Note: Descriptions are shown in the official language in which they were submitted.
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INSTALLING SUBMERGED SUPPORT STRUCTURES
BACKGROUND OF THE INVENTION
This invention relates to the installation of seabed (or river bed) mounted
support
structures that generally project above the surface of the sea (or river).
A possible application for such support structures is for the support of wind
or water
current driven turbines, or wave energy powered devices.
In particular the present invention relates to methods of construction of
support structures
and to the installation for such support structures regardless of their
purpose.
Although said support structures will generally project above the surface of
the sea or river
in which the support structure is installed, the upper part of the support
structure may be
removed if desired after installation has been completed so that in such cases
the
remainder of the support structure i.e. a so-called fixed component may be
left completely
submerged.
It has been found that when providing mounting support structures, for
example, for
submerged off-shore seabed mounted turbine installations a major difficulty in
connection
with such installatios resides in the time required for installing such an
installation in that
the present modes of installation involves the use of large installation
vessels such as a
crane-barge or jack-up barge to be present on site to complete foundation
works. In
practice such vessels are necessary to position the structure but lengthy
installation times
for such vessels not only result in very high costs per installation but also
reduce the
numbers of installations a given vessel can complete in a given time.
OBJECTS OF THE INVENTION
It is an object of the present invention to provide methods of installing and
the
construction of support structures capable of being installed in the sea or in
a river bed that
generally project above the surface of the sea or river regardless of their
intended purpose
but which are generally intended for the support of wind or water current
driven turbines,
or wave energy powered devices.
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It is a particular object of the invention to provide means whereby such
support structures
can be installed even under adverse conditions such as where there is the
likelihood of
strong currents or waves, with reduced attendance required for the
installation vessel.
STATEMENTS OF THE INVENTION
According to a first aspect of the invention there is provided a method of
installing a
support structure required to be installed in a sea or river bed, involving so
constructing the
support structure that is capable of being temporarily self standing on the
sea or river bed
prior to and throughout the carrying out of operations required permanently to
anchor the
support structure to the sea or river bed.
Conveniently the support structure is in the form of an elongate column for
supporting a
submergeable water driven turbine and/or a wind driven turbine.
Preferably the installing of the support structure including the step of
anchoring the
structure to the sea or river bed by means of piles or similar anchoring means
Preferably the support structure incorporates a plurality of anchoring
positions for
cooperation with support structure support foot units, and wherein each said
foot unit is
adapted to receive and locate a support structure anchoring pile or like means
which is
driven/sunk into the sea or river bed by means supported from the support
structure for
enabling the handling and sinking of the piles or like means.
Conveniently the elongate column like support structure is designed so that it
can be
lowered to the sea or river bed and positionally adjusted to allow for any
lack of flatness of
the sea or river bed by adjusting the position of each individual bed engaging
foot, prior to
the sinking of the associated pile .
If considered necessary the method can include the step of adding additional
weight to the
structure In the event that the support structure during the being moved by
currents,
waves or wind so as to maintain installation period of the its installation is
at the risk of
being in insufficient frictional contact with the sea or river bed during the
installation
process.
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A further aspect of the invention provides a support structure capable of
being installed in
a sea or river bed, wherein the structure is arranged to be sufficiently heavy
as to be
temporarily self standing on the sea or river bed by being heavy enough to be
held in
position by friction with the seabed , and wherein said structure incorporates
a plurality of
anchoring positions for cooperation with positionally adjustable sea or river
bed engaging
support feet units with each said unit being adapted to receive and locate a
support
structure anchoring pile which is driven/sunk into the sea or river bed by
means supported
from the support structure for enabling the handling and sinking of the piles.
In a preferred construction a temporary additional structure can be provided
at the top of
the support structure, for mounting/housing facilities for carrying out any
operations
required to sink the piles being used toi anchor the support structure to a
sea or river bed.
In accordance with an further aspect of the invention there is provided a
support structure
capable of being installed in the sea or river bed, wherein the support
structure is
constructed as to be self installable structure in that it is temporarily self
standing
throughout operations required permanently to anchor the support structure to
the sea or
river bed.
In accordance with a further aspect of the invention there is provided a
support structure
for installation on a sea or river bed including a plurality of anchoring
positions provided
with support structure support feet units, means adapted to receive and locate
a
predetermined number of support structure anchoring piles, and means supported
from
the support structure for enabling the handling and sinking of piles such that
serve to
anchor the support structure to the sea or river bed.
