FR3032727A1 - GEOTEXTILE OF REINFORCEMENT, EROSION CONTROL AND VEGETATION AID - Google Patents

Abstract

Geotextile reinforcement, erosion control, and aid for revegetation made from natural or synthetic fibers, characterized in that: • the synthetic fibers are, at the very least, biofragmentable and advantageously biodegradable, • and in that the geotextile consists of a knitted grid (101, 102) obtained by the so-called "knit stitch" technology, in particular on a RACHEL knitting machine, with or without insertion of wefts, the fibers, cords or strands constituting the grid being interconnected by binding son (103) biodegradable.

Description

FIELD OF THE INVENTION The invention is in the context of the application of the geotextiles of slope reinforcement, for example after completion of engineering works. BACKGROUND OF THE INVENTION civil, trench type for highways, railways, urban development, riverbanks and waterways, or other works. It also relates to such a geotextile intended to favor the revegetation of such slopes, following said civil engineering works.

These geotextiles can also be used to stabilize river banks or to rehabilitate previously polluted sites or sites that have undergone mining-type work.

PRIOR STATE OF THE ART Environmental standards make it increasingly necessary to restore a plant aspect to a zone of civil engineering works resulting, for example, from the construction of trenches, roads, railways, mining, etc. It is thus known to combine at the same time the achievement of this goal of re-vegetation reinforcement embankments thus made. For this purpose, it is customary to use plies or mats, made from intermingled natural fibers, and especially woven, from strands of coconut fibers, flax, jute or hemp. Such mats or webs are fixed on the embankment in question by any means. Most of these natural fibers are produced in Asian countries, including India and Bangladesh, but also in South America. The production of such mats therefore require their importation, especially by sea, thus generating a carbon footprint which, more and more, we seek to overcome. The quality and availability of these materials are also subject to the climatic conditions of producing countries, for example related to monsoons.

35 Moreover, their cost is subject to variations, and difficult to control.

Finally, their service life is variable, difficult to control and their performance remains poor and especially random, given their very artisanal manufacturing process.

Fascines are also known, that is, bundles of branches used traditionally to fill ditches, to repair roads or to build defense structures, and which are also used at embankments and embankments. river banks, and rivers that are also to be revitalized, or to reduce or even avoid the phenomena of erosion of run-off or waving, as is the case on canals and rivers. demonstrates however that such fascines play little part in the effectiveness of reinforcement of such slopes or in the fight against erosion.

In fact, the objective sought by the present invention is to propose an alternative to these natural and old products in order both to serve as reinforcement for such slopes, to enable the fight against erosion and, finally, to facilitate vegetation, more mastered and sustainable. It is also sought to introduce reinforcements that are more significant in terms of mechanical properties (from 10 to 150 KN for example), allowing a scientific and rational approach to situations, thus ensuring better safety and reliability of the structures. SUMMARY OF THE INVENTION , the invention proposes a reinforcing geotextile, erosion control, and greening aid made from natural or synthetic fibers. According to the invention, the synthetic fibers are at least biofragmentable and advantageously biodegradable. In addition, the geotextile consists of a knitted grid obtained by the so-called "knit stitch" technology, especially on RACHEL knitting machine, as marketed by the KARL MAYER or LIBA companies, with or without insertion of frames. In other words, the invention proposes to use a knitted structure based on natural fibers, bio-sourced, or based on biofragmentable synthetic fibers, that is to say that after a few years, all that remains is small residues, typically a few millimeters without pollutant effects in the treated area, or even completely biodegradable, the constituent elements of the knit being bound together by binding threads, also based on natural fibers, organic -sourced or synthetic biodegradable.

3032727 3 Such a geotextile or geofilet is therefore able to ensure, after its installation, a means of combating surface erosion, and especially the maintenance of the soil and in particular the topsoil in place. Depending on the design of the structure in depth or on the surface, this type of geotextile makes it possible to conserve moisture, able to promote the acceleration of the growth of the vegetation for a period of two to five years. in the majority of cases, being that the vegetation takes over after: the disappearance of the material in question. According to one characteristic of the invention, the grid consists of fiber strands or wirings in production sense and in cross direction, of relatively large dimensions, typically capable of having a title of 100,000 dtex, these strands being bonded together by small binding yarns, the size or title of which is likely to be between 70 and 4000 dtex. Binding yarns can be made of PLA (polylactic acid), obtained in a known manner from corn starch. According to another characteristic of the invention, the fibers of the invention have a high water retention capacity, typically up to 600% of their weight with controlled biodegradability over two to five years.

