MC200004A1 - Work intended to create a barrier on a submerged bottom and method for doing so - Google Patents

Description

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DUPLICATE i -7 JAN99 09 53

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10. "A structure designed to create a barrier on a submerged seabed and the method for doing so."

Alain LAVERGNE LACROIX

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The invention presented here relates to a structure designed to create a barrier on a submerged seabed. Such a barrier makes it possible to protect a marine area for the purpose of its development.

25 The invention also relates to a method of constructing such a structure.

In this technical field, French patent 2,749,330 is particularly well known. The invention presented therein is an improvement over traditional techniques which are often 30 damaging in terms of the environment and water pollution.

This document discloses a structure designed to create a barrier on a submerged seabed in order to protect a maritime area and allow for its development. Its defining characteristic is that it consists of several caissons acting as shock absorbers, which are submerged and adapted to large waves.

depths / said caissons are joined together by means of assembly which also act as a sealing joint between two caissons, the caissons ensuring the support of an artificial continental shelf.

Such a structure presents several disadvantages.

Firstly, each caisson forms a single wave-damping element. Many caissons are needed to build a barrier.

This addition of numerous small-sized boxes represents a high installation time and cost.

Furthermore, the caissons are interconnected. The large number of caissons required results in a significant number of connections to be made, using a complex assembly technique that necessitates underwater work.

Another drawback is access to the structure during its construction. According to French document 2 749 330, this access is only possible by sea. This route is long and expensive.

The present invention makes it possible to overcome the drawbacks of current techniques.

It reduces the time and difficulty of installation. To achieve this, it has the advantage of offering caissons incorporating several damping chambers. This allows for the construction of a large length of the barrier in a single piece.

Another objective of the invention is to optimize the anchoring of the caisson.

To achieve this, the boxes feature recesses that facilitate fixing and reduce the number of structural elements required for anchoring.

The specific structure of the caisson proposed in this work, featuring several juxtaposed damping chambers, allows it to take on the shape of a barge. This

The barge is particularly advantageous because it allows the caisson to be brought to the site by simple towing.

The container is therefore larger in size than state-of-the-art structures without this hindering its transport and handling.

This caisson structure also aims to allow the installation of ancillary elements on the caisson, including a watertight screen, a wave break, or a jetty for land access. This last point is important because it further optimizes the construction phases by allowing access for vehicles or personnel by land to the site itself.

Another advantage of the structure is that it allows the caissons to be mounted either directly on the excavation or on an anchoring framework itself embedded in the seabed. The caissons therefore adapt perfectly to the site's configuration.

Other goals and advantages will appear during the description that follows, which is however only given as an indication.

The present invention relates to a structure intended to create a barrier on a submerged bottom in order to protect a maritime area to allow its development, characterized by the fact that it comprises at least one submerged caisson having several juxtaposed damping chambers allowing to form the support of a continental shelf while damping the action of the swell.

The present invention further relates to a method for constructing a structure intended to create a barrier on a submerged seabed, suitable for implementation by the structure according to the invention, characterized in that the trench intended to receive the caisson is prepared, a caisson is built in a dry dock and towed to the site, and then...

contact the caisson and the excavation by controlled ballasting of the caisson, the caisson or subtractor is anchored by piles, the ballasting is finalized by adding solid elements in the damping chambers.

The present invention also relates to a method of constructing a structure intended to create a barrier on a submerged bottom, suitable for implementation by the structure according to the invention, characterized by the fact that an anchoring framework is positioned on the site, the anchoring framework is embedded by piles, a caisson is built in a shipyard and towed to the site, the caisson is brought into contact with the anchoring framework by controlled ballasting, and the caisson and the piers of the anchoring framework are joined together.

The work according to the invention may be presented in the embodiments introduced below.

The caisson has a barge-like shape allowing it to be towed to the construction site.

The caisson is equipped with main recesses in the caisson structure cooperating with piles or piers to achieve the anchoring of the caisson.

