EP4198203A1 - Process of anchoring a floating platform on a rocky seabed - Google Patents
Process of anchoring a floating platform on a rocky seabed Download PDFInfo
- Publication number
- EP4198203A1 EP4198203A1 EP21306851.3A EP21306851A EP4198203A1 EP 4198203 A1 EP4198203 A1 EP 4198203A1 EP 21306851 A EP21306851 A EP 21306851A EP 4198203 A1 EP4198203 A1 EP 4198203A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- line
- grout
- trench portion
- core
- plates
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
- 238000004873 anchoring Methods 0.000 title claims abstract description 33
- 238000000034 method Methods 0.000 title claims abstract description 26
- 238000007667 floating Methods 0.000 title claims abstract description 10
- 239000011440 grout Substances 0.000 claims abstract description 72
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 23
- 239000010959 steel Substances 0.000 claims abstract description 23
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 7
- 238000004140 cleaning Methods 0.000 claims description 4
- 229910001294 Reinforcing steel Inorganic materials 0.000 claims description 3
- 239000011435 rock Substances 0.000 description 6
- 238000005553 drilling Methods 0.000 description 3
- 230000007613 environmental effect Effects 0.000 description 3
- 238000009434 installation Methods 0.000 description 3
- 230000006835 compression Effects 0.000 description 2
- 238000007906 compression Methods 0.000 description 2
- 239000004576 sand Substances 0.000 description 2
- 239000002689 soil Substances 0.000 description 2
- 238000009933 burial Methods 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- 238000002955 isolation Methods 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
Images
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
- B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING
- B63B21/00—Tying-up; Shifting, towing, or pushing equipment; Anchoring
- B63B21/24—Anchors
- B63B21/26—Anchors securing to bed
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
- B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING
- B63B21/00—Tying-up; Shifting, towing, or pushing equipment; Anchoring
- B63B21/24—Anchors
- B63B21/26—Anchors securing to bed
- B63B21/29—Anchors securing to bed by weight, e.g. flukeless weight anchors
-
- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D27/00—Foundations as substructures
- E02D27/32—Foundations for special purposes
- E02D27/52—Submerged foundations, i.e. submerged in open water
-
- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D27/00—Foundations as substructures
- E02D27/32—Foundations for special purposes
- E02D27/52—Submerged foundations, i.e. submerged in open water
- E02D27/525—Submerged foundations, i.e. submerged in open water using elements penetrating the underwater ground
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
- B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING
- B63B21/00—Tying-up; Shifting, towing, or pushing equipment; Anchoring
- B63B21/24—Anchors
- B63B21/26—Anchors securing to bed
- B63B2021/262—Anchors securing to bed by drag embedment
Definitions
- the present invention deals with a process of anchoring a floating platform on a rocky seabed, comprising connecting a mooring steel chain to a connecting point and to the platform.
- Drilled and grouted piles usually have a 3m diameter. Installing them requires digging a 20m deep hole, and filling the annulus between the pile and the rock with grout. They require investigating the seabed over a depth of more than 20m.
- the solution of drilled and grouted piles is in fact very challenging for water depths where jack-ups cannot be jacked, e.g. for water depths over 60m.
- drilling is subject to risks, such as weather and ocean conditions, and technical problems such as hole collapse, very hard rock, management of cuttings....
- the number of drilling contractors is quite limited in the world.
- Gravity based structures filled with sand and gravel represent an alternative. However, they lead to large structures occupying a surface of about 20m x 20m. They require thousands of tons of sand or gravel for ballasting. In the end, they are also quite expensive, and have a non-negligible environmental footprint because of their footprint and influence over the water column.
- An aim of the invention is to provide an anchoring process adapted to a rocky seabed allowing reducing costs and environmental footprint.
- the invention proposes a process of anchoring a floating platform on a rocky seabed, comprising the following steps:
- the process comprises one or several of the following features, taken in isolation or any technically feasible combination:
- the invention also deals with an anchoring system adapted for anchoring a floating platform on a rocky seabed, the anchoring system comprising:
- the anchoring system 10 is adapted for anchoring a floating platform 12 (symbolized by a square in Figure 1 ) to a rocky seabed 14.
- rocky it is meant here that the seabed 14 comprises rocks 16, to which the anchoring system is fixed.
