TECHNICAL FIELD The invention pertains to the field of manufacturing facing elements for reinforced soil structures. The invention more particularly describes a casting element used to form an anchoring element in the rear face of a facing element intended to receive a reinforcement strip for example. The invention also describes a method of manufacturing a facing element using said casting element. TECHNOLOGICAL BACKGROUNG

A stabilized soil structure combines a compacted backfill, a facing made of a plurality of facing elements and reinforcements usually connected to the rear faces of the facing elements. The reinforcements are placed in the compacted backfill with a density dependent on the stresses that might be exerted on the reinforced soil structure. Thrust forces in the soil are dissipated by friction between the reinforcements and the backfill.

The facing elements used in a reinforced soil structure are generally in the form of prefabricated concrete slabs or blocks, arranged as panels to cover the front face of the structure.

The reinforcements are generally in the form of strips placed in the backfill. They are secured to the facing elements by mechanical connecting members also known as anchoring elements that may take several forms. Generally, these anchoring elements appear in the form of substantially C-shaped hollow curved portions in the body of the facing element, extending in the rear face of the facing element from a first opening to a second opening and around an anchorage core. The reinforcement strips are introduced inside the hollow curved portion of the anchoring elements to form a loop around the anchorage core. Both ends of a reinforcement strip extend into the backfill.

Once the reinforced soil structure is complete, the reinforcements transmit high loads, in some cases of up to several tons. Their connection to the facing elements needs to be robust in order to maintain cohesion of the structure. Document EP 2 372 027 Al provides examples of anchoring elements in the rear face of a facing element that improves robustness of the anchorage core to the loads applied by the reinforcement strips.

Manufacturing of the anchoring elements in the rear faces of the facing elements involves the use of a casting element that is inserted in a mould which gives the facing element its shape. Casting material that is poured into the mould is displaced by the casting element thereby creating the hollow curved portion that forms the anchoring element once the casting material has cured.

Document EP 2 370 027 Al mentioned above uses a hollow sleeve that is embedded in the facing element once the casting material has cured and the mould is removed. Using a hollow sleeve is an expensive way of manufacturing anchoring elements insofar as each sleeve remains in its facing element and cannot be removed and reused. Furthermore, some casting material can accidentally enter the sleeve in which case the facing element hosting the sleeve is ruined. Another solution provided by document EP 2 850 251 Bl consists in using a casting element made of two or more solid parts that can be joined together when the facing element is cast, and then disconnected, rotated and removed once the casting material has cured. A two-part construction for this removable rigid casting element assembly is necessary in order to expand the opening of the hollow curved portion in the rear face of the facing element. A solid one-piece casting element could not be removed from the facing element once the casting material is solidified. On the other hand, having thin openings creates friction between the reinforcement strips and the material of the facing element at the openings of the anchoring element in the rear face of the facing element.

To increase the opening angle of the hollow curved portion at the first and second openings, the casting element of EP 2 850 251 Bl has a wider cross-section at the first and second openings than around the anchorage core. A disadvantage of such a casting assembly is that it creates split lines or other surface defects in the anchoring element at the junction between the two parts of the casting assembly. These defects give rise to friction that can damage the reinforcements over time. Furthermore, fabrication of such a casting assembly is relatively expensive and mounting and unmounting of the casting assemblies requires several steps to connect/disconnect both parts and remove them from the hollow curved portion. There exists a need to provide a simpler, more reliable solution to manufacture anchoring elements in facing elements used in reinforced soil structures that overcomes the disadvantages mentioned above.

SUMMARY OF THE INVENTION To overcome the above-recited drawbacks, the invention provides a reusable casting element configured to be arranged in a mould for manufacturing a facing element intended for a reinforced soil structure, the reusable casting element being configured to displace casting material used during manufacturing of the facing element so as to form a hollow curved portion in the facing element extending from a first opening in a rear face of the facing element to a second opening in the rear face, the hollow curved portion surrounding an anchorage core in the facing element between the first opening and the second opening, wherein the reusable casting element is flexible and capable of resilient deformation in an intermediate state, the intermediate state corresponding to a deformation of the reusable casting element between a first shape and a second shape,

wherein the first shape corresponds to a first state of the reusable casting element after the reusable casting element is removed from the facing element or before insertion of the reusable casting element into the mould,

wherein the second shape corresponds to a second state of the reusable casting element when the reusable casting element is arranged in the mould during manufacturing of the facing element, surrounding at least partially the anchorage core.

