FR2571075A1 - Method for floating and immersing various volumes of large dimensions such as prefabricated caissons for the construction of maritime works and device for implementing this method - Google Patents

Abstract

Method for floating and immersing various volumes of large dimensions such as prefabricated caissons for the construction of maritime works, characterised in that prefabricated caissons 1 comprising a lateral wall 2 and an open base 6 are equipped with inflatable floats 3 distributed along the said lateral wall, these caissons fitted with floats being brought by floating, after inflation of these floats, to the desired site where they are then immersed by reducing the volume of gaseous fluid contained in the said inflatable floats. The invention also relates to a device enabling this method to be implemented.

Description

Flotation and immersion process for various large volumes such as prefabricated caissons for the construction of maritime structures, and device for implementing this process.

The present invention relates to a process for flotation and immersion of various large volumes, for example prefabricated caissons for the construction of maritime structures such as quays, dikes, jetties, piles and submerged pillars, etc.

It also relates to the device used for the implementation of this flotation and immersion process and of the process for the construction of maritime structures which results therefrom.

According to a known technique for constructing maritime structures of the aforementioned kind, large prefabricated cylindrical caissons provided with a concrete bottom cast in one piece with the side wall of said caissons or with a removable steel bottom, are moved by flotation, then filled with water, on the site, so as to sink and beach them in the desired locations.

The submerged caissons are then ballasted with an embankment and, in the case of docks or jetties, covered with a surface coating.

This process has a number of drawbacks.

Due to the fact that the cylindrical boxes have diameters frequently greater than 20 m, their removable or non-removable bottom often has an area of several hundred square meters; it is therefore understandable that these boxes are extremely heavy and expensive and that their bottom plays a large part in the importance of their gravity and their cost price.

It does not guarantee the maintenance of an acceptable trim when towing the floating caissons to the disposal site.

 I1 implies a risk of overturning the cylindrical boxes during their immersion.

 I1 does not allow any intervention on the duration or the trajectory of the driving-in movement of the caissons, during their immersion, and does not offer any facility for raising them, for example to perform a positioning correction.

An objective of the present invention is, in particular, to remedy the aforementioned drawbacks of the methods of construction of maritime structures implementing the transport by flotation of prefabricated caissons and the immersion of these caissons on the site of use.

According to the process of the invention, this object is achieved thanks to a remarkable flotation and immersion process by the fact that prefabricated boxes comprising a side wall and an open base are equipped with inflatable floats distributed along said wall. lateral, these boxes provided with floats being brought by flotation, after inflation of the latter, on the site of use where they are then immersed, totally or over most of their height, by reducing the volume of gaseous fluid contained in said inflatable floats.

The flotation and immersion process according to the invention provides several interesting advantages.

 It uses boxes without bottom, the execution of which therefore requires less raw material, so that these boxes are lighter and more economical.

 It offers the possibility of easily adjusting the draft of the caissons according to their weight, when they are towed to the site of use.

It gives the possibility of keeping a better attitude during towing and immersion.

 I1 allows slower and more precise immersion of the caissons.

 I1 provides the possibility of easily reassembling the boxes, for example to correct the positioning of the latter.

The objects, characteristics and advantages mentioned above and others still will emerge more clearly from the description which follows and from the appended drawings in which
Figure 1 is an axial sectional view, schematic, of a cylindrical box equipped with inflatable floats for the implementation of the method of the invention.

Figure 2 is a plan view of Figure 1.

Figure 3 is a view similar to Figure 1 and showing the box equipped with its inflated floats, in the floating position.

Figure 4 shows the box during immersion obtained by the deflation of the floats.

Reference is made to the said drawings to describe an interesting example of implementation, although in no way limitative, of the flotation and immersion process according to the invention, as well as an example of execution of the elements allowing this implementation.

A description is given hereinafter of a very advantageous application of the invention to the movement and immersion of prefabricated caissons intended for the construction of maritime structures such as quays, dikes, piers, piles and submerged pillars, etc. ., but it should be noted that the invention can also be applied to the transport and immersion of other large hollow bodies. For this reason, the term box used in the rest of the present description and in the claims should be considered more generally to designate any hollow body of large dimensions comprising at least one peripheral wall.

The prefabricated boxes 1 which can be used for implementing the method of the invention have a side wall 2 or closed peripheral wall and an open base 6. They are also open at the top. These boxes can have various shapes: cylindrical (as illustrated in the drawing), cubic, parallelepipedic, frustoconical, etc. They are generally executed in reinforced concrete and can have very large dimensions: for example a height of the order of 12 to 19 m and a diameter of the order of 24 m, which can represent a weight of the order of 1500 t. They have a widened lower end constituting a sole 2a.

According to the method of the invention, the flotation of these boxes without bottom, during their towing on the grounding site and their immersion are obtained by means of a plurality of inflatable floats 3 distributed, preferably regularly, along of the side wall 2 of said boxes. These inflatable floats 3 are arranged on the side of the internal face of the side wall 2 (as shown in the drawings) or on the side of the external face of said wall, or both on the side of the internal face and on the side of the external face of the latter.

These floats are advantageously constituted by inflatable tubes of elongated shape, arranged vertically or substantially vertically and, for caissons with a height of the order of 12 to 19 m and a diameter of 24 m, can, for example, have a height of the order of 11 to 15 m and a diameter of the order of 4 m. According to an interesting embodiment, they are made of a high-resistance canvas envelope, enclosed in a protective metal mesh.

