EP0557401B1 - Erosion control device - Google Patents

Abstract

PCT No. PCT/FR91/00887 Sec. 371 Date May 7, 1993 Sec. 102(e) Date May 7, 1993 PCT Filed Nov. 12, 1991 PCT Pub. No. WO92/08848 PCT Pub. Date May 29, 1992.An elongated tubular assembly comprising a plurality of tubular units disposed in end-to-end relationship, each unit comprising a lower section (1) composed of a variably rigid impermeable contact base (3), and an upper section (2) with a variably rigid protruding hull (5) designed to deviate surrounding fluid flows, the lower (1) and upper (2) parts being connected to each other at least along their longitudinal edges encompassing to such extent an internal space in which a ballast (15) can be admitted through registered hull openings (7), such flexible base and hull combination being designed to give stability to a light-weight version of said unit even in an environnment of heavy fluids, somewhat in the manner of a flat fish, for works including but not limited to ground erosion control and flood control.

Description

The present invention relates to a modular device for controlling the erosion and migration of soils in the environment of a fluid, composed of a contact base on the ground with variable rigidity, surmounted by a hull of elongated shape, making it possible to produce fascines or cords having stability in a heavy fluid such as water, the main functions of which are on the one hand to act on the speed of the erosion fluid to influence the sedimentation of the loose elements of the soil which are in transit, on the other hand to slow down the migration and erosion of the soil by opposing it with a stationary implant. The base with variable rigidity is inspired by the morphology of a flat fish. Its combination with a hull promoting a laminar flow of the fluid ensures the efficiency and stability of the device in a heavy fluid such as water. The juxtaposition of modules in cords, placed end to end and / or perpendicularly also makes it possible to constitute reservoirs useful for flood control, the construction of settling basins, aquaculture, and to protect vulnerable objects such as cables, networks and pipes in an active environment.

Ambient fluids (air and water) are factors which generally contribute to soil erosion in both marine and terrestrial environments, due to the erosion velocity which they can reach either naturally or under the effect of human interventions.

A sea or river current retarder can be assimilated by analogy with the artificial reproduction of a sedimentary wrinkle (mega-ride, etc.) ascending the current ascending from the bottom, and thus promoting the sedimentation and the regrouping of loose elements in transit. in new natural sedimentary wrinkles so as to simulate a delta or estuary profile regenerating the soft banks.

Traditionally such a sedimentary action has been sought as a marginal function of heavy and oversized coastal structures. Even if these works are not oversized, they are most often made by filling envelopes in flexible geotextile material (rolls, bags ..) with a heavy ballast such as sand or concrete which alone ensures its deployment. Thus weighted, these devices take a semi-cylindrical shape of elongated wing and tend to burrow gradually in the sand under their own weight. To combat this progressive burial, other techniques consist, as in US Pat. No. 690,585 (HOLMBERG), placing the retarder on a mat made of porous geotextile material anchored in the ground by peripheral pockets (FIG. 1a).

In the case where these relatively rigid and convex retarders are fixed on a flexible and porous mat, the hydrostatic pressure undergone by the wing is transmitted almost entirely through the porous mat in the ground under the device and can have the effect of lift it up and tip it over. In addition, these devices can only be deployed when ballasted and are heavy, fragile, bulky, unsightly and irremovable. When built in great lengths, they suffer from longitudinal fragility and can break when the soil is modified.

Other technologies are used for soil stabilization such as hardening of the soil by a coating made of self-blocking and articulated heavy elements. As in the case of the porous carpets mentioned in the HOLMBERG patent, the hydrostatic overpressure undergone by the upper face of the covering makes its way through the joints of the elements and causes an injection of water under the device which can have the effect of bury by sand fluidization on the underside. To combat this progressive burial, other techniques consist, as in GB patent A2160246 O'HEA, of channeling and denting the interstices of the articulated elements so as to obtain a “venturi” effect of suction from the underside of the device towards the upper side. However, these venturi-effect devices must, in order to be effective, favor a direction of flow, as on the side of an aircraft, so that the flake shape can be used. In the case of maritime structures, no direction of flow of the fluid can be favored and the improvement obtained may not work in all the directions of flow of the fluid.

