Contractor examines a steel pile cage which provides additional strength for concrete inserted in bored foundation excavations.
Steel reinforced cages are inserted into underground bored (piled) excavations to give strength to the concrete that will be poured into the pile. These cages are usually fabricated on site, first by tying the structure together by using wire and then by welding the cage so it can be lifted safely into position. A heavy structure, like a tall building or a bridge, is usually built on piles if the ground beneath its base does not have an adequate weight-bearing capacity to support the structure. The piled foundation becomes an integral part of the structure that carries and transfers the load of the structure to stable weight-bearing ground, which may be located at some depth below the ground surface Historically, piles were made from timber but now are more likely to be fabricated from steel or steel-reinforced concrete. Deep foundation rotary bored piles are constructed by using a huge drilling rig mounted on a crawler crane (often with a combined weight of 40-80 tonnes). This rig will drill vertically into the ground inside a circular steel casing that has been driven down using a special vibrating hammer to provide temporary support to the excavation. The excavated ‘spoil’ is brought up periodically on the drill screw and is spun or shaken off. When a pile has been excavated to the design depth, a steel reinforced cage is inserted and the pile is filled with concrete. Once the concrete has set, the temporary casing is withdrawn using the vibrating hammer. Piles are drilled in a particular pattern and, once a section of piles is completed, a concrete ‘pile cap’ is formed over them which will distribute the weight of the structure evenly between the piles.
Size: 3310px × 3309px
Location: London, UK
Photo credit: © qaphotos.com / Alamy / Afripics
License: Licensed
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