HEK piles - Vroom Funderingstechnieken
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HEK piles

The HEK pile is a cast in-situ, fully displacing screw pile, used in projects for which piles must be installed either vibration-free and/or without excessive noise.

The HEK pile can take different forms; it can be formed with grout injection or as a combi screw tubular pile. The system uses a smooth steel casing with a loose screw point. A hydraulic drill attachment screws this in to the required depth, after which the reinforcements are inserted and the concrete poured. The casing is then removed, with the screw point remaining in the ground. The pile can then be reinforced over the whole length. Depending on the pile driving rig and the nature of the ground, a pile length of up to 48 metres is feasible. The system creates a high load-bearing capacity.

Features of HEK piles 

  • Adjustments to pile specifications may be possible up to shortly before the start of the project and sometimes even during the project.  
  • They can absorb both relatively high compressive force and tensile strain.  
  • They displace soil, so virtually no soil rises to the surface.  
  • The pile system is installed free from vibrations and without excessive noise by means of screwing in the piles.  
  • HEK piles can be reinforced over the entire length with a cage, and can therefore absorb both relatively high compressive force and tensile strain.  
  • They can be finished slightly above the required working level.
Areas of application of HEK piles
  • HEK piles are suitable for the foundations of projects in a built-up area, or where displaced earth coming to the surface or vibrations are unwanted.
  • HEK piles are especially suitable for urban projects in the infrastructure and energy sectors (including wind turbine construction).

Special aspects of HEK piles 

Vroom Funderingstechnieken (Vroom Foundation Technology) can advise you on the use of HEK piles, and the most appropriate type, for any sort of ground. HEK combi piles have a pre-fab concrete core and are highly suited to underground car-parks, tunnels and cellar structures that are lowered into the ground. See also the product description. HEK casing piles can be compared with steel tube screw piles in the mini-sector. In this instance, both the screw point and casing remain in the ground.

Monitoring during formation of the pile

Thanks to the moment of torque registration, pull-down force and drilling time, the operator has access to up-to-date information on the pile being formed and can thus flag discrepancies in the nature of the ground or take appropriate action. The moment of torque, the insertion speed and the friction coefficient serve as an indication for adhering to the sounding.  Water ingress in the screwed tube during the screwing-in process is monitored with a plumb line or stone.

Monitoring following formation of the pile

Because we do our own quality control we are able to respond quickly. If there is any doubt about the pile grade and/or at the principal's request in relation to the project, HEK piles formed by Vroom Funderingstechnieken can be acoustically audited and assessed by an independent firm of engineering consultants.

Concrete quality is tested by drilling into and testing concrete from the core of the pile.

Vroom Funderingstechnieken produces HEK piles using a proprietary process devised as part of internal quality control and in line with nationally-applicable standards. Concrete (and grout) for HEK piles is obtained from certified concrete mixing plants.

Allow us to advise you 

We at Vroom Funderingstechnieken prepare our leaflets and website with the greatest possible care and attention. However, no rights can be derived from such content. If you use information from our leaflets or our website without verification or further advice, this is at your own risk.

Vroom Funderingstechnieken accepts no liability for the correctness and/or suitability of the information for the purpose you envisage. Should you have any questions about the use of our products for actual projects we advise you to contact our sales department.

Technical specifications

General

  • Sealing strip keeps the tube clean and dry while the HEK pile is being screwed in/drilled.
  • Raking piles tilting at gradients of up to 1:3, depending on situation and pile length.
  • Available equipment: concrete pump, loader and bucket.
  • Machine noise level c. 90 dB. The system is considered to be low-vibration to vibration-free.

Drilling rig

  • Continuously regulated, depending on the hydraulic drill attachment.
  • Moment of torque 250 - 500 kNm.
  • Pull down 150 - 400 kN.

Grout injection

HEK piles can be formed with grout injection if required for the integrity of the structure or where the work requires this.

Concrete grade

Grades C20/25, C25/30, C30/37 and C35/45.

Reinforcement

B500B grade, as per Eurocode 2.
It is possible to reinforce the full length of the pile, and the reinforcement can also be recessed.

Bearing capacity

Geotechnical bearing capacity as per Eurocode 7 (NEN 6743).

The screw point is a welded constructed point, adapted to the particular geotechnical circumstances. In some cases the point is cast rather than welded. The ratio of foot-shaft is optimised to Dfoot< √ 1.5 x Dshaft.

The load-bearing coefficients to be used are those stated in Eurocode 2, Eurocode 7 (NEN-EN 12699) and the pile toe level is the bottom of the screwed-in tube.

Pile base coefficient
αp = 0.63
β= 1.0 (Dfoot< √ 1.5 x Dshaft)
S = 1.0 Bearing pile shaft friction αs = 0.009 (αs = 0.009 when using grout injection)

Shaft friction when using tension piles 
αt = 0.009 (αt = 0.009 when using grout injection)

Load/deformation behaviour
As per Eurocode 7 (NEN 6743, type 1, fig. 6 and 7) Load spectrum Depending on the diameter and the nature of the ground the piles may be subjected to both compression and tensile forces.

Load spectrum
Depending on the diameter and the nature of the ground the piles may be subjected to both compression and tensile forces.

Structural aspects

Available tube diameters, dimensions in mm: Shaft (diameter of toe) 

  • 273 (330) * 
  • 324 (395) * 
  • 356 (435) * 
  • 380 (465)  
  • 406 (495)  
  • 456 (560) 
  • 530 (650) 

Other diameters available. Maximum pile length approx. 48 metres, depending on the diameter of the pile and nature of the ground. Long pile lengths will be considered on request.

*Formation of these diameters may be carried out without grout injection.

Process

Vervaardigingsproces schroefpalen type VGS (+grout) 

  1. The steel tube is positioned above the screw point that is at the right point at ground level. 
  2. The hydraulic drilling rig uses the pull-down force to screw in the tube to the correct depth.
  3. Once the tube has reached the correct depth, the reinforcement is inserted. 
  4. Wet concrete is deposited in the tube using a concrete pump or bucket. 
  5. The tube is then removed by vibrating or unscrewing, where the screw point remains in place. 
  6. The pile is finished and the machine is moved to the next position.

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Can we help you with your project?

Contact Paul Bochem. Dial +31(0)299 409 541 or send us an e-mail.

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