Ground investigations, contracts and testing 513standard under the various work classifications. BS8004 can be quoted for working stresses
on the various types of pile, but this is not provided for in limit-state design to Eurocode EC7.
It is not the intention in this chapter to give model clauses for piling work. These can be
drafted with the guidance of the ICE model specifications, BS8004 or other codes, particu-
larly EC7, BSEN 1536 for bored pile execution, BSEN 12699 for displacement piles and
BSEN 14199 for minipiles. Some matters which require particular attention are listed below:
Setting out.The responsibility for setting out is clear if the piling contractor is the main
contractor. The Engineer has no responsibility in the matter but should check the positions of
the piles from time to time, since if these are inaccurately placed the remedial work can be very
costly. Problems arise when a piling sub-contractor does the setting-out from a main contrac-
tor’s grid-lines. If these are inaccurate or if, as sometimes happens, the numbering is obscured
(or level pegs are confused with line pegs) then there can be major errors in pile positions and
the main contractor may decline to accept responsibility for the cost of the replacement piling.
If the specification does not define the responsibility for setting out, the piling sub-contractor
must have a clear understanding with the main contractor on this matter.
Ground heave.In the case of the Method 1 type of contract the Engineer, in specifying
the type and principal dimensions of the pile, must accept responsibility for the effects of
ground heave, as described in Section 5.7. However, if the contract is of the Method 2 category
the matter is not so clear, and piling contractors are reluctant to accept responsibility for
ground heave, either for remedial work to risen piles, or for repairing damage to surrounding
structures. In the case of both Method 2 and Method 3, the authors are of the opinion that
as it is the Contractor who decides on the type and dimensions of the pile, and therefore
should have experience of ground heave effects, the Contractor should accept full responsi-
bility for the site operations. If pre-boring or other measures are insufficient to prevent
ground heave, the Contractor would be well advised to decline to tender.
Loss of ground due to boring.The consequences of a loss of ground while boring for
piles were described in Section 5.7. The responsibilities for these are similar to those
for ground heave.
Noise and vibration.The Contractor is responsible for selecting the plant for installing
piles and is therefore responsible for the effects of noise and vibration (see Section 3.1.7).
The current statutory and local authority regulations limiting noise emissions should be
stated in the specification (or conditions of contract).
Piling programme.If the Engineer wishes to install the piles for the various foundations
in a particular sequence to suit the main construction programme the sequence should be
stated in the specification, since it may not be the most economical one for the piling
contractor to follow.
‘Set’of driven piles.This should not be stated in precise terms in specifications for driven,
or driven and cast-in-place piles. The ‘set’for a particular site and working load cannot be
established until preliminary piles have been driven and the driving records checked against
the ground conditions assumed in design. The set may have to be modified as a result of
loading tests.
Tolerances.Tolerances in plan position, vertical deviation from the required rake, and
deviation in level of the pile head should be specified. Suitable values for tolerances are
given in Section 3.4.12.
Monitoringof piling is mandatory under EC7-1 Clause 7.9 and the BSEN standards for
execution of special geotechnical works, in accordance with a method statement and ‘pile
installation plan’which are consistent with the design.