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Control of Foundation Piles:

Foundation piles are constructed as accurately as possible as per designs and drawings either vertically or to the specified batter. Ultimate care must be taken with respect to the installation of single piles or piles in two different groups. Tolerances for Pile Construction are given below as a reference.

Permissible Tolerances for foundation Piles
Liner Driving work in Progress

Tolerances for Foundation Pile as per IS2911:

  • For vertical driven or bored cast-in-situ piles an angular deviation of 1.5 percent and for raker piles an angular deviation of 4.0 percent should not usually be exceeded except exceptional cases.
  • Foundation piles should not deviate more than 75.00 mm or 1/6 times of its diameter whichever is less and for piles having more than 600mm diameter deviation should be 75.00mm or 1/10 times of its diameter whichever is higher from their designed coordinates at the operational level of the piling rig/platform. 
  • In case of a single pile in a column, positional tolerance should not be more than 50 mm or 1/6 times of its diameter whichever is less and for piles having more than 600mm diameter deviation should be maximum of 100mm.
  • In some exceptional cases, greater tolerance may be prescribed for marine piles/driven over water and for raking piles. 

Beyond the above tolerances for pile and to such an extent that the resultant eccentricity of applied load cannot be taken care of by the redesign of pile cap or pile ties, the Foundation piles must be replaced or extended by one or more additional piles.

Foundation Piles alignment checking in progress
Pile Alignment Checking in Progress

Permissible Tolerances for Foundation Piles as per MORTH:

Precast Concrete Pile for foundation:

Sl NoDescriptionTolerance (millimetre)
i.Cross-sectional dimensions± 5.00
ii.Length± 25
iii.Surface irregularities5 mm with 3 m straight edge
iv.Bow for total length1mm/m length (max. 20mm)

Driven Piles for foundation:

Sl NoDescriptionTolerance (millimetre)
i.Cross-sectional dimensions+50 mm, -10 mm
ii.Deviation75 mm
iii.Tilt1 in 150
iv.Pile top level± 25 mm

Bored Piles for foundation:

Sl NoDescriptionTolerance (millimetre)
i.cross-sectional dimensions+50 mm, -10 mm
ii.Deviation50.00 mm
Iii.Tilt1 in 150
iv.Pile top level± 25 mm

Raker (inclined) piles for foundation:

Sl NoDescriptionTolerance (millimetre)
i.Maximum rake for bored piles1/6
ii.Maximum rake for cast-in-situ piles1/6
iii.Maximum rake for precast driven piles1/4

Control of Bentonite Slurry for Piling:

Where bentonite slurry is used to maintain the stability of the pile borehole, the properties of the material must be carefully controlled at stages of mixing, supply to the borehole and immediately before concrete is placed. The permissible Tolerances for bentonite piles are as under:

  • The fresh bentonite slurry density: 1.05-1.10 g/cc as per subsoil condition
  • The density of return bentonite for pile (boring only): below 1.12 g/cc
  • The marsh cone viscosity of bentonite suspension should be between 30 to 40 second for foundation piles
  • pH value: It should be between 9.5 and 12 for bentonite slurry
  • The silt content: less than 1% for fresh bentonite slurry
  • The sand content of return bentonite (boring only): below 2.5%
  • The liquid limit of bentonite: is not less than 400%

The property as mentioned above of bentonite slurry shall act as controlling factors for preventing contamination of bentonite the slurry for clay and silt.

Other Limitations and Guidelines for Pile Foundation:

  • The pile construction materials shall conform to the specifications for materials given in Section 1000.
  • Minimum cement content of Foundation piles concrete should be 400kg/cum.
  • The minimum water-cement ratio of design concrete mix should be 0.40
  • Concrete slump for precast concrete pile should be 75mm-150mm, and for the cast in-situ concrete pile by tremie pipe should be 150mm-200mm
  • Concrete placing with the help of tremie pipe shall be a continuous operation from the toe level to the cutoff level of the pile.
  • Piles shall be cast up to a minimum height of 600 mm above the cutoff level of the pile foundation.
  • Tremie pipe should have a uniform and smooth cross-section inside.
  • No pile shall be constructed within 3.0m of a newly cast pile until at least 24 hours after completion.

Defective Pile:

  • If defective piles are formed, they shall be removed or left in Position whichever is suitable without influencing the performance of the nearby piles or the cap as a whole. After redesigning of the pile group, supplementary piles shall be provided to replace them as necessary.
  • If there is significant variation between the pile depths at which nearby piles in a group meet refusal; a boring shall be done nearby to determine the root of this difference. If the boring proves that the soil comprises pockets of highly compressive material below the level of the shorter pile, it may be required to take all the pile to a level below the bottom of the zone containing such pockets.
  • Any variation from the designed location of the pile, alignment with coordinates or load capacity of any pile shall be noted, and satisfactory measures are taken well before the concreting of the pile cap or plinth beam.
  • After three days of pile casting manual chipping may be permitted; while breaker for chipping shall not be allowed before seven days after pile concreting.

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Summary
Tolerances for Foundation Piles - Important Guidelines
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Tolerances for Foundation Piles - Important Guidelines
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Ultimate care must be taken with respect to the installation of single piles or piles in two different groups. Tolerances for Pile Construction are given below as a reference.
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Construction Civil
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