Installation of bored piles by a kelly-bar with or without a casing pipe (diameter 620mm, depth up to 31m)

Using of casing pipes is applied for drilling through unstable grounds to prevent caving of walls of a borehole.

Immersion of casing pipes should be done during a borehole drilling by means of a rotor and a rig. The rotor provides a column by swinging movement.

The rotor and the rig spin a casing pipe into the ground using the weight of the rig and a powerful winch.

Pulling of these casing pipes is made by means of a power applied by the winch through a system of polyspasts.

For a pile installation is required to use concrete with strength no less than class B15, W4-12. Concrete mix should be agile and has a cone slump 16-20cm at the fraction of applied chip 5-20mm.

Piles can be reinforced by a space frame made from armatures of periodic profiles (die-rolled section) not less than class AIII and if it’s required by rigid reinforcement. Pile reinforcing is made according to additional calculation.

This technology of bored piles installation by a kelly-bar with or without a casing pipe enables to install the following constructions:

  • single piles;
  • pile clusters;
  • “slurry-type walls” structures from tangent and contiguous bored piles.

“Slurry-type walls” structure is a frame filling and bearing structure, which enables to build underground structures close to existing buildings, as well as inside of operating premises.

Casing pipe enables the following:

  • block horizons of running soils;
  • provide security of piling works;
  • control parameters of a borehole;
  • guarantee high quality of a hole concreting.


Advantages of the technology:

  1. High reliability enables to control a drilling process with achieving of a base layer.
  2. No dynamic and vibration impacts to soils.
  3. Enables drilling and extracting of boulders encountered at the depth.
  4. Having a reinforced frame in a borehole, it enables to fill it through a concrete pipe. If the technology is observed there is no necking.
  5. Verification of the real engineering and geological conditions to the project requirements is fulfilled while drilling.
  6. Possibility to install a widening at the bottom of a pile (a foot of pile) enables to use a pile’s bearing capacity in full.

Specifics of the technology:

  1. In some cases it is required to find another design decisions that allows using of a pile bearing capacity in a full.
  2. To prevent boiling (pile heave) while drilling water saturated soils it is required to make a big ground plug or return pressure by water or mud solution.


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2015 KGS-Astana