Note: Descriptions are shown in the official language in which they were submitted.
81796770
PILE COMPRISING A SUBSTANTIALLY CYLINDRICAL SHAFT
Description
The invention concerns a driven pile comprising a substantially cylindrical
shaft,
wherein the shaft provides a first pile end and a second pile end, wherein a
socket is
arranged on the driven pile in the region of the second pile end, wherein the
socket or
the driven pile has an abutment In the region of the second pile end so that a
further
driven pile can be inserted with a first pile end as far as .a maximum
Insertion depth
defined by the abutment.
Driven piles of the kind set forth in the opening part of this specification
are
already part of the state of the art and are shown for example in WO
2013026510 Al.
Driven piles are driven into the bedrock by a driving apparatus. The term
bedrock is
used for example to denote the ground. When the first driven pile has been
driven Into
the bedrock a further driven pile can be Inserted into the upper end of the
driven pile
which has already been driven in. The further driven pile isjoined to the
first driven pile
by the action of force which Is also implemented by the driving apparatus. In
the state
of the art that join is made by frictional engagement and force-locking
engagement.
The state of the art however does not always guarantee that the force for
separating
two or more driven piles is greater than the initial joining force which has
been-applied
with the driving apparatus. In other words the tensile force which the driven
piles which
are driven into each other can carry is too low for many areas of use. An
Increase in
that tensile force above a'value of the joining force applied for joining the
piles Is only
possible with difficulty. Other systems operate for example with the
incorporation = of
additional components like for example spreader elements to increase the
tensile force
between the individual piles by the tip of the driven piles being widened. In
that case
however cracks can occur, which In turn give rise to problems In regard to the
tensile
force and strength and stability of the connected driven piles and complicate
the
system.
The object of the invention is to avoid the above-described disadvantages and
to provide a driven pile which is improved over the state of the art.
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81796770
According to an aspect of the invention, there is provided a driven pile
comprising a substantially cylindrical shaft, wherein the shaft provides a
first pile end
and a second pile end, wherein a socket is arranged on the driven pile in the
region
of the second pile end, wherein the socket or the driven pile has an abutment
in the
region of the second pile end so that a further driven pile can be inserted
with a first
pile end as far as a maximum insertion depth defined by the abutment, wherein
the
socket and/or the driven pile in the region of the second pile end provides or
provide
in the interior at least one undercut portion extending at least substantially
to the
abutment, wherein the undercut portion is provided by the change in the
cross-section of the socket from a substantially circular cross-section at the
second
pile end to a cross-section at the inner abutment, that deviates from the
circular
cross-section.
According to another aspect of the invention, there is provided a
method of joining at least two driven piles as described above, wherein the
method
includes the following steps: driving a driven pile into a bedrock with a
driving
apparatus, wherein the driven pile is driven with the first pile end leading
into the
bedrock, inserting a further driven pile with the first pile end into the
socket of the
preceding driven pile, that is provided with an undercut portion, and driving
it in by
means of a driving apparatus, driving in to the required depth of the
arrangement of
driven piles, wherein in the driving-in operation the first pile end adapts to
the internal
contour of the socket, and filling the arrangement of driven piles with a
filling material
for impeding return deformation of the first pile end which is deformed by
virtue of the
undercut portion.
The fact that the socket and/or the driven pile in the region of the
second pile end in the interior provides or provide at least one undercut
portion
extending at least substantially as far as the abutment ensures that, after a
further
driven pile has been inserted and driven in, under the effect of a force, it
is joined in
positively locking
la
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relationship to the driven pile which has been previously driven into place,
by virtue of
the undercut configuration. By virtue of that join the arrangement comprising
interconnected driven piles can withstand very high tensile forces in
comparison with
the state of the art. In addition no further components like spreader elements
are
required.
Further advantageous embodiments are defined in the appendant claims.
