Drilling methods for concrete piles: Insight into the techniques and advantages

Drilling rig for the production of in-situ concrete pilesIn the world of construction, drilling methods play a decisive role in the construction of stable foundations. There are different manufacturing methods. For example, Kelly drilling or auger drilling (SOB pile).

In the drilling process, deep, vertical holes are drilled into the ground using drilling equipment and filled with steel cages and concrete. The pile is essentially responsible for transferring the static loads of the structure as well as dynamic forces acting on the structure into the ground. Overall, pile drilling is an indispensable foundation technique in modern construction, making it possible to erect higher and heavier structures as well as building in poor geological conditions. This in order to withstand the challenges of the times.

In-situ concrete bored piles have the great added value that they make buildings possible in poor geological conditions and also allow the realization of building dimensions that would not or hardly be possible with other measures.


In-situ concrete bored piles: Definition & types

In-situ bored concrete piles are load-bearing elements that are cast directly on site from reinforced concrete. These are available in different versions. These include, for example, the classic Kelly bored piles, auger bored piles and the innovative full displacement piles. Different drilling equipment is used for all types.

Importance of drilling methods for in-situ concrete bored piles

Pile cutter and drilling equipment for the construction of pilesDrilling processes play a decisive role in the production of of in-situ concrete piles. They not only enable precise positioning, but also adaptation to different floor types and conditions on site. Thanks to these drilling methods, deep foundations can be laid and excavations secured.

In-situ concrete bored piles take on the loads in deep foundation projects and transfer them to the stable subsoil. They are indispensable in various construction projects such as tunnels, roads, bridges and flood protection measures.

Drilled pile walls that are contiguous, tangential or secant are often used to secure excavation pits. These are used to secure the excavation pit and stabilize slopes. Sometimes they can also be attached directly to existing buildings.

What are the different drilling methods for in-situ concrete bored piles?

SOB bored piles

Drilling methodAuger bored concrete piles (SOB piles) are produced by using a continuous flight auger. While the auger is being pulled out, the pile is concreted through the hollow core of the auger. This enables higher drilling performance compared to conventional cased bored piles. In addition, the pile reinforcement is inserted into the still fresh concrete to ensure the corresponding internal load-bearing capacity of the pile.

Kelly drilling

Kelly drillingKelly drilling is a tried and tested method. It is one of the most common dry rotary drilling methods. It is suitable for almost all types of soil and rock, especially solid soils. Kelly drilling tends to be used for larger pile diameters (from a size of approx. 500 mm). A well-known feature of this process is the drill pipe, known as a Kelly bar. This is extendable and therefore makes it possible to reach very large drilling depths.

Displacement pile

Manufacture drilling rig for displacement pileDisplacement piles are in-situ concrete bored piles in which a displacement drilling head is screwed and pressed into the ground by a rotary drilling rig. In contrast to other methods, the displacement method does not use an auger to convey the material to be drilled, but a smooth drill pipe with a displacement body at the end displaces it sideways. Once the drilling depth has been reached, the drill pipe is pulled out and fresh concrete is poured in at the same time. The reinforcement cage is then immediately pressed into the not yet hardened concrete. The process can be used in a wide range of soil types as long as it is displaceable soil. This ranges from sandy gravel, silt and clay to soft organic soils. The advantage of full displacement piles: Rather less expensive pile construction method. There is hardly any extracted drilling material that has to be disposed of.

Brextor® - pile breaking method for in-situ concrete bored piles

Pile cutterEfficient, safe and high-quality pile head processing! Brextor® is the innovative solution for processing concrete piles (single piles and pile walls) that is faster, more precise and more environmentally friendly than conventional methods.

Brextor® – A Swiss quality product that is patented worldwide and has already been used in many construction projects worldwide.

Advantages of the drilling process

The various drilling methods for in-situ concrete piles offer a number of advantages, particularly with regard to a wide variety of construction sites, specifications or conditions:

Drilling rigDisplacement piles:

+ Cost-effective

+ Environmentally friendly

+ Almost no drilling waste disposal

+ Very efficient production method

– Only smaller drilling diameters

– Can only be used in displaceable foundations

Kelly drilling method

+ Can be used in almost all floor conditions

+ Can be used from diameter 600 to 3000 mm

+ Piped or unpiped possible

+ Very deep drill holes possible

– Drilled material must be disposed of

SOB Piles

+ Withstand high pressure, transverse and buoyancy loads

+ High drilling performance

+ Also suitable for pre-drilling in solid floor layers

+ Low noise and vibration

Brextor®: the experts for pile breaking

The drilling process is not the end of the work for the deep foundation. Concrete bored piles with steel reinforcement must be exposed and removed (cropped) after the drilling process. This is done using a wide variety of methods.

With the patented Brextor® milling process the dismantling force is under control at all times. The core and surface tension is broken in a single work step. But that’s not all! Brextor® contributes to efficient and sustainable pile head processing:

Pile breaking with Brextor Increased construction quality

Perfectly finished piles without cracks in the pile body or spalling on the pile skin, no bent or torn reinforcements and a height accuracy of +/- 1 cm.

💵 Reduced construction costs

The demolition material consists of 80% gravel 0-30mm and can be reused directly on the construction site. In addition, Brextor® requires less working space than conventional demolition methods. This not only saves costs for transport and disposal, including fees, but also eliminates the need to purchase and supply replacement material. Furthermore, the preparatory work is reduced by eliminating the need for a cut at the definitive demolition height, and the cleaning effort is much lower than with conventional demolition methods.

Shortened processing time

A pile, e.g. with a diameter of 1 m and a removal height of of 1m can be processed within 40 minutes. Thus a Daily output of up to 16 piles possible. With Brextor® you also get a reliable performance and therefore increased planning security.


With Brextor®, the demolition material (80% gravel 0-30mm) can be reused directly on the construction site. In addition, Brextor® requires less working space. This saves excavation and replacement material. Due to the direct reuse of the demolition material on the construction site and the saving of excavation and replacement material, transports can be saved. In addition, landfills are less burdened.

👷Increased health & safety at work

No heavy physical labor is required for pile processing, which massively reduces the risk of health hazards such as HAVS syndrome. Brextor® also avoids working in danger zones.

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