Bored piles
Encyclopedia: Bored piles
Bored pilesCompliant with DIN EN 1536
Bored piles are used as foundation elements when high loads need to be transferred to deeper, more stable soil layers. During construction, soil is loosened and excavated. The volume of soil excavated may correspond to the entire volume of the pile or only a part of it.
A well-known method in special civil engineering is the bored pile, also known as a large-diameter bored pile. Construction is carried out using rotary drilling rigs, hydraulic casing-setting machines and specialised drilling tools.
Our pile systems in accordance with DIN EN 1536 include:
- Bored pile
- Partial displacement bored pile (TVB)
- Auger Bored Pile (SOB)
Hamburg Kasematten: Herstellung unter beschränkter Höhe im Greiferverfahren
© PORR
Applications
Bored piles are used as deep foundation elements for a variety of building construction, structural engineering and infrastructure projects.
These include, amongst others: Construction with height restrictions is possible.
- Bridges Industrial buildings
- Residential and commercial buildings
- Office buildings and hotels
- Adjacent to sensitive structures
Using several bored piles arranged side by side, we also construct bored pile walls to stabilise excavation pits.
Benefits / Features
Bored piles are available in a range of designs to suit different subsoil conditions and project requirements.
Features of bored piles
- Low-noise and low-vibration installation
- Suitable for use in densely built-up areas as well as near structures sensitive to settlement
- Transfer of tensile, compressive and horizontal loads to load-bearing soil layers
- Can be installed where headroom is limited
- Construction of vertical and inclined piles with an inclination of up to 4:1
- Possible penetration through obstacles and solid soil layers
- Use as individual piles or as part of bored pile walls
- Can be constructed as energy piles for use in geothermal systems
Features of Partial displacement bored piles (TVB)
- Construction involving partial displacement of the soil
- Material requirements vary depending on the project
- Reduced soil extraction compared to conventional drilling methods
- Installation of the reinforcement cage within the protection of the core tube
- Can be constructed as an energy pile
- Construction of vertical and inclined piles with an inclination of up to 4:1
- Low-noise and low-vibration construction
Features of Auger Bored Piles (SOB)
- Construction using the continuous auger method
- Also suitable for pre-drilling in compact soil layers
- Low-noise and low-vibration construction
- Construction speed depends on subsoil conditions and project requirements
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.
