EP2550406B1 - Retaining wall with reinforced earth elements in the backfill - Google Patents

Abstract

The invention relates to a building including a facing, a backfill at the back of the facing, synthetic reinforcement strips distributed in the backfill, and a connection system between the reinforcement strips and the backfill. The connection system includes fasteners having the shape of a continuous closed loop, each including two first portions for hooking to the facing and, alternating with the first portions along the closed loop shape, two second portions extending towards the back of the facing where they are folded back to form two loops inside of which at least one reinforcement strip extends.

Description

The present invention relates to the techniques of building structures in reinforced soil.

These structures traditionally comprise a siding, a fill that fills a rear side of the facing, reinforcement elements distributed in the backfill to mechanically stabilize it, and a connection system between the reinforcing elements and the embankment.

We are interested here in the reinforcing elements which are in the form of flexible synthetic bands. This type of reinforcement is commonly used because of its mechanical performance and its good resistance to corrosion.

There are different types of facing each having their preferred areas of application. In particular, we find concrete facings, prefabricated or cast in place, and siding made of metal lattices.

For concrete siding, the connection of reinforcement strips to concrete is traditionally a source of difficulty. Wherever possible, intermediate connecting parts working in bending or shearing should be dispensed with. One possibility is to provide in the concrete facing element a passage that will follow the request for reinforcement once installed and to anchor the band facing. A solution of this type is described in WO2007 / 102070 . However, this type of solution forces the direction of reinforcement strips immediately behind the siding, which may, in some configurations of the retaining structure, pose difficulties in implementation.

There is therefore a need for a connection mode retaining good mechanical properties while offering good flexibility as to the possible configurations of the reinforcing strips.

Trellis-type facings are rarely associated with embankment reinforcement elements in the form of flexible synthetic bands. One reason may be that by hanging the bands on the trellis, they are made directly visible on the front of the book, which exposes them to accidental or intentional damage. In addition, trellis-type facings are often associated with stony embankments that do not provide an environment conducive to the use of reinforcement based flexible bands. There is also a need to overcome these limitations.

A construction structure is proposed, comprising a cladding, a backfill on a rear side of the cladding, synthetic reinforcement strips distributed in the backfill, and a connection system between the reinforcement strips and the backfill. The connection system comprises continuous closed loop fasteners each having two first clipping portions to the cladding and, alternately with the first portions along the closed loop shape, two second portions extending rearwardly. facing where they are folded to form two loops within which passes at least one reinforcing strip.

The use of continuous closed loop fasteners makes it possible to firmly connect the strips to the facing avoiding intermediate parts subjected to shear forces. The continuity of the closed loop limits the risk of losing the connection by deformation of the fasteners due to the large tensile forces that they may suffer from the reinforcement strips because of the backfill load. The topology of the fastener allows it to be put in place in various configurations.

It can be arranged a guiding device between on the one hand the two loops formed by the second portions of a fastener and on the other hand the reinforcement strip passing inside these two loops, so that this device works in compression in response to traction exerted by the reinforcing tape.

In one embodiment of the structure, the fastener is metallic and substantially rigid. Such an embodiment is particularly suitable when the facing is in the form of a lattice, the first portions of a fastener then being placed around at least one bar belonging to the lattice.

If the cladding comprises several elements of lattice, it may be possible to use a fastener to contribute to the assembly of these elements, placing its first portions around at least two bars respectively belonging to two adjacent lattice elements.

In particular, the embankment of a retaining structure may consist of two layers, one adjacent to the truss facing, made of a material of coarse granulometry, such as pebbles, and the other located in greater depth and made finer material such as earth or sand. In this case, the rigid fastener makes it possible to remove from the facing the cusp points of the synthetic reinforcement strips, by making them extend essentially into the layer of finer material, while rigid fasteners extend into the layer. of coarser material to connect the reinforcement strips.

In another embodiment of the work, the fastener is a flexible belt based on closed loop wound fibers. In this case, the guiding device, if there is one provided between the two loops formed by the second portions of a fastener and the reinforcement strip passing inside these two loops, may comprise a first curved surface for receiving the reinforcing strip and a second curved surface for receiving the two loops of the second portions of the flexible belt, the first and second surfaces having their respective curvatures in two perpendicular planes. Spacers may be provided to separate the second portions of the flexible belt received on the second curved surface of the guide device to ensure better transmission of forces at the connection.

