EP3061871A1 - Gravity structure for a maritime civil-engineering construction and associated manufacturing method - Google Patents

Abstract

The subject of the invention is a gravity structure intended for a maritime civil engineering construction, comprising a raft (2) configured to be laid on a sea floor and secured to a barrel (3) directed in a main direction that is substantially orthogonal to said slab. , characterized in that the gravity structure (1) comprises at least one anchor (10) extending in said barrel (3) and in the raft (2), the gravity structure (1) being configured so that, in a service position of the gravity structure (1), said at least one anchor (10) is anchored in the sea floor.

Description

The subject of the invention is a gravity structure intended for a maritime civil engineering construction and a related manufacturing method.

A known gravity structure comprises a raft configured to be laid on a sea floor and secured to a barrel directed in a main direction substantially orthogonal to the floor.

The maritime civil engineering construction for which such a gravity structure is intended is for example a wind turbine at sea or a bridge.

In the service position, that is to say when the gravity structure rests on the sea floor, the shaft is disposed substantially vertically and is surmounted by a mast itself equipped with a nacelle and pale when the maritime construction is a wind turbine, surmounted by a pile and an apron when the construction is a bridge.

Given the mechanical constraints, particularly due to the winds and the swell, acting on the gravity structure, as well as its dimensions, it is essential to ensure the stability of the gravity structure in the service position.

To do this, it is necessary to prepare the seabed before the installation of the gravity structure by preliminary dredging, followed by a layer of leveling and a possible layer of scour protection.

But the raft, provided in the form of a cylinder, must have a very large diameter, of the order of a few tens of meters, which implies that the area of marine soil to be prepared is itself very wide.

Due to the large dimensions of the structure, and in particular the dimensions of the slab, it is also necessary to provide large quantities of concrete and steel, materials which generally constitute the gravitational structure.

It also results from the large dimensions of the gravity structure that the process of installation at sea in the service position of the gravity structure is long and complex to implement.

In addition, it is necessary to fill the drum with ballast to complete the installation of the gravity structure, which is all the more expensive as the material, for example ballast sand, must be routed from a port or a dredging area.

The object of the invention is to at least partially overcome these disadvantages.

For this purpose, the subject of the invention is a gravity structure intended for a maritime civil engineering construction, comprising a raft configured to be laid on a sea floor and secured to a barrel directed in a main direction that is substantially orthogonal to said raft, characterized in that the gravity structure comprises at least one anchor extending in said barrel and in the raft, the gravity structure being configured so that, in a service position of the gravity structure, said at least one tie rod anchor is anchored in said sea floor.

Thanks to the gravity structure according to the invention, the stability of the gravity structure is partly ensured by said at least one anchor.

Thus, the dimensions of the gravity structure, and in particular the diameter of the slab, can be reduced, for example by 20 to 30%, compared with the state of the art, which results in a decrease in the quantities of concrete and concrete. steel necessary for the manufacture of the gravity structure, as well as a reduction in the size of the area of the sea floor to be prepared before installation of the gravity structure in the service position.

It also results that the gravitational structure is less heavy than in the state of the art, and can therefore be more easily transported and then installed, for example with the aid of a heavy-lift vessel, which is not possible for a heavier structure of the prior art without the need to mobilize a vessel of exceptional capacity.

In addition, the reduced dimensions of the gravity structure ensure that the forces exerted on the gravity structure by the swell are weaker.

Another advantage of the invention lies in the fact that the anchor or tie rods pre-force vertically the barrel of the gravity structure, which, on the one hand, improves the stability of the gravitational structure and, on the other hand, on the other hand, possibly reduces the number of other prestressing devices to be provided for the drum.

An additional advantage is that, due to the reduced size and weight of the gravity structure according to the invention, a water filling of the barrel is sufficient to ensure the stability of the gravity structure on the sea floor. Thus, the method of manufacturing the gravity structure according to the invention overcomes the transport and filling of the ballast material which is necessary for the gravity structure according to the state of the art, as already mentioned.

