OFFSHORE STRUCTURE HAVING AT LEAST ONE FAIRLEAD

Abstract

Disclosed is a structure such as a floating structure, including at least one fairlead for guiding an anchoring element thereof at an anchoring point, the fairlead including a guide to guide the anchoring element in translation between the structure and the anchoring point, a unit for moving the anchoring element in translation in the guide in order to place the anchoring element under tension, and a lock to prevent the anchoring element from moving in translation in the guide, for mooring the structure to the anchoring point. The unit for moving the anchoring element in translation in the guide is integrated into a distinct part separate from the rest of the structure of the fairlead, and this part and the rest of the structure of the fairlead include the retractable coupling unit thereof.

Description

The present invention relates to an offshore structure.

More specifically, the invention relates to such an offshore structure, and in particular to a floating structure of this nature.

Still more particularly, the invention relates to offshore structures such as floating energy production supports or the like, construction platforms, drilling platforms, loading and unloading buoys, or even floating platforms for exploiting renewable marine energies such as offshore wind-based installations or energy production plants based on ocean thermal energy, etc.

Such floating structures must be kept in position, whereas they are subject to different forces, and in particular drift forces for example generated by marine currents, the swell, wind, etc.

To keep these structures in position for example on an operating site, anchoring means are for example used implementing a set of anchoring lines made up in whole or in part of chains, in particular at their ends.

Such lines are then for example arranged regularly around the structure to be moored or anchored, and extend between said structure and respective mooring or anchoring points for example on the seabed.

One can then see that the mooring and anchoring lines, the first ends of which in the form of chains are attached on said mooring and anchoring points, rise to the floating unit and are associated therewith through the chain entry guiding means.

These guide means are also known in the technical field as fairleads.

These fairleads are in fact mechanical devices that include fastening and attachment means on the floating structure and guide means for a chain.

These fairleads are also associated in one way or another with means for placing said chains under tension and means for locking the chains in order to moor said structure.

The tensioning means may for example include winches or windlasses or the like, while the systems for locking the chains are also called chain stoppers.

Different embodiments of these various means are already known in the state of the art.

Thus for example, these winches or windlasses can be placed on the deck of the floating unit.

Other embodiments take the form of the integration of said tensioning means and said chain locking systems directly into the fairlead.

In general, the tensioning means then make it possible to place the anchoring chains at the desired tension in order to moor and anchor the floating structure correctly, before the chain stoppers are activated to lock the chains and keep them in position, which thus makes it possible to moor the floating structure.

The chain stoppers are generally continuously self-locking during the tensioning if a concern arises within the tensioning device.

Reference may for example be made to document U.S. Pat. No. 5,934,216 for a description of such a guiding fairlead.

The latter in fact incorporates tensioning means and locking means as previously described.

One can see, however, that such structures are relatively complex and expensive to produce.

Furthermore, most of the time, such tensioning means are only used quite rarely.

Indeed, in such offshore structures, for example floating, the monitoring and adjustment, as well as tension reaction of the anchoring means, may for example be done every year, or every five years, and one can see that the fairlead structures as described in the prior US document are not at all effective in terms of the cost to use ratio.

The invention therefore aims to resolve these problems.

To that end, the invention relates to an offshore structure such as a floating structure, of the type including at least one fairlead for guiding an anchoring element thereof at an anchoring point, said fairlead comprising guide means that are able to guide the anchoring element in translation between the structure and the anchoring point, means for moving the anchoring element in translation in the guide means in order to place said anchoring element under tension, and locking means able to prevent the anchoring element from moving in translation in the guide means, for mooring the structure to the anchoring point, characterized in that the means for moving the anchoring element in translation in the guide means are integrated into a distinct part separate from the rest of the structure of the fairlead, and in that this part and the rest of the structure of the fairlead comprise retractable coupling means thereof.

