Pile Design and Construction Practice, Fifth edition

Ground investigations, contracts and testing 517

Hollow precast concrete piles can be checked for alignment in a similar way to steel tubes.
It would be advantageous if manufacturers of jointed precast concrete piles were to provide
a central hole in each unit, or in a proportion of the piles cast, down which an inclinometer
could be lowered on the completion of driving.
The use of accelerometers and strain transducers to measure stresses in piles at the time
of driving has been described in Section 7.3. This equipment gives a useful check on
workmanship at the construction stage.

11.3.2 Driven and cast-in-place piles

Table 11.2 is a suitable form of record. Generally the procedure for recording driving
resistances and sets is similar to that described in the preceding section, but in the case of
proprietary piles the piling contractor decides the criteria for the final set.
The concrete should be tested for compliance with the specification for materials and mix-
ing and cubes or cylinders taken daily for compression tests. The quantity of concrete placed
in the shaft of each pile should be recorded as a check against the possible collapse of the soil
during the withdrawal of the tube. By checking the level of the concrete as each batch is
placed an indication is given of possible ‘necking’of the shaft. The volume of concrete in an
enlarged base should be recorded as a check on the design assumptions for the diameter of
base. A check should be made on the level of the reinforcing cage after withdrawing the drive
tube on every pile driven. This is a safeguard against the concrete being lifted with the tube.
Thin shell piles should be inspected before placing the concrete by shining a light down
the hole. This reveals any torn or buckled shells.

11.3.3 Bored and cast-in-place piles

The Table 11.3 record gives information required in the ICE Specification and complies
generally with EC7, Clause 7.9, but as for displacement piles, records have to be provided

Figure 11.5Measuring set and temporary compression on driven pile (a) Arrangement of straight-edge
and paper card (b) Pencil trace showing set and temporary compression.

Paper fixed to

pile by adhesive

tape

Pencil

Fixed support

Straight-edge

held against face

of pile

Temporary

compression Set per blow

(a)

(b)