Moreover, the maintenance and control of anchor rods are simple to implement. It is for example possible to check and adjust, if necessary, the residual tension of each tie rod by a known weighing technique (or "lift-off test").

According to another characteristic of the invention, the barrel comprises an end opposite the slab, and said at least one anchor extends from the end opposite the slab into the barrel.

According to another characteristic of the invention, the gravity structure comprises at least one guide tube of said at least one anchor extending from the end opposite the base to the floor.

According to another characteristic of the invention, the barrel is hollow and comprises a column and a conical base.

According to another characteristic of the invention, each guide tube being disposed in a longitudinal wall of the mast and in the open air in the conical base.

According to another characteristic of the invention, the gravity structure comprises a removable platform.

According to another characteristic of the invention, the gravity structure comprises at least two tie rods.

The subject of the invention is also a method of manufacturing a gravity structure intended for a maritime civil engineering construction, from a raft configured to be laid on a sea floor and secured to a shaft directed in a main direction. substantially orthogonal to said slab, the manufacturing method comprising a step of placing at least one anchor so that said at least one tie rod extends into the barrel and the slab, the gravity structure being configured to in a service position the anchor is anchored in the sea floor.

According to another characteristic of the invention, the step of placing said at least one anchor is preceded by a step of placing at least one guide tube of said at least one anchor s extending from one end of the barrel opposite to the slab, to the slab.

According to another characteristic of the invention, the method comprises a step prior to the steps of setting the tie rod, comprising a step of installing the gravity structure on a sea floor, the shaft being erected in a vertical position.

According to another characteristic of the invention, the method comprises a step of filling in water with an immersed inner part of the gravitational structure.

According to another characteristic of the invention, the step of placing said at least one anchor comprises a step of installing the removable platform at one end of the barrel opposite the floor.

According to another characteristic of the invention, the method comprises a step of drilling by a drilling tool disposed in said at least one guide tube, during which the drilling tool digs a hole in the sea floor, then the pulling is introduced into the guide tube and into the drilled hole.

According to another characteristic of the invention, the step of placing said at least one anchor comprises a step of sealing said at least one anchor during which the borehole is subjected to an injection of grout.

According to another characteristic of the invention, the step of placing said at least one anchor comprises a step of tensioning said at least one anchor made at an upper anchorage.

• la figure 1 illustre une structure gravitaire selon la présente invention ;
• la figure 2 illustre la structure gravitaire de la figure 1 dans une application à une éolienne en mer ;
• la figure 3 illustre la structure gravitaire de la figure 1 dans une application à un pont à hauban ;
• les figures 4a à 4e illustrent un procédé de fabrication de la structure gravitaire de la figure 1 ; et
• la figure 5 est une vue en coupe d'un détail de la figure 1.

Other features and advantages of the invention will become apparent on reading the description which follows. This is purely illustrative and should be read in conjunction with the attached drawings in which:

• the figure 1 illustrates a gravity structure according to the present invention;
• the figure 2 illustrates the gravitational structure of the figure 1 in an application to a wind turbine at sea;
• the figure 3 illustrates the gravitational structure of the figure 1 in an application to a cable stayed bridge;
• the Figures 4a to 4e illustrate a method of manufacturing the gravitational structure of the figure 1 ; and
• the figure 5 is a sectional view of a detail of the figure 1 .

Gravitational structure

As visible at figure 1 , a gravity structure 1, intended for a maritime civil engineering construction, comprises a raft 2 configured to be laid on a seabed S and integral with a barrel 3 directed in a main direction substantially orthogonal to the raft 2.

On the figure 1 , the gravity structure 1 is illustrated in a position corresponding to a construction phase before installation of the wind turbine in which the gravity structure rests on the sea floor S which was possibly prepared for the installation of the gravity structure 1 by preliminary operations known to those skilled in the art.

Once installed, the raft 2 is in contact with the ground S while the barrel 3 is erected vertically.

As visible on the figure 1 , the barrel 3 comprises a column 4 forming the upper part of the barrel 3 and a base 5 forming the lower part of the barrel 3.

Column 4 has a generally tubular shape.