In addition, these floor covering devices are heavy and mutilating for the environment.

The present invention aims to remedy these drawbacks or at least to mitigate them satisfactorily, while providing better control of soil erosion by a simple and versatile device (marine or terrestrial) whose structure does not spare any communication between the underside of the device and its upper face, whose morphology, of variable rigidity inspired by that of flat fish, allows greater lightness of the module and whose main means of stabilizing the ground is not to harden it by a uniform coating, but to wave it step by step in the manner of sedimentary wrinkles existing on beaches and deserts.

One of the characteristics of the present invention is to allow the assembly of modular sedimentation cords which are light and of low profile, meeting the characteristics and constraints of traditional sedimentation cords (fascines), not only in the wind fluid but also in a heavy fluid such as water. It may also be imperative to change the location and / or orientation of these devices to obtain a better reconstitution effect, taking into account the marine factors involved in the work area.

On the emerged parts of the ground, light and flexible devices adapted to the constraints of the wind fluid, are used to fix the dunes behind windbreak nets which are either placed on the ground (Figure 1c), or arranged vertically (Figure 1).

One of the aims of the present invention is to fix the underwater dunes by a light device, easy to install, suitable for maritime fluid and to remedy the drawbacks of heavy and massive structures or at least to mitigate them satisfactorily, while obtaining better control of soil erosion using a simple and multifunctional device (marine, river and land).

This object is achieved in accordance with the invention by means of a modular assembly having the characteristics of claim 1 comprising a lower part provided with means for fixing to the ground and an upper part provided with means for attenuating the energy of the erosion fluids - these means comprising a shell of variable rigidity while the fixing means comprise a non-permeable base of variable rigidity, the side facing the ground is subjected to a first hydrostatic pressure lower than the hydrostatic pressure acting on the upper face of said fixing means and resulting from the pressing force of the erosion fluids on the hull. In addition, the lower and upper parts are integral with each other at least on their peripheral edges, thereby delimiting an interior volume capable of being filled at least partially by ballast or by ia elastic material, the means of which fixing and / or energy attenuation means can be made, this elastic material can form a single block with said means, or by cables, pipes, or networks.

According to a first embodiment, the upper part is removably fixed on the lower part.

According to another embodiment, the device is hollow and integral.

According to yet another embodiment, the device is full and made of a single elastic block

According to an advantageous characteristic, the ends of the hull comprise modular assembly means adapted to cooperate with the corresponding means of devices of the same type to produce an assembly of generally continuous shape; said assembly means comprising a male profile fitting into a female profile to form a continuous longitudinal chain and / or a cheek profile at least partially and without discontinuity following the lateral flanks of the upper part to form lateral chains.

Because of its waterproof anti-burial base, such a device arranged in a direction crossing the direction of the erosion fluids receives a hydrostatic thrust which it cannot transmit to the ground because of the waterproofing of its base. Therefore, the device creates a differential of pressure on either side of this impermeable base surface and is pressed against the ground by a force all the greater the greater the energy of the erosion fluids.

In a coastal application, the slowing effect produced by this modular device goes hand in hand with a sedimentary effect. Arranged in parallel rows substantially perpendicular to the erosion current, the modular device slows the current and sediments the sediments.

Arranged in substantially converging rows towards a bottleneck, the effect of the modular device is then to accelerate the current and cause the dispersion of the sediments and therefore controlled erosion.

Although the field of the present invention naturally extends to the control of land erosion as well as that of marine erosion by slowing down the erosion fluids, it will be better understood in the light of existing examples of its maritime or river erosion control applications.