The box is equipped with secondary recesses for the installation of anchoring devices or the passage of tools.

The caisson is equipped with shafts for the passage of operators or pipes.

The structure may consist of several caissons connected to each other by metal gabions filled with riprap and sealed together by cement injection.

It features a ground access cover positioned on the caisson.

It features a removable waterproof screen positioned on the housing to prevent any dispersion of fines out to sea during the backfilling stages.

It features a wave-proof wall positioned over all or part of the caisson and equipped with a deflector.

The caisson is fixed via piles onto an anchoring framework embedded by piles.

The base of the box includes a pedal to prevent scouring.

The base of the box may include, on the wider side, a stability fin.

The accompanying drawings are provided as illustrative and non-limiting examples. They represent one embodiment according to the invention. They will allow the invention to be easily understood.

Figure 1 is a top view of the box in a preferred embodiment.

Figure 2 illustrates a barrier made up of two boxes according to a cross-section along lines 1-1 of figure 3.

Figures 3 and 5 are cross-sectional views along lines 3-3 of Figure 1, in two different embodiments.

Figures 4 and 6 are cross-sectional views along lines 4-4 of Figure 1, in two different embodiments.

Figures 3 and 4 differ from figure 1, however, by the presence of a stability fin not shown in figure 1.

Figures 7, 8 and 9 schematically illustrate the assembly of additional elements of the structure in particular modes of implementation.

Figures 10 and 11 illustrate possible applications of the invention, in overall section.

The present invention relates to the construction of a set of building elements which, combined with each other, constitute a structure enabling, in particular, a

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Innovative wave damping.

The structural elements that make up the building will generally be:

1. a raised platform 27 5 2. a suspended beach 2 8

3. a surge basin 29

4. at least one marine hydraulic caisson

This structure is associated with a low-polluting construction process and remains virtually invisible after its completion. The structure allows for the creation and protection of a multi-layered marine reserve.

This structure is preferably not visible in calm seas, which is essential to enjoy the aesthetics of the seascape as opposed to classic structures imposing a concrete wall several meters high along the horizon.

The structure presented here makes it possible to create a barrier between a wide side 21 and a land side 22 as illustrated in figure 1.

Figures 10 and 11 also illustrate an overall presentation of such a work in two modes of embodiment, according to the method of fixing the box(es) 1.

According to the invention, the structure comprises at least one caisson 1. The caisson(s) 1 are submerged, meaning they are not visible above the water in calm seas. The water level 2 is therefore located above the caisson(s) 1, as shown in Figures 3 to 9.

Figures 1 and 2 illustrate the presence on a box l of several juxtaposed damping chambers 3. 30 Box 1 is a symmetrical and substantially elongated construction.

In a preferred mode, this construction is called a barge and is built in a naval form that allows the transport of the

caisson 1 by sea, by simple towing.

The invention fulfills the following essential objectives:

Protection against swell:

A significant portion of the swell is dampened inside the marine hydraulic caisson 1, in a chamber 3 designated as the damping chamber, and possibly by additional dissipative elements. The openings 25 formed in the walls of the chambers 3 exposed on the wide side 21 allow for this damping, as shown in particular in Figures 1, 4, and 5.

- By its appropriate dimensions, caisson 1 causes the breaking of the swell into a natural basin also designed and arranged to exhaust the energy of said breaking and to promote, by the choice of rocks, their origin, their size as well as their arrangement, the development of the marine flora and fauna of the breaking basin.

Exterior landscaping:

The structure allows for the creation and protection of coastal developments such as:

creation of a suspended beach, creation of a lagoon, creation of a continental shelf, creation of a port

- Environmental protection, creation of marine reserves

The first set of boxes can be implemented in the following way:

The caissons are prefabricated on an industrial naval dockyard site and are transported by sea.

The caissons are placed side by side as in figure 2 and form a support.

They are designed to dissipate wave energy and help support a continental shelf.

