U.S. patent application number 13/149000 was filed with the patent office on 2011-12-29 for installing submerged support structures.
Invention is credited to Peter L. Fraenkel.
Application Number | 20110318113 13/149000 |
Document ID | / |
Family ID | 40527208 |
Filed Date | 2011-12-29 |
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United States Patent
Application |
20110318113 |
Kind Code |
A1 |
Fraenkel; Peter L. |
December 29, 2011 |
INSTALLING SUBMERGED SUPPORT STRUCTURES
Abstract
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.
Inventors: |
Fraenkel; Peter L.; (London,
GB) |
Family ID: |
40527208 |
Appl. No.: |
13/149000 |
Filed: |
February 12, 2010 |
PCT Filed: |
February 12, 2010 |
PCT NO: |
PCT/GB10/00258 |
371 Date: |
September 16, 2011 |
Current U.S.
Class: |
405/224 |
Current CPC
Class: |
E02B 2017/0056 20130101;
E02D 27/425 20130101; E02B 17/02 20130101; E02B 17/027 20130101;
E02D 27/52 20130101; F05B 2240/97 20130101; E02D 13/04 20130101;
F05B 2240/95 20130101; E02D 27/42 20130101 |
Class at
Publication: |
405/224 |
International
Class: |
E02D 5/54 20060101
E02D005/54; E02D 29/09 20060101 E02D029/09; E02D 5/74 20060101
E02D005/74 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 12, 2009 |
GB |
09022898.8 |
Claims
1.-15. (canceled)
16. 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.
17. A method as claimed in claim 16, in which the structure is in
the form of an elongate column for supporting a submergible water
driven turbine and/or a wind driven turbine.
18. A method as claimed in claim 16, and including the step of
anchoring the structure to the sea or river bed by means of piles
or similar anchoring means.
19. A method as claimed in claim 18, and wherein 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.
20. A method as claimed in claim 19, and wherein each said foot
unit is positionally adjustable relative the sea or river bed in
such manner that the support structure can be set to a required
level and orientation relative to the sea or river bed.
21. A method as claimed in claim 20, wherein the support structure
is designed so that it can be lowered to the sea or river bed,
leveled by the adjustment means 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.
22. A method as claimed in claim 20, and including the step of
grouting with cementicious material each individual pile in the
position into which it has been inserted into the sea or river
bed.
23. A method as claimed in claim 19, and including the provision of
a temporary structure provided at the top of the support structure,
and wherein the operations are required to sink the piles.
24. A method as claimed in claim 16, and including the step of
adding additional weight to the structure in the event that the
support structure, during the installation period, is moved by
currents, waves or wind so as to maintain sufficient frictional
contact with the sea or river bed during the installation
process.
25. A method as claimed in claim 24, and including the step of
removing, after the anchoring piles have been installed, any
additional weight together with any equipment involved in
installation of the support structure such that the support
structure can no longer displace relative to the sea or river
bed.
26. 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.
27. A support structure as claimed in claim 26, wherein the
structure is in the form of an elongate column or supporting a
submergible turbine.
28. A support structure as claimed in claim 26, and further
including a temporary additional structure at the top of the
support structure, and characterised in that facilities are
provided at the temporary structure for carrying out any operations
required to sink the piles.
29. A support structure as claimed in claim 28, wherein the
temporary structure is arranged to be able to carry additional
weight whereby in the event that the support structure, during the
installation thereof, is at the risk of being moved by currents,
waves or wind so as to maintain sufficient friction with the sea or
river bed during the installation process, appropriate additional
weight can be added to the temporary structure to maintain
acceptable friction of the support structure with the sea or river
bed.
30. A support structure as claim 26, and further including
temporary footings that can be adjusted for height and alignment to
permit the structure to be leveled before fixing to the sea or
river bed, the force for so doing being provided by hydraulic
jacks, screw jacks or any other such component.
Description
BACKGROUND OF THE INVENTION
[0001] 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).
[0002] A possible application for such support structures is for
the support of wind or water current driven turbines, or wave
energy powered devices.
[0003] 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.
[0004] 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.
[0005] 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
installations 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
[0006] 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.
[0007] 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
[0008] 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.
[0009] Conveniently the support structure is in the form of an
elongate column for supporting a submergible water driven turbine
and/or a wind driven turbine.
[0010] 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
[0011] 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.
[0012] 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.
[0013] 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.
[0014] 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.
[0015] 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 to anchor the support
structure to a sea or river bed.
[0016] 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.
[0017] 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.
[0018] 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.