The binding fibers and the wicks or cords are chosen in particular from natural fibers, selected from the group consisting of flax, hemp, jute, coconut, bamboo, alfalfa, nettle, or in the group including polylactic acid (PLA), aliphatic polyesters such as PGA (poly glycolic acid), polyhydroxyalkanoates (PHAS), polybutylene adipate (PBA) or succinate (PBS) and copolymers thereof. These different materials are known for their biodegradability. It can be envisaged a mixture of synthetic fibers and natural fibers, as well for the wicks or cabled, as for the son of binding. Thus, one can provide a core 30 made of synthetic fiber (s) surrounded by a sheath made of natural fibers. Likewise, it is also possible to provide a binding bar made of synthetic fibers and a binding bar made of natural fibers. It is also possible to envisage using other biopolymers in the form of fibers, monofilament or multifilament yarns, or even ribbons having controlled biodegradability properties. The grid of the invention has openings, for example of rectangular shape, whose dimensions are typically between 3 and 300 millimeters, in order to meet the various functions it must fulfill. Its weight per unit area is advantageously between 100 and 2000 g / m2.

BRIEF DESCRIPTION OF THE FIGURES The manner in which the invention may be embodied and the advantages thereof will be apparent from the following exemplary embodiments given by way of indication and not by way of limitation with the aid of the appended figures. Figure 1 is a schematic representation of a grid according to the invention seen from above, Figure 2 is a sectional view. Figure 3 illustrates the establishment of this grid on an embankment. FIG. 4 is a schematic representation of a variant of the grid of FIG. 1.

Fig. 5 is a schematic representation of another variant of the invention, of which Fig. 6 is a sectional representation. Figures 7 and 8 are schematic representations illustrating the knitting of two different types of grids according to the invention.

DETAILED DESCRIPTION OF THE INVENTION FIG. 1 therefore shows a schematic representation of a first embodiment of the invention.

In the present case, it is a grid in which the wired or wicked wires 101 are oriented in the production direction (warp direction), said grid comprising wired wires or wicks 102 inserted in the cross direction (weft) . These threads or threads 101, 102 are joined to each other by means of binding threads 103, which change by making stitching columns since they work on needles. Several types of binding can be envisaged, as described in more detail in relation to FIGS. 7 and 8. This grid thus defines apertures 104, 105, the dimensions of which depend on the applications envisaged. The dimensions of these openings can typically vary from 3 to 300 millimeters. The size of these openings is a function of the characteristics of the site to be treated, including the nature of the soil, the importance of the slope, the type of erosion factors, the desired vegetation.

These grids are obtained on RACHEL loom (as marketed by KARL MAYER), with weft insertion. The constituent materials of the warp and weft cords 101, 102 are, in the example described, made of the same biodegradable material and, for example, of biodegradable synthetic fibers of the PLA or PGA type. They are preferably made of natural fibers, as known from the prior art and typically, in jute, coconut fiber, hemp or flax, and from yarns composed of mixed fibers: hemp, nettle, alfalfa, etc. On the other hand, their bond is ensured by a much thinner binding yarn, made for example of cellulosic fiber, of cotton, linen and / or PLA, with a title typically close to 70 to 4000 dtex. FIG. 2 is a sectional view of FIG. 1. The structure thus produced, in which the fiber cords are not intermingled more or less randomly, like the woven nets of the prior art, but regularly positioned relative to each other. to others, have a number of advantages. Firstly, the warp-type yarns are rectilinear and non-wavy, unlike a traditional woven structure; they can be put under load under the weight of the earth, in particular of revegetation, without deforming significantly, and thus without altering the installation on the slope of the ground thus equipped; the arrangement of the weft yarns acts as microbutures 106 (see FIG. 3), making it possible to retain the soil and in particular the underlying vegetated soil; such microbutts are non-existent with the traditional woven structures, which have two symmetrical main faces and the same relief. FIG. 4 shows a variant of FIG. 1, in which the transverse wires 402 are arranged in continuous frames, the wires or cords 401 in the production direction being positioned in the same manner as in FIG. Indeed, on the installations of knit looms equipped with a large framer, that is to say working in very large widths and equipped with a multi-frame transfer store, the 35 frames are traditionally necessarily cut on On the other hand, on machines of the RACHEL type with a single-frame device (such as Karl Mayer VS type), it is possible to insert said frame continuously, and so on. obtain return loops 407, 408, which can advantageously be used for the attachment of this type of geotextile on the floors and slopes of the slopes to be protected.

FIG. 4 also shows stakes 409 or fastening plugs introduced at the loops 407, 408 thus generated. De facto, the quality of the fixation of the geotextile, and in this case of the grid on the ground, is optimized, and it also conditions a faster vegetation and a better recovery of efforts of stability of the structures by the roots. -Same. It is conceivable that by playing on the one hand, on the dimensions of the fibers or wicks and the size of the openings on the other hand, there is a panoply of structures adapted to be adapted to the different requirements. Typically, the resistance of the fibers or wicks can be varied in both directions (from 10 to 300 KN / m or more), which may be different, as well as the dimensions of the void and solid areas to optimize, more or less. less important, the vegetation depending on the plants to be developed, as well as the water retention capacity, the friction in the soil according to the slopes and the duration of the biodegradability.