Further details and advantages of the present invention will be described more
fully hereinafter by means of the specific description with reference to the
embodiments by way of example illustrated in the drawings in which:
Figure 1 shows a detail view of two joined driven piles,
Figures 2a and 2b show cross-sections of the driven pile, and
Figures 3a through 3c show individual steps in joining the driven piles.
Figure 1 shows a sectional view of two driven piles I (not illustrated in
their
entirety). The driven piles 1 are formed from a substantially cylindrical
shaft 2 providing
a first pile end la and a second pile end lb. As shown in Figure 1 the first
pile end la
fits in the socket 3 of a further pile 1. In that case the first pile end la
is driven into the
socket 3 as far as the abutment 9. At the second pile end lb the socket 3 has
a
substantially constant socket wall thickness WMcon. Starting from the first
pile end lb
along the maximum insertion depth T which is defined by the abutment 9 the
socket
wall thickness varies from the constant socket wall thickness WMcon to the
variable
socket wall thickness WMvar. That variation in the wall thickness affords an
undercut
portion 8 which extends at a maximum angle a in the interior of the socket 3
of
between 1.5 and 3 measured relative to a longitudinal axis L. In other words
that
undercut portion 8 is provided by the change in the cross-section of the
socket 3 from
a substantially circular cross-section Qk at the second pile end lb to a cross-
section
Qa which deviates from a circular cross-section Qk and which is disposed at
the inner
abutment 9. Figure 1 shows a section A-A which is described more fully in
Figure 2b
and shows the change in cross-section from the cross-section Qk to Qa as a
plan
view.
The driven pile 1 which is of a substantially tubular configuration, with its
shaft
2, is of a substantially constant shaft wall thickness Ws at least along its
maximum
insertion depth T, starting from the first pile end la. In this embodiment
that shaft wall
thickness Ws is less than the socket wall thickness WMvar and WMcon. Due to
the
smaller shaft wall thickness Ws the shaft 2 is deformed, and not the region of
the
socket 3, that is formed by the greater socket wall thicknesses WMvar and
WMcon. In
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other words, the driven pile 1 is more easily deformable at least in the
region along the
insertion depth T by virtue of the smaller shaft wall thickness Ws and/or also
a softer
material structure, than the remaining region of the driven pile 1. The
material from
which the driven pile 1 is made is at least partially and preferably
completely ductile
cast steel or ductile cast iron. The abutment 9 is a contact surface which is
in the form
of a kind of shoulder substantially perpendicular to the longitudinal axis L
of the driven
pile 1. By virtue of the configuration in the form of a shoulder the first
pile end la can
no longer penetrate more deeply into the driven pile 1 upon coming into
contact with
the abutment 9. By virtue of the upsetting of the shaft 2 under the effect of
force the
shaft 2 must adapt to the contour of the undercut portion 8 in the region
thereof. That
takes place along the insertion depth T. As a result, that involves a very
gentle uniform
deformation of a round cross-section to a cross-section with a plurality of or
even only
one undercut portion 8. The gentle uniform deformation ensures that no cracks
are
formed in the shaft 2. In accordance with that principle driven piles 1 can be
anchored
in a suitable bedrock in a condition of being secured together without using
individual
components to resist tensile forces or ¨ if necessary also individually - .
Figure 2a shows the second pile end 1 b of the socket 3. The socket wall
thickness is constant in the region of the second pile end lb. The circular
cross-
section Qk thus forms a constant socket wall thickness WMcon. Subsequently the
first
pile end la of a further pile 1 is introduced internally into that constant
socket cross-
section WMcon until it reaches the abutment 9 under the action of the force
involved
and is upset there. The first pile end la is not shown in Figure 2a.