The fastener in the form of a flexible strap is particularly suitable when the facing is made of molded material incorporating, in at least one anchoring region, a passage of flattened section formed between two emergence points located on a rear face of the facing adjacent to the embankment. The first portions of the flexible belt are then placed inside the passage formed in the anchoring region of the facing. The flexibility of the belt allows to orient the reinforcement strips in the embankment without being too constrained by the directions imposed by the passage at its points of emergence of the facing. In a particular embodiment, the passage comprises two portions adjacent to the two emergence points and each arranged to orient parallel to an emergence plane substantially perpendicular to the rear face of the facing an elongated element engaged in said passage, two curved portions. respectively extending the two portions adjacent to the emergence points and arranged to deflect the element out of the emergence plane, and a connecting portion interconnecting the two curved portions and having at least one loop lying outside the plane of emergence.

In another aspect, there is provided a method of constructing a reinforced soil structure, comprising: (i) forming a siding on a front side of the structure; (ii) installing on the facing continuous closed loop fasteners each having two first clipping portions to the cladding and, alternating with the first portions along the closed loop shape, two second portions extending towards the cladding portion; back of the facing where they are folded to form two loops; (iii) connecting synthetic reinforcing strips to the facing, by passing at least one reinforcing strip inside the two loops formed by the second portions of a fastener; and (iv) backfilling a back side of the facing where the reinforcing strips connected to the facing extend with the fasteners.

When the facing is in the form of a lattice, the fasteners may be substantially rigid and arranged by passing their first portions around at least one bar belonging to the lattice.

When the facing is of molded material incorporating, in at least one anchoring region, a passage of flattened section formed between two emergence points located on a rear face of the facing, the fastener may be a flexible belt based on closed-loop coiled fibers. The siding connection of the reinforcing synthetic strips can then include the steps of folding the flexible belt back onto itself and engaging one end of the folded belt in said passage at one of the emergence points, threading the belt folded in the passage until the exit to the other point of emergence of the passage, to balance the belt lengths out of the two emergence points by leaving said first portions in the passage, to join the two ends of the belt opposed to the facing to form the loops of said second portions, and to pass at least one reinforcing strip within the two loops.

• la figure 1 est un schéma de principe, en coupe latérale, d'un ouvrage de soutènement en sol renforcé;
• les figures 2 et 3 sont des schémas, en coupe et en perspective, illustrant le trajet suivi au niveau du parement par une bande synthétique de renforcement dans un premier exemple de réalisation;
• la figure 4 est une vue en perspective d'une pièce utilisable pour définir le trajet d'une bande de renforcement à l'intérieur d'un élément de parement dans le premier exemple de réalisation;
• la figure 5 est une vue d'une attache utilisable pour connecter une bande de renforcement au parement dans le premier exemple de réalisation;
• la figure 6 est une vue en perspective d'un dispositif de guidage utilisable entre l'attache et la bande de renforcement dans le premier exemple de réalisation;
• les figures 7 à 9 sont des schémas illustrant des étapes d'installation d'une bande de renforcement dans le premier exemple de réalisation; et
• la figure 10 est une vue en perspective d'un parement, d'une attache et d'une bande de renforcement dans un second exemple de réalisation.

Other features and advantages of the present invention will appear in the following description of a nonlimiting exemplary embodiment, with reference to the accompanying drawings, in which:

• the figure 1 is a schematic diagram, in lateral section, of a retaining structure in reinforced soil;
• the Figures 2 and 3 are diagrams, in section and in perspective, illustrating the path followed at the facing by a synthetic reinforcement strip in a first embodiment;
• the figure 4 is a perspective view of a usable part for defining the path of a reinforcing strip inside a facing element in the first embodiment;
• the figure 5 is a view of a fastener usable for connecting a reinforcement tape to the facing in the first embodiment;
• the figure 6 is a perspective view of a guiding device usable between the fastener and the reinforcing strip in the first embodiment;
• the Figures 7 to 9 are diagrams illustrating steps of installing a reinforcing tape in the first embodiment; and
• the figure 10 is a perspective view of a facing, a fastener and a reinforcing tape in a second embodiment.