In a preferred construction each said foot unit is associated with a
adjustment means for
enabling the positioning of a pile in its anchoring position to be selectively
adjusted.
In a preferred arrangement the support structure incorporates a facility for
enabling the
installation of piles serving permanently secure the support structure to the
sea or river
bed, in such manner as to allow support structure installation vessel involved
with the
installation of the support structure to leave the region of installation as
soon as the
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support structure is positioned correctly with required pile handling
equipment mounted
upon it.
Conveniently, the necessary equipment may be installed ashore so that the
entire self-
installing support structure can be quickly lowered into the desired location
whereby the
delivery vessel may leave the site.
According to a still further aspect of the present invention, there is
provided a jacket type
support structure with at least one footing assembly on which the support
structure can
stand securely on the sea or river bed with the upper part of the support
structure tall
enough to project above the water surface.
Conveniently, in situations where it is desirable for the final support
structure to be
submerged, a removable upper part may be fitted which projects above the
surface for the
installation phase for the support structure phase and which following the
installation
phase is subsequently removable.
Conveniently the upper part is removed using a crane mounted upon a boat.
In a preferred construction the support structure is provided with three or
four footing
assemblies.
Preferably, the support structure is designed so that it can be lowered to the
sea or river
bed, levelled to allow for the lack of flatness of the sea or river bed to
enable each footing
assembly to be fixed to the sea or river bed by drilling through each such
assembly, the
insertion of pin-piles and the grouting said pin piles in place.
Conveniently the drilling process is carried out from a temporary structure
mounted on top
of the jacket of ajacket type support structure.
In the event that the support structure during the installation period of the
its installation is
at the risk of being moved by currents, waves or wind extra weight may be
added to the
temporary structure to maintain sufficient friction with the sea or river bed
during the
installation process, and wherein the extra weight may be removed together
with the
installation equipment after anchoring pin-piles have been installed so the
support
structure can no longer displace relative to the sea or river bed.
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From the above it will be noted that the invention provides a structure
capable of being
installed in the sea (or in a river), which is designed to be temporarily self
standing by
being heavy enough to be held in position by friction with the seabed and
which has
facilities to support equipment needed to permanently affix it to the sea (or
river) bed
5 using pin-piles or other fixtures capable of penetrating the sea (or river)
bed through
tubular permanent footings integral with the jacket structure. If necessary
extra weight to
generate sufficient friction to prevent movement may be temporarily provided
as ballast
added to the structure and removed after the pin-piling operation has been
completed.
Thus there is provided a structure with a jacketed base having one or more
permanent
tubular footings which can be drilled through from a platform mounted above
water level
into the sea or river bed, and into which pin-piles may be inserted and
grouted into place.
In particular the structure includes temporary footings that can be adjusted
for height and
alignment to permit the structure to be levelled before fixing to the sea or
river bed, the
force for so doing being provided by hydraulic jacks, screw jacks or any other
such
appropriate mechanisms.
Conveniently said temporary adjustable footings may be attached either in
board or
outboard of the permanent footings of the jacket or concentric with the
permanent
footings.
Conveniently the structure has provision for conductor tubes to be positioned
and aligned
between the above water surface platform or superstructure and tubular
permanent
footings close to sea level, such that a drill string can be deployed from a
drilling rig on the
superstructure through the conductor tube and the tubular footings so as to
drill a hole for
foundation pin-piles or alternatively to hammer apin pile into the seabed.
BRIEF DESCRIPTION OF THE DRAWINGS
For a better understanding of the invention and to show how to carry the same
into effect
reference will now be made to the accompanying drawings in which:-
Figure 1 schematically illustrates the general construction of a support
jacket structure
involving the concepts of the invention;
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Figures 2A, 2B, 2C and 2D respectively illustrate to a larger scale the
features of the
construction of support feet involved with the structure shown in Figure 1;
Figure 3A schematically illustrates a first positioning of the support feet of
the structure
shown in Figure 1 relative to a sea or river bed;
Figure 3B schematically illustrates a further possible positioning of the
support feet of the
structure shown in Figure 1 relative to a sea or river bed; and
Figures 4 to 10 schematically illustrate successive stages in anchoring the
support jacket
structure of Figure 1 to a sea or river bed using pin piles.
