FR2631359A1 - Removal of sand from sea or river bed - by machine which creates turbulence so that sand is suspended in water - Google Patents

Abstract

The machine is for removing sand from river beds or from the sea bed in coastal waters. The machine (8) is mounted between the hulls of a catamaran (2) and its lower end extends downwards to the sea or river bed (24). The machine is provided with turbulence generators which create a sufficient turbulence so that the sand is removed from the sea or river bed and becomes suspended in the water. The suspended sand is then carried away by the tidal or river current (15). USE - Removal of sand from river or sea bed.

Description

The present invention relates to a device for dredging the seabed
Although not exclusively, the device according to the invention is more particularly intended for the desensitization of coastal areas and channels, where in particular accumulate the sediments brought by the tides and deposited in these places.

Various devices are already known for dredging funds. For example, a ship can be equipped with a plow which may be associated with an air ejection system and which comes into contact with said bottom. The displacement of the plow, as well as the air ejected by the system, cause the sediments to be suspended, which are then entrained by the current.

Another example consists in pumping a mixture of water and sediments to then reject it on the surface, the current evacuating the suspended sediments.

Other devices use more or less sophisticated mechanical systems to allow the sediments to be suspended and, possibly, their extraction.

Whatever the solutions adopted, the devices used to allow dredging and, in particular, the desensitization of the seabed are expensive, requiring further maintenance. Furthermore, since they are generally mounted on ships powered by engines from which they draw energy for their proper functioning, environmental problems (pollution, noise pollution) appear.

The object of the present invention is to overcome these drawbacks and relates to a device for dredging aquatic bottoms, the design of which is simple, maintenance-free and does not cause any environmental damage.

To this end, the device for dredging seabeds is remarkable, according to the invention, in that it comprises vortex generators, of elongated shape, disposed respectively in planes substantially orthogonal to the water plane being connected to a support, said generators, the longitudinal direction of each of which is substantially inclined relative to the direction of the current, being capable of coming at least near said bottom so as to generate vortices, approximately parallel to the direction current, resulting in the suspension of the sediments deposited on said bottom.

Thus, the dredging of the sediments is carried out only by the kinetic energy of the current and by the vortex generators to suspend the sediment thanks to the vortices generated by the generators, said sediments then being entrained by the current. Furthermore, the device according to the invention does not require any energy source and any equipment annexed to its proper functioning, which, consequently, does not cause any nuisance for the environment and does not involve any particular maintenance.

Advantageously, said vortex generators are aligned in a direction transverse to the direction of the current.

In a particular embodiment, said vortex generators are aligned parallel one after the other. Thus, each generator generates a vortex causing the sediment to be suspended.

However, in a preferred embodiment, said generators are aligned symmetrically one after the other. Thus, said generators generate vortices in opposite directions with respect to each other, promoting the turbulence effect produced by each of them.

According to another characteristic, each vortex generator is shaped as a fin projecting from said support, the end edge of each fin, connecting its leading edge to its trailing edge, coming into contact with said bottom. Advantageously, said end edge of each of said fins can be provided with scraping means, thus promoting the suspension of said sediments and their aspiration by said generated vortices.

Furthermore, in a preferred embodiment, said support can be a floating body. In this case, said generators can advantageously be fixed to an arm connected to said floating body. Preferably, said arm is then pivotally mounted on said floating body around a substantially horizontal axis.

In addition, controllable lifting means of said arm, from a low position, for which said vortex generators are in contact with the bottom, to a high position, for which said vortex generators are distant from said bottom, are provided on said floating body, said controllable lifting means allowing said arm to be locked in the high position.

According to another characteristic, said floating body is provided at its downstream and upstream ends with links connected to fixed points. Thus, the links make it possible to maintain said floating body in an appropriate position, said floating body also being able to move parallel to the plane of the water so as to sweep a large area.

The figures of the appended drawing will make it clear how the invention can be implemented. In these figures, identical references designate similar elements.

Figure 1 shows a schematic plan view of a particular embodiment of the device according to the invention.

FIG. 2 represents a top view of the device according to the arrow F of FIG. 1.

Figures 3 to 6 illustrate es different phases of operation of the device according to the invention.

