Cellular confinement system

Abstract

A cellular confinement system (1) for soil stabilization, comprising strips (10) arranged next to each other, wherein adjacent strips (10) are attached together at local attachment areas (11) spaced along the strips (10), wherein portions (12) of each strip (10) located between two local attachment areas (11) are allowed to bend to conform the cellular confinement system (1) into an array of cells (13) for receiving filler material, wherein each strip (10) comprises a polymer matrix (20) and at least one reinforcement (21) embedded within the polymer matrix (20) and extending over the entire length of the strip (10), each reinforcement (21) being obtained by grouping a plurality of filaments (22) together, the reinforcement (21) being pretensioned so that a residual force is conserved in the reinforcement (21) once it is embedded into the polymer matrix (20). A manufacturing process involving co-extrusion of said matrix (20) and reinforcement (21) is disclosed.

Description

Cellular confinement SystemTechnical Field

[0001] The present disclosure is relative to geosynthetic cellular confinement systems that are typically used for civil and environmental applications.Background Art

[0002] Various soil-working operations such as load support for pavements, hardstands, storage platforms, railway embankment sub-structures, soil soft embankments, unstable slopes, and retaining structures, or slope erosion protection for high embankments for highways, railways, earthen dikes, mine overburden dumps and other applications require solutions for control of erosion, for subgrade soil stabilization or for controlled load distribution on the ground. To these ends, it is known to use 3-dimensional geosynthetic cellular structures also called cellular confinement systems.

[0003] For example, it is known from document W02007074448 to lay a plurality of strips arranged in a side- by-side pattern to form such a cellular confinement system. In particular, each strip is segmentally bonded to an adjacent strip at spaced-apart bonding areas, the bonding areas being offset along the length of the strips from one strip to another. The bonding areas are arranged in such a way that stretching the structure across its width forces the strips portions between each bonding areas to bend or curl away from each other in order to form cells. The cells are then filled with filling material and the system acts as a reinforced soil mattress.

[0004] However, such a cellular system is not sufficiently resistant to withstand efforts due to the load exerted on the structure. In fact, significant plastic deformations of more than 3 % have been measured in cases where HDPE strips are installed close to the pavement surface due to the vehicle loads. Such deformation rates may result in a substantial loss in dimensional stability. In addition, the product being typically installed for a very long service life, it may deteriorate with time due to creep and fail to efficiently stabilize soil.

[0005] In order to enhance the creep behavior, such strips may be stretched (biaxially or uniaxially) to orient the polymer molecules and improve the strength and stiffness of the material. Once stretched, the strips are then heat-set or annealed to lock in the orientation and relieve any internal stresses for dimensional stability and strength retention over time.

[0006] In other examples, strips may comprise sewn threads along the length of the strips in order to improve creep resistance. However, threads feature natural slack due to their waved configuration so their effectiveness as reinforcement remains questionable. When used in civil engineering with soil backfill, the exposed threads can be damaged, thus reducing even more their role as reinforcement.

[0007] In another example, it is known from RU204834U1 to employ a lamination-based process whereby fibri Hated monofilament tapes or extruded polymer tapes are pressed onto a pre-extruded polymer sheet via calendering. The resultant bonding mechanism is primarily surface adhesion combined with partial polymer penetration into the fibrillated structure. The interface between reinforcement and polymer remains distinct, with limited interdiffusion of polymer chains, thereby lacking a continuous polymer-reinforcement phaseboundary. Moreover, since the reinforcements are pressed into a side surface of the strip, the reinforcement thus extends near said surface and is exposed to an exterior side of the strip. This asymmetric position of the reinforcement in the strips’ cross section can lead to inefficient load distribution and cause the detachment of the reinforcement from the strip during the service of the product in situ. In addition, the reinforcement may be damaged by filling material and lack robustness during its service life.

[0008] The present disclosure aims to propose a solution to at least part of the above-mentioned problems.Summary

[0009] The present disclosure relates to a cellular confinement system for soil stabilization, comprising strips arranged next to each other, wherein adjacent strips are attached together at local attachment areas spaced along the strips, wherein portions of each strip located between two local attachment areas are allowed to bend to conform the cellular confinement system into an array of cells for receiving filler material, wherein each strip comprises a polymer matrix and at least one reinforcement embedded within the polymer matrix and extending over the entire length of the strip, each reinforcement being obtained by grouping a plurality of filaments together, the reinforcement being pretensioned so that a residual force is conserved in the reinforcement once it is embedded into the polymer matrix.

[0010] Although it is particularly advantageous, pretension of the reinforcement remains optional.

[0011] The reinforcement is thus entirely contained inside the material of the strip. In other words, apart from the two end faces resulting in the cut of the strip, the entire outer surface of the reinforcement, constituted by its longitudinal sides, are covered by the material of the strip.