DETAILED DESCRIPTION OF THE DRAWINGS
Referring now to Figure 1 the support structure 1 illustrated therein includes
a jacket
structure 2 including an upstanding monolithic column like main body 3
supported by a
support leg assembly 4 formed by four similar support foot units 5 which are
equiangularly
disposed around the column 3. Each foot unit 5 includes a central tubular
structure
formed by an inner tube SA and an outer tube 5B to be considered in detail
herein after
and a sea or river bed engaging foot 7 that is connected with the outer tube
5B. The outer
tube forms part of the assembly 4 that is itself connected to the main body 3
of the
structure 2 by way of a generally horizontal member 8 connecting with the
lower end
region 9 of the main body 3 of the structure 2 and an inclined member 10
connecting with
the main body 3 of the structure 2 at a location above the associated
horizontal member 8.
Each sea/river bed engaging foot is mounted to the lower end of the tube 58 by
way of a
pivotal connection arrangement 11 that allows the foot 7 to be raised or
lowered relative
to the outer tube 5B as required to co-operate with the profile of the sea or
river bed
region upon which the foot 7 is required to rest. The arrangement of the
concentric tubes
can be regarded as the anchorage footings for the jacket structure.
The connection arrangement 11 is such that the foot 7 is able to tilt relative
to the inner
tube 5A so as to be angularly disposable relative to the vertical axis of the
central structure
of the associated support foot structure 5 The foot 7 is also axially
displaceable up and
down relative to the assembly 4 thereby facilitating acceptable co-operation
between the
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foot 7 and the adjacent sea or river bed SB in such manner as to enable
support
adjustments to be effected to ensure that the main body 3 of the jacket
structure 2 is level
with the body vertical.
Since it is intended that the jacket structure 2 should be firmly and securely
anchored to
the sea or river bed SB the support leg assemblies 4 and the support
structures 6 are
intended to be secured to the sea or river bed.
In the embodiment illustrated it is intended that the structure 2 is to be
anchored to the
sea or river bed by pin piles (not shown in Figure 1) that are positionally
located by the
support foot units 5.
In other words the foot units 5 have an essentially dual purpose of which one
serves to
provide firm support to the jacket strucrture2 during its initial installation
i.e., during a
positioning and anchoring process and the second of which is to facilitate the
insertion of
the pin piles.
For the purposes of the jacket positioning and anchoring stages of the
installation
processes the upper part of the jacket mounts a temporary superstructure 12
such that the
latter is located above the water level WL.
The superstructure 12 may carry means such as a crane or other forming of
lifting and
positioning means 13 for handling the pin piles and other elements that are
required during
the positioning and anchoring stages of the support structure 1. These
elements can
comprise a drilling rig, pile driving apparatus together with the various
elements of
equipment associated with hole drilling and the positioning and lowering of
the pin piles.
The super structure 12 can additionally serve to receive any additional
weights 14 that are
considered necessary to hold the jacket in its required position during its
installation that is
to ensure the friction with the sea or river bed SB during installation
remains effective to
prevent any movement under the influence of currents waves and/or wind.
In relation to the position and anchoring of the structure 2 a further
important feature
which is illustrated by Figure 1 is the provision of a conductor tube 15 shown
in the process
of being positioned by the crane 13 to engage with the top of one of the inner
tubes 5A of
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the foot units S. This conductor tube 15 is intended to be clamped or held in
position at
the top of the inner 5A in order to provide guidance and protection during
drilling and pin
pile installation and grouting, as will be described hereinafter with the help
of further
Figures of the drawings.
It is important to note that generally in practice the conductor tube 15 will
be lowered into
position and guided by wire cables (not shown) attached to the top of the
jacket foot unit
inner tube 5A and threaded through a pair of 'eye bolts' (not shown) near the
base of the
conductor tube 15. In this way the cables will guide the conductor tube 15
accurately into
position.
The mechanisms for effecting such adjustment will be described in more detail
herein after
and may not necessarily be positioned as shown in the Figures of this
Application. It should
be noted that the jacket structure 2 can mount/carry other forms of structure
to that as
shown. For example, a lattice framework or a multiplicity of vertical columns.
Reference will now be made to Figures 2A - 2D which illustrate the
construction of the feet
units 5 in greater detail and to a larger size. -
In particular these Figures 2A - 2D show as has been previously mentioned that
the
adjustable feet units 5 may be used for levelling the structure 1 after it has
been lowered
by a crane-barge or other transport vessel to the sea (or river) bed SB. In
the embodiment
used to illustrate the principles involved it can be seen that there are two
hydraulic rams or
jacks 16 provided upon each foot unit 5 that can be operated from above the
surface
either together or differentially so as to raise or lower the foot 7 or to
incline it at an angle.