Figure 7 shows the area that can be scanned by the floating body of the device.

The device for dredging the seabed according to the invention is particularly suitable for the desensitization of the seabed, coastal areas, channels, river beds and the like.

The device 1, shown in Figures 1 and 2, includes a support 2 which, in the particular embodiment illustrated, is a floating body 3 whose design is, for example, similar to a catamaran. Consequently, the floating body 3 is made up of two identical and parallel hulls or floats 4A and 43 linked together by end crossmembers 5.

According to the invention, the device 1 comprises vortex generators 6 which are connected to the end 7 of an arm 8, the other end 9 of which is pivotally mounted about a horizontal axis 10 linked at its respective ends to the hulls 4A and 4B.

As shown in FIGS. 1 and 2, these vortex generators 6 have an elongated shape and are arranged respectively in planes substantially orthogonal to the horizontal plane defined by the surface of the water 11, on which said device floats.

Furthermore, in FIG. 2, the longitudinal direction 14 of each vortex generator 6 is inclined relative to the direction 15 of the current, and, as this FIG. 2 shows, to the median loxiitudinal axis 16 of the floating body 3 which is arranged parallel to said direction 15. The vortex generators 6, two of which have been shown in FIG. 2, are aligned in a transverse direction 17 substantially perpendicular to the median longitudinal axis 16 and to the direction of the current 15. One could , of course, provide a different number of vortex generators.

In addition, in the illustrated embodiment, the two generators 6, located respectively on either side of the median longitudinal axis 16, are arranged symmetrically with respect to each other, so that their longitudinal directions 14 converge towards each other in the vicinity of the rear end crossmember 5, in the direction of the axis 16.

These generators 6, as will be seen in more detail with reference to FIG. 4i, - are intended to come at least close to the bottom so as to generate vortices, approximately parallel to the direction of current, causing the suspension of the sediments deposited on the bottom, similar to the fins arranged projecting on the wings of aircraft and which convert the laminar flow of air flowing over the wings into turbulent and then swirling flow.

Structurally, each vortex generator 6 is shaped, for example, into a fin 20 projecting from the end 7 of the arm 8. The free end edge 21 of each fin, connecting its leading edge 22 to its trailing edge 23, being capable of coming into contact with the bottom 24.

In addition, a link 26 connected at its opposite end to a fixed point (not shown) is provided on each cross member 5 of the floating body 3, the two links 26 making it possible to keep the floating body 3 substantially parallel to the direction of the current 15, in a specific area.

Furthermore, in this embodiment, controllable lifting means 27 of the arm 8 are provided on the floating body 3. These means 27 allow said arm to pass from a low position, for which the generators 6 or fins 20 are at bottom contact 24, at a high position, for which the generators 6 or fins 20 are distant from said bottom. These controllable lifting means 27 maintain the arm 8 in the high position and also allow the arm to be unlocked, which then pivots, under the action of its own weight, around its axis of articulation 10 to come at least near the bottom 24 by its trunnion generators 6.

These means 27, symbolically represented by a rectangle in FIG. 2, can be fixed to the shell 4A and can comprise, for example, a controllable winch or the like capable of lifting the arm 8, keeping it in the high position, thus that its unlocking.

The dredging of the sediments 28 from the bottom 24 is carried out by means of the vortex generators 6 or fins 20. As can be seen in FIGS. 1 and 2, the fins 20, by virtue of their shape and their arrangement, generate, under the action current 15 and the pressure difference applied on their main faces, vortices 30 which make it possible to "take off" the sediments 28 deposited on the bottom 24 and to entrain them in said vortices. The sediments 28, put in suspension, are then evacuated by the current 15, which thus makes it possible to dredge the silted area.

Furthermore, due to the fact that the fins are inclined symmetrically with respect to one another, they generate vortices of opposite direction (FIG. 2), which optimizes their action.

The fins then make it possible to convert the laminar flow of water into swirling flow, thanks to which the sediments 28 are suspended and then entrained by the current.

In addition, to promote "suction" of the sediment 28 in the vortices 30, scraping means, such as blades, not shown in the figures, can be associated with the fins 20, preferably in the vicinity of their edge. free end 21. These scraping means thus fragment the sediments (sand, alluvium, small stones) to allow them to be suspended and evacuated by eddies30. The end edge, as well as the leading edge, of each fin, can be cut to ensure the fragmentation of the sediments.