- the strength of the anchoring system depends on the strength of rock (from very weak to very strong) and the level of fracturation (from highly weathered/fractured (Rock Quality Designation: worse) to no weathered/fractured (Rock Quality Designation: excellent).
- the platform 12 for example hosts a wind turbine (not shown).
- the platform 12 floats on a body of water 18 (see, ocean or lake) extending over the seabed 14.
- the anchoring system 10 comprises a trench portion 20 located in the seabed 14 and extending along a line L, an anchor structure 22 located in the trench portion, grout 24 located in the trench portion, and a mooring steel chain 26 connected to the platform 12 and to a connecting point 28 of the anchor structure.
- the anchoring system 10 is advantageously designed to resist efforts F applied by the mooring chain 26 on the anchor structure 22, for example up to 10000kN.
- the anchoring system 10 is advantageously designed to have a lifespan of at least 25 years.
- said efforts F apply compression to the anchor structure 22 along the line L.
- the line L is advantageously straight.
- the line L follows the seabed 14 and is for example horizontal in case of a flat seabed.
- a transverse direction T is also defined as perpendicular to the line L and horizontal.
- the line L may be inclined in order to follow a seabed with a gentle slope.
- the efforts F are for example parallel to the seabed 14 (case of a catenary mooring system).
- a portion 30 of the mooring chain 26, extending from the connecting point 28, lies on the seabed 14 and/or on the grout 24.
- the portion 30 and the line L advantageously define an angle ⁇ smaller than 30°, and preferably smaller than 10°. This means that most of the efforts F are exerted on the anchor structure 22 along the line L.
- the mooring chain 26 does not have a portion 30 lying on the seabed 14 and/or on the grout 24, and defines an angle ⁇ with a horizontal plan at the connecting point 28. This may happen when the efforts F are large.
- the angle ⁇ remains smaller than 10°.
- the trench portion 20 may be natural, from previous digging, or preferably from dedicated digging.
- the trench portion 20 for example has a U-shaped or V-shaped section 32 perpendicularly to the line L.
- the trench portion 20 for example has a length L1 along the line L comprised between 5.0m and 40m, advantageously between 10m and 30m.
- the trench portion 20 for example has an average horizontal width L2 perpendicularly to the line L, said width being comprised between 0.3m and 2.5m, advantageously between 0.5m and 2.0m.
- the trench portion 20 for example has an average depth L3 comprised between 1.0m and 5.0m, advantageously between 1.0m and 2.5m.
- the anchor structure 22 comprises a core 34 extending along the line L, steel plates 36 welded to the core and extending from the core radially with respect to the line L, and two grout lines 38, 40 extending along the line L.
- the anchor structure 22 only has one grout line, or includes more than two grout lines.
- the anchor structure 22 is entirely located in the trench portion 20. In other words, the anchor structure 22 is below the seabed level.
- the anchor structure 22 advantageously extends over more than 90% of the trench portion 20 along the line L.
- the anchor structure 22 is advantageously fully surrounded by the grout 24 around the line L.
- the grout aims at ensuring a sealing of the anchor structure 22 with the surrounding seabed 14.
- the core 34 consists of a steel H-beam 42 extending along the line L.
- H-beams are usually standardized items, also known as "I-beams".
- the core 34 defines or forms the connecting point 28, which is for example located at an extremity of the core along the line L.
- the core 34 may include a plurality of steel H-beams mechanically connected to each other along the line L, or a grid of reinforcing steel bars at least partly surrounded by the grout 24.
- the steel H-beam 42 and the above-mentioned variants, are adapted to withstand compression efforts, as well as traction efforts along the line L.
- the core 34 comprises or consists of a steel chain. In that case, the core 34 is adapted to withstand only traction efforts along the line L.
- the H-beam 42 defines a first open housing 44 and a second open housing 46 transversely opposed to each other.
- the plates 36 are preferably orthogonal to the line L.
- the plates 36 are rectangular.
- three edges 48, 50, 52 of each plate 36 are welded to the web and flanges of the H-beam 42.
- a first group 36A of the plates 36 is received in the first housing 44, and a second group 36B of the plates is received in the second housing 46.
- the grout lines 38, 40 are adapted to deliver grout within the trench portion 20 when grout is injected under pressure in them, for example at one of their extremities along the line L.