The figure 1 illustrates the application of the invention to the construction of a retaining wall in reinforced soil. A compacted embankment 1, in which reinforcements 2 are distributed, is delimited on the front side of the structure by a facing 3 which, in the example shown in FIG. figure 1 , is constituted by juxtaposing prefabricated elements 4 in the form of panels, and on the rear side by the ground 5 against which is erected the retaining wall.

The reinforcements 2 consist of synthetic reinforcements in the form of flexible strips extending in horizontal planes behind the facing 3. It may in particular be reinforcing strips based on polyethylene fibers wrapped in polyethylene.

The reinforcing strips 2 are attached to the prefabricated elements 4 assembled to form the facing 3. These elements 4 are for example reinforced concrete. In the example shown, they are in the form of panels. They could also have other forms, including block. When the concrete of such an element 4 is poured, a passage is reserved along a predefined path for a reinforcement strip in order to perform the anchoring strip-element. After being installed along this route, each band has two sections that leave the element to be installed in the embankment.

1. a) mettre en place une partie des éléments de parement 4 afin d'être en mesure d'apporter ensuite du matériau de remblai sur une certaine hauteur. De façon connue, le montage et le positionnement des éléments de parement peuvent être facilités par des organes d'assemblage placés entre eux. Les positions prévues sur les éléments de parement 4 pour les bandes 2 sont choisies de façon que certaines d'entre elles se placent à un même niveau horizontal lors du montage;
2. b) apporter du matériau de remblai et le compacter progressivement jusqu'à atteindre le prochain niveau prévu pour la mise en place des bandes de renforcement 2;
3. c) installer une ou plusieurs bandes de renforcement 2 en les attachant au parement et en les étalant sur le remblai 1 à ce niveau;
4. d) apporter du matériau de remblai par-dessus les bandes de renforcement 2 qui viennent d'être installées. Ce matériau de remblai est compacté au fur et à mesure de son apport;
5. e) répéter les étapes b) à d) si plusieurs niveaux de bandes sont prévus par rangée d'éléments de parement 4;
6. f) répéter les étapes a) à e) jusqu'à atteindre le niveau supérieur du remblai.

To build the structure, you can proceed as follows:

1. a) set up part of the cladding elements 4 in order to be able to then bring backfill material to a certain height. In known manner, the mounting and positioning of the facing elements can be facilitated by connecting members placed between them. The positions provided on the facing elements 4 for the strips 2 are chosen so that some of them are placed at the same horizontal level during assembly;
2. b) providing backfill material and progressively compacting it to the next planned level for placing reinforcement strips 2;
3. c) installing one or more reinforcement strips 2 by attaching them to the siding and spreading them on the embankment 1 at this level;
4. d) provide backfill material over the reinforcement strips 2 that have just been installed. This backfill material is compacted as and when it is added;
5. e) repeat steps b) to d) if multiple levels of bands are provided per row of facing elements 4;
6. f) Repeat steps a) to e) until reaching the upper level of the embankment.

During the supply and compaction of the backfill material, reinforcement strips 2 already installed in the lower levels are stretched. This tensioning results from the friction between the strips and the backfilled material and ensures the reinforcement of the structure.

The Figures 2 and 3 illustrate a possible configuration of reinforcement strips at concrete siding, as described in WO 2007/102070 A2 . At their points of emergence out of a facing element, the two sections of a strip 2 are parallel to an emergence plane P, with no offset perpendicular to the plane P (as shown in FIG. Figures 2 and 3 ) or with such an offset (see international application no. PCT / FR2009 / 052353 ). When mounting the facing 3, the elements 4 are generally oriented so that the emergence plane is horizontal.

