Bored piles
Encyclopedia: Bored piles
Bored pilesCompliant with DIN EN 1536
Bored piles are used as foundation elements where high loads must be transferred to deep, load-bearing soil layers. Soil is loosened and extracted during the pile manufacture. An entire pile volume’s worth of soil may be extracted during the process, or just part of it.
A well-known method used in specialist civil engineering is the bored pile, also known as the large bored pile. Bored piles are fabricated using rotary drilling rigs, hydraulic casing machines and specialist drilling equipment.
Our DIN EN 1536 compliant pile systems include:
- Bored piles
- Partial displacement bored piles (PDP)
- Continuous flight auger piles (CFA piles)
Hamburg Kasematten: Herstellung unter beschränkter Höhe im Greiferverfahren
© PORR
Applications
We use bored piles as deep foundation elements for all kinds of constructions.
Suitable projects include:
Bridges
Industrial buildings
Residential and commercial structures
Office buildings and hotels
Construction projects near sensitive areas or structures
These piles can be used in limited height conditions.
We can also arrange multiple bored piles in a line to create bored pile walls as a form of temporary construction pit system.
Advantages
Owing to the many possible variants, these piles can provide economically optimised solutions for every construction site situation and soil type.
The advantages of bored piles
- Bored piles can be fabricated with little noise and no vibration. This pile system is particularly suitable for foundation works in built-up areas and where neighbouring buildings are vulnerable to the effects of vibration.
- Bored pile dimensions can be tailored to suit high tensile and compressive loads. Moreover, large-diameter bored piles are resistant to bending and very well suited to taking horizontal strain.
- Gripper boring procedures with casing machines enable bored piles to be used in limited height conditions.
- Perpendicular piles and raking piles can be used at angles of up to 4:1.
- Piles can be bored straight through obstructions and hard soil layers.
- Equipment can be used flexibly for pile fabrication, enabling a variety of construction types including bored pile walls.
- They can even be used as energy piles, with the bored piles conducting geothermic energy.
The advantages of partial displacement bored piles (PDP)
- Small-diameter partial displacement bored piles can be quickly and economically installed with limited material consumption.
- In addition, the displacement effect ensures higher load bearing capacities than conventional bored piles.
- As the soil is partially displaced, this also reduces transport and disposal costs for the extracted cuttings.
- The reinforcement cage is constructed within the protection of the large hollow stem before concreting.
- This method can even be used for energy piles, with the PDP piles conducting geothermic energy.
- Perpendicular piles and raking piles can be used at angles of up to 4:1.
- These piles can be installed with no vibration and little noise.
The advantages of continuous flight auger piles (CFA piles)
- High drilling capacity makes these piles an economical choice.
- They are also suitable for pre-drilling through hard soil layers.
- These piles can be installed with no vibration and little noise.
Basic principles
Quality assurance
Quality assurance in construction work requires the observation of both European and national standards. The design and manufacture of bored piles are governed by Eurocode 7 and DIN EN 1536 and subject to the recommendations of the “Pfähle” working group (EA Piles). The self-monitoring and documentation of construction execution are also regulated by manufacturing standards.
Bored pile fabrication procedures must be individually tailored to the requirements of the specific method used. This requires specialist knowledge and experience in the field, together with sound instincts on the part of the machine operator. Large specialist machinery must be handled with sensitivity and due attention to the optimum adjustment of manufacturing parameters if the desired pile resistance is to be achieved.
We ensure high execution quality with:
- Individually tailored procedures
- Adherence to the requirements of DIN EN 1536, Eurocode 7 and EA Piles
- Clear processes overseen by our quality management system in accordance with DIN EN 9001:2005
- Static and dynamic pile loading tests
- Pile integrity tests
Design variants
Herstellungsverfahren Bohrpfahl
© PORR
As a general rule, the borehole is supported by casing until the concrete is introduced. Where piles are particularly long, however, there is a risk that casing may become stuck in the subsoil or may even break off.
In this scenario, boreholes may be supported with casing at the top, while deeper layers are instead supported by a pressurised liquid. This prevents the bore wall from breaking up or sagging. The soil is loosened and extracted using a kelly drill or, with particularly long bored piles, a cable dredger and gripper drill.
The supporting liquid, which will later be displaced by fresh concrete, generally consists of a suspension of bentonite clay. This clay can also be used to manufacture cast in situ concrete diaphragm walls. Where groundwater or supporting liquid is present, underwater concrete must be made and inserted.
Herstellungsverfahren Teilverdrängungsbohrpfahl
© PORR
Partial displacement bored piles (PDP) are created by screwing in a continuous auger drill with a large hollow stem diameter while maintaining lateral soil displacement and only partially extracting the soil to a previously determined depth. The auger drill is equipped with a waterproof seal in the form of a non-recoverable foot plate. After the reinforcement cage has been inserted into the hollow auger stem, concrete is pumped in and filled right up to the surface. The auger drill is then removed, generally without rotating. The foot plate detaches at this point and pumping and extraction continue as the vacated space is immediately backfilled with concrete.
Herstellungsverfahren Schneckenbohrpfahl
© PORR
Bored piles using a continuous auger drill with a small hollow stem are also referred to as continuous flight auger piles (CFA piles). With this method, the soil is not laterally displaced. Instead, as the auger drill is extracted, the soil is completely removed. The reinforcement cage is inserted or vibrated into the fresh concrete after pouring. CFA piles are an extremely economical solution for relatively low pile loads and pile lengths, and comparatively quick to manufacture. The vibration-free and low-noise fabrication process makes this option particularly well suited to inner-city projects.