- the grout line 38 extends in the first housing 44, for example through holes 54 cut in the first group 36A of plates.
- the grout line 40 extends in the second housing 46, for example through holes 56 cut in the second group 36B of plates.
- the grout 24 for example could be a Portland grout and is adapted for curing underwater.
- the grout 24 advantageously fills the trench portion 20 up to seabed level over at least 90% of the anchor structure 22 along the line L.
- the grout 24 is adapted to develop a shear friction against the trench portion 20 rocky walls of as a minimum 100 kPa.
- the mooring chain 26 is adapted to be tensioned by the floating platform 12 and to transmit/apply the efforts F to the anchor structure 22.
- the seabed 14 is first surveyed for example by a remotely operated vehicle 60. Goal is to detect possible obstacles which could cause issues with the installation. One may also rely on previous knowledge of the seabed 14 such as bathymetry and seabed imagery.
- the trench portion 20 is provided in the seabed 14.
- the trench portion is dug using a subsea trencher 65 commonly used for pipeline or cables burial.
- the remotely operated vehicle 60 and the subsea trencher 65 are equipment known in themselves and available from the market.
- the trench portion 20 is an existing one, and does not have to be dug.
- the trench portion 20 is cleaned, advantageously using water jets 67 ( Figure 6 ) directed at walls 69 of the trench portion.
- the jets 67 are for example produced by the remotely operated vehicle 60.
- the anchor structure 22 is installed, for example pre-assembled and lowered, in the trench portion 20, as shown in Figure 6 .
- grout is injected in the trench portion 20, in the example via the grout lines 38, 40 from a source 70, in order to obtain the grout 24.
- grouting is stopped when the trench portion 20 is full of grout, or at least when the anchor structure 22 is surrounded by grout.
- the mooring chain 26 After curing of the grout 24, the mooring chain 26 is connected to the connecting point 28 and to the platform 12, and is tensioned. As a variant, the mooring chain 26 may have been connected to the connecting point 28 before grouting.
- the mooring chain 26 exerts the efforts F on the anchor structure 22.
- the above mentioned portion 30 of the mooring chain 26 lies on the seabed 14 and/or the grout 24, or the mooring chain 26 defines the angle ⁇ with a horizontal plan.
- the anchoring process is adapted to the rocky seabed 14 and preferably catenary mooring solutions and allows reducing costs and the environmental footprint.
- Design is fast. Limited soil investigation, for example over the top 3m of the seabed 14, is enough. All pieces of equipment are available in the market and easy to procure.
- the final assembly of the anchor structure 22 can be done locally. Installation is fast and requires only a dynamic positioning vessel. No pretension is needed.
- a second trench portion 120 is provided in the seabed 14.
- the second trench portion 120 extends along a second line LL, preferably straight.
- the second line LL and the line L converge towards the connecting point 28 and define an angle ⁇ together.
- the second line LL and the line L also define a median axis M.
- the angle ⁇ is advantageously comprised between 20° and 90°.
- a second anchor structure 122 is installed in the second trench portion 120
- the second anchor structure 122 is analogous to the anchor structure 22.
- the second anchor structure 122 comprises a second core 134 extending along the second line LL, steel plates 136 welded to the core and extending from the second core radially with respect to the second line LL, and at least a grout line 138 extending along the second line LL.
- the second core 134 is mechanically connected to the connecting point 28.
- grout 124 is injected in the grout line 138 in order to fill the second trench portion 120.
- the plates 136 are at least partly surrounded by the injected grout 124.
- the portion 30 of the mooring chain 26 and said median axis M define a third angle ⁇ at the connecting point 28.
- the third angle ⁇ is advantageously smaller than 30°, and preferably smaller than 10°.
- the efforts F are split between the two halves (defined by the median axis M) of the anchoring system shown in Figure 8 .
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- Engineering & Computer Science (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- Ocean & Marine Engineering (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Mining & Mineral Resources (AREA)
- Paleontology (AREA)
- Civil Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Structural Engineering (AREA)
- Piles And Underground Anchors (AREA)
Abstract
A process of anchoring a floating platform (12) on a rocky seabed (14), comprising the following steps:
- providing at least one trench portion (20) in the seabed (14), the trench portion extending along a line (L),
- installing an anchor structure (22) in the trench portion, the anchor structure comprising a core (34) extending along the line, steel plates (36) welded to the core and extending from the core radially with respect to the line, and at least a first grout line (38),
- injecting grout (24) in said first grout line in order to fill the trench portion with grout, the plates being at least partly surrounded by the injected grout, and
- after curing of the injected grout, connecting a connecting point (28) of the core (to the platform using a mooring chain (26).