For the final stability of the structure, caissons 1 can be equipped with three types of reservations.

The first part concerns the main reservations 4 in the resistant structure of the caisson 1 in order to carry out the base and anchoring of the caisson 1 either directly to the ground of foundations by means of large capacity piles, or by means of an anchoring framework 18.

The reservations can be tubular as illustrated in Figure 1. Figure 5 also shows the cooperation of the main reservations 4 with piles 5 for anchoring in the subtratum.

Figures 3 and 4 show the fixing of the caisson 1 onto an anchoring frame 18.

As shown, this framework 18 may include:

a primary framework 18a comprising piles 5 embedded in the ground 24

a secondary framework 18c formed of cross braces and constituting a reinforcement of the framework 18.

- A connecting frame 18b suitable for receiving the caisson 1 via its main openings 4. The connecting frame 18b will include piers 6 cooperating with the openings 4.

The caisson may also include secondary openings 7 in the caisson's load-bearing structure for the passage of smaller tools such as drilling openings for additional geotechnical investigation and intervention, or soil sampling, for example, or drilling openings for the installation of micropiles, tiebacks, injection tubes, and sonic surveys. These openings 7 are accessible above water level and allow the use of tools

said to be traditional in special foundations, or when it is not necessary to support the structure with high-capacity piles, (the main 4 reservations are then filled).

As shown in figure 5, the secondary reservations 7 may be tubular.

Finally, we will preferentially create reservations in shaft 8 for prestressing the structure.

These inspection wells (8) may also contain additional components such as:

Compressed air lines are useful for generating a pneumatic wave breaker offering modulated protection depending on the agitation and in calm seas; it should be noted that the creation of bubble curtains is also interesting for the fight against water pollution.

- High-pressure pipelines for energy recovery.

Dry pipes for various uses.

Depending on the configuration of the work to be carried out, several caissons 1 connected by metal gabions 9 filled with rocks sealed together by injection of cement, in particular in the form of grout, can be put in place.

In particular, during construction, the caissons are capped with structural elements that allow:

- to create a watertight screen between the wide side 21 and the land side 22 and to work without risk of pollution from the open water. Such a screen 11 and its positioning are illustrated in Figure 8. It is removable and will be taken off after construction.

- to create land access for the ballasting of all or part of the caissons 1 by means of a land access ramp 10 as illustrated in Figures 7 and 8, suitable for receiving vehicles 14 and/or operators by a

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platform 16 resting on caisson l by posts 17.

- to design temporary protection against swell during the works.

to construct a wave break wall 12, especially if a breaking basin cannot be created at specific points. Such a wall 12 is illustrated in Figure 9, where it includes a deflector 13 protecting the landward side 22 and potentially allowing land access.

Each caisson 1 is ballasted to a certain height to ensure its placement and stability. The ballast comes partly from materials extracted during the construction of its trench and partly from quarry materials. These materials correspond to the solid elements 26 illustrated in Figures 4 and 6.

The general interior layout consists of using the surface of the bottom of room 3 and establishing a marine reserve there.

When caisson 1 is directly anchored in the ground 24, an anti-scour pedal 20 must be made on the base 19 of caisson 1 to ensure the risk of scour at the foot of the structure.

When the box 1 rests on a frame 18, stability fins 23 appearing in figure 3 will preferentially be formed at the base 19 of the box l.

The invention also relates to a method of constructing a structure.

In the first case, this process is implemented when the caisson 1 is directly anchored in the substrate.

In this case, the process can be implemented in the following embodiment, which consists of:

- construct the caisson in a naval dockyard

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- prepare pit 24 intended to receive caisson 1; tow caisson 1 to the site

- bring the caisson 1" into contact with the seabed by controlled liquid ballasting

- Carry out adjustments, checks and additional secondary drilling if necessary

establish the special foundations from the work platforms

- to carry out the solid ballasting of the structure using solid elements 26

- install additional enclosures 1 according to the determined protection plan

to make the connections between each caisson 1 by gabions 9 in rockfill and sealing the rockfill between them by injection of cement grout.