The inflatable tubes constituting the floats 3 are closed at their upper and lower ends, or only at their upper extremi-tee, their lower extremity remaining open to the maniered of a plunger bell.

The upper and lower ends of the inflatable tubes are reinforced by means of a metal cap 3a, 3b, respectively, having, for example, the shape of a spherical cap or approximately, in order to present the necessary robustness. When the inflatable tubes are provided with an open base, the latter is reinforced by a metal crown.

The reinforced upper and lower ends 3a, 3b of the inflatable tubes are secured to fixing means 4 (for example slings provided with a fastening and closing assembly device known per se) allowing them to be hooked, in a removable manner, at the upper and lower parts, respectively, of the side wall 2 of the boxes which are equipped with additional attachment org-anes such as robust rings 5 solidly anchored in the thickness of said side wall and accessible on the internal face and / or on the external face of the latter. The locking and / or opening of the float fixing means can or can be done manually or automatically with remote control from the tug.

Each inflatable tube 3 is thus fixed, by its reinforced upper and lower ends 3a, 3b, to the upper and lower parts, respectively, of the side wall 2 of the box, during the execution of the towing and immersion operations.

The inflatable tubes 3 are fitted with an inflation and bleed valve and are connected, by means of suitable flexible supply and distribution pipes, to a control and distribution console of a pneumatic distribution installation allowing them to be inflated or to deflate them, together or separately, this control and distribution console being, for example, installed on the tug. We do not describe, in order not to overload the description and the drawings, the compressed air distribution system or other gaseous fluid used to inflate or deflate the floats, such distribution systems being well known in the art of pneumatic automation.

The pipeline valves and fittings are positioned on the reinforced ends of the inflatable tubes and, preferably, on the metal cap 3a reinforcing the upper end of said inflatable tubes.

For the implementation of the method of the invention, the floats 3 are fixed to the side wall 2 of the box 1, all along the internal and / or external surface of the latter, with regular spacing and in sufficient number to ensure the buoyancy of said box, when inflated to an adequate pressure (Figure 3).

The box 1 equipped with the floats is then brought, by towing or otherwise, to the site of use. The floats are then deflated, which has the effect of canceling the buoyancy of the assembly and of causing its immersion and its sinking towards the seabed (Figure 4), the water indeed entering freely inside of the box 1 through its lower opening 6 and causing it to submerge.

It is observed that, both during the towing phase or other mode of movement as during the immersion phase, the possibility of inflating or inflating each float separately, makes it possible to control the trim of the box and to make any corrections desirable.

After immersion and positioning of the box in the intended location, the floats 3 are detached from the wall 2 and are recovered for new use.

The submerged caissons 1, totally or over most of their height, are then ballasted with an embankment made up of sand and / or quarry waste and, in the case of construction of quays or piers, the ballasted caissons are finally covered with a surface coating.

Claims (10)

1. - Flotation and immersion process for various large volumes such as prefabricated caissons for the construction of maritime structures, characterized in that prefabricated caissons (1) comprising a side wall (2) and an open base (6), are equipped with inflatable floats (3) distributed along said side wall, these boxes provided with floats being brought by flotation, after inflation of the latter, on the site of use where they are then immersed while decreasing the volume of gaseous fluid contained in said inflatable floats. 2. - Method according to claim 1, characterized in that the inflatable floats (3) are arranged along the internal face of the side wall (2) of the boxes (1) or along the external face of said side wall . 3. - Method according to claim 1, characterized in that the inflatable floats (3) are arranged both along the inner face of the side wall (2) of the boxes and along the outer face of said side wall . 4. - Method according to any one of claims 1 to 3, characterized in that one uses for the flotation and the immersion of the caissons (1), floats (3) constituted by inflatable tubes of elongated shape that it is installed vertically along the side wall (2) of said boxes. 5. - Method according to any one of claims 1 to 4, characterized in that the stability of the caissons (l) during the flotation and immersion phases and the adjustments of attitude possibly necessary are obtained by inflation and / or the inflation of the floats (3) fitted. said boxes, for example by means of a pneumatic distribution installation, known per se. 6. - Device for implementing the flotation and immersion process of various large volumes such as prefabricated caissons for the construction of maritime structures, characterized in that it comprises - on the one hand, a prefabricated box (1) comprising a side wall (2), an open top and a base (6) also open, said side wall being provided with attachment members (5) for example arranged on the side of its internal face and / or on the side of its external face, and; - on the other hand, a plurality of inflatable floats (3) provided with fixing means (4) making it possible to hang them, in a removable manner, along the side wall (2) of the box (1), on the internal side and / or on the external side of said wall. 7. - Device according to claim 6, characterized in that the floats (3) are constituted by inflatable tubes of elongated shape and whose reinforced ends (3a, 3b) are provided with fixing means (4) for hanging them , vertically, removably, at the upper and lower parts of the side wall (2) of the boxes (1) fitted with complementary fastening members (5). 8. - Device according to claim 6, characterized in that the floats (3) are constituted by inflatable tubes of elongated shape intended to be installed vertically, said tubes comprising a closed upper end and a lower end or open base, these ends being reinforced and provided with fixing means (4) making it possible to hook them, in a removable manner, to the upper and lower parts of the side wall (2) of the boxes (1) equipped with complementary fastening members (5). 9. - Device according to any one of claims 6 to 8, characterized in that the side wall (2) of the boxes (1) has an enlarged base constituting a sole (2a). 10. - Device according to any one of claims 6 to 9, characterized in that it comprises a pneumatic distribution installation known per se, making it possible to inflate and deflate the floats (3) together or separately.