- providing at least one trench portion (20) in the seabed (14), the trench portion extending along a line (L),
- installing an anchor structure (22) in the trench portion, the anchor structure comprising a core (34) extending along the line, steel plates (36) welded to the core and extending from the core radially with respect to the line, and at least a first grout line (38),
- injecting grout (24) in said first grout line in order to fill the trench portion with grout, the plates being at least partly surrounded by the injected grout, and
- after curing of the injected grout, connecting a connecting point (28) of the core (to the platform using a mooring chain (26).
Description
- The present invention deals with a process of anchoring a floating platform on a rocky seabed, comprising connecting a mooring steel chain to a connecting point and to the platform.
- It also deals with a corresponding anchoring system.
- The growing industry of offshore wind and oil and gas projects pushes states or developers to consider more and more offshore areas. In some of them, soil conditions may represent a challenge to common industry practices for the installation of mooring points, such as drag anchors, driven piles or suction piles. Indeed, these technologies are not suited to a rocky seabed.
- Drilled and grouted piles usually have a 3m diameter. Installing them requires digging a 20m deep hole, and filling the annulus between the pile and the rock with grout. They require investigating the seabed over a depth of more than 20m. The solution of drilled and grouted piles is in fact very challenging for water depths where jack-ups cannot be jacked, e.g. for water depths over 60m. There is also limited experience in drilling with a vessel using dynamic positioning and a heave compensated platform. Moreover, drilling is subject to risks, such as weather and ocean conditions, and technical problems such as hole collapse, very hard rock, management of cuttings.... The number of drilling contractors is quite limited in the world.
- This explains why using piles for anchoring purposes is expensive.
- Gravity based structures filled with sand and gravel represent an alternative. However, they lead to large structures occupying a surface of about 20m x 20m. They require thousands of tons of sand or gravel for ballasting. In the end, they are also quite expensive, and have a non-negligible environmental footprint because of their footprint and influence over the water column.
- An aim of the invention is to provide an anchoring process adapted to a rocky seabed allowing reducing costs and environmental footprint.
- To this end, the invention proposes a process of anchoring a floating platform on a rocky seabed, comprising the following steps:
- providing at least one trench portion in the seabed, the trench portion extending along a line,
- installing an anchor structure in the trench portion, the anchor structure comprising a core extending along the line, steel plates welded to the core and extending from the core (34) radially with respect to the line, and at least a first grout line extending along the line,
- injecting grout in said first grout line in order to fill the trench portion with grout, the plates being at least partly surrounded by the injected grout, and
- after curing of the injected grout, connecting a connecting point of the core (34) to the platform using a mooring chain.
- In other embodiments, the process comprises one or several of the following features, taken in isolation or any technically feasible combination:
- providing the trench portion includes digging the seabed along the line using a subsea trencher;
- the line is straight;
- the plates are perpendicular to the core;
- the trench portion has a length along the line comprised between 5.0m and 40m;
- the trench portion has an average horizontal width perpendicularly to the line, said width being comprised between 0.3m and 2.5m;
- the trench portion has an average depth comprised between 1.0m and 5.0m;
- the trench portion has a U-shaped or V-shaped section perpendicularly to the line;
- the mooring chain has a portion lying on the seabed and exerting efforts on the anchor structure, said portion of the mooring chain and the line defining an angle at the connecting point, the angle being smaller than 30°;
- the core comprises a steel H-beam, a plurality of steel H-beams mechanically connected to each other along the line, or a grid of reinforcing steel bars at least partly surrounded by the injected grout;
- the core comprises a steel H-beam defining a first open housing and a second open housing transversely opposed to each other, a first group of said plates being received in the first open housing, and a second group of said plates being received in the second open housing;
- said first grout line extends along the first open housing and successively crosses holes respectively defined by the first group of plates, the anchor structure further comprising a second grout line extending along the second open housing and crossing holes respectively defined by the second group of plates;
- the process further comprises cleaning the trench portion before injecting grout, said cleaning using water jets directed at walls of the trench portion; and
- the process further comprises: providing a second trench portion in the seabed, the second trench portion extending along a second line, the second line and the line converging towards the connecting point; installing a second anchor structure in the second trench portion, the second anchor structure comprising a second core extending along the second line steel plates welded to the second core and extending from the second core radially with respect to the second line and at least a grout line extending along the second line the second core being mechanically connected to the connecting point; and injecting grout in said grout line in order to fill the second trench portion with grout, said plates being at least partly surrounded by the injected grout.