The assembly according to the invention may comprise one or more of the following features, considered alone or according to any technically possible combination:

• • the distinct part in which the movement means of the anchoring element are incorporated includes a support frame for said movement means, suitable for being engaged on the rest of the guide fairlead, and including means for centering this part and locking it in position on the rest of the fairlead, the locking means being movable by the first actuators, between an active coupling position of the frame on the rest of the guide fairlead, and a retracted position releasing this part to allow it to be detached from the rest of the fairlead;
  • the centering means comprise centering lugs able to cooperate with centering elements complementary to the rest of the fairlead allowing the alignment and the centering of the locking means, and the locking means comprise locking pins movable by the first actuators, between an active locking position, protruding in corresponding locking holes of the rest of the fairlead, and a released retracted position;
  • the means for movement in translation of the anchoring element comprise a carriage for movement and tensioning of the anchoring element, movable in a to-and-fro movement, on guideways of the distinct part, by at least one second actuator;
  • the carriage for movement and tensioning of the anchoring element includes means for grasping the anchoring element movable by at least one third actuator, between an active position for grasping of the anchoring element in order to allow the movement of said anchoring element by the tensioning carriage when the latter moves in a direction under the action of said at least one second actuator, and a retracted position for freeing the latter, allowing the carriage to return in the other direction under the action of said at least one second actuator or the release of the distinct part from the rest of the fairlead;
  • the locking means able to lock the translation of the anchoring element in the guide means comprise stop means for the latter, movable under the control of at least one fourth actuator, between an active stop position to lock the anchoring element and a retracted position to release said element;
  • it includes control means of the actuator in order to:
    • control the first actuators of the locking means in the locking position of the distinct part on the rest of the guide fairlead,
    • control the or each third actuator of the grasping means in the active grasping position of the anchoring element,
    • control the or each fourth actuator of the locking means of the anchoring element in the released retracted position of the anchoring element,
    • control the or each second actuator for moving the carriage to tense or relax the anchoring element,
    • control the or each fourth actuator of the locking means of the anchoring element in the active abutting position to lock the anchoring element,
    • control the or each third actuator of the grasping means in the retracted released position of the anchoring element,
    • control the first actuators of the locking means in the retracted released position of the distinct part to allow it to be detached from the rest of the fairlead;
  • the actuators comprise jacks;
  • the distinct part includes means for attaching to handling means thereof;
  • it includes a plurality of guide fairleads arranged around it, and the handling and movement means of the distinct part are suitable for moving said part between at least some of said fairleads.

The invention will be better understood upon reading the following description, provided solely as an example, and in reference to the appended drawings, in which:

FIG. 1 shows a schematic side view of an offshore structure according to the invention;

FIG. 2 shows a perspective view of part of such an offshore structure showing the installation of a fairlead thereon;

FIG. 3 shows a perspective top view of such a fairlead;

FIG. 4 shows a perspective bottom view of such a fairlead;

FIGS. 5 and 6 show perspective top and bottom views, respectively, of a part incorporating means for moving an anchoring element in translation of an offshore structure according to the invention;

FIG. 7 shows a perspective view illustrating grasping means included in the composition of an anchoring fairlead of an offshore structure according to the invention;

FIG. 8 shows a perspective view illustrating locking means included in the composition of an anchoring fairlead of an offshore structure according to the invention;

FIG. 9 illustrates the structure and operation of control means for actuators included in the composition of an anchoring fairlead of a structure according to the invention; and

FIGS. 10 to 13 illustrate the operation of an anchoring fairlead of a structure according to the invention.

These figures, and in particular FIG. 1, show an offshore structure such as a floating structure, which is designated by general reference 1.

This structure 1 is moored on the seabed 2, via anchoring and mooring means.

Said anchoring and mooring means for example comprise anchoring lines, for example made up of chains.

One of said mooring and anchoring chains is for example designated by general reference 3.

One of the ends of said chain 3 is associated with an anchoring and mooring point 4 on the seabed 2, and its other end is associated with the floating structure for example through a guide fairlead, designated by general reference 5 in said FIG. 1.

Such anchoring and mooring lines and such fairleads are for example regularly distributed around the floating structure 1, and then make it possible to moor the latter on the seabed to keep it in position.

In FIG. 2, the installation of such a fairlead is shown in more detail.

In this FIG. 2, the floating offshore structure is visible, for example designated by general reference 1, the anchoring and mooring line made up of the chain, designated by general reference 3, and the fairlead designated by general reference 5.

This fairlead 5 then for example makes it possible to guide the anchoring element 3, to place it under tension and lock it in position, in order to keep the structure in position, as previously described.

As will be described in more detail hereinafter, said fairlead then includes means that make it possible to move the anchoring element in translation in order to place it under tension and means making it possible to lock said anchoring element in position at the desired tension, to moor the structure 1 on the anchoring point, for example the point 4.

FIGS. 3 and 4 show one possible example embodiment of such a fairlead.