[0012] In a particular example in which the reinforcement presents a substantially polygonal cross section, each of the longitudinal sides of the reinforcement is covered by the material of the matrix, at any point along its length. In general, a perimeter of a cross section of the reinforcement is entirely covered by the material of the matrix.

[0013] Each reinforcement may be obtained by grouping filaments together, in particular by extrusion. In examples, the filaments pass through the predefined channels at the coextrusion machine, which separates them into the reinforcements that are present in the final product.

[0014] In examples, each reinforcement comprises a plurality of individual filaments grouped together, each filament extending along the entire length of the reinforcement.

[0015] It is understood by “individual” that each filament originally constitutes an independent object, and that the reinforcement is obtained by agglomeration of said independent objects together. For example, such filaments are distinct from fibers obtained by fibrillation of a strip, which would constitute dependent objects.

[0016] The use of a reinforcement provides increased tensile resistance and limits plastic deformation of the structure. Furthermore, the fact that it is embedded within the strip protects it from installation damage and allows maintaining a thin strip shape with no protruding part. Due to the flexibility of the materials used the system is fast and easy to install on the ground.

[0017] In addition, according to the present disclosure the strips do not require any stretching operation as described above in the prior art as the reinforcements are naturally oriented along the length of the strips. The manufacturing of the strip is thus facilitated.

[0018] Pretension of the reinforcement(s) advantageously allows a residual force to be conserved within the reinforcement, which helps attenuating the creep effect on the cellular confinement system over time. In fact, starting in a pretensioned state, more time will be necessary to elongate the reinforcement in comparison with a non-pretensioned reinforcement. In addition, part of the creep deformation will be directly removed since the strip creation and the product performance will be increased (i.e. less deformation when loaded).

[0019] The features set out in the following paragraphs can optionally be implemented, independently of one another or in combination with one another:

[0020] In examples, the reinforcements have a greater creep modulus than the matrix.

[0021] In examples, said residual force is substantially equal or superior to 5%, or 10% of the tensile strength of the reinforcement. In a particular example, the residual force is substantially equal to 10% of the tensile force of the reinforcement thus providing a correct compromise between easy implementation and creep behavior improvement. The tensile strength typically corresponds to the effort threshold leading to the rupture of the reinforcement and is typically expressed in N / filament or kN / reinforcement channel.

[0022] In examples, the reinforcements are located in a middle region of a thickness of the strip. In other words, in the direction of the thickness of the strip, each side of the reinforcement is covered by substantially the same thickness of sheath material (matrix). This way, the strip may be symmetrical along a median plane formed by the strip, and its mechanical behavior is thus improved (i. e. load distribution to the sheath and adjacent reinforcements).

[0023] In a particular example, the reinforcement comprises PET, and the matrix comprises HDPE.

[0024] In examples, yarns are made of high-tenacity polyester.

[0025] Said yarns may present a circular cross section. In other examples, any cross-section shape is possible.

[0026] In examples, a cross-section of each filament constituting a reinforcement is of substantially constant dimension and shape along the entire length of said reinforcement.

[0027] In examples, all filaments of each reinforcement feature the same length, and / or each filament of each yarn feature the same length.

[0028] Each individual filament may present a thickness, when measured transversally to an elongation direction of the reinforcement, that ranges between 0,2mm and 1 mm. that corresponds to approximately 500 - 10000 of linear density (dtex).

[0029] In examples, the cellular confinement system comprises a bonding primer between the reinforcement and the polymer matrix, the bonding primer being suited to adhere both to the reinforcement material and to the polymer matrix material.

[0030] As a particular example, the bonding primer may be suited to both adhere to LLDPE or HDPE in which the matrix can be made of, and to PET in which the reinforcements can be made of, in examples.

[0031] Thanks to the bonding primer, the reinforcement can feature an enhanced adhesion to the sheath (matrix), thus preventing relative translation of the reinforcement along the sheath in the elongation direction of the reinforcement. As a result, a better mechanical behavior of the strip is obtained.

[0032] In examples, the bonding primer is applied along the entire length of the reinforcement.

[0033] In other examples, the bonding primer is applied on one or several portions of the length of the reinforcement, the sum of each portion being smaller than the total length of the reinforcement.

[0034] In examples, the bonding primer is applied by diving the reinforcement into a bath of bonding primer, prior to co-extrusion with the sheath.

[0035] In examples, the bonding primer is a chlorinated polyolefin-based primer or a silane-based primer.

[0036] In examples, filaments of the at least one reinforcement are twisted around an elongation direction of the reinforcement into one or more yarns forming the reinforcement. In other words, the filaments may be twisted in a manner similar to that of a rope.

[0037] Such a twisted configuration allows an outer surface of the reinforcement to present partially transversal edges each constituting an obstacle to the sliding direction of the reinforcement. Such a configuration is thus suited to facilitate prevention of relative translation between the reinforcement and the matrix.