[0019] 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
support structure is positioned correctly with required pile
handling equipment mounted upon it.
[0020] 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.
[0021] 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.
[0022] 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.
[0023] Conveniently the upper part is removed using a crane mounted
upon a boat.
[0024] In a preferred construction the support structure is
provided with three or four footing assemblies.
[0025] Preferably, the support structure is designed so that it can
be lowered to the sea or river bed, leveled 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.
[0026] Conveniently the drilling process is carried out from a
temporary structure mounted on top of the jacket of a jacket type
support structure.
[0027] 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.
[0028] 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 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.
[0029] 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.
[0030] In particular the structure includes temporary footings that
can be adjusted for height and alignment to permit the structure to
be leveled 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.
[0031] 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.
[0032] 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 a pin pile into the seabed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] 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:--
[0034] FIG. 1 schematically illustrates the general construction of
a support jacket structure involving the concepts of the
invention;
[0035] FIGS. 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 FIG. 1;
[0036] FIG. 3A schematically illustrates a first positioning of the
support feet of the structure shown in FIG. 1 relative to a sea or
river bed;
[0037] FIG. 3B schematically illustrates a further possible
positioning of the support feet of the structure shown in FIG. 1
relative to a sea or river bed; and
[0038] FIGS. 4 to 10 schematically illustrate successive stages in
anchoring the support jacket structure of FIG. 1 to a sea or river
bed using pin piles.
DETAILED DESCRIPTION OF THE DRAWINGS
[0039] Referring now to FIG. 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 5A 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.
[0040] 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.
[0041] 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 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.
[0042] 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.
[0043] 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 FIG. 1) that are positionally located by the support
foot units 5.
[0044] In other words the foot units 5 have an essentially dual
purpose of which one serves to provide firm support to the jacket
structure 2 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.
[0045] 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.
[0046] 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.
[0047] 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.
[0048] In relation to the position and anchoring of the structure 2
a further important feature which is illustrated by FIG. 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 the foot units 5. 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.
[0049] 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.
[0050] 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.
[0051] Reference will now be made to FIGS. 2A-2D which illustrate
the construction of the feet units 5 in greater detail and to a
larger size.
[0052] In particular these FIGS. 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.
[0053] The FIGS. 2A-2D illustrate how both vertical and angular
adjustment may be obtained and then fixed by pressurizing 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.
[0054] As may be noted from FIGS. 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.
[0055] As may be seen from FIGS. 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.
[0056] It will be understood that tilting can be combined with the
height adjustment as is enabled by the construction of the leg
assembly.
[0057] 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.
[0058] Referring now to FIGS. 3A and 3B these FIG. 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 FIG. 2. As can be seen from FIGS. 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 FIG. 3A or they can be mounted
on outrigger structures outside the foot units 5 as shown in FIG.
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 more space is made available for the
drilling and pin-pile installation and additionally this
arrangement simplifies the structure of the footings.
[0059] It will be noted that in the embodiments shown in FIGS. 3A
and 3B the foot units 5 are effectively totally separate from the
arrangement of FIG. 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 FIGS. 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.
[0060] Referring now to FIGS. 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 FIG. 4 illustrates
a first stage in the procedure for permanently fixing the jacket
footings to the sea (or river) bed (SB) Whilst FIG. 4 represents by
way of example an embodiment 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
FIG. 4.
[0061] Thus FIG. 4 in fact illustrates the stage at which the
conductor tube 15 has been lowered into the inner tube 5A of the
tubular structure of the jacket foot unit 5 until its lower end 20
rests on the sea (or river) bed. SB Once in this position it is
clamped at the top end (not shown in FIG. 4) to the temporary
superstructure 12 (not shown in FIG. 4).
[0062] FIG. 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 FIG. 1 or 5) but mounted 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 drill string but this is
not illustrated.
[0063] FIG. 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.
[0064] Cementitious grout may 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 FIG.
7.
[0065] 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.
[0066] FIG. 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 300 mm but other levels, of engagement may be used to
suit the conditions.
[0067] FIG. 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 15. This level can be
calculated from the volume of grout needed to fill a space of known
dimensions or sensors can be used to detect when the correct level
is reached.
[0068] 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.
[0069] FIG. 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.
[0070] 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.
[0071] 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.
[0072] 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.
[0073] In particular the structure includes temporary footings that
can be adjusted for height and alignment to permit the structure to
be leveled before fixing to the seabed, the force for so doing
being provided by hydraulic jacks, screw jacks or any other such
appropriate mechanisms.
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