Said guide fairlead is still designated by general reference 5 in these figures.

Said guide fairlead then includes means for fastening on the floating structure, said fastening means being designated by general reference 10 in these figures.

Said fastening means 10 comprise any appropriate fastening platen, intended for example to be fastened by welding, bolting or the like, on the floating structure 1.

Guide means 11 for the anchoring structure 3 are for example mounted hingedly on said fastening platen 10.

The fairlead comprises guide means 11 for moving the anchoring element in translation therein, for tensioning said anchoring element and locking means able to lock the translation of the anchoring element in the guide means, for mooring the floating structure on the corresponding anchoring point.

Such a structure is known in a general manner from the aforementioned US document.

In the offshore structure according to the invention and specifically in the or each anchoring and mooring fairlead thereof, the means for moving the anchoring element in translation in the guide means are incorporated into a distinct part and separated from the rest of the structure of the fairlead, and said part and the rest of the structure of the fairlead include retractable coupling means thereof.

In these figures, the rest of the structure of the fairlead is designated by general reference 12, and the distinct and separate part in which the means for moving the anchoring element in translation are integrated is designated by general reference 13.

Indeed, said distinct part 13 separated from the rest of the fairlead assumes the form of a support frame of the means for moving the anchoring and mooring element.

Said support frame is designated by general reference 14 in these figures, and it is suitable for being engaged and attached on the rest of the structure of the guide fairlead.

Said frame then includes means for alignment and centering and locking in position on the rest of the fairlead.

Thus for example and as illustrated more clearly in FIG. 4, the means for centering said frame 14 on the rest of the structure of the fairlead 12 comprise centering lugs, one of which is for example designated by general reference 15 in said FIG. 4, which is suitable for being engaged on and cooperating with a complementary centering element 16 of the rest of the fairlead, to make it possible to align and center said parts on one another.

Said centering element is for example formed by a protruding tab intended to receive the corresponding lug.

Such centering means are for example provided on each side of said parts.

The distinct and separate part 13 also includes means for locking the latter in the assembly position on the rest 12 of the fairlead.

There are for example four of said locking means, which are designated by references 17, 18, 19 and 20 in FIG. 4.

Said locking means are then for example distributed in pairs, for example on each side of the frame 14.

Said locking means are then movable between an active coupling position of the frame 14 on the rest of the guide fairlead 12 and a retracted released position of said frame to allow it to be detached from the rest of the fairlead.

Indeed and as illustrated for example in FIG. 4, each of the locking means, for example 20, of the part 13 includes a locking pin, one of which is for example designated by general reference 21, for said locking means 20.

Said pin is then movable by a first actuator 22, for example electromechanical, between a retracted released position of the frame 14 relative to the rest of the fairlead 12, to allow it to be placed in position or removed, and an active locking position, in which said locking pin 21 protrudes in a corresponding locking hole of the fairlead, said hole for example being designated by general reference 23, in the example of the pin 21 and the first actuator 22 of the locking means 20.

One can then see that when these pins and these first actuators are in the retracted position and the corresponding pins are therefore freed from the corresponding holes of the rest of the fairlead, the frame 14 can be freed from the rest of the structure of the fairlead 12.

Conversely, when said frame 14 must be placed in position on the rest 12 of said fairlead, it suffices to place the centering lugs, for example 15, on the complementary centering elements, for example 16, thereof, to make it possible to place the frame 14 correctly and align it on the rest of the fairlead 12.

Once in this centered position and in the aligned and correct position of the frame, the first actuators such as the actuator 22 are activated to move the locking pins such as 21, into the corresponding locking holes such as 23, locking said part 13 on the rest of the fairlead in order to lock the frame in position on the fairlead.

As previously indicated as well, this distinct and separate part or frame 13 or 14 also includes means for moving the anchoring element 3.

FIGS. 5 to 7 show an example embodiment of said movement means.

In these figures, the distinct and separate part 13 and the component frame 14 thereof are visible.

Indeed, in these figures, the means for moving the anchoring element 3 are designated by general reference 25 and for example comprise a carriage for moving and tensioning the anchoring element.

This carriage is designated by general reference 26 in these figures and is movable in translation, in a to-and-fro movement, on corresponding guideways 27 and 28, for example, of the frame 14.

Said movement of the carriage 26 is imparted by at least one second actuator interposed between said carriage 26 and the rest of the frame 14.