The figure 2 schematically illustrates a facing element that can be used in certain embodiments, with the path of a reinforcing strip. As is usual, this element 4 is made of molded concrete. A path is defined inside the element 4 between the two emergence points 6 of the two sections of the strip on the rear face 7 of the element (face adjacent to the backfill). The path corresponding to the element of the figure 2 is illustrated by the figure 3 . It has two rectilinear portions 8 extending perpendicularly to the rear face 7 of the element from the emergence points 6. In each straight portion 8, the band remains in its emergence plane P. The rectilinear portions 8 s 'extend over at least half the body thickness of element 4, measured perpendicular to its face 7. This avoids bad stressing of the concrete in the vicinity of the rear face 7. Each rectilinear portion 8 of the path of the strip is extended by a respective curved portion 9 where the strip is deflected out of the emergence plane P. Au Beyond this curved portion 9, the strip 2 extends along the front face of the element, slightly set back from this front face so as not to be visible on the surface of the structure. The two curved portions 9 are interconnected by a connecting portion which has a loop 10 located outside the emergence plane P.

In practice, the concrete of the element 4 is not poured by having installed the synthetic strip directly in the mold. Instead, a guide piece 15 such as that shown in FIG. figure 4 .

This part 15 comprises a rigid plastic sheath whose inner section is of flattened shape to form the passage which will receive a reinforcing strip 4. The sheath is shaped according to the predefined path to be followed by the strip 4 in the thickness of the concrete element. It thus comprises portions 18, 19, 20 which define the rectilinear portions 8, the curved portions 9 and the connecting portion 10 described with reference to FIGS. Figures 2 and 3 . The ends 16 of the sleeve widen to facilitate the introduction of the strip 4. Between these two ends 16, the piece 15 has a tongue 17 projecting from the concrete to stiffen the sleeve and ensure its positioning during the casting of the concrete of the element. A traction member such as a cable, a cord or a strap 12 may be placed inside the sleeve to subsequently set up the reinforcing strip.

Although the widened ends 16 of the sheath allow some deflection of the strips 2 at the back of the facing 4, these deviations are limited especially parallel to the plane P emergence of the strips out of the concrete. To overcome this limitation, it is possible to make use of a fastener in the form of a flexible belt such as that shown in FIG. figure 5 .

This flexible belt-shaped fastener 30 is made of closed loop wound fibers, for example polyester fibers of the Same type as those used in reinforcement strips 2. A cladding for example canvas, may be placed around the wick formed by the winding of the fibers.

The representation of the figure 5 suggests what will be the configuration of the flexible belt fastener 30 once installed in the structure: two portions 30A are curved and will form two loops engaged together along the path defined by the sleeve 15 in the facing element , while two other portions 30B, which alternate with the portions 30A along the closed-loop shape of the fastener 30, will be used to connect a reinforcing strip 2.

This connection between the fastener 30 and the reinforcement strip 2 is preferably effected by means of a guiding device 40 whose figure 6 shows an example of realization. In this example, the guiding device comprises two guides 32, 33 nested one inside the other. The first guide 32 is intended to receive the loop portions 30B of the fastener 30, while the second guide 33 is intended to receive the reinforcement strip 2 to make it turn back inside the embankment 1. The guide 32 has a curved surface 34 for deflecting and guiding the loop portions 30B, extended by two wings substantially parallel. Similarly, the second guide 33 has a curved surface 36 for deflecting and guiding the reinforcing strip 2, extended by two wings 37.

The wings 35 of the first guide 32 have rib-shaped spacers 38 for separating the guided portions 30B of the flexible belt received on the curved surface 34. A spacer rib 39 can also be provided on the curved surface 34 itself. even.

Once the assembly is completed, the portions 30B of the belt 30 follow the guide 32 along the wings 35 and tilting around the curved surface 34. They are kept separated from one another by the spacers 38, 39 to prevent the two sections of fiber strand that compose it overlap. The reinforcing strip 2 comes to bypass the guide 33, following the wings 37 and the curved surface 36.

The surfaces 34, 36 have their respective curvatures along two perpendicular planes. They will be positioned so that the plane in which the first guide 32 has its curvature is substantially horizontal, which allows to position the reinforcement strips 2 horizontally in the embankment. Between the curved surfaces 34, 36, the guiding device works in compression, which is a preferred mode of solicitation. Between these two surfaces 34, 36, the two guides 32, 33 can abut one another by means of a flat surface. In a variant, the guiding device 40 may be made as a one-piece piece of the same shape as that formed by joining the two guides 32, 33 previously described.

The Figures 7 to 9 illustrate the mounting of the connection system comprising a flexible belt 30 as described with reference to the figure 5 and a guiding device 40 as described with reference to the figure 6 .