The invention simplifies the mounting and unmounting of a casting element in the mould used to manufacture a facing element for a reinforced soil structure by providing a flexible casting element that can be removed easily in one go by pulling it out of the hollow curved portion of the facing element.

The flexibility and ability to resiliently deform of the casting element enables it to reversibly change from the first shape into the second shape virtually indefinitely, without requiring excessive force or complex mounting/unmounting procedures. The flexible reusable casting element of the invention is not in two parts in the area located around the anchorage core and thereby does not create surface defects around the anchorage core in the hollow curved portion.

The "intermediate state " corresponds to a progressive and resilient deformation of the reusable casting element, which occurs at least when the reusable casting element is being removed from the facing element after hardening of the casting material. In some embodiments, the reusable casting element is also in an "intermediate state" when the reusable casting element is forced from a first unstrained state into a second strained state when inserted into the mould.

According to an embodiment, the first state and the second state are identical, and the first shape and the second shape are identical.

It is indeed possible to have a reusable casting element that is capable of resilient deformation when the reusable casting element is removed from the already cast facing element, but otherwise has the same shape when inserted in the mould and when removed from the mould.

According to another embodiment, the first state is a resting unstrained state of the reusable casting element and the second state is a strained state of the reusable casting element.

In this other embodiment, the first shape differs from the second shape.

According to an embodiment, the reusable casting element may further comprise a first end portion and a second end portion opposite the first end portion, at least one among the first end portion and the second end portion comprising first connection means configured to maintain the reusable casting element in the second state and force it into the second shape during manufacturing of the facing element. According to an embodiment, the first end portion and the second end portion of the reusable casting element may comprise first connection means.

Having first connection elements on both the first end portion and the second end portion enables connecting both end portions together to keep the reusable casting element in the second state. This is particularly advantageous when the second state differs from the first state and corresponds to a strained state of the reusable casting element. According to an embodiment, the first connection means of the first end portion may be linked to the first connection means of the second end portion to form a releasable locked contact when the reusable casting element is maintained in the strained state. According to an embodiment, the first end portion may be separated from the second end portion by a gap when the reusable casting element is maintained in the second state.

When a gap separates both end portions, the size of the anchorage core can be increased so that it may withstand higher tensile or shear forces.

According to an embodiment, the first end portion may be in contact with the second end portion when the reusable casting element is maintained in the second state.

A direct contact between both end portions of the reusable casting element enables a firmer connection of both end portions to force the reusable casting element into the second shape.

According to an embodiment, the first connection means may be adapted to engage in a releasable locked contact with a support structure comprising second connection means capable of forming a releasable locked contact with the first connection means.

A support structure with second connection means capable of engaging with the first connection means is particularly advantageous as the support structure can help maintain the reusable casting element in the strained state. This effect can be further enhanced when the support structure has a shape that is at least partly complementary to that of the reusable casting element.

According to an embodiment, the first connection means may be chosen from among a screw and thread type connection, two clips having a complementary shape, a magnetic connection, an adhesive connection.

According to an embodiment, the first shape in the first state may be curved. A curved shape for the reusable casting element in the first state is particularly advantageous as it reduces the deformation of the casting element when it is manipulated in the mould, in particular when it is pulled out of it once the facing element is cast. This embodiment is even more advantageous when the first and second states are different, and the second state is a strained state. When the reusable casting element is curved in the unstrained state, occurrence of split lines or surface defects that would otherwise create bumps or other defects in the hollow curved portion is prevented or reduced. A curved casting element requires little strain to transform it from the first shape into the second shape, which contributes to increasing its lifetime.

According to an embodiment, the first shape in the first state may be configured so that a strain applied to the reusable casting element in the second state is within a twenty percent range of removal strain applied to the reusable casting element when the reusable casting element is removed from the facing element after manufacture of the facing element.

When the reusable casting element is curved or already bent in its first shape, the strain applied to the casting element to force it into the second shape is reduced. However, the casting element is also subject to a removal strain when it is pulled out of the manufactured facing element. An intermediate curvature for the casting element reduces both the strain required to force the casting element into the second shape and the removal strain. The advantage of this embodiment is particularly strong when the first shape differs from the second shape and the first state is an unstrained state of the casting element whereas the second state is a strained state of the casting element. According to an embodiment, the reusable casting element may further comprise reinforcement inserts embedded in the reusable casting element.