Typically, the size of the cords or wicks can vary from 2 to 10 millimeters in diameter and have a titer of between 200 and 100,000 dtex. In addition, their resistance is likely to range between 150 and 2000 newtons. These 25 which bear the resistance of the geotextile, depending on the constructions, from ten KN / m up to 300 KN / m, or even more if necessary. Current applications are between 20 and 150 KN / m. According to a variant shown in relation to FIGS. 5 and 6, is associated with the grid of the type described above, a web 510, typically made of non-woven or constituted by a woven fabric, a knit or a net with very small openings of 50 to 120 microns in nonwovens and up to 3000 microns in sail, for the purpose of closing the openings of the grid 501, 502, 503, and more precisely to constitute filtration. Typically, this nonwoven or net has a basis weight of 10 to 400 g / m2.

This membrane or web 510, obviously also made of natural material (flax, hemp, coconut or jute) or biobased (PLA) and in any case biodegradable, has the advantage of retaining fine particles of earth of soil on which is placed and fixed the geotextile, and therefore, in some cases, to promote protection against erosion by helping 5 the confinement of the soil, especially when laying on the slope of a newly built structure. This sail is also likely to fulfill the function of anticontamination or pollution recovery in some cases. This web or membrane is attached to the grid concomitantly with the realization of the latter directly on the production machine. FIGS. 7 and 8 show two types of binding that can be used in the context of the invention.

These bindings are intended to secure the cords or wicks constituting the grid itself, those arranged in the production sense (machine direction) and those in the cross direction (weft direction) This joining occurs by blocking the intersection points. However, it is ensured, by adjusting the wire rates and their voltage, not simultaneously "strangle" the 20 wired or wicks, so that they retain all their capacity for volume and water retention, in view of the aid to the attachment of the soil and aid in its revegetation. It is thus possible to make the binding threads act by making them work on one or two different bars, with more or less tight wrapping of the cord shown in FIG. 7), or in bonding with chains 25 and sectional frames (FIG. 8). Tighter weave induces cable compression and promotes anti-slip and anti-erosion features.

Thus, in the binding mode described in connection with FIG. 7, the warp-in-line cable is interposed between the two sets of wires which work in symmetrical single-knit fashion. This binding has the advantage of a very good control of the geometry of the grid; This may be of interest for applications in which the geotextile in question must maintain the terrain on a steep slope.

On the other hand, in the binding mode of FIG. 8, more latitude and more space are left between the mesh columns, which are linked by a sectional frame, and thus allow the use of larger cords or wicks.

The whole of the interest of the grid according to the invention is conceived which has a certain number of advantages, amongst which we can mention: the use of synthetic biosourced wires, which can be made by fine title , resistant and cost optimized by their industrial production, unlike natural fibers, whose achievement in fine title is very expensive; the use of natural fibers which can be obtained locally; the possibility of obtaining a wider range of titles than the prior art, and consequently the obtaining of mechanically more resistant structures; the use of possibly larger and stiffer fibers because arranged rectilinearly and not necessarily corrugated as in the case of weaving. - optimized production costs due to the implementation of an industrial process that is now largely controlled; - better management of the product's lifespan.

Claims (11)

REVENDICATIONS1. Geotextile reinforcement, erosion control, and aid for revegetation made from natural or synthetic fibers, characterized in: - in that the synthetic fibers are, at least, biofragmentable and advantageously biodegradable, - and in that the geotextile consists of a knitted grid obtained by the so-called "knitted mesh" technology, in particular on a RACHEL knitting machine, with or without insertion of wefts, the fibers, cords or strands constituting the grid being connected between them by biodegradable binding threads. 2. Geotextile according to claim 1, characterized in that the grid consists of strands of fibers or cabled in the production sense and in the cross direction, of relatively large head and diameter, said strands or cords being interconnected by son tying of smaller dimensions. 3. Geotextile according to claim 2, characterized in that the wicks or cords constituting the grid have a titer of between 200 and 100,000 dtex. 4. Geotextile according to one of claims 2 and 3, characterized in that the binding son have a title between 70 and 4000 dtex. 5. Geotextile according to one of claims 1 to 4, characterized in that it has a water retention capacity of up to 600% of its weight. 25 6. Geotextile according to one of claims 1 to 5, characterized in: - in that the natural fibers are selected from the group consisting of flax, hemp, jute, coconut, bamboo, alfalfa, nettle; and in that the synthetic fibers are selected from the group consisting of polylactic acid (PLA), aliphatic polyesters such as PGA (poly glycolic acid), polyhydroxyalkanoates (PHAS), polybutylene adipate (PBA) or succinate ( PBS) and their copolymers. 7. Geotextile according to claim 6, characterized in that the locks or cords the binding threads 35 consist of a mixture of synthetic fibers and natural fibers. 3032727 10 8. Geotextile according to one of claims 2 to 5, characterized in that the binding son are made of PLA (polylactic acid). 9. Geotextile according to one of claims 1 to 8, characterized in that the grid has 5 openings, whose dimensions are between 3 and 300 millimeters. 10. Geotextile according to claim 9, characterized in that the openings are of rectangular shape. 10 11. Geotextile according to one of claims 1 to 10, characterized in that the grid is associated with a woven or knitted veil or a nonwoven, the veil or the nonwoven being made of biodegradable material, the opening of which filtration is between 50 and 3000 micrometers. 15