• les figures 1a à 1c représentent des vues en perspectives des dispositifs de ralentisseurs conventionnels;
• les figures 2a et 2b représentent des vues en perspective des dispositifs de la présente invention sur différents sites;
• les figures 3a à 3c représentent des vues en perspectives de différents modes de réalisation du dispositif de la présente invention;
• les figures 4a à 4c représentent des vues en perspective de différents modes de réalisation du dispositif de la présente invention;
• la figure 5 représente une vue en perspective d'une variante de réalisation;
• la figure 6 représente une vue en perspective d'un mode de réalisation du dispositif de la présente invention avec des moyens d'ancrage; et,
• la figure 7 représente une vue en perspective d'un assemblage modulaire de plusieurs dispositifs selon l'invention.

The invention will be illustrated by the description which follows, accompanied by the appended drawings in which:

• Figures 1a to 1c show perspective views of conventional retarder devices;
• Figures 2a and 2b show perspective views of the devices of the present invention on different sites;
• Figures 3a to 3c show perspective views of different embodiments of the device of the present invention;
• Figures 4a to 4c show perspective views of different embodiments of the device of the present invention;
• Figure 5 shows a perspective view of an alternative embodiment;
• Figure 6 shows a perspective view of an embodiment of the device of the present invention with anchoring means; and,
• FIG. 7 represents a perspective view of a modular assembly of several devices according to the invention.

Figures 1a to 1c illustrate the prior art.

According to FIG. 2a, the device R according to the invention for slowing down erosion (current C, wind V) is associated in a modular fashion with other devices of the same type to produce an assembly (R1, R2 ... Rn) which is placed relative to the shore in one or more contiguous rows partially submerged producing a maritime and wind accretion effect. In general, the device R comprises a lower part 1 provided with means for fixing to the ground and an upper part 2 provided with means for attenuating the energy of the erosion fluids. The attenuation means comprise a protruding hull of variable stiffness 5.

In FIG. 2b, the device for slowing down erosion, object of the present invention, comprises at least one module (R) having an impermeable base and a hull. It can be placed indifferently on a submerged or emerged soil and its optimum accretion effect is obtained when the direction of the module R makes a right angle with the direction of the dominant erosion fluid in the environment considered (current, tide, rain runoff , wind ...).

Figure 3a shows the device of the invention made in two parts. The upper part 2 is provided with means for attenuating erosion fluids and produced in the form of a protruding rigid hull 5 of profi! parabolic convex vertex with horizontal peripheral edges. The upper part 2 is secured to a lower part 1 by preferably removable attachment means such as bolting 6.

The lower part 1 comprises means for fixing to the self consisting of an impermeable base 3 facing the ground. The waterproof base 3 has dihedral faces 3a, the junction angle of which is for example greater than 100 ° and extends inside the hull 5 by a horizontal strip 3b forming a peripheral skirt and at its longitudinal ends at l outside of the hull 5 by a flap 3c which avoids the erosion phenomena associated with disturbances at the end of the hull and can possibly participate in assembly with another module or in anchoring to the ground thanks to notches 21 receiving appropriate fastening members (straps ...). The longitudinal ends of the device define an opening between the base 3 and the hull 5.

FIG. 3b represents a device made up of a plane impermeable base 3 and a closed hull 5, the lateral faces of which consist of dihedral planes extending in an inclined fashion on either side of an edge vertex and extending by flattened peripheral edges, while the longitudinal ends 5a, 5b are produced respectively with a male / female profile so as to be nestable from one module to another. The angle of the dihedrons is chosen for example around a value of 90 ° so as to give the erosion fluid an upward movement which will slow it down. The hull is optionally provided with orifices 7 provided with plugs 8 for introducing a ballast, which may advantageously be of absorbent foam, for example for storing a liquid.

FIG. 3c represents a module of the device of the present invention, the hull of which is parabolic and has flattened peripheral edges. The hull 5 is pierced with orifices 7 allowing the loading of ballast, which can be masked in particular from the inside by a plug or a non-return valve 8. The waterproof base 3 is provided at least on its longitudinal edges with a peripheral skirt 12 penetrating into the ground with a depth sufficient to obstruct the lateral propagation of the pressures of the erosion fluids under the device The ends 10 and 11 are produced respectively with a male convex and female concave profile so that two modules of the same type can be nested one inside the other with an at least partial effect of ball joint and constitute a continuous longitudinal chain.