Reinforcement inserts, such as for example metal grids or strips, increase the mechanical strength of the casting element. It renders the casting element more resistant to flexion when removed from the facing element or when forced into the second shape.

According to an embodiment, the reusable casting element may be a flexible hollow sheath in the first shape and is configured to be filled with a material to change from the first shape into the second shape. A flexible hollow sheath or sleeve offer the advantage of being easier to transport from one site to another since its size is considerably reduced in the first shape. The sheath or sleeve can for example be made of a geotextile material.

In particular, the hollow sheath may be filled with any one of the material chosen from among: fill material, a gas, a liquid, sand, rocks, concrete.

Using such materials provides mechanical stability to the reusable casting element in the second shape, so that it is not deformed when casting material is poured into the mould.

According to an embodiment, the reusable casting element may further comprise a protective sheath surrounding the reusable casting element. A protective sheath may further protect the casting element from the casting material and from friction to which it can be subjected when removed from the facing element. The sheath remains in the facing element after removal of the reusable casting element.

According to an embodiment, the reusable casting element may be made of polyurethane.

Polyurethane is a material that is compatible with most casting elements used to fabricate facing elements, in particular concrete, and provides the casting element with both enough mechanical strength and flexibility to facilitate mounting and unmounting of the casting element and extend its lifetime.

The invention also pertains to a kit comprising a reusable casting element as described above.

According to an embodiment, the kit may further comprise a support structure capable of engaging with the reusable casting element to maintain the reusable casting element in the second state.

In particular, the support structure may engage with the reusable casting element to form a system that is capable of displacing casting material used during manufacturing of the facing element to form a hollow curved portion with identical opening angles at the first opening and at the second opening.

The reusable casting material generally has a substantially constant or decreasing cross- section from the first end portion to the second end portion thereof. The support structure when it is engaged with the reusable casting element, expands the cross section at the second end portion which leads to a wider second opening in the rear face of the facing element, thereby reducing friction of the reinforcement with the material of the facing element.

According to an embodiment, the reusable casting element may have a width that gradually decreases from the first end portion to the second end portion.

A decreasing width facilitates extraction of the reusable casting element as it reduces friction of the second end portion against surfaces of the hollow curved portion. This in turn extends the lifetime of the reusable casting element.

The invention also pertains to a method for manufacturing a facing element for a reinforced soil structure using a reusable casting element configured to be arranged in a mould for manufacturing the facing element, the reusable casting element being configured to displace casting material used during manufacturing of the facing element so as to form a hollow curved portion in the facing element extending from a first opening in a rear face of the facing element to a second opening in the rear face, the hollow curved portion surrounding an anchorage core in the facing element between the first opening and the second opening,

wherein the reusable casting element is flexible and capable of resilient deformation between a first shape and a second shape,

wherein the first shape corresponds to a first state of the reusable casting element after the reusable casting element is removed from the cast facing element or before insertion of the reusable casting element into the mold,

wherein the second shape corresponds to a second state of the reusable casting element when the reusable casting element is arranged in the mould during manufacturing of the facing element, surrounding at least partially the anchorage core,

the method comprising: - mounting the reusable casting element on the mould,

- adding casting material to the mould to form the facing element, and

- removing the reusable casting element from the mould by pulling on one end portion of the reusable casting element, thereby subjecting the reusable casting element to a removal strain forcing the reusable casting element to resiliently deform and slide out of the hollow curved portion and relax into the first shape when the reusable casting element is outside of the facing element.

Such a method for manufacturing a facing element requires little effort as the casting element only needs to be bent and attached to the mould. The casting element can be removed in one step by sliding it out of the hollow curved portion of the facing element once the casting material has cured. The flexibility of the reusable casting element allows it to slide out of the anchoring element without being damaged, and without exerting an excessive force on the casting element.