The Figures 2A-2D illustrate how both vertical and angular adjustment may be
obtained
and then fixed by pressurising the rams or jacks 16. The upper ends 17 of the
rams or jacks
16 are pivotally connected to a bracket 18 mounted to the leg unit outer tube
5B whilst the
lower ends 19 of the rams or jacks are pivotally connected to the inner tube
5A connected
to the associated leg unit foot 7.
As may be noted from Figures 2A and 2B differential operation of the rams or
jacks 16
appropriately tilts the associated leg unit foot 7. The tilt is schematically
indicated by the
tilt angle indication arrows TA.
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As may be seen from Figures 2C and 2D the rams or jacks 16 can be operated to
raise or
lower the leg unit foot 7 relative to the remainder of the leg unit 5. The
vertical adjustment
is schematically indicated by the arrows VA.
It will be understood that tilting can be combined with the height adjustment
as is enabled
by the construction of the leg assembly.
In practice, other forms of adjustment may be used such as screw jacks (either
electrically
or hydraulically activated), inflatable bags (inflated with liquid or gas) or
indeed any
convenient device capable of applying the necessary forces may be used. If
necessary more
than two such rams or jacks 16 may be provided so as to share the loads. It
will be shown
that said lifting or jacking devices only require to be functional for the
duration of the
installation process and may either be abandoned (i.e. sacrificial) or
recovered for re- use
on other projects afterwards.
Referring now to Figures 3A and 3B these Figures 3 illustrate how the
adjustable foot units
5 need not necessarily be located at positions concentric with the footings 5D
of the
support structure 2 the case of Figure 2. As can be seen from Figures 3A and
3B the foot
units 5 can either be mounted on footings 5D located within the spread of the
assembly 4
as shown in Figure 3A or they can be mounted on outrigger structures outside
the foot
units 5 as shown in Figure 3B. The former arrangement is considered to be more
economical with materials while the latter is possibly more stable as a
structure. By
positioning the adjustable foot units 5 separately from the jacket structure
footings 5D moe
space is made available for the drilling and pin-pile installation and
additionally this
arrangement simplifies the structure of the footings.
It will be noted that in the embodiments shown in Figures 3A and 3B the foot
units 5 are
effectively totally separate from the arrangement of Figure 1 in which the
tubes 5A and 5B
form footings for the structure and which are additionally intended to receive
the
conductor 15. In the case of the embodiments of Figures 3A and 3B the foot
units 5 each
incorporate an inner element 5E depending from the associated horizontal bar
11 and an
concentric outer tubular element 5F.
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Referring now to Figures 4 to 10 which disclose successive stages in the
anchoring of a
jacket support structure 2 as shown in the previous Figures by means of pin
piles . Thus
Figure 4 illustrates a first stage in the procedure for permanently fixing the
jacket footings
to the sea (or river) bed (SB) Whilst Figure 4 represents by way of example an
embodiment
5 in which the adjustable feet units 5 are concentric with the footings 5B of
the support
structure 1. It should be noted that since as explained in the previous
paragraph said
adjustable foot units 5 may also be employed separately from the jacket
structure 2 in
which case they would not be visible n Figure 4.
Thus Figure 4 in fact illustrates the stage at which the conductor tube 15 has
been lowered
10 into the inner tube 5A of the tubular structure of the jacket foot unit 5
until its lower end
rests on the sea (or river) bed. SB Once in this position it is clamped at the
top end (not
shown in Figure 4) to the temporary superstructure 12 (not shown in Figure 4).
Figure 5 illustrates how a drill string 21 can be lowered through the thus
positioned
conductor tube 15 and driven by a drilling rig (not illustrated in Figure 1 or
5) but mounted
15 on the superstructure 12 located above the conductor tube 15. Whilst,
normally a rotary
drill 22 will be used, it is also possible to hammer drive a pile (not shown)
through the
conductor tube 15 tube into the sea bed SB if the ground conditions of the sea
or river bed
are suitable. The hammer (not shown) can be dropped through the conductor tube
15.
Cuttings arising from such operations can be flushed out using water pumped
through the
20 drill string but this is not illustrated.