On the figure 7 , we see a molded concrete facing element 4 in which has been incorporated a part 15 of the kind of that of the figure 4 . The flexible fastener 30 is fixed to the strap 12 prepositioned in the sheath, near one of the flared ends 16 of the sheath located at one of the emergence points 6 of the flattened section passageway formed in the concrete by the piece 15. At the other end 16, it pulls on the strap 12, which engages the flexible fastener 30 folded on itself in the passage and is advanced along this passage, to the bring out element 4 as shown on the figure 8 . Traction 12 is then continued on the webbing 12 and / or the fastener 30 so as to balance the double lengths of belt emerging from the facing element 4. At this point, the two portions 30A of the tie 30 in the form of flexible belt have been positioned in the passage formed by the sheath of the part 15, and we can set up the guide device 40 at the two portions 30B of the fastener 30 which are furthest from the facing, as shown on the figure 9 .

For this installation, the device 40 is installed in the two loops formed by the portions 30B of the belt, applied against the curved surface of the guide 32. These two loops are made parallel and spaced from each other in the guide device 40 using spacers 38. Then the reinforcing strip 2 is passed inside the two loops 30B by making it follow the curved surface of the other guide 33. It may be possible to use the strap 12 to hold the band 2 in place by tying this strap around the device 40. The band 2 can then be put in tension. Its orientation in a horizontal plane can be chosen as desired by the designer of the structure taking into account the flexibility of the fastener 30.

Another embodiment of the reinforced soil structure is shown on the figure 10 . In this case, the facing is made of wire mesh 54 and the fastener 80 in the form of continuous closed loop is rigid.

The rigid fastener 80 can be made by shaping one or more metal rods and welding the ends to themselves to ensure continuity of the closed-loop shape. The shaping of the fastener gives it two curved portions 80A intended to hang behind one or more metal bars belonging to the lattice 54 and, alternately with the portions 80A along the closed loop shape, two other portions 80B curves for the connection of a reinforcing strip.

This connection uses a guiding device which, in the example, comprises a single plate-shaped guide 90 folded so as to have an inner face bearing against the curved portions 80B of the fastener and a curved outer face to receive a reinforcing strip 2. The plate forming the guide 90 works in compression when the connected reinforcing strips are taut at the back of the facing.

The rigid fastener 80 is robust and very easy to set up on the mesh-type facing 54. It may possibly contribute to the assembly of adjacent lattice panels 54A, 54B as shown in FIG. figure 10 , being placed around several bars respectively belonging to these panels 54A, 54B.

A system of connection strips-siding of the kind of the figure 10 is well adapted to multi-layer embankments, including a first layer against the ground 5 against which the structure is erected and a second layer of relatively coarse material, such as pebbles, placed on the front face of the structure to aesthetic purposes. The first layer, where the strips 2 extend, is made of a finer material than the second layer to avoid damaging the synthetic strips.

The fastener 80 makes it possible to prevent the reinforcement strips 2 from being visible on the front face of the structure. In addition, shifting the bands 2 backward improves the fire resistance of the structure because they are less quickly exposed to a rise in temperature in front of the facing.

It will be understood that the invention is not limited to the particular embodiments which have been described above, many variants being conceivable without departing from the scope defined by the appended claims.

Claims (15)

1. Building structure, comprising:

   - a facing (4; 54);

   - backfill (1) on a rear side of the facing;

   - synthetic reinforcing strips (2) distributed through the backfill; and

   - a connection system (30, 40; 80, 90) between the reinforcing strips and backfill,

   characterised in that the connection system comprises fasteners (30; 80) in the shape of a continuous closed loop, each comprising:

   - two first portions (30A; 80A) for hooking to the facing; and

   - two second portions (30B; 80B), alternating with the first portions along the closed loop shape, extending towards the rear of the facing where they are folded back to form two loops inside of which at least one reinforcing strip (2) passes.
2. Structure as claimed in claim 1, further comprising at least one guide device (40; 90) disposed between the two loops formed by the second portions (30B; 80B) of a fastener (30; 80) on the one hand and the reinforcing strip (2) passing inside said two loops on the other hand so as to work in compression in response to a tension exerted by the reinforcing strip.
3. Structure as claimed in claim 1 or 2, in which the fastener (80) is substantially rigid.
4. Structure as claimed in claim 3, in which the facing (54) is provided in the form of mesh, the first portions (80A) of a fastener (80) being placed around at least one bar of the mesh.
5. Structure as claimed in claim 4, in which the facing (54) comprises several mesh elements (54A, 54B), at least one fastener (80) having its first portions (80A) placed around at least two bars of two adjacent mesh elements respectively.
6. Structure as claimed in any one of claims 3 to 5, in which the backfill (1) comprises:

   - a first layer through which the reinforcing strips (2) extend; and

   - a second layer disposed between the first layer and the facing (54), through which at least certain ones of the fasteners (80) extend, the second layer of the backfill being a material that is less fine than the first layer.
7. Structure as claimed in claim 1 or 2, in which the fastener is a flexible strap of fibres wound in a closed loop.
8. Structure as claimed in claim 7, further comprising at least one guide device (40) disposed between the two loops formed by the second portions (30B) of a fastener (30) on the one hand and the reinforcing strip (2) passing through the interior of said two loops on the other hand, the guide device comprising a first curved surface (36) for receiving the reinforcing strip (2) and a second curved surface (34) for receiving the two loops of the second portions (30B) of the flexible strap, the first and second surfaces having their respective curvatures in two perpendicular planes.
9. Structure as claimed in claim 8, in which the guide device (40) has spacers (38, 39) for separating the second portions (30B) of the flexible strap (30) received on the second curved surface (34) of the guide device.
10. Structure as claimed in any one of claims 7 to 9, in which the facing (4) is made from a moulded material incorporating, in at least one anchoring region, a passage with a flattened section formed between two emergence points (6) disposed on a rear face (7) of the facing adjacent to the backfill, and in which the first portions (30A) of the flexible strap (30) are placed inside said passage.
11. Structure as claimed in claim 10, in which said passage comprises two portions (8) adjacent to the two emergence points (6) and each disposed so as to orient an element of elongate shape engaged in said passage parallel with an emergence plane (P) substantially perpendicular to said rear face (7), two curved portions (9) respectively extending said portions adjacent to the emergence points and disposed so as to divert said element outside of the emergence plane, and a connecting portion linking the two curved portions to one another and having at least one loop (10) disposed outside of the emergence plane.
12. Method of building a structure with reinforced earth, comprising:

    - erecting a facing (4; 54) on a front side of the structure;

    - fitting fasteners (30; 80) in the shape of a continuous closed loop on the facing, each having two first portions (30A; 80A) for hooking to the facing and, alternating with the first portions along the closed loop shape, two second portions (30B; 80B) extending towards the rear of the facing, where they are folded back to form two loops;

    - connecting synthetic reinforcing strips (2) to the facing by passing at least one reinforcing strip through the inside of the two loops formed by the second portions of a fastener;

    - backfilling a rear side of the facing where the reinforcing strips connected to the facing by means of the fasteners extend.
13. Method as claimed in claim 12, in which at least one guide device (40; 90) is interposed between the two loops formed by the second portions (30B; 80B) of a fastener on the one hand and the reinforcing strip (2) passing through the inside of said two loops on the other hand, so that the guide device works in compression once the reinforcing strip has been tensioned.
14. Method as claimed in claim 12 or 13, in which the facing (54) is provided in the form of mesh and in which the fasteners (80) are substantially rigid and positioned by passing their first portions (80A) around at least one bar of the mesh.
15. Method as claimed in claim 12 or 13, in which the facing (4) is made from a moulded material incorporating, in at least one anchoring region, a passage with a flattened section formed between two emergence points (6) disposed on a rear face (7) of the facing, in which the fastener (30) is a flexible strap of fibres wound in a closed loop, the operation of connecting the synthetic reinforcing strips (2) to the facing comprising:

    - folding the flexible strap back on itself and engaging one end of the folded-back strap in said passage on a level with one of the emergence points;

    - threading the folded back strap through said passage until it comes out through the other emergence point of the passage;

    - making the lengths of strap outside the two emergence points equal by leaving said first portions (30A) in the passage;

    - joining the two strap ends opposite the facing in order to form said loops of the second portions (30B); and

    - passing at least one reinforcing strip (2) inside the two loops.

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