- The invention also deals with an anchoring system adapted for anchoring a floating platform on a rocky seabed, the anchoring system comprising:
- at least one trench portion located in the seabed and extending along a line,
- an anchor structure at least partly located in the trench portion, the anchor structure comprising a core extending along the line, steel plates welded to the core and extending from the core radially with respect to the line, and at least a first grout line extending along the line,
- grout located in the trench portion, the plates being at least partly surrounded by the grout, and
- a mooring steel chain connected to a connecting point of the core, the mooring chain being intended to be connected to the platform.
- The invention and its advantages will be better understood upon reading the following description, given solely by way of example and with reference to the appended drawings, in which:
-
Figure 1 is a schematic side view of an anchoring system according to the invention, -
Figure 2 is a schematic upper view of the anchoring system shown inFigure 1 , -
Figure 3 is a schematic perspective view of an anchor structure of the anchoring system shown inFigures 1 and2 , -
Figures 4 to 7 are schematic side views showing successive phases of the construction of the anchoring system shown inFigures 1 and2 , in order to illustrate a process according to the invention, and -
Figure 8 is a schematic upper view an anchoring system according to a variant of the system shown inFigures 1 and2 . - An
anchoring system 10 according to the invention will now be described with reference toFigures 1 to 3 mainly. - The
anchoring system 10 is adapted for anchoring a floating platform 12 (symbolized by a square inFigure 1 ) to arocky seabed 14. - By "rocky", it is meant here that the
seabed 14 comprisesrocks 16, to which the anchoring system is fixed. The strength of the anchoring system depends on the strength of rock (from very weak to very strong) and the level of fracturation (from highly weathered/fractured (Rock Quality Designation: worse) to no weathered/fractured (Rock Quality Designation: excellent). - The
platform 12 for example hosts a wind turbine (not shown). Theplatform 12 floats on a body of water 18 (see, ocean or lake) extending over theseabed 14. - The
anchoring system 10 comprises atrench portion 20 located in theseabed 14 and extending along a line L, ananchor structure 22 located in the trench portion,grout 24 located in the trench portion, and amooring steel chain 26 connected to theplatform 12 and to a connectingpoint 28 of the anchor structure. - The
anchoring system 10 is advantageously designed to resist efforts F applied by themooring chain 26 on theanchor structure 22, for example up to 10000kN. Theanchoring system 10 is advantageously designed to have a lifespan of at least 25 years. - In the example shown, said efforts F apply compression to the
anchor structure 22 along the line L. - The line L is advantageously straight. The line L follows the
seabed 14 and is for example horizontal in case of a flat seabed. A transverse direction T is also defined as perpendicular to the line L and horizontal. - As a variant (not shown), the line L may be inclined in order to follow a seabed with a gentle slope.
- The efforts F are for example parallel to the seabed 14 (case of a catenary mooring system).
- For example, a
portion 30 of themooring chain 26, extending from the connectingpoint 28, lies on theseabed 14 and/or on thegrout 24. Theportion 30 and the line L advantageously define an angle α smaller than 30°, and preferably smaller than 10°. This means that most of the efforts F are exerted on theanchor structure 22 along the line L. - As a variant (not shown), the
mooring chain 26 does not have aportion 30 lying on theseabed 14 and/or on thegrout 24, and defines an angle δ with a horizontal plan at the connectingpoint 28. This may happen when the efforts F are large. - Generally the angle δ remains smaller than 10°.