BRIEF DESCRIPTION OF THE FIGURES

Other features and advantages of the present invention will become apparent from the description below of some non-limiting illustrative embodiments, with reference being made to the attached drawings, in which : - figure 1 is a schematic sectional view of a reinforced soil structure comprising a plurality of facing elements with reinforcements connected to the rear faces of the facing elements via anchoring elements ;

- figure 2 is a schematic sectional view of a facing element and an anchoring element thereof; - figures 3a-3b are schematic respectively sectional and perspective views of a reusable casting element;

- figures 4a-4c are schematic sectional views of several examples of reusable casting elements;

- figures 5a-5b are schematic sectional views of a reusable casting element engaged with a support structure ; - figure 6 is a schematic sectional view of another example of a reusable casting element.

For the sake of clarity, the dimensions of features represented on these figures may not necessarily correspond to the real-size proportions of the corresponding elements. Like reference numerals on the figures correspond to similar elements or items. DETAILED DESCRIPTION

The invention addresses issues arising during manufacturing of facing elements intended to be used in reinforced soil structures. More particularly, the invention provides a simple, convenient and cost efficient way of creating anchoring elements in the rear face of facing elements, by using a reusable casting element. The reusable casting element, as well as a method in which it can be used, are presented below.

Figure 1 is a schematic sectional view of a reinforced soil structure 100. The structure comprises a front face made of facing elements 10 arranged so as to form a wall. Backfill 12 is arranged on the rear side 13 of the facing elements 10. A secure connection between the facing elements and the backfill is ensured with the use of reinforcements 11, anchored to the rear face of the facing elements and extending into the backfill 12.

As illustrated on figure 2, an anchoring element in the form of a hollow curved portion 20 is arranged in the rear face 14 of the facing element 10 to connect the reinforcements 11 to the facing elements. This hollow curved portion 20 comprises a first opening 21, a second opening 22 and a channel arranged in the material of the facing element that surrounds an anchorage core 15 between the first opening 21 and the second opening 22.

The opening angle 23 of the first opening 21 and second opening 22 is generally large, to avoid undue friction of the reinforcement 11 against the material of facing element 10. As illustrated on figure 2, a reinforcement 11 is inserted in one of the openings, forms a loop around the anchorage core 15 and exits the hollow curved portion 20 at the other opening. Both ends of the reinforcement 11 extend into the backfill 12.

A facing element 10 is usually manufactured by pouring casting material, for example concrete, in a mould that gives the facing element its shape. After hardening of the casting material, the facing element can be removed from its mould. To create the hollow curved portion 20 it is customary to use a casting element or casting assembly which displaces the casting material before it hardens in the mould. Figures 3a- 3b, 4a-4c, 5a-5b and 6 provide examples of reusable casting elements according to the invention. As shown on figure 3a, the reusable casting element 1 can be a flexible structure made up of only one piece having a first end portion 2 and a second end portion 3. In a first, resting unstrained state, the reusable casting element 1 has a first shape 31, in which the first end portion 2 and the second end portion 3 are spaced apart from each other. The cross section of the reusable casting element 1 at the first end portion 2 is larger than its cross-section at the second end portion 3. This enables the first end portion 2 to convey a suitable shape to the first opening 21 of the facing element 10, by providing it with a sufficiently wide opening angle 23. A larger cross-section at the first end portion 21 also provides a larger grip surface that can facilitate extraction of the reusable casting element 1 once the facing element is cast. Indeed, after the facing element is cast, the reusable casting element is extracted by pulling it out of the hollow curved portion 20, for example by exerting a pulling force on the first end portion 2.

In other embodiments that are not represented, the cross-section of the first end portion 2 may be substantially the same as that of the second end portion 3. In that case, a support structure can be attached to the first end portion 2 to provide a sufficiently large opening angle to the first opening 21. As represented on figure 3a, the reusable casting element 1 can be bent into a second shape 32, in which the second end portion 3 is brought closer to the first end portion 2 than in the first shape 31. In this second shape 32 the reusable casting element 1 is maintained in a strained state and occupies a volume that corresponds to most of the hollow curved portion 20 of the cast facing element 10. To force the reusable casting element 1 into the second shape 32, the mould 30 may comprise structures 33 onto which the reusable casting element 1 can be attached or with the help of which it can be blocked in this second shape 32.

As can be seen on figure 3a, the change from the first shape 31 to the second shape 32 implies a larger deformation of the reusable casting element 1 at the second portion 3 than at the first portion 2. The material in which the reusable casting element 1 is made can take advantage of this fact and have a higher elasticity at the second end portion 3 than at the first end portion 2. For example, this elasticity may gradually increase from the first end portion 2 to the second end portion 3.