In the example described in these figures, a pair of second actuators of this type is shown, which are arranged on either side of said frame between it and the carriage.

Said second actuators are designated by references 29 and 30, respectively, in these figures.

These actuators then make it possible, based on their power supply command, to move said carriage 26 forward or backward in a to-and-fro movement, along the guideways 27 and 28.

The command of the power supply of said actuators will be described in more detail hereinafter.

Said carriage 26 also includes means for grasping the anchoring element, i.e., the chain 3.

Said grasping means are for example designated by general reference 31 in said FIGS. 5 to 7.

Said grasping means 31 for example comprise a member for grasping the anchoring element, said member being designated by general reference 32 in these figures.

Said grasping member 32 is then movable, by at least one third actuator, between an active position for grasping of the anchoring element, in order to allow the movement of said anchoring element, by the tensioning carriage 26 when the latter moves in a direction under the action of said at least one second actuator, and a retracted position for freeing the latter, allowing the carriage 26 to return in the other direction, under the action of said at least one second actuator or the release of the distinct part or frame 13 or 14 from the rest of the fairlead 12.

Indeed, this part or grasping member 32 is for example mounted articulated on the rest of the carriage and is for example movable by a pair of third actuators designated by general references 33 and 34 in these figures, between its retracted position and its active position.

This grasping part 32 then has any appropriate shape making it possible to grasp the chain or on the contrary to let it go in order to release it.

This then allows said means to adjust the tension of the anchoring element, by moving it in the fairlead, based on the needs to react tension or on the contrary to release it.

As previously mentioned, the fairlead also includes locking means that are able to lock the translation of the anchoring element 3 in the guide means 11, to lock the anchoring element in position and therefore to moor the floating structure.

Said locking means for example comprise means movable under the control of at least one fourth actuator, between an active locking position to lock the anchoring element and a retracted position for releasing said anchoring element.

Indeed and as illustrated for example in FIG. 8, the locking means, which are designated by general reference 40 in this figure, for example comprise a clamp-forming member.

Said member 40 then for example includes two opposite locking jaws, designated by references 41 and 42 in this FIG. 8, and which are movable between a closed active locking position for locking the anchoring element 3 in the fairlead and an open retracted position for releasing said anchoring element, under the control of at least one fourth actuator, designated by general reference 43 in this figure.

This then makes it possible to lock or, on the contrary, release the anchoring element relative to the fairlead.

The chain stoppers are generally continuously self-locking during the tensioning if a concern arises within the tensioning device.

The operation of these various actuators is controlled by a power control system, which in turn is controlled by a monitoring computer.

These actuators for example comprise jacks.

The control structure of the power supply of these actuators and its operation are illustrated in FIG. 9, in which one can see the first, second, third and fourth actuators, respectively 17 to 20, 29 and 30, 33 and 34, and lastly 43.

These are then controlled by a system for monitoring their power supply, designated by general reference 50 in this figure, which in turn is controlled by a monitoring computer 51.

FIGS. 9, and 10 to 13, illustrate the various steps and positions of the various actuators previously described of the structure, and make it possible to illustrate and describe the operation of the fairlead included in the composition of the structure according to the invention.

Thus and first of all, during a step 60, the distinct part 13 is placed in a centering position on the rest of the fairlead 12.

In 61, the first actuators 17, 18, 19 and 20 are steered toward their active position to lock said distinct part in position on the rest of the fairlead.

This is illustrated in FIG. 10.

In 62, the third actuators 33 and 34 are steered to move the grasping means 31 of the anchoring element 3, toward their active grasping position thereof, as illustrated in FIG. 11.

In 63, the fourth actuator 43 of the locking means 40 of the anchoring element 3 is steered toward the open position to release the anchoring element 3.

The anchoring element 3 is kept in position by the grasping means 31.

In 64, the second actuators 29 and 30 are steered to move the carriage 26 and drive the anchoring element 3 with it, in order to move it in translation in the fairlead and for example to tense it.

In 65, the fourth actuator 43 is steered to close the clamp of the locking means 40 and lock the anchoring element 3 in position in the fairlead.

In 66, the third actuators 33 and 34 are steered to move the grasping means 31 of the anchoring element 3 toward their retracted position.