- The
trench portion 20 may be natural, from previous digging, or preferably from dedicated digging. - As symbolized in
Figure 5 , thetrench portion 20 for example has a U-shaped or V-shapedsection 32 perpendicularly to the line L. - The
trench portion 20 for example has a length L1 along the line L comprised between 5.0m and 40m, advantageously between 10m and 30m. - The
trench portion 20 for example has an average horizontal width L2 perpendicularly to the line L, said width being comprised between 0.3m and 2.5m, advantageously between 0.5m and 2.0m. - The
trench portion 20 for example has an average depth L3 comprised between 1.0m and 5.0m, advantageously between 1.0m and 2.5m. - As shown in
Figure 3 , theanchor structure 22 comprises a core 34 extending along the line L,steel plates 36 welded to the core and extending from the core radially with respect to the line L, and twogrout lines - As variants (not shown), the
anchor structure 22 only has one grout line, or includes more than two grout lines. - In the example, the
anchor structure 22 is entirely located in thetrench portion 20. In other words, theanchor structure 22 is below the seabed level. Theanchor structure 22 advantageously extends over more than 90% of thetrench portion 20 along the line L. - The
anchor structure 22 is advantageously fully surrounded by thegrout 24 around the line L. The grout aims at ensuring a sealing of theanchor structure 22 with the surroundingseabed 14. - In the example, the
core 34 consists of a steel H-beam 42 extending along the line L. H-beams are usually standardized items, also known as "I-beams". - Advantageously, the
core 34 defines or forms the connectingpoint 28, which is for example located at an extremity of the core along the line L. - As variants (not shown), the
core 34 may include a plurality of steel H-beams mechanically connected to each other along the line L, or a grid of reinforcing steel bars at least partly surrounded by thegrout 24. - The steel H-
beam 42, and the above-mentioned variants, are adapted to withstand compression efforts, as well as traction efforts along the line L. - As another variant (not shown), the
core 34 comprises or consists of a steel chain. In that case, thecore 34 is adapted to withstand only traction efforts along the line L. - The H-
beam 42 defines a firstopen housing 44 and a secondopen housing 46 transversely opposed to each other. - The
plates 36 are preferably orthogonal to the line L. - For example, the
plates 36 are rectangular. Advantageously, threeedges plate 36 are welded to the web and flanges of the H-beam 42. - In the example, a
first group 36A of theplates 36 is received in thefirst housing 44, and asecond group 36B of the plates is received in thesecond housing 46. - The grout lines 38, 40 are adapted to deliver grout within the
trench portion 20 when grout is injected under pressure in them, for example at one of their extremities along the line L. - The
grout line 38 extends in thefirst housing 44, for example throughholes 54 cut in thefirst group 36A of plates. - Similarly, the
grout line 40 extends in thesecond housing 46, for example throughholes 56 cut in thesecond group 36B of plates. - The
grout 24 for example could be a Portland grout and is adapted for curing underwater. - The
grout 24 advantageously fills thetrench portion 20 up to seabed level over at least 90% of theanchor structure 22 along the line L. - Advantageously, the
grout 24 is adapted to develop a shear friction against thetrench portion 20 rocky walls of as a minimum 100 kPa. - The
mooring chain 26 is adapted to be tensioned by the floatingplatform 12 and to transmit/apply the efforts F to theanchor structure 22. - A process of anchoring the floating
platform 12 on theseabed 14, using theanchoring system 10, will now be described with reference toFigures 4 to 7 . - Optionally, as shown in
Figure 4 , theseabed 14 is first surveyed for example by a remotely operatedvehicle 60. Goal is to detect possible obstacles which could cause issues with the installation. One may also rely on previous knowledge of theseabed 14 such as bathymetry and seabed imagery. - Then the
trench portion 20 is provided in theseabed 14. For example, as shown inFigure 5 , the trench portion is dug using asubsea trencher 65 commonly used for pipeline or cables burial. - The remotely operated
vehicle 60 and thesubsea trencher 65 are equipment known in themselves and available from the market. - As a variant, for example in case of a rough seabed with some benches, the
trench portion 20 is an existing one, and does not have to be dug. - Optionally, the
trench portion 20 is cleaned, advantageously using water jets 67 (Figure 6 ) directed atwalls 69 of the trench portion. Thejets 67 are for example produced by the remotely operatedvehicle 60. - Then, the
anchor structure 22 is installed, for example pre-assembled and lowered, in thetrench portion 20, as shown inFigure 6 . - Afterwards, grout is injected in the
trench portion 20, in the example via thegrout lines source 70, in order to obtain thegrout 24. - Advantageously, grouting is stopped when the
trench portion 20 is full of grout, or at least when theanchor structure 22 is surrounded by grout. - After curing of the
grout 24, themooring chain 26 is connected to the connectingpoint 28 and to theplatform 12, and is tensioned. As a variant, themooring chain 26 may have been connected to the connectingpoint 28 before grouting. - Then the
mooring chain 26 exerts the efforts F on theanchor structure 22. Depending on the efforts F, the above mentionedportion 30 of themooring chain 26 lies on theseabed 14 and/or thegrout 24, or themooring chain 26 defines the angle δ with a horizontal plan.. - Thanks to the above features, the anchoring process is adapted to the
rocky seabed 14 and preferably catenary mooring solutions and allows reducing costs and the environmental footprint. Design is fast. Limited soil investigation, for example over the top 3m of theseabed 14, is enough. All pieces of equipment are available in the market and easy to procure. The final assembly of theanchor structure 22 can be done locally. Installation is fast and requires only a dynamic positioning vessel. No pretension is needed. - As a variant of the above process of anchoring, shown in
Figure 8 , asecond trench portion 120 is provided in theseabed 14. - The
second trench portion 120 extends along a second line LL, preferably straight. - The second line LL and the line L converge towards the connecting
point 28 and define an angle β together. The second line LL and the line L also define a median axis M. - The angle β is advantageously comprised between 20° and 90°.