• longueur 60 cm,
• largeur 9 cm,
• hauteur 6 cm avec profil parabolique,
• base imperméable posée (non solidaire) sur la partie inférieure, vitesse moyenne du courant ambiant chargé en sable (rivière) 7,5 Km/h

In particular, a prototype was produced, the overall dimensions of which are:

• length 60 cm,
• width 9 cm,
• height 6 cm with parabolic profile,
• waterproof base placed (not integral) on the lower part, average speed of the ambient current loaded with sand (river) 7.5 km / h

A complete accretion of sand is obtained (complete covering of the device in one hour.

In FIG. 4a, the wall of the base 3 of substantially parabolic shape can usefully be thicker in the center than at the edges, thus increasing the contact of the device with the loose soil under the base surface. Ports 7 allow the circulation of the erosion fluid and the sedimentation inside the hollow internal volume of the device.

FIG. 4b shows a device in which the internal volume situated between the lower part 1 and the upper part 2 is partially filled by accretion of ballast 15 (aggregates) and comprises orifices 7 for filling near the sum of the hull 5. We obtain thus a gradual improvement in the stability of the device.

FIG. 4c shows a one-piece device which can be hollow or solid, and has an upper part 2 and a lower part 1.

The interior volume is filled in this case with the same elastic material of the fixing and attenuation means including the base 3 and the hull 5 respectively.

During the implementation of the device of the invention, the underside of the impermeable base 3 is subjected to a first hydrostatic pressure in depression relative to a second hydrostatic pressure applied under the effect of the erosion fluids , on the upper face of the base 3 and / or of the hull 5.

FIG. 5 illustrates an advantageous embodiment comprising in particular an impermeable base 3 and a hull 5 provided with a longitudinal recess 5a allowing rapid penetration of ballast, erosion fluids, natural sediment or the introduction by adaptation of a traditional geotextile retarder.

FIG. 6 illustrates an embodiment of the device comprising blind cavities 18 formed on the side wall at the bottom of the hull 5 extending on the peripheral edges. The cavities 18 receive anchoring members 9 added and adapted to overflow from the peripheral edge and sink into the ground. These cavities can also be used for handling the device.

Figure 7, in association with Figure 3c, shows the method of assembling the modular devices of the invention in two directions. The female end 11 has cheeks 14 formed by extensions of the hull 5 which come to marry the side walls of the hull 5 of a module of the same type to constitute an assembly of generally continuous shape in side chain. The male end 10 with a convex and / or projecting profile fits into the female end 11 with a concave and / or tucked-in profile.

In general and with reference to all of the drawings, it should be specified that the device, once placed on the ground or embedded in the ground cannot move vertically or laterally under the action of erosion fluids, or float in the ambient fluid thanks to the lower part 1, which is provided with means for fixing to the ground consisting of the base 3 possibly assisted by the anchoring members 9 or the ballast 15 depending on the tearing forces. The fixing of the device is reinforced by any means of ballasting or anchoring as a function of the respective densities of the device and of the erosion fluid as well as of the energy of said fluid in the working area which can be reduced to their minimum by l absence of Archimedes' strength under the device.

The base 3 of the device is subjected, on its underside, to a first hydrostatic pressure which is in depression relative to the hydrostatic pressure of the ambient erosion fluid due to the impermeability of the base surface which can, for example , be completed laterally by the waterproof skirt 12 penetrating into the ground.

When the erosion fluid. for example rain, sea current, tide, wind, increases its velocity of erosion, the impermeability of the base surface obstructs the communication of this pressure to the ground under the device and the base and hull of variable stiffness accentuate the gap of hydrostatic pressure by their suction effect relative to the pressure of the erosion fluids on and / or inside the hull.

The surfaces materialized by the base 3 and the hull 5 also produce a suction cup effect which presses the device on the ground.