This makes it possible to free the carriage 26, in order to make it possible, by steering the second actuators 29 and 30, optionally to return the latter to the grasping position of the anchoring element to start the operation over, which in fact makes it possible, as illustrated in FIG. 9, to close a loop by step 67, in order to make it possible to adjust the tension of the anchoring element 3.

When this adjustment is complete and the anchoring element 3 is under the correct tension and locked in the fairlead 12 by the locking means 40, the first actuators 17 to 20 can then be steered, as illustrated by reference 68, toward their retracted position releasing the distinct part 13 from the rest of the fairlead 12.

This then for example makes it possible to free this distinct part 13.

One can then see that this operation includes a certain number of steps and that the command means of the actuator are able to:

• • control the first actuators of the locking means in the locking position of the distinct part on the rest of the control fairlead,
  • control the or each third actuator of the grasping means in the active grasping position of the anchoring element,
  • control the or each fourth actuator of the locking means of the anchoring element in the released retracted position of the anchoring element,
  • control the or each second actuator for moving the carriage to tense or relax the anchoring element,
  • control the or each fourth actuator of the locking means of the anchoring element in the active locking position of the anchoring element,
  • control the or each third actuator of the grasping means in the retracted released position of the anchoring element, and lastly
  • control the first actuators of the locking means in the retracted released position of the distinct part for example to allow it to be detached from the rest of the fairlead.

Thus, once this distinct part is released from the rest of the fairlead, it is possible for example to move this part toward at least one other fairlead for example equipping the offshore structure.

Indeed and as previously indicated, such an offshore structure for example includes a plurality of guide fairleads, for example arranged regularly around it.

It is then possible to use handling means such as a crane or the like, to move said distinct part 13, between at least some of said fairleads and to adapt it and attach it thereon, to make it possible to adjust the tension of the corresponding anchoring elements.

This then makes it possible to use only one distinct part for different fairleads, said part being equipped with movement means making it possible to set or adjust the tension of the anchoring element.

To that end, and as illustrated for example in FIG. 3, the distinct part 13 and in particular the frame 14 thereof includes anchor plates, for example attachment means associated with the handling means.

These plates are for example designated by general references 60, 61, 62 and 63 in this FIG. 3.

A plate is thus for example provided in each corner of this distinct part 13.

Of course, other embodiments may also be considered.

It will be noted in this respect that the actuators that have been described previously may for example include different types of jacks, for example hydraulic, pneumatic or other jacks.

These are then for example connected to an off-board control station and for example placed on the offshore structure.

Such a structure then has a certain number of advantages, since the fairleads, or in any case the fairlead parts, associated with the offshore structure have the simplest and most reduced structure possible.

The movement means making it possible to place the corresponding anchoring element under tension are in fact incorporated into a distinct part separated from the rest of the fairleads, which makes it possible to move them with said part, between these different fairleads in order to adjust the tensions of the anchoring elements on each of them.

Thus, a single part of this type may be used and shared between different fairleads.

This results in a simplification of the rest of the fairleads and lower manufacturing costs for the function.

This also makes upkeep easier for these movement means, since they can be very easily accessible.

Of course, still other embodiments can be considered.

Claims

1. An offshore structure (1) including at least one fairlead (5) for guiding an anchoring element (3) thereof at an anchoring point (4), said fairlead (5) comprising guide means (11) that are able to guide the anchoring element (3) in translation between the structure (1) and the anchoring point (4), means (26) for moving the anchoring element (3) in translation in the guide means in order to place said anchoring element (3) under tension, and locking means (40) able to prevent the anchoring element (3) from moving in translation in the guide means (11), for mooring the structure to the anchoring point, wherein the means for moving the anchoring element (3) in translation in the guide means (11) are integrated into a distinct part (13, 14) separate from the rest of the structure (12) of the fairlead, and wherein this part and the rest of the structure of the fairlead comprise retractable coupling means (15, 16, 17, 18, 19, 20) thereof.

2. The offshore structure according to claim 1, wherein the distinct part (13) in which the movement means of the anchoring element are incorporated includes a support frame (14) for said movement means, suitable for being engaged on the rest (12) of the guide fairlead, and including means for centering (15, 16) this part (13) and locking (17, 18, 19, 20) it in position on the rest of the fairlead, the locking means being movable by the first actuators (22), between an active coupling position of the frame (14) on the rest of the guide fairlead (12), and a retracted position releasing this part to allow it to be detached from the rest of the fairlead.

