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What is a Caisson Foundation?
A caisson foundation, also known as a pier foundation, is a waterproof retaining structure that can be used as a bridge pier, in the construction of a concrete dam, or for ship repair. It is a foundation consisting of a prefabricated hollow box or cylinder sunk into the earth to a desired depth and then filled with concrete. Caisson is a foundation. Bridge piers and other constructions that require a foundation beneath rivers and other bodies of water are frequently constructed with this material. This is due to the fact that caissons can be sunk into position after being floated to the project site. Caisson foundations are similar to pile foundations in appearance, but they are built in a different way.
When enough bearing strength soil is found beneath surface layers of weak materials like as fill or peat, it is utilised. It’s a type of deep foundation that’s built above ground level and then sunk to the desired depth by excavating or dredging material from inside the caisson.
Caissons (sometimes known as “piers”) are built by digging a deep pit in the ground and filling it with concrete. Steel reinforcement is sometimes used for a section of the caisson’s length. If a geotechnical engineer determines that the soil is appropriate to sustain the construction weight, caissons are drilled either to bedrock (called “rock caissons”) or deep into the overlying soil strata (called “soil caissons”). When caissons lie on the ground, they are commonly “belled” at the bottom.
Functions of Caisson Foundation
The complex’s foundation system and the soils beneath it prevent it from sliding vertically. Most soils sink when a load is placed on them. When the building settles but the utilities do not, this creates a problem.Differential settlement is even more important than settlement. This happens when different areas of your building settle at different rates, resulting in cracks, some of which may compromise the building’s structural stability. In certain rare cases, though, soils may swell, forcing your construction upwards and causing similar issues. As a result, in order to sustain the building, the foundation system must operate in tandem with the soils.
Watertight boxes made of massive timbers with an open top are known as box caissons. They are usually floated to the desired position and then sunk into the ground using a masonry pier. Excavated caissons are caissons that are placed within an excavated site, as the name implies. These are usually cylindrical in shape and have a concrete backfill. Floating caissons, often known as floating docks, are cylindrically cavityd prefabricated boxes. Small cofferdams that are placed and subsequently pumped dry and filled with concrete are known as open caissons. These are commonly employed in the construction of piers.Pneumatic caissons are enormous, waterproof cylinders or boxes that are mostly utilised for underwater construction.
Drilled Pier Foundations
A drilled pier is a deep foundation system that is built by pouring new concrete into a drilled shaft and reinforcing it with steel. The shaft is built utilising rotary methods, either with a self-contained drill unit or with a crane mounted drill unit. The hole is dug deeper into the soil or rock until it reaches the required bearing stratum. If caving soils or water infiltration become a problem, temporary or permanent steel casings may be employed to preserve the sides of the drilled pit. High axial and lateral loads can be supported by drilled shafts. Shaft diameters typically range from 18 to 144 inches. Drilled shafts (also known as caissons, drilled piers, or bored piles) have shown to be a cost-effective and high-performance deep foundation solution.
Caissons made of concrete A 10′′ or 12′′ diameter hole is bored into the earth and 3 to 4 feet into bedrock. A sort of foundation wall, porch, patio, mono post, or other building that requires structural support.Concrete is poured into the caisson hole after two or more “sticks” of reinforcing bars (rebar) are inserted and run the length of the hole. When there is bad soil, a caisson is employed to rest on an underlying stratum of rock or satisfactory soil. Construction of Caissons The cutting edge is floated to the breakwater by towboat and connected to the caisson guide after some early form work and concrete pours. Concrete is poured into steel moulds that have been constructed.
Inside the box, forms are made around the air domes, and concrete is poured between them. Dredge wells are the open tubes that form above the air domes. The air domes are removed when the caisson reaches the riverbed, and soil is extracted through the lengthy dredge well tubes, as illustrated in the animation below. The caisson sinks to the bottom of the river. Excavation will continue until the caisson reaches the desired depth.Concrete is poured into the bottom 30 feet of the hollow dredging wells as a last phase, and the tops are capped.
Open Caisson Foundation:
Caisson foundations are a type of deep foundation that is built above ground level and then submerged to the required level by excavating or dredging material within the caisson. Caisson foundations (also known as pier foundations) are constructed by auguring a deep hole in the ground and filling it with concrete.It’s frequently utilised in the construction of bridge piers and other structures that need to be supported beneath rivers and other bodies of water.We will study about caisson foundations, types of caisson foundations, and how caisson foundations are built in this section.
The top and bottom of an open caisson are both open; they are hollow chambers with a cutting edge at the bottom.By eliminating dirt from inside the shaft (chamber), the shafts sink into place until the bearing reaches the stratum. An open caisson usually enters through a dry or wet building area or a man-made island. To raise the ground surface above the sea level, a sand island is created. As a result, a dry region is obtained in which to submerge the caisson; the sand island’s size should be sufficient to give a working space around the caisson. It is not viable to immerse the caisson in dry areas, built-in overflow, or a barge before transporting it to its final site in this situation.
Pneumatic Caisson Foundation:
When the surrounding earth cannot be dug satisfactorily, a pneumatic caisson is necessary.When there is a chance of a steady flow of water or difficult impediments during submersion, it also functions.Pneumatic caissons have an open bottom and a closed top.
A working chamber at the bottom of the pneumatic caisson maintains compressed air for the stress required to prevent water and dust from entering the chamber.The pneumatic caisson’s production process is similar to that of open caissons, and the working chamber remains airtight.Open caisson foundations have the same ultimate load-carrying capability and slicing-edge.
Caisson foundations, also known as pier foundations, are prefabricated hollow substructures designed to be constructed.
Caisson foundations is a form of deep foundation that is built above ground level, then submerged to the required level by excavating.
Caisson is used as a foundation for bridges piers, and abutments in rivers, seas, lakes, breakwaters, and other shore construction work.