In a second case, the method according to the invention is implemented when the box 1 is fixed on an anchoring frame 18 itself embedded in the ground 24.

In this case, the process can be implemented in the following embodiment, which consists of:

dimensioning and constructing an anchoring framework 18

Space-based metal construction workshop: building caisson 1 in a naval form

- prepare the trench 24 intended to receive the anchoring frame 18

tow the anchor frame 18 to the site

- Position the anchoring frame 18 and bring the piles 5 into contact with the seabed by controlled ballasting

drill and embed the 5 piles into the bedrock from the working platforms

- tow container 1 to the site

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Install caisson 1 on anchor frame 18 using controlled ballasting

to secure caisson 1 to foundation piers 6 by keying and cementing piers 6 and caisson 1

to carry out the solid ballasting of the structure

- Install the other enclosures 1 according to the determined protection plan

- connect the seabed and the caissons together by gabions 9 in rockfill and sealing the rockfill together by injection of cement grout.

In addition to the two processes described above, the same completion of the work can be added, namely:

- the installation of a temporary watertight screen 11 and a land access jetty 10 on the submerged caissons 1 to allow the development of the overtopping basin and the continental shelf by sea and land without the spread and pollution of the fill material towards the open sea, and then the removal of these elements 10 once the work is completed

the connection of the caissons l of the two outer edges of the protection project determined to the coastline by penetration of the end sections of the caissons l into the existing coastal terrain.

Once the caissons 1 have been joined and strongly anchored to the ground 24 the general backfilling work phase must be designed in such a way as to prevent any dispersion of fines 15 and contamination with the open sea.

To do this, it is advisable to implement a temporary waterproof screen 11 between the future embankment to be built and the wide side 21.

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The top of the submerged caissons 1 is at a shallow depth (1 to 3.00 m maximum).

It is then easy to set up a screen 11 as defined for example in figure 8.

5 This screen 11, depending on the importance of the work envisaged, can

it can be a simple metal facing such as removable sheet piles or a more substantial one such as a secondary reinforced concrete caisson.

The recovery and treatment of polluting elements, which are essentially fine particles 15 likely to contaminate the open sea during the 10 backfilling, are easily carried out by decantation on the bottom of the caissons 1.

Land access for ballasting all or part of the caissons is from the jetty 10 which is temporarily fixed on top of the caissons l.

15 Of course these temporary installations are sufficiently resistant and altimetrically stabilized to withstand the swells during the works and are folded up at the end of the general backfilling.

Environmental protection is thus perfectly respected.

Furthermore, the temporary installation can be designed and constructed as permanent if a surge basin cannot exist at any given time.

A wave wall is then formed, which can be permanent. It is quite clear that the choice of foundations is influenced by the most comprehensive soil investigation possible.

However, it should be noted that seabed surveys are very expensive. The scale of the various soundings, corings, and tests, depending on the size of the project and the available budget for the study phases, often necessitates reducing even the most comprehensive study to a more concise one. Essential geotechnical investigations can then be carried out during the construction phase.

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Indeed, the works according to the invention are equipped with secondary reservations 7 which allow, as appropriate, in situ sampling by coring, suitability and injection testing, the essential preliminary tests 5 on the actual capacity of the tie rods and micropiles or piles to be made.

A structure located near another structure may rest on a very different type of soil. Therefore, following further investigations, it may be decided for one to be anchored to the subsoil by high-capacity piles, and for the other to be simply placed on the soil consolidated by injection, for example.

The foundation techniques are then different but the different reservations 4, 7 with which each caisson 15 1 is equipped make it possible to meet all these choices and thus offer the Owner the requirement in relation to the builders of the best value for money.