The base 3 and the skirt 12 are preferably made with an impermeable elastomeric material and the adhesion to the ground can be reinforced by producing reliefs on the underside of said base in the manner of tire treads.

The device can be made in one piece by rotational molding of polyethylene. Concrete, possibly reinforced, can also be an appropriate material when it covers a structure with a spring.

The device of the invention is made so as to withstand the forces of erosion fluids which can reach 12 tonnes per m ² on the shore and 100 kg per m ² in the event of wind erosion.

The device of the invention can also be used for example to take off the wind from a dune in the course of erosion or to slow down the runoff on a mountainous mining area with open sky, respectively causing the increase of the dune and the elevation of the relief.

In an advantageous embodiment of the concave base surface facing the ground, the large span of the base surface of variable rigidity allows its bending and the contact of the concave arch with the underlying sediment opposing the forces of slip or tear. Upon installation, the ballast anchoring means inherent in the invention allow the device to be firmly anchored in the ground.

In an advantageous embodiment, the peripheral edges of the hull 5 are tangent to the horizontal or with a convex drape, and thus make it possible to reinforce the fixing of the device once embedded in the ground by resisting tearing away by the fluids of erosion.

In another advantageous embodiment, the base 3 is flexible and comprises a solid impermeable canvas plane at rest which becomes concave when it is placed in position.

In order to give an upward movement to the erosion fluids, the hull 5 will be protruding, for example, of parabolic, semi-cylindrical, or dihedral shape and of peripheral edges horizontal or penetrating into the ground.

According to an advantageous embodiment, the ratio of dimensions between width and height is preferably greater than 1.5 so that the base surface can have a width equal for example to 3 times the height and a length included for example between 1.5 and 6 times the width.

The orifices 7 may have a variable section of a few centimeters or square decimetres of regular shape and preferably oval in order to be able to be hidden from the inside. Because of its lightness, the device can be used on drop offs of the channel and be suspended by any anchoring fixed in the cavities 18 or in the notches 21.

In the case where the lower part and the upper part are not in one piece, they are then assembled by bolts or by any assembly method compatible with the chemical and mechanical qualities of the material.

Claims (9)

1. An elongated tubular assembly for the realization of alignments aimed at the control of soil erosion or soil migration in a fluid environment, said elongated tubular assembly comprising: a plurality of tubular units disposed in end-to-end relationship, each unit having a lower section (1) and an upper section (2), said lower section (1) having longitudinal edges and composed of a variably rigid impermeable contact base (3), said upper section (2) having longitudinal edges and a variably rigid protruding hull (5) designed to deviate surrounding fluid flows, the lower section (1) and the upper section (2) being connected to each other at least along their longitudinal edges defining an internal space therebetween in which a ballast (15) can be admitted through registered hull openings (7) in said upper section, said variably rigid base and hull combination being designed to give stability to said unit even in an environment of heavy fluid flow to control soil erosion or soil migration.
2. An elongated tubular assembly according to claim 1, being made of a single solid variably rigid piece of material.
3. An elongated tubular assembly according to claim 1 characterized by the upper part (3) being connected in disassemblable manner with the lower part (2).
4. An elongated tubular assembly according to claim 1 characterized by the sides, ends and edges having dovetailing male and female shaped elements (1,5,10, 11,14) and seats (18) and slots (21) allowing the anchoring, welding, fastening, transport, stacking and installation of a plurality of tubular units in longitudinal and lateral assemblies in one or more layers.
5. An elongated tubular assembly according to claim 1 which includes registering units to define a barrier, said registered hull openings (7) being on the side where a surrounding fluid must be contained.
6. An elongated tubular assembly according to claim 1, the variable rigidity of which is obtained by the base (3) having a generally concave underside.
7. An elongated tubular assembly according to claim 1, the variable rigidity of which is achieved by the base (3) wall having variations of thickness along its width.
8. An elongated tubular assembly according to claim 1 characterized by being hollow, and having a longitudinal slot along the hull (5).
9. An elongated tubular assembly according to claim 1 the lower section (1) and upper section (2) are made of a single piece with an enclosed structure.

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