One example of a material particularly suitable for the reusable casting element 1 is polyurethane. This material is chemically resistant to concrete (one the most common materials used to manufacture facing elements), is capable of resilient deformation without being damaged in the process and is easy and cheap to produce. Other materials or mix of different materials can be used for the reusable casting element.

In another, unrepresented embodiment, the first shape and the second shape can be identical, in which case the reusable casting element is only subjected to a resilient deformation when it is pulled out of the facing element after hardening of the casting material in the mould. In such an embodiment, the first and second states of the reusable casting element are both unstrained states.

Figure 3b provides a perspective view of one example of a reusable casting element 1. The reusable casting element may typically have a substantially rectangular cross-section, which is adapted to form hollow curved portions 20 into which reinforcement strips can be inserted.

Figures 4a to 4c provide other examples of reusable casting elements 1 that can be used to create an anchoring element in a facing element 10.

On figure 4a, the second end portion comprises first connection means 41 which enable a releasable lock contact with a corresponding connection means 43, either on the first end portion (not represented) or on the mould 30, for example. These first connection means may for example be a threading adapted to receive a screw, a clip that cooperates with an element having a complementary shape, a magnetic connection, and adhesive connection, a zip, a recess that can be inserted into a protrusion or vice versa. As can be seen on figure 4a, a support structure 50 can be used to provide a sufficiently wide opening angle 23 to the second opening 21. This support structure 50 may for example be a protrusion in the mould 30 or another piece having a shape adapted to engage with the reusable casting element 1 and force it into the second shape 32. Instead of having a releasable locked contact between the first connection means 41 and corresponding connection means 43, it is also possible to have first connection means 41 arranged on both the first end portion 2 and the second end portion 3, so that both first connection means 41 are connected to each other to force the reusable casting element 1 into the second shape 32.

As seen on figure 4b the first end portion 2 does not necessarily contact the second end portion 3 in the strained state. On figure 4b, a gap 45 remains between both end portions in the second shape 32. First connection means 41 of the first end portion 2 and the second end portion 3 can be joined together in releasable locked contact via a connector 44 such as a key or a C-shaped lock for example. Joining two first connection means 41 arranged on the first and second end portions can also be done when both end portions are in direct contact (as in the situation illustrated on figure 4a).

Figure 4b further illustrates the possibility of surrounding the reusable casting element 1 with a protective sheath 40. This protective sheath can reduce friction between the reusable casting element 1 and the material of the facing element 10, for example when the reusable casting element is withdrawn from the manufactured casting element. The protective sheath can also act as a protection against the possible corrosive nature of the casting material used to manufacture the facing element 10, or to protect the casting element from being tainted or damaged by contact with the casting material, or for example, humidity. The protective sheath 40 can be intended to stay in the facing element when the reusable casting element 1 is removed. The protective sheath 40 can then serve as a permanent protection for the reinforcement strip 11 that is inserted in the hollow curved portion 20;. The protective sheath 40 can for example provide protection against moisture, or against the corrosive nature of the material in which the facing element 10 is made. According to another embodiment the reusable casting element may itself be a hollow sheath or sleeve. In such an embodiment, in the first shape, the reusable casting element can be folded and stored in a very compact format. To force the sheath or sleeve into the second shape, the reusable casting element can be fileld with material, such as for example fill material, rocks, sand, a gas (pressurized air, carbon dioxide for example), a liquid (for example oil or water) or concrete. The material is preferable chosen so that it allows the reusable casting element to maintain its second shape while casting material is poured into the mould. The illustration of figure 4c could therefore also represent a sheath 40 that acts as a sleeve, filled with some material forcing it into its second shape during the manufacturing process of the facing element. After removal from the facing element, or just before removal, the material that fills the sheath 40 is removed and the sheath can shrink to a first shape, more compact than the second shape.

Figure 4c provides another example of a reusable casting element 1 in which both the first end portion 2 and the second end portion 3 comprise first connection means 41. These connection means can be used to mount the reusable casting element 1 into the mould 30, and to force it into the second shape 32 via a cooperation with corresponding connection means 43 on the mould 30.