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REFERENCES

1. BOX

2. WATER LEVEL

5.3. DEPRECIATION CHAMBER

4. MAIN RESERVATION

5. STAKE

6. BATTERY

7. SECONDARY RESERVATION 10 8. WELL

9. Gabion

10. LAND ACCESS BOAT

11. WATERPROOF SCREEN

12. Wave Breaker 15 13. Deflector

14.ENGINE

15.FINES

16. PLATFORM

17.POLES

20 18. ANCHOR FRAME 18a. PRIMARY FRAME 18b. CONNECTING FRAME 18c. SECONDARY FRAME 19. BASE OF THE BOX 25 2 0. PEDAL

21. WIDE SIDE

22.LANDSIDE

23. Stabilizing Fin 24. Mud or Soil

30 2 5. OPENINGS

26. SOLID ELEMENTS 2 7. LAND 28. SUSPENDED BEACH

BREAKDOWN BASIN

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Claims (14)

DEMANDS 1. Structure intended to create a barrier on a submerged seabed in order to protect a maritime area to allow its development, characterized by the fact that it includes at least one submerged caisson (1) having several juxtaposed damping chambers (3) allowing to form the support of a continental shelf while damping the action of the swell. 2. Structure according to claim 1 characterized in that the caisson (1) has a barge shape allowing it to be towed to the site of the structure. 3. Work according to one of claims 1 or 2, characterized in that the caisson (l) is provided with main reservations (4) in the structure of the caisson (1) cooperating with piles (5) or piers (6) to achieve the anchoring of the caisson (l). 4. Work according to any one of claims 1 to 3 characterized in that the caisson (1) is provided with secondary reservations (7) for the installation of anchoring means or the passage of tools. 5. Work according to any one of claims 1 to 4 characterized in that the caisson (l) is provided with shafts (8) for the passage of operators or conduits. 6. Work according to any one of claims 1 to 5 characterized in that it comprises several caissons (l) connected to each other by metallic gabions (9) filled with riprap and sealed together by cement injection. 7. Work according to any one of claims 1 to 6 characterized by the fact 18 that it features a boardwalk for land access (10) positioned on the caisson (1). 8. Work according to any one of claims 1 to 7 characterized in that it has a removable watertight screen (11) positioned on the caisson (1) to prevent any dispersion of fines (15) towards the open sea during the backfilling stages. 9. Work according to any one of claims 1 to 8 characterized in that it has a wave wall (12) positioned on all or part of the caisson (1) and equipped with a deflector (13). 10. Work according to claim 3 in combination with any one of claims 1, 2, 4 to 9 characterized in that the caisson (1) is fixed by means of piles (6) on an anchoring framework (18) embedded by piles (5). 11. Work according to any one of claims 1 to 9 characterized in that the base (19) of the box (1) includes an anti-scour pedal (20). 12. Work according to claim 10, characterized in that the base (19) of the box (1) has, on the wide side (21), a stability fin (23). 13. A method for constructing a structure intended to create a barrier on a submerged seabed, suitable for implementation by the structure according to claims 1, 2 and 3 in combination with any one of claims 11 or 4 to 9, characterized in that: The pit (24) intended to receive the caisson (1) is being prepared. 19 - a barge-shaped caisson (l) is towed from the shipyard to the site; the caisson (1) is brought into contact with the slipway (24) by controlled ballasting of the caisson (1) The caisson (l) is anchored to the substrate by means of piles (5) - the ballasting is finalized by adding solid elements (26) in the damping chambers (3). 14. A method for constructing a structure intended to create a barrier on a submerged seabed, suitable for implementation by the structure according to claims 10 or 12, characterized in that: An anchoring frame (18) is positioned on the site, - the anchoring framework (18) is embedded by piles - a caisson (1) in the shape of a barge is built in a shipyard and towed to the site, The caisson (1) is brought into contact with the anchoring frame (18) by controlled ballasting. - the caisson (1) and the piles (6) of the anchoring frame (18) are joined together. (5) , crossed out: null; added: null LAVERGNE-LACROIX