Precast Piles – What You Need to Know

Precast piles are mainland Europe’s leading foundation choice and Aarsleff have been installing them in the UK for over 30 years. Supplied by sister company, Centrum Pile, our combined knowledge and expertise means we can deliver projects of almost any scope and size. We’ve answered eight of the most commonly asked questions about precast piles below.

What are precast piles used for?

Due to the possibility of carrying vertical and horizontal loads as well as bending moments, precast piles are used for the foundation of all sorts of engineering structures under virtually every soil condition. Piles can be a single section, or several sections can be jointed to provide longer piles for deeper ground conditions.

How are precast piles installed?

  • Rig delivery into site and setup process, to include permit signature, site inspection, platform inspection, internal induction.
  • Pile delivery arrival and wagons entering site and sighted next to rig
  • Pile unloading, this includes from pile delivery and laying piles down on floor beside pile pin positions. Rig used as a crane for this purpose, you could include methods of unloading on wagons with edge protection etc
  • Pitching piles, lifting from the floor with the hammer line and offering piles into the helmet, then aligning pile over the pile position and ensuring the verticality in x and y
  • Driving piles, and levelling carrying out lift offs to check position as you go including jointing if required and taking final 3 sets
  • Testing of pile

Where are precast piles used?

Piles can be provided in various sizes, formed in high strength concrete, with varying reinforcement. They are particularly useful where there is a need for very deep piles, typically up to 40 meters, in soft ground or in aggressive or contaminated soils.

What is the different between precast and Insitu piles?

The fundamental difference between a driven pile foundation and bored pile foundation lies in their point of manufacture. A driven pile is formed off-site under factory-controlled conditions and a bored pile is manufactured on site and in place.

Bored pile foundations, also known as replacement piles, are typically poured in place and provide support for structures, transferring their load to layers of soil or rock that have sufficient bearing capacity and suitable settlement characteristics. Driven piles are sometimes referred to as displacement piles because in the process of driving the pile into the ground, soil is moved radially as the pile shaft enters the ground. There may also be a component of movement of the soil in the vertical direction.

What are the advantages of precast piles?

  1.  Piles can be precast to the required specifications.
  2.  Piles of various size, length, and shape can be made in advance and used at the site. As a result, the progress of the work will be rapid.
  3.  A pile driven into granular soil compacts the adjacent soil mass and as a result, the bearing capacity of the pile is increased.
  4.  The work is neat and clean and creates no spoil arisings. The supervision of work at the site can be reduced to a minimum. The storage space required is very much less.
  5.  Driven piles may conveniently be used in places where it is advisable not to drill holes for fear of meeting groundwater under pressure.
  6.  Driven piles are the most favoured for works over water such as piles in wharf structures or jetties.
  7.  Driven piles maintain their shape during installation. They do not bulge in soft ground conditions and are typically not susceptible to damage from the installation of subsequent piles.
  8.  Driven piles require no curing time and can be driven in natural sequence rather than skipping alternate piles, thus minimising the moving of the equipment and speeding up installation time.
  9.  The equipment and installation methods are time-tested and well proven. Advances in materials, equipment, methods, and testing continually combine to improve the efficiency of driven piles.
  10. Fewer traffic movements are required to and from a site when compared to alternate piling methods.

What are the disadvantages of precast piles?

  • Advance planning is required for handling and driving, as well as the heavy equipment on site
  • Withstand handling stresses during transportation and installation, pre-cast or pre-stressed concrete piles must be adequately reinforced
  • Driven piles may not be suitable where the ground has poor drainage qualities
  • Driven piles may not be suitable for compact sites, where the foundations of structures nearby may be affected by the vibrations caused by the installation

How long do precast piles last?

Curing precast concrete in the correct environment is essential to longevity of life. Aarsleff install Centrum Piles – cast in-house by our sister company, Centrum Pile. Centrum piles are cured in a factory coded to ISO 9001 and are all certified to BS EN 12794. Quality is of upmost importance and is monitored for every pile, with full traceability built into the Centrum Pile System. This quality assurance combined with Aarsleff’s delivery expertise means that you can be assured of the quality of your solution.

What size are precast piles?

  1. Precast concrete piles are available in various lengths and sizes to suit specific requirements. Our Centrum precast piles are cast in standard square sections from 200mm to 400mm and from 4m in length, increasing in 1m increments to standard lengths of up to 14m.Larger pile sizes are used for large infrastructure projects such as wind turbines, pylons, river bridge foundations, bridge abutments, piers and marine construction.Smaller pile sizes can be used for the above projects but are also used in residential developments and areas with restricted access.Determining the size of precast piles can also vary depending on the below factors:
    • Type of soil and its properties
    • Weight of load coming onto the pile

How deep do precast piles go?

With the benefit of using pile joints, precast concrete piles can be driven to lengths longer than 30m. Often concrete precast piles can be driven down to 30m, however, in special circumstances, such as offshore projects, piles can be driven down to a maximum of 150m.

There is no established depth for foundations; nor is there a simple way of determining suitable depths. Instead, there is a very wide range of foundation types and depths suitable for different applications, depending on considerations, such as:

  • The nature of the load requiring support
  • Ground conditions
  • The presence of water
  • Space availability
  • Accessibility
  • Sensitivity to noise and vibration

Shallow foundations are suitable at a depth of around <2.5 m, any deeper and you would need to look at a suitable piling solution. If the foundations are to be in close proximity to an adjacent structure, care must be taken to ensure the excavation works do not undermine it, nor is additional pressure exerted upon it. The foundation may need to be at least the same depth as the adjacent building’s foundation base.

Conclusion

Precast Piles are a versatile foundation solution, perfect for many needs across different sectors. Aarsleff’s commitment to delivering operational excellence in ground engineering means we are laser focused on creating value within your scheme. Contact us today to discuss your next project.  

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A leading UK ground engineering specialist, focusing on multi-discipline excellence and value engineering. We design and deliver some of the UK’s largest ground engineering projects.

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1947. Central Jutland, Denmark. Per Aarsleff borrowed 10,000 Danish Kroner from his father’s life insurance, bought an excavator, and founded Northern Europe’s leading contracting company.

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