The base 5 has a generally conical shape which flares from the mast 4 to the raft 2.

Column 4 and base 5 are hollow.

As visible on the figure 1 the base 5 is completely submerged while the column 4 is partially submerged.

The raft 2 comprises an inner portion 6 at the base 5 extended by an outer portion 7.

The raft 2 has a generally circular shape of substantially constant thickness under the base 5 and may have a slope or radial slope (a bevel) on its outer portion 7.

The gravitational structure 1 is advantageously provided temporarily, as will be explained below, a removable platform 8 disposed at an upper end 9 of the column 4.

In other words, the raft 2 constitutes the lower end of the gravity structure 1 while the platform 8 is disposed at an upper end 9 of the gravity structure 1.

The gravity structure 1 comprises at least one anchor 10 extending in the shaft 3 and in the raft 2.

In the figures, two anchors 10 are shown.

Nevertheless, the invention is not limited to this number, and it is of course conceivable to provide the structure 1 with a single anchor or, on the contrary, to provide the structure 1 with a plurality of tie rods distributed over the circumference of the column.

The gravity structure 1 is configured so that each anchor 10 is anchored in the sea floor S.

As visible on the figure 1 the tie rods 10 extend from the platform 8 into the barrel 3 and the raft 2.

In other words, one 11 of the ends 11, 12 anchors 10, otherwise called upper and lower anchors, is disposed in the upper end 9.

As visible on the figure 1 , the upper anchorage 11 of each tie rod 10 is placed in close proximity to the upper face of the barrel 3.

The other end 12 is disposed in the marine soil S.

Each anchor 10 is stretched between its ends 11, 12, which ensures a vertical prestressing of the barrel 3.

As visible on the figure 1 the gravity structure 1 comprises two guide tubes 13, each of the tubes 13 being associated with one of the tie rods 10.

In other words, each tie rod 10 extends in a guide tube 13 from the upper end 9 to the raft 2.

Advantageously, each guide tube 13 protects the anchor 10 associated.

As illustrated on figures 1 and 5 each guide tube 13 is arranged in a longitudinal wall 14 of the column 4 and in the open air in the conical base 5.

The guide tubes make it possible to guide the threading of the anchor rods 10 as well as the displacement of a drill, as will be explained hereinafter.

As particularly visible in the figure 5 , an element of fastening 15, comprising an anchoring piece 16, for example of trumpet type, and a cover 17 covering an anchor block (not shown). The gravity structure 1 also comprises a specific connection device disposed in a surface 18 of the raft 15 which interfaces with the seabed S.

The gravitational structure 1 is illustrated in an application to a wind turbine at sea at the figure 2 and in an application to a bridge at the figure 3 .

In the application of the figure 2 , the platform 8 was removed before anchoring a mast 20 carrying a nacelle 21 and pale 22 at the head of the column 4.

The figure 5 illustrates at reference 19 elements for securing the mast 20 to the gravity structure 1.

In the application of the figure 3 platforms 8 were removed before towers 24 and an apron 23 were erected on the upper ends 9 gravity structures 1.

Manufacturing process

As visible on the figure 4a , a method of manufacturing the gravity structure 1 comprises a step of installing the substructure comprising the shaft 3 and the raft 2, but not the anchors 10.

During this step, the raft 2 is placed on the sea floor S prepared beforehand while the barrel 3 is erected substantially vertically.

A water filling of the barrel 3, concomitant with the laying of the substructure allows the substructure to immerse gradually to the contact of the raft 2 with the seabed S.

Then, as illustrated in Figures 4b and 4c , the manufacturing method comprises a step of installing the platform 8 at the upper end 8 of the drum 3. This step is preferably performed by a crane ship.

Once the platform 8 in place, it brings all E equipment necessary for the installation of the tie rods.

Advantageously, in a previous step not illustrated, that is to say before the step of installation of the raft 2 on the seabed S, each guide tube is placed in the barrel 3 during the construction of the substructure 1, before transport to the installation site.

As visible on the figure 4d , the manufacturing method then comprises a step of placing each anchor 10 in the associated guide tube 13.