- A
second anchor structure 122 is installed in thesecond trench portion 120 - The
second anchor structure 122 is analogous to theanchor structure 22. Thesecond anchor structure 122 comprises asecond core 134 extending along the second line LL,steel plates 136 welded to the core and extending from the second core radially with respect to the second line LL, and at least agrout line 138 extending along the second line LL. - The
second core 134 is mechanically connected to the connectingpoint 28. - Then
grout 124 is injected in thegrout line 138 in order to fill thesecond trench portion 120. Theplates 136 are at least partly surrounded by the injectedgrout 124. - Advantageously, the
portion 30 of themooring chain 26 and said median axis M define a third angle γ at the connectingpoint 28. The third angle γ is advantageously smaller than 30°, and preferably smaller than 10°. In other words, the efforts F are split between the two halves (defined by the median axis M) of the anchoring system shown inFigure 8 . - Thanks to the features of the above described variant, anchoring is stronger.
Claims (15)
- A process of anchoring a floating platform (12) on a rocky seabed (14), comprising the following steps:- providing at least one trench portion (20) in the seabed (14), the trench portion (20) extending along a line (L),- installing an anchor structure (22) in the trench portion (20), the anchor structure (22) comprising a core (34) extending along the line (L), steel plates (36) welded to the core (34) and extending from the core (34) radially with respect to the line (L), and at least a first grout line (38) extending along the line (L),- injecting grout (24) in said first grout line (38) in order to fill the trench portion (20) with grout (24), the plates (36) being at least partly surrounded by the injected grout (24), and- after curing of the injected grout (24), connecting a connecting point (28) of the core (34) to the platform (12) using a mooring chain (26).
- The process according to claim 1, wherein providing the trench portion (20) includes digging the seabed (14) along the line (L) using a subsea trencher (65).
- The process according to claim 1 or 2, wherein the line (L) is straight.
- The process according to any one of claims 1 to 3, wherein the plates (36) are perpendicular to the core (34).
- The process according to any one of claims 1 to 4, wherein the trench portion (20) has a length (L1) along the line (L) comprised between 5.0m and 40m.
- The process according to any one of claims 1 to 5, wherein the trench portion (20) has an average horizontal width (L2) perpendicularly to the line (L), said (L2) width being comprised between 0.3m and 2.5m.
- The process according to any one of claims 1 to 6, wherein the trench portion (20) has an average depth (L3) comprised between 1.0m and 5.0m.
- The process according to any one of claims 1 to 7, wherein the trench portion (20) has a U-shaped or V-shaped section (32) perpendicularly to the line (L).
- The process according to any one of claims 1 to 8, wherein the mooring chain (26) has a portion (30) lying on the seabed (14) and exerting efforts (F) on the anchor structure (22), said portion (30) of the mooring chain (26) and the line (L) defining an angle (α) at the connecting point (28), the angle (α) being smaller than 30°.
- The process according to any one of claims 1 to 9, wherein the core (34) comprises a steel (42) H-beam, a plurality of steel H-beams mechanically connected to each other along the line (L), or a grid of reinforcing steel bars at least partly surrounded by the injected grout (24).
