.
Construction involves cofferdams, drilled shaft foundations, cast in place substructure and piers, high strength structural steel plate girders and cast in place concrete deck with an asphalt riding surface.
Following completion of the new structures, the temporary cofferdams will be removed and the site restored.
The scope of the civil work Granite will complete includes construction of cofferdams, workpads and guide walls; removal and replacement of the existing riprap and bedding; the installation of geotextile and geomembrane fabrics and placement of all earthfill materials.
The temporary cofferdams would be removed and the site restored after completion of the new structures.