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NDT tests may be carried out and rated only by an
inspector with adequate qualification. Level 2 of standard
EN 473 can be considered adequate qualification. The
tests are documented for each joint in a test record to be
attached to the inspection record of the piling.
7.6 Pile cut-off
Steel piles are cut at the design cut-off elevations at right
angles to their longitudinal axis. Cutting may be performed
by a cutting wheel or a flame cutter. Any possible burrs
from cutting are removed by a grinding wheel. The required
squareness of the finished cut-off end is <2.0 % and
flatness <2 mm in relation to the perpendicularity of the
axis of the pile unless otherwise indicated in the design.
Working in the immediate vicinity of the cut off of the piles is
prohibited. Safety distance to pile cutting is 2x the length to be
cut or at least 5 m.
If possible, the piles are cut while still attached to the piling
rig. The piles are recommended to cut immediately after the
installation, so the piling rig can safely lift the removed part away.
The length of the pile pipe should be optimized before installation
to prevent long stumps and to make cutting easy. Long stumps
(vertical piles over 3 m and inclined piles over 2 m) are cut and
lifted in co-operation with excavator one pile at the time. When
the length of the stump is 1-3 m, for examples wedges or other
tools are used to guide the falling to right and safe direction.
It is recommended that ends of steel piles are closed after
cutting so that no foreign matter gets inside. Reliable
closing of the pile ends of RD pile wall structures is essential
for job safety since there is the risk of compressed air and
drilling sludge suddenly discharging up through already
installed piles when drilling close to the target level.
The rules of procedure must be paid particular attention when
cutting RR/RD piles so that the part to be removed can not
be lifted / fell directly away. In this case the part which will be
removed must be "peeled open". Due to the manufacturing
methods of pile pipes, there might be stresses left in them.
Therefore cutting of pile by "peeling" must be made in
sequences shown in Figure 16. Longitudinal cut, for the whole
length of the part to be removed, must be made first. After the
longitudinal cut has been made, the pile can be cut normally
from the design cut-off elevation. Cutting must be started
from the point where longitudinal cut has ended.
Figure 16. Cutting a pile by “peeling”.
7.7 Pile cleaning
The cleanness of RR and RD piles with a closed lower end to
be concreted is checked before concreting and any possible
impurities are removed.
RD piles are generally flushed with compressed air in connection
with the extraction of the pilot bit. Any possible drilling mud in the
piles is rinsed off with water. A pile can normally be assumed to
be clean when the water rising up is clean.
The possible cleaning of piles with an open lower end is
planned and implemented case by case.
7.8 Reinforcement and concreting of piles
Reinforcement steels are to conform to EN 10080; other
steels can be used if their properties meet the requirements
of EN 1992-1.
Bar reinforcement of steel piles is done according to Ch. 2,
Sec. 4.6.2 of PO-2016, taking into account, for instance, the
minimum amounts of longitudinal steels, clearance between
steel bars, limitations on concentric longitudinal bar layers,
and transverse steels. According to Standard EN 12699
(Displacement piles), the thickness of the concrete cover
between the inner surface of a pile and the outer surface of
principal reinforcement must be at least 40 mm. When smaller
diameter pipe is used as reinforcement, the minimum concrete
cover is 25 mm according to PO-2016.
The assembly and joining of rebar cages is done according
to Ch. 2, Secs. 5.5.1 and 5.5.2 of PO-2016 whereas the jigs
and centralisers and installation are in accordance with Secs.
5.5.3 and 5.5.4 of PO-2016. It must be ensured that the pile is
clean before the reinforcement is installed in it.
The portions of Secs. 5.7.1, 5.7.2, 5.7.3 and 5.7.4 of PO-2016
applicable to steel pipe piles are observed in concreting.
Concrete is mixed and its compliance verified according to
Standard EN 206-1.
The design strength class of concrete, grouting mortar or
injection grout must be at least C20/25, and the mixing
ratio and consistency of fresh concrete must conform to
Ch. 2, Tables 3.1 and 3.2 of PO-2016, when steel piles are
dimensioned as composite structures. If the concrete or
grouting mortar serves only as a filler to prevent potential
slight corrosion inside piles, strength class C16/20 is also
possible – even C12/15 with RR piles with a closed lower end
– assuming that the concrete is not subject to chemical or
freeze-thaw stress.
The ingredients used in the production of the concrete, grouting
mortar and injection grout must conform to PO-2016 as follows:
•
cement EN 197-1
•
aggregate EN 12620
•
water EN 1008
•
admixtures EN 206-1 and EN 934-2.
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