To do this, the method comprises a step of drilling by a drilling tool brought into contact with the sea floor S after having moved in each guide tube 13.

During this step, the drilling tool digs a hole T in the marine soil S.

Then, the drilling tool is extracted from the guide tube13; the anchor 10 is then introduced into the associated guide tube 13 and then into the drilled hole T.

Preferably, the drilling step comprises a preliminary step of drilling a pre-hole facilitated by the specific connection device provided at the interface of the slab and the sea floor, according to a method known to those skilled in the art.

Next, the method comprises a step of sealing each anchor 10 in the associated borehole T by grouting around the anchor 10 in the borehole T.

The manufacturing method also comprises a tensioning step performed at the upper anchor 11, on the platform 8, advantageously by a cylinder of great stroke, because of the large free length, of each tie rod 10.

After installation and tensioning of the tie rods 10, the platform 8 is demobilized, possibly to another gravity structure, as visible in FIG. figure 4e .

As already mentioned, the invention provides a preload which can be associated in parallel with prestressing cables equipping the structure 1 and known to those skilled in the art, while at the same time allowing a reduction in the dimensions and weight of the gravitational structure.

Claims (14)

Gravity structure for a marine civil engineering construction, comprising a raft (2) configured to be laid on a sea floor (S) and secured to a shaft (3) directed in a main direction substantially orthogonal to said base (2), characterized in that the gravity structure (1) comprises at least one anchor (10) extending in said barrel (3) and in the raft (2), the gravity structure (1) being configured so that, in a service position of the gravity structure, said at least one anchor (10) is anchored in the sea floor (S). Gravity structure according to claim 1, wherein the shaft (3) comprises an end (9) opposite to the base (2), and wherein said at least one anchor (10) extends from the end (9). ) opposite to the raft in the barrel (3). Gravity structure according to claim 2, the gravity structure comprising at least one guide tube (13) of said at least one anchor (10) extending from the end (9) opposite the base (2) into the write off (2). Gravity structure according to the preceding claim, wherein the shaft (3) is hollow and comprises a column (4) and a conical base (5), each guide tube (13) being arranged in a longitudinal wall of the column (4) and in the open air in the conical base (5). Gravity structure according to one of claims 1 to 4, comprising a removable platform (8). Gravity structure according to one of claims 1 to 5, comprising a plurality of tie rods (10). Method of manufacturing a gravity structure intended for a maritime civil engineering construction, from a raft (2) configured to be laid on a sea floor and secured to a shaft (3) directed in a substantially orthogonal main direction audit (2), the process of manufacture comprising a step of placing at least one tie rod (10) so that said at least one tie rod extends in the barrel (3) and in the raft (2), the gravitational structure being configured so that in a service position the anchor (10) is anchored in the sea floor. Manufacturing method according to claim 7, wherein the step of placing said at least one anchor (10) is preceded by a step of placing at least one guide tube (13) of said at least one tie rod (10) extending from one end (9) of the shank (3) opposite the base (2), to the base (2). Manufacturing method according to one of claims 7 or 8, comprising a step prior to the steps of introduction of tie rod, comprising a step of installation of the raft (2) on a sea floor, the shaft (3) being erected in a vertical position. Manufacturing method according to one of claims 7 to 9, comprising a step of filling with water a submerged inner portion of the gravity structure. Manufacturing method according to one of claims 8 to 10, wherein the step of placing said at least one anchor (10) comprises a step of installing a removable platform (8) at one end (9) the barrel (3) opposite the base (2). Manufacturing method according to one of claims 8 to 11, comprising a step of drilling by a drilling tool disposed in said at least one guide tube, during which the drilling tool digs a hole in the sea floor, then the tie is introduced into the guide tube and into the drilled hole. Manufacturing method according to claim 12, wherein the step of placing said at least one anchor comprises a step of sealing said at least one anchor during which the borehole is the object of a grout injection. Manufacturing method according to one of claims 11 to 13, wherein the step of placing said at least one anchor comprises a step of tensioning said at least one anchor made to an upper anchorage ( 11).

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