Hong Kong Regulations

BUILDING (CONSTRUCTION) REGULATIONS - REGULATION 26

Pile foundations

(1) All pile foundations shall be of adequate load carrying capacity and of
recognized type suitable for the ground conditions.

(2) The allowable load on pile foundations shall be determined by-

   (a)  acceptable foundation engineering principles; or

   (b)  tests on the foundations on site, with an adequate factor of safety
        appropriate to the type of pile, taking into account ground
        conditions, the method of installation and group effects.

(3) Where pile foundations are installed through a stratum which is likely to
undergo consolidation after the foundations are in place-

   (a)  the frictional resistance of the consolidating stratum and the
        overlying soil shall not be taken into account in the determination of
        the load carrying capacity; and

   (b)  the downward frictional force exerted from the consolidating strata
        and the overlying soil shall be considered as imposed load.

(4) Subject to the provisions of subregulation (5), the spacing of piles shall
be determined with due regard to the nature of the ground, the method of
construction and the group effects and shall be sufficient to prevent damage
to the piles or any adjacent construction.

(5) The centres of all piles deriving their resistance mainly from friction
and of all driven piles shall be placed-

   (a)  not less than the length of the perimeter of the pile or 1 m,
        whichever is the greater, from the centres of adjacent piles; and

   (b)  not less than half the length of the perimeter of the pile or 500 mm,
        whichever is the greater, from the site boundary.

(6) Where piles are placed in such proximity that the load carrying capacity
of the piles may be affected by other piles a pile group shall be deemed to
exist and the allowable load on any group of piles shall not exceed the sum of
the load carrying capacities of the piles in the group multiplied by a group
reduction factor determined in accordance with subregulation (7).

(7) The group reduction factor shall be determined by recognized foundation
engineering principles with respect to the bearing capacity and settlement of
the pile group taking into account all the circumstances including the nature
of the ground, the length and spacings of the piles, the size of the group and
the method of construction.

(8) The driving of piles shall take into account the properties and
deformation characteristics of the pile, hammer and cap-block in order that
the driving energy will be applied in such a manner so as not to damage the
material of the pile.

(9) Subject to the provisions of subregulation (8), all driven steel and
precast reinforced concrete piles shall be designed with an average
compressive stress on the nominal cross sectional area at working  load not
exceeding-

   (a)  0.4 uw/F, in the case of precast reinforced concrete piles; and

   (b)  0.6 fy/F, in the case of steel piles, where fy is the yield stress of
        the steel, uw is the specified grade strength of the concrete, and F
        is the design safety factor on driving, with a minimum value of 2 for
        dead and imposed loads and 1.6 for combined dead, imposed and
        wind loads. (Enacted 1990)