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JACKED REINFORCED CONCRETE PILE
(vibration free)

The jacked reinforced concrete pile is built up of sections which are pressed into the ground by a hydraulic system. An existing building or a ballast arrangement provides the reaction necessary for this. The pile is built up of reinforced concrete sections placed on top of each other or is built of steel tubes welded on top of each other. Soil can be excavated from the pile through the hollow pile core so that the pile reaches the required depth without a large reaction being required. When the pile is at the correct depth, an enlarged base is made by compacting metal containers with a dry mortar mixture under the pile. The pile core is filled with concrete. This working method is vibration free.

Since light, dismountable machines are used, this system is extremely well suited for working under difficult conditions and in very confined working spaces.

The jacked reinforced concrete pile is mainly used for underpinning work. The reaction required in this case is usually provided by the building itself by means of a new concrete floor cast on site. Anchors are concreted into this concrete floor and holes are left open through which the piles are pressed. The photograph at the top of this page shows how this method works. By using this technique it is possible to fix the piles onto the floor at a preload.

The minimum working height is 0.8 m. As a result it is possible to force a jacked reinforced concrete pile under an existing foundation. This existing foundation is then used as the counterweight for jacking the pile.

 



APPLICATIONS OF JACKED REINFORCED CONCRETE PILES:
  • for underpinning foundations;
  • where the work has to be carried out vibration free, such as in underpinning the foundation of an unstable structure, near loaded foundation piles or in the vicinity of equipment sensitive to vibrations;
  • when the working height is limited; a reinforced concrete jacked pile can for example be placed under existing foundations;
  • in places which are difficult to reach, for example a cellar or basement; the equipment required can be brought through a very small opening;
  • it is possible to work without welding and without use of combustion engines (at danger of explosion);
  • where work has to be carried out at low noise levels;
  • when very compacted layers of sand are present making it impossible to use pile driving;
  • various applications of this technique in related areas, for example:
    • a steel tube jacked into the ground by using the same method can be used as a casing tube for a hydraulic lift;
    • this technique can also be used to jack sheet-pile walls into the ground.



TECHNICAL INFORMATION ON JACKED REINFORCED CONCRETE PILES:

  • Concrete pile sections:
    Diameter 280 mm, 310 mm, 350 mm;
    Length of concrete pile sections 1 m, 1.75 m, 2 m;
    Grade of concrete: C30/37;
  • Diameter of tubular steel sections: 133 mm, 168 mm, 219 mm, 273 mm, 324 mm, 355 mm, 406 mm, 457 mm, larger sizes are available on request; Length of tubular sections: adjusted to the working conditions;
  • Diameter of pile base: maximum of 1.7 x diameter of pile shaft
  • Length of pile: depends on the depth of the bearing stratum, in principle unrestricted;
  • Maximum bearing capacity: up to 1200 kN, depending on the bearing stratum;
  • Maximum rake: 3:1;
  • Required reaction: in accordance with the specifications, minimum of 100 kN, usually 200 - 400 kN;
  • Minimum working height: 0.8 m, with a minimum access width of 0.5 m;
  • Monitoring and testing:
    The condition of the pile shaft can be checked before the core of the pile is filled with concrete. If necessary the pile tip level can be checked by taking soil samples from the hollow pile core;
  • Settlement of the pile tip due to a compressive force: Compacting the enlarged base ensures that the soil round the pile tip is compressed producing a load-settlement behaviour similar to that of a pure displacement pile.

Subject to alteration

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