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SCREW SPLICED CONCRETE PILE

The screw spliced concrete pile is built up of prefabricated reinforced concrete sections. Each concrete section has a continuous central reinforcement bar with a screw thread. The sections are joined together by means of this screw thread so that a pile is built up with continuous reinforcement. The splice can resist compressive forces, tensile forces and bending moments. In order to prevent corrosion, the screw splice can be protected from the environment by enveloping it in grease and by fitting a sealing ring.

The pile sections are manufactured with great precision. In particular the end faces are tooled so that they are exactly at right angles to the pile axis. In this system it is impossible to fit the sections together skewed, so that a completely straight pile axis is produced.

The screw spliced system is an improvement compared to the methods used for connecting sections in the past with respect to flexural rigidity, straightness of the pile, tensile strength, flexural strength, corrosion resistance, reliability and cost price. Due to the improved mechanical properties of the splice it has become possible to provide this sectional pile with an enlarged base or base plate.

The pile is driven with a drop hammer. A special elastic driving cap has been developed for this which provides the best alignment between the drop hammer and the pile. This means that as much as possible of the pile-driving energy is used to drive in the pile and only a small amount of this energy is transmitted to the surroundings in the form of vibrations. This technique also makes it possible to drive the piles deep into the bearing stratum by using a relatively small drop hammer, so that a large bearing capacity can be attained. Various sizes of pile-driving rigs are available for this pile system. The pile is very suitable to be used in places where the working space is confined or the access is limited.



APPLICATIONS OF SCREW SPLICED PILES:
  • when the working height is limited or access space is confined;
  • as a tension pile;
  • when the pile has to resist bending moments or horizontal forces;
  • when the building time is short;
  • if a horizonatally rigid pile is required in the event that there are obstacles in the ground;
  • it is possible to work without the danger of explosion;
  • electrical machines can mostly be used, so that no exhaust gases are released.



TECHNICAL INFORMATION ON SCREW SPLICED PILES:

  • Dimensions 210 mm 280 mm
    length of concrete pile sections: 1,5 m 1,5m oder 2m
    grade of concrete: C35/45 C35/45
    central bar: GEWI reinforcement bar 20 mm 28 mm
    grade of steel 500/550 500/550
    minimum tightening moment 350 Nm 500 Nm;
  • The slices near or above the ground water table (usually the splice between the top two sections of the pile) are protected against corrosion by fitting a closed cell polyethylene sealing ring and enveloping them in grease;
  • Maximum angle deviation of pile head: 0.01 rad;
  • The pile can be provided with an enlarged base or a base plate.
    side of triangular base plate or base  
    surface area of base
    210 mm

    365 mm
    0,0573 m
    280 mm

    485 mm
    0,102 m;
  • Length of pile: depending on soil conditions up to a maximum of approx. 30 m;
  • Mechanical properties
    allowable shaft bearing capacity  
    allowable tensile force
    allowable bending moment for a pile
    under compressive force
    210 mm
    550 kN
    90 kN

    7,5 kNm
    280 mm
    950 kN
    180 kN

    16,5 kNm

    In the case of small or large axial forces and in tensile forces, the allowable bending moment in the pile only depends to a slight extent on the distribution of the reinforcement. The same requirements (reinforcement percentage) should be set on the central reinforcement bar for the forces which arise during the transport or pile-driving of the pile and in most cases during use as are set on a prefabricated concrete pile.

  • Maximum rake 6:1;
  • Minimum working height of 3 m, minimum access width required from 0.7 m;
  • Minimum distance from centre of pile to a wall: from 400 mm, depending on the dimensions of the pile, the required type of machine and the working space available;
  • Monitoring and testing: recording the set of the pile per number of blows.

Subject to alteration

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