The device according to the invention therefore uses the kinetic energy of the current without calling on complex and expensive mechanical systems. The device does not present any risk of nuisance for the environment (pollution, noise, ...) and does not require, moreover, any particular maintenance.

The dredging of a bottom, in particular silted up, of a coastal bay by the device according to the invention described with reference to Figures 1 and 2 can be carried out as follows.

In FIG. 3, the current 15 is substantially zero since the sea is at high tide. Therefore, the arm 8 of the floating body 3 is in the high position and maintained in this position by the controllable lifting means 27, so that the generators 6 or fins 20 are distant from the bottom 24. The floating body is held substantially in the appropriate position by the links 26.

As soon as the tide goes down, FIG. 4, generating a current 15, the controllable lifting means 27 release the arm 8 which pivots around the axis 10 under the action of its own weight so that the end edges 21 of the fins 20 come into contact with the bottom 24. When the fins reach their low position, they generate vortices 30 thanks to the downward current 15, which causes the "separation" and the suspension of the sediments 28 which, sucked by the vortices 30 , are then driven offshore by the ebb tide current 15.

When the sea has retreated offshore, Figure 5, the floating body 3 rests on the bottom 24 of which part of the sediment has been dredged. The arm 8, pivoting about its articulation axis 10, returns to the high position while being locked by the controllable means 27.

When the tide rises, Figure 6, the articulated arm 8, carrying the tourbillon generators 6, is held in the high position. The reference 32 represents the sediments removed and evacuated under the action of the vortex generators 6 during the preceding ebb tide illustrated in FIG. 4.

FIG. 7 shows the area 34 which can be scanned by the floating body 3. Thanks to the links 26, the body 3 can oscillate, under the action of currents transverse to the downward current 15, in a plane parallel to the plane of the water, which allows the whirlpool generators to dredge a large area 34 of sediment.

It is therefore conceivable that, by using a plurality of floating bodies 3 arranged side by side, it is possible to carry out dredging, and in particular the desensitization, for example of a bay or a channel.

Claims (10)

1 - Device for dredging seabeds, characterized in that it comprises whirlpool generators (6), of elongated shape, respectively disposed in planes substantially orthogonal to the water plane by being connected to a support (2 ), said generators (6), the longitudinal direction (14) of each of which is substantially inclined relative to the direction of the current (15), being capable of coming at least near said bottom (24) so as to generate vortices (30), approximately parallel to the direction of the current, causing the sediment (28) to be suspended on said bottom (2li). 2 - Device according to claim 1, characterized in that said vortex generators (6) are aligned in a direction (17) transverse to the direction of the current (15). 3 - Device according to claim 2, characterized in that said vortex generators are aligned parallel one after the other. 4 - Device according to claim 2, characterized in that said vortex generators are aligned symmetrically one after the other. 5 - Device according to any one of claims 1 to 4, characterized in that each vortex generator (6) is shaped as a fin (20) projecting from said support, the end edge (21), connecting the leading edge (22) to the trailing edge (23) of each fin, coming into contact with the bottom. 6 - Device according to claim 5, characterized in that said end edge (21) is provided with scraping means, intended to come into contact with said bottom. 7 - Device according to one of the preceding claims 7 to 6, characterized in that said support (2) is a floating body (3). 8 - Device according to claim 7, characterized in that said vortex generators (6) are fixed to an arm (8) connected to said floating body (3). 9 - Device according to claim 8, characterized in that said arm (8) is pivotally mounted about an axis (10) substantially horizontal on said floating body (3). 10 - Device according to claim 9, characterized in that controllable lifting means (27) of said arm (8), from a low position for which said vortex generators (6) are in contact with the bottom, towards a position upper, for which said vortex generators (6) are distant from said bottom, are provided on said floating body (3), said lifting means (27) making it possible to keep said arm (1) locked in the high position.  it - Device according to one of claims 7 to 10, characterized in that said floating body (3) is provided at its upstream and downstream ends with links 26 connected to fixed points-s.