Large diameter bored pile under casing

The large diameter bored pile with temporary steel casing is a cast-in-place cylindrical concrete pile. The pile is a non-displacement pile, bored by means of a recoverable steel casing and - if necessary - water overpressure.

Construction chart

Construction sequence

Installation process in accordance with the requirements of NBN EN1536:1999

1. Positioning and drilling of the first section of the drill casing (recoverable steel casing as temporary support during the boring process)

2. While drilling, the drill casing – inside equipped with a drilling head fixed on a rod - is oscillated into the soil. (back and forth movement / twisting in place)

3. & 4. As the drilling process progresses, soil is removed from the borehole by the excavating tool (« bucket barrel » excavating the pile shaft) and additional sections of casing are jointed (added) to protect the soil from collapsing into the borehole during drilling. When drilling in non-cohesive soils below the groundwater level, a water overpressure (delta h) should be created in the temporary casing.

5. After reaching the design depth, clean-up of the borehole front, removal drilling tool, drilling fluid (water) pumped out from the bore.
Formation of the pile : insertion and lowering of the reinforcement cage, pouring of the concrete. In the presence of water, concreting is carried out by means of a plunger tube to avoid segregation of the concrete (tremie pipe technique).

6. During the continuous concreting process, the temporary casing elements are progressively withdrawn whereby the concrete forms the pile shaft.

Fields of application

• Executed as single pile, contiguous or secant pile wall

• Suitable for high point loads, important horizontal loads and bending moments

• Bearing or embedment in firm strata or hard rock possible

• Obstacle drilling (when other techniques cannot be implemented)

• Important installation depths (up to > 50 m)

• Create piles with a cut-off level beneath the working platform level possible

• Infrastructure works, important industrial projects, large buildings

Environmental impact

• Vibration-free

• Pile with soil extraction: removal of spoil from the job site is required

• Provision should be made to handle the eventual drilling liquid

• A stable, dry and flat work platform is required.

Technical specifications

• Extensive range of standard diameters from 620 up to 1.500 mm

• The temporary casing is a guarantee to a stable boring: it acts as support during the boring process and prevents any possible collapse of the subsoil

• Concreting is carried out by means of a plunger tube to avoid segregation of the concrete (tremie pipe technique).

• To reduce the part of the pile to be cut off, the execution of non-concreted lengths is possible

• The completed pile is reinforced.

• Execution possible with injection along the pile shaft and/or at the pile base

• Execution possible with enlarged base

• Possible execution with limited inclination

• Allowable bearing capacity up to 13,800 kN

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