- The process according to any one of claims 1 to 8, wherein the core (34) comprises a steel (42) H-beam defining a first open housing (44) and a second open housing (46) transversely opposed to each other, a first group (36A) of said plates (36) being received in the first open housing (44), and a second group (36B) of said plates (36) being received in the second open housing (46).
- The process according to claim 11, wherein said first grout line (38) extends along the first open housing (44) and successively crosses holes (54) respectively defined by the first group (36A) of plates (36), the anchor structure (22) further comprising a second grout line (40) extending along the second open housing (46) and crossing holes (56) respectively defined by the second group (36B) of plates (36).
- The process according to any one of claims 1 to 12, further comprising a step of cleaning the trench portion (20) before injecting grout (24), said cleaning using water jets (67) directed at walls (69) of the trench portion (20).
- The process according to any one of claims 1 to 13, further comprising:- providing a second trench portion (120) in the seabed (14), the second trench portion (120) extending along a second line (L2), the second line (L2) and the line (L) converging towards the connecting point (28),- installing a second anchor structure (122) in the second trench portion (120), the second anchor structure (122) comprising a second core (134) extending along the second line (L2), steel plates (136) welded to the second core (34) and extending from the second core (134) radially with respect to the second line (L2), and at least a grout line (138) extending along the second line (L2), the second core (134) being mechanically connected to the connecting point (28), and- injecting grout (124) in said grout line (138) in order to fill the second trench portion (120) with grout, said plates (136) being at least partly surrounded by the injected grout (124).
- An anchoring system (10) adapted for anchoring a floating platform (12) on a rocky seabed (14), the anchoring system (10) comprising:- at least one trench portion (20) located in the seabed (14) and extending along a line (L),- an anchor structure (22) at least partly located in the trench portion (20), the anchor structure (22) comprising a core (34) extending along the line (L), steel plates (36) welded to the core (34) and extending from the core (34) radially with respect to the line (L), and at least a first grout line (38) extending along the line (L),- grout (24) located in the trench portion (20), the plates (36) being at least partly surrounded by the grout (24), and- a mooring steel chain (26) connected to a connecting point (28) of the core (34), the mooring chain (26) being intended to be connected to the platform (12).
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP21306851.3A EP4198203A1 (en) | 2021-12-20 | 2021-12-20 | Process of anchoring a floating platform on a rocky seabed |
PCT/EP2022/086741 WO2023117966A1 (en) | 2021-12-20 | 2022-12-19 | Process of anchoring a floating platform on a rocky seabed |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP21306851.3A EP4198203A1 (en) | 2021-12-20 | 2021-12-20 | Process of anchoring a floating platform on a rocky seabed |
Publications (1)
Publication Number | Publication Date |
---|---|
EP4198203A1 true EP4198203A1 (en) | 2023-06-21 |
Family
ID=79316705
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP21306851.3A Withdrawn EP4198203A1 (en) | 2021-12-20 | 2021-12-20 | Process of anchoring a floating platform on a rocky seabed |
Country Status (2)
Country | Link |
---|---|
EP (1) | EP4198203A1 (en) |
WO (1) | WO2023117966A1 (en) |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
NL7112844A (en) * | 1970-09-18 | 1972-03-21 | ||
US20140161538A1 (en) * | 2012-12-12 | 2014-06-12 | Dallas Joel Meggitt | System and method for undersea micropile deployment |
US10030349B2 (en) * | 2010-05-28 | 2018-07-24 | Lockheed Martin Corporation | Undersea anchoring system and method |
-
2021
- 2021-12-20 EP EP21306851.3A patent/EP4198203A1/en not_active Withdrawn
-
2022
- 2022-12-19 WO PCT/EP2022/086741 patent/WO2023117966A1/en unknown
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
NL7112844A (en) * | 1970-09-18 | 1972-03-21 | ||
US10030349B2 (en) * | 2010-05-28 | 2018-07-24 | Lockheed Martin Corporation | Undersea anchoring system and method |
US20140161538A1 (en) * | 2012-12-12 | 2014-06-12 | Dallas Joel Meggitt | System and method for undersea micropile deployment |
Also Published As
Publication number | Publication date |
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WO2023117966A1 (en) | 2023-06-29 |
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