Figure 2b shows the section A-A which was shown in Figure 1 in the side view
of the arrangement comprising two driven piles 1. The variable socket wall
thickness
WMvar occurs with increasing insertion depth T (shown in Figure 1) from the
constant
socket wall thickness WMcon shown in Figure 2a. The change in the socket wall
thickness from WMcon to WMvar affords the undercut configuration 8. In this
embodiment the undercut configuration 8 is produced by a trilobular
configuration. In
other words the cross-section Qa which differs from a substantially circular
cross-
section Qk is provided by the shape of a trilobular configuration, three
undercut
regions 8a, 8b and 8c being produced by the trilobular configuration. A cross-
sectional
shape other than a trilobular configuration is also possible in the production
of at least
one undercut portion 8. The end of the undercut portion 8 in the interior of
the socket 3
and/or the driven pile 1 is afforded by the abutment 9. The variable socket
wall
thickness WMvar can be both greater in its thickness than the constant socket
wall
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thickness WMcon and also smaller than same. This provides that when the first
pile
end la is being driven in the diameter of the shaft 2 is portion-wise
stretched and also
compressed. As a result the periphery of the shaft 2 is completely retained
upon
upsetting of the shaft 2 in the region of the undercut portion 8, even if the
diameter of
the shaft 2 is expanded portion-wise and reduced elsewhere. By virtue of that
deformation of the circular cross-section for example to a trilobular
configuration or a
polygonal configuration, the periphery is not changed upon portion-wise
alteration of
the shaft 2 in the region of the first pile end la. This very careful
variation in cross-
section at the shaft 2 prevents cracks being formed ¨ cracking would lead to a
reduction in the tensile strength of joined driven piles.
Figure 3a shows portions of a driven pile 1 which is placed with its first
pile end
la over the second pile end lb of a further driven pile 1 with a socket 3. It
is possible
to see the undercut portion 8 and the abutment 9. The shaft diameter DSA of
the shaft
2 is almost the same as the opening cross-section of the socket 3 at the
second pile
end lb.
Figure 3b shows how the shaft 2 of the pile 1 is introduced into the socket 3
of
a further driven pile 1. In this case the shaft 2 begins to adapt to the
inside wall of the
socket 3. A slight change in cross-section or a portion-wise change in the
shaft
diameter DSA at the shaft 2 begins.
Figure 3c shows how the shaft 2 of the driven pile 1 was placed in the socket
3
of a further driven pile 1. The shaft diameter DSA' has adapted portion-wise
to the
inside dimensions of the socket 3. By virtue of upsetting of the shaft 2 by
the co-
operation of the abutment 9 and the undercut portion 8 the shaft diameter DSA
is
increased or reduced in size relative to the adapted shaft diameter DSA'.
After
connection of the at least two driven piles 1 by upsetting in the undercut
portion 8 a
filling material 10, preferably concrete or concrete emulsion, is introduced
in order to
prevent subsequent return deformation of the shaft 2 under a tensile loading
after the
filling material 10 has hardened.
Referring to Figures 3a, 3b and 3c it can be seen that the method of joining
at
least two driven piles 1 comprises at least the following steps:
- driving a driven pile 1 into a bedrock with a driving apparatus, wherein the
driven pile 1 is driven with the first pile end la leading into the bedrock,
- inserting a further driven pile 1 with the first pile end la into the socket
3 of
the preceding driven pile 1, that is provided with an undercut portion 8, and
driving it in
by means of a driving apparatus,
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- driving in to the required depth of the arrangement of driven piles 1,
wherein
in the driving-in operation the first pile end la adapts to the internal
contour of the
socket 3 by crack-free deformation, wherein tensile securing is afforded by
virtue of the
at least one undercut portion 8 ¨ which is preferably afforded by the change
in cross-
section from a substantially circular cross-section to the cross-section in
the form of a
trilobular configuration - ,
- possibly inserting further driven piles 1 and driving them in as described
in the
preceding steps, and
- filling the arrangement of driven piles 1 with a filling material 10,
preferably
concrete or concrete emulsion, for impeding return deformation of the first
pile end la
which is deformed by virtue of the undercut portion 8.
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