3. The offshore structure according to claim 2, wherein the centering means comprise centering lugs (15) able to cooperate with centering elements (16) complementary to the rest of the fairlead (12) allowing the alignment and the centering of the locking means, and the locking means comprise locking pins (21) movable by the first actuators (22), between an active locking position, protruding in corresponding locking holes (23) of the rest of the fairlead, and a released retracted position.

4. The offshore structure according to claim 1, wherein the means for movement in translation of the anchoring element comprise a carriage (26) for movement and tensioning of the anchoring element (3), movable in a to-and-fro movement, on guideways (27, 28) of the distinct part, by at least one second actuator (29, 30).

5. The offshore structure according to claim 4, wherein the carriage (26) for movement and tensioning of the anchoring element (3) includes means (31, 32) for grasping the anchoring element (3) movable by at least one third actuator (33, 34), between an active position for grasping of the anchoring element (3) in order to allow the movement of said anchoring element by the tensioning carriage (26) when the latter moves in a direction under the action of said at least one second actuator (29, 30), and a retracted position for freeing the latter, allowing the carriage (26) to return in the other direction under the action of said at least one second actuator (29, 30) or the release of the distinct part from the rest of the fairlead.

6. The offshore structure according to claim 5, wherein the locking means (40) able to lock the translation of the anchoring element (3) in the guide means comprise stop means (41, 42) for the latter, movable under the control of at least one fourth actuator (43), between an active stop position to lock the anchoring element and a retracted position to release said element.

7. The offshore structure according to claim 6, further comprising control means (50, 51) of the actuators to:

control the first actuators (17 to 20) of the locking means in the locking position of the distinct part on the rest of the guide fairlead,

control the or each third actuator (33, 34) of the grasping means in the active grasping position of the anchoring element,

control the or each fourth actuator (42) of the locking means of the anchoring element in the released retracted position of the anchoring element,

control the or each second actuator (29, 30) for moving the carriage to tense or relax the anchoring element,

control the or each fourth actuator (43) of the locking means of the anchoring element in the active abutting position to lock the anchoring element,

control the or each third actuator (33, 34) of the grasping means in the retracted released position of the anchoring element,

control the first actuators (17 to 20) of the locking means in the retracted released position of the distinct part to allow it to be detached from the rest of the fairlead.

8. The offshore structure according to claim 2, wherein the actuators comprise jacks.

9. The offshore structure according to claim 1, wherein the distinct part (13, 14) includes means (60, 61, 62, 63) for attaching to handling means thereof.

10. The offshore structure according to claim 9, further comprising a plurality of guide fairleads arranged around it, and wherein the handling and movement means of the distinct part are suitable for moving said part between at least some of said fairleads.

11. The offshore structure according to claim 2, wherein the means for movement in translation of the anchoring element comprise a carriage for movement and tensioning of the anchoring element, movable in a to-and-fro movement, on guideways of the distinct part, by at least one second actuator.

12. The offshore structure according to claim 3, wherein the means for movement in translation of the anchoring element comprise a carriage for movement and tensioning of the anchoring element, movable in a to-and-fro movement, on guideways of the distinct part, by at least one second actuator.

13. The offshore structure according to claim 1, wherein the locking means able to lock the translation of the anchoring element in the guide means comprise stop means for the latter, movable under the control of at least one fourth actuator, between an active stop position to lock the anchoring element and a retracted position to release said element.

14. The offshore structure according to claim 2, wherein the locking means able to lock the translation of the anchoring element in the guide means comprise stop means for the latter, movable under the control of at least one fourth actuator, between an active stop position to lock the anchoring element and a retracted position to release said element.

15. The offshore structure according to claim 3, wherein the locking means able to lock the translation of the anchoring element in the guide means comprise stop means for the latter, movable under the control of at least one fourth actuator, between an active stop position to lock the anchoring element and a retracted position to release said element.

16. The offshore structure according to claim 4, wherein the locking means able to lock the translation of the anchoring element in the guide means comprise stop means for the latter, movable under the control of at least one fourth actuator, between an active stop position to lock the anchoring element and a retracted position to release said element.

17. The offshore structure according to claim 3, wherein the actuators comprise jacks.

18. The offshore structure according to claim 4, wherein the actuators comprise jacks.

19. The offshore structure according to claim 5, wherein the actuators comprise jacks.

20. The offshore structure according to claim 6, wherein the actuators comprise jacks.