Tolerances of errors in pile foundation construction allows maximum errors that can be occur during manufacturing process. Beyond these tolerances, the piles may be rejected for use.
Different types of pile foundations have different tolerances for their fabrications which are discussed below.
Tolerances of Errors in Pile Foundation ConstructionFollowing are tolerances for various types of piles:
1. Steel bearing pilesDimensional tolerances of steel bearing pile sections shall comply with the BS 4360. Fabrication tolerances for steel bearing piles and related steelwork shall comply with BS 5950: Part 2.
2. Precast concrete pilesThe manufacturing tolerances for precast concrete piles shall comply with the following requirements: (a) The external cross-sectional dimensions shall be within 0 mm and +6 mm of the specified dimensions. (b) The wall thickness of hollow spun concrete piles shall be within 0 mm and +25 mm of the specified thickness. (c) There shall be no irregularity exceeding 6 mm in a 3 m length along the face of the pile measured using a 3 m straight edge. (d) There shall be no irregularity exceeding 25 mm in a 3 m length along the internal face of hollow spun concrete piles measured using a 3 m straight edge. (e) The centroid of any cross-section of the pile shall not be more than 12 mm from the straight line connecting the centroids of the end faces of the pile. For the purpose of determining the centroid, the centroid of any cross-section of a hollow pile shall be determined by assuming that the pile has a solid section.
3. Hand-dug caissons foundationsThe centre of each section of the shaft shall lie within 50 mm of the centreline of the whole shaft.
4. Tolerances for pile installations(1) Piles, including hand-dug caissons and mini-piles, shall be installed to within the tolerances stated in Table -1. (2) Piles that do not comply with the specified tolerances shall not be forcibly corrected.
Table-1: Tolerances of installed piles
|Land Piles||Marine Piles|
|Deviation from specified position in plan, measured at cut-off level||75mm (15mm for mini-piles)||150mm|
|Deviation from vertical||1 in 75 1 in 100 for mini-piles||1 in 25|
|Deviation of raking piles from specified batter||1 in 25|
|Deviation from specified cut-off level||25mm|
|The diameter of cast-in-situ piles shall be at least 97% of the specified diameter.|