Figure 6 shows how, after the drilling operation is completed, a pin-pile 23
can be lowered
through the conductor tube 5 suspended on a cable 24. Said cable also carries
grout hoses
which are not illustrated but which are necessary for subsequent operations
yet to be
described.
Cementitious grout may be be pumped through grout hoses (not shown) attached
to the
pin pile 23 which guide the cementitious material into and through bores (not
shown)
within the pin pile so as to emerge from the base of the pin pile thereby to
fill the
concentric void arising from the drilling between the pin-pile and the drilled
seabed with a
grout infilling. Sufficient grout is pumped into the void so as completely to
fill the void to
the level of the seabed SB as is schematically illustrated at 25 in Figure 7.
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Completion of this grout filing operation can be confirmed using a sensor or
sensors at
seabed level (not illustrated) which will react to the emergence of grout 15
from below.
Figure 8 shows that after the grout injected through the pin-pile to form the
grout filling 25
has set, the conductor 15 is lifted a short distance until it is only engaged
with the jacket
inner tube 5A by a small amount, sufficient to hold it in place despite
currents or waves. In
the Figure the lower end of the conductor 15 is indicated at 26 The small
mount may be of
the order of 200 or 300mm but other levels, of engagement may be used to suit
the
conditions.
Figure 9 shows how more grout can then either be injected through grout hoses
connected
to drillings (not shown) in the top part of the pin-pile or directly into the
annular void
between the pin-pile 24 and the interior of the footing inner tube 5A. This
annular void is
filled with cementitious grout 26 until it reaches the level of the base of
the conductor tube
. This level can be calculated from the volume of grout needed to fill a space
of known
15 dimensions or sensors can be used to detect when the correct level is
reached.
The hoses and lowering cable 24 are then disconnected from the pin pile 23 and
raised
back to the superstructure work platform 12 on top of the structure. The
separation of
hoses and cables can be accomplished by various means which are not
illustrated. For
example the couplings can be split and held together by a pin which can be
withdrawn by
either pulling a cable from above the surface of the sea or energising an
electrical solenoid,
by divers or Remotely Operated Vehicles (ROVs) may also be used to undertake
the
disconnection. There are also a number or proprietary products specially
designed to
permit remote controlled separation of cable and hose connections which may be
used for
this purpose.
Figure 10 shows the completed footing after the conductor tube 15 and all
cables and
hoses have been detached. It can be seen that the pin-pile 23 is now securely
grouted into
both the ground and the footing tube and provides a means to carry much larger
shear or
up-lift forces between the structure and the seabed. The surface area of the
pin-pile is
designed to be sufficient to carry the loads at low enough stress levels to
avoid
delamination of the grout.
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At this stage the adjustable feet 7 are either abandoned and left in situ or
provision maybe
made to detach and remove them for reuse. Finally the temporary superstructure
12, the
crane 13 and associated equipment, the conductor tube(s) 15 and any other
tools, together
with any ballast 14 added for stability during drilling can be removed by a
vessel with a
crane. A smaller and less costly vessel may be used for this purpose than the
one needs to
bring and position the entire jacket structure 2. The second vessel may also
bring other
equipment needed for completion of the installation, such as wind or tidal
turbines, above
surface housings or decks, etc. Alternatively if the jacket structure 2 is
required to be
entirely submerged a detachable upper portion may at this stage be removed or
replaced
with specialised equipment.
From the above it will be noted that the proposals of the invention provides a
structure
capable of being installed in the sea (or in a river), which is designed to be
temporarily self
standing by being heavy enough to be held in position by friction with the
seabed and
which has facilities to support the equipment needed to permanently affix it
to the sea (or
river) bed using pin-piles or other fixtures capable of penetrating the sea
(or river) bed
through tubular permanent footings integral with the jacket structure. If
necessary extra
weight to generate sufficient friction to prevent movement may be temporarily
provided as
ballast added to the structure and removed after the pin-piling operation has
been
completed.
Thus there is provided a structure with a jacketed base having one or more
permanent
tubular footings which can be drilled through from a platform mounted above
water level
into the sea or river bed, and into which pin-piles may be inserted and
grouted into place.
In particular the structure includes temporary footings that can be adjusted
for height and
alignment to permit the structure to be levelled before fixing to the seabed ,
the force for
so doing being provided by hydraulic jacks, screw jacks or any other such
appropriate
mechanisms.