The above examples mostly rely on mounting the reusable casting element 1 on the mould 30 used to form the facing element 10. However, the reusable casting element 1 may also be used in combination with a support structure 50 that itself is mounted on the mould 30. Figures 5a and 5b provide two examples of such an assembly which can be regarded as a kit.

Figure 5a represents a reusable casting element that can be attached to a support structure 50 via first connection means 41, which engage in a releasable locked contact with second connections means 42 arranged in the support structure 50. The shape of the support structure 50 can be selected in order to efficiently cooperate with the second shape 32 of the reusable casting element 1, in particular so that once both pieces are engaged in a releasable locked contact, the reusable casting element 1 is maintained in its strained state and is mounted on the mould 30. The support structure 50 enables manufacturing a hollow curved portion 20 that has a second opening 22 with a sufficiently wide opening angle 23. In particular, the support structure 50 allows maintaining a sufficiently thin thickness at the second end portion 3 of the reusable casting element 1 so that it may be pulled out of the facing element 10 without exerting a compressive strain and undue friction on the reusable casting element 1.

It is to be noted, that an embodiment in which the reusable casting element 1 has a large cross-section at the second end portion 3 and at the first end portion 2 can be implemented, in particular when the reusable casting element 1 is made of a material that is both resiliently compressible and resiliently flexible. Such materials may further be used in combination with hollow cores that force the reusable casting element 1 into its second shape while also maintaining a desired shape for the anchorage core 15. The hollow core can be arranged around the core, and the reusable casting element 1 is then wound around the hollow core. This prevents unwanted compression of the reusable casting element 1 when casting material is poured in the mould 30. Such an embodiment is not represented on the appended figures.

Figure 5b provides another example of a kit in which a reusable casting element 1 cooperates with a support structure 50. The support structure 50 comprises recesses 51 and protrusions 52 onto which the reusable casting element 1 can be fixed to force and maintain it in the second shape 32. Figure 5b further illustrates a reusable casting element 1 with a cross-section that decreases from the first end portion 2 to the second end portion 3. A first cross-section 4 at the first end portion 2 is larger than a second cross-section 5 at the second end portion 3. This decrease in thickness and cross-section allows an easier extraction of the reusable casting element 1 once the facing element 10 is manufactured. The second end portion 3 of the reusable casting element 1 is subjected to fewer frictional constraints when it is pulled out of the facing element.

Further possible improvements to the reusable casting element 1 are represented on figure 6. The reusable casting element 1 can comprise reinforcement inserts 6, such as embedded metal grids or strips, that extend the lifetime of the reusable casting element 1. These inserts add strength, preferably at the second end portion 3 of the reusable casting element 1, to avoid any inelastic deformation thereof. The inserts can be made of a composite material which improves resistance of the reusable casting element 1 to frictional forces or to tensile stress. The reinforcement inserts 6 may also take the form of ribs.

Another improvement illustrated on figure 6 is found in the curved first shape 31 of the reusable casting element 1. In particular, the first shape 31 in the resting unstrained state may be curved so that a strain applied to the reusable casting element 1 in the strained state is within a twenty percent range of the strain applied to the reusable casting element when the reusable casting element 1 is removed from the facing element 10.

A curved shape reduces the total deformation that the second end portion 3 undergoes when the reusable casting element 1 is forced into the second shape 32. This prevents the appearance of surface defects such as split lines in the hollow curved portion 20, in particular around the anchorage core and the second opening.

The examples described above in connection with figures 3a-3b, 4a-4c, 5a-5b and 6 comprise features that can be easily combined with each other. The reusable casting element 1 presented above, and the kit in which it may appear (especially a kit further comprising a support structure 50) can be used in a method to manufacture a facing element 10. Such a method consists in providing a mould 30 for the manufacture of the facing element 10. Then the reusable casting element 1 or the reusable casting element and a support structure 50 are mounted on the mould and the reusable casting element 1 is forced into the second shape 32. Then, casting material is poured into the mould, and then cured. Once the casting material is hard, the support structure 50 (if any is present) can be removed and then the reusable casting element 1 can be slidably pulled out of the facing element 10, for example by pulling on the first end portion 2 thereof. The reusable casting element 1 presented above, the kit in which it can be used and the method of manufacturing a facing element 10 all provide a cost-effective, reliable and easy way of forming an anchoring element in a facing element intended for a reinforced soil structure.