[0038] It may be advantageous to combine twisting filaments into one or more yarns and adjunction of a bonding primer in order to further block the reinforcement into the sheath.

[0039] In examples, the reinforcements of the strip are parallel to each other, and / or the filaments of each reinforcement extend parallel to each other.

[0040] In examples, the local attachment areas are substantially linear along a width of the strip, and wherein the reinforcements are perpendicular to the attachment areas.

[0041] In examples, the reinforcements have a substantially constant cross-sectional shape.

[0042] In examples, a cross-section of each filaments of the at least one reinforcement features a substantially constant dimension and shape along the entire length of said reinforcement.

[0043] In examples, the reinforcements have a cross-sectional area in a range of 0,3mm2to 12mm2, preferably of 0,87mm2to 7,2mm2.

[0044] In examples, the reinforcements comprise filaments of polymeric material, in particular PET filaments.

[0045] In examples, the reinforcements comprise metallic filaments.

[0046] In examples, the strips have apertures between the local attachment areas. Such apertures increase the interaction between the infill material and the strips by interlocking the soil grains. In examples, the apertures are located between two reinforcements of the strip, along the width of the strip. In other words, the apertures are located in a non-reinforced part of the strip.

[0047] In examples, the strips comprise fasteners to attach them to each other. For example, such fasteners may be used to attach two determined length portions of strips end to end and / or to connect strips at local attachment areas.

[0048] In examples, local attachment areas comprise stitching yarns, the strips being stitched together by the stitching yarns at local attachment areas. Stitching yarns may thus provide improved resistance to the local attachment areas.

[0049] In examples, the stitching yarns are made of polymer.

[0050] In examples, the stitching yarns are made of the same material as the reinforcements.

[0051] In examples, the local attachment areas comprise a polymeric cover to protect the stitching yarns. The polymeric cover may be welded, glued, or fixated in any appropriate manner know to art over the stitching yarn in order to cover them. For example, this may be useful to protect the stitching yarns from damage during filling by the infill material or from chemical deterioration due to acidic or basic materials.

[0052] In examples, the polymeric cover is of the same material as the matrix.

[0053] In examples, the local attachment areas comprise welding points, for example obtained by ultrasonic welding, wherein both adjacent strips are welded together.

[0054] The present disclosure further comprises a method for manufacturing a cellular confinement system, the method comprising: co-extruding polymeric material and a plurality of filaments into groups forming at least one reinforcement to form a strip-shaped co-extruded product having a polymer matrix, wherein the reinforcements are embedded within the polymer matrix and extend continuously along the coextruded product, and wherein the reinforcements (21) are pretensioned before co-extrusion with the polymer matrix (20) so that a residual force is conserved in the reinforcement (21) once it is embedded into the polymer matrix (20); cutting the co-extruded product into strips; and assembling the strips to configure the cellular confinement system as a stack of strips including two end strips and a plurality of intermediate strips between the two end strips, wherein each intermediate strip has a first side attached to an adjacent strip of the stack at first local attachment areas spaced apart along the strips and an opposite second side attached to another adjacent strip of the stack at second local attachment areas spaced apart along the strips, wherein the second local attachment areas are offset with respect to the first local attachment areas along the longitudinal direction of the strips, wherein portions of each strip located between two first local attachment areas or between two second local attachment areas are allowed to bend to conform the cellular confinement system into an array of cells for receiving filler material.

[0055] In examples, the filament bobbins unwind with a certain force so that the filaments are pulled and experience some pretension.

[0056] In examples, before the coextrusion the filaments pass through rollers or any other device that need a certain force to cross, so that some pretension is applied to the filaments.

[0057] The method may further comprise diving each reinforcement into a bonding primer before co-extrusion of said reinforcement with the polymer matrix, said bonding primer being suited to adhere both to the reinforcement material and to the polymer matrix material.

[0058] The method may further comprise twisting filaments of the at least one reinforcement around an elongation direction of the reinforcement into one or more yarns, prior to co-extrusion of the reinforcement with the polymer matrix.

[0059] In examples, the strips are welded to each other at the first and second local attachment areas.

[0060] In examples, the strips are welded using ultrasonic welding.

[0061] In examples, the strips are attached to each other with fasteners.

[0062] In examples, local attachment areas comprise stitching yarns, the strips being stitched together by the stitching yarns at the first and second local attachment areas.

[0063] In examples, the method further comprises texturing at least one side of the co-extruded product or of the strips.

[0064] In examples, the texturing comprises pressing an embossed surface onto one or both sides of the coextruded product.

[0065] In examples, the method further comprises puncturing the co-extruded product or the strips to form apertures between the first local attachment areas and between the second local attachment areas.

[0066] In examples, the method further comprises coating the strips with a protective layer.

[0067] In examples, the method comprises impregnating the strips with additives.Brief Description of Drawings

[0068] Other features, details and advantages will be shown in the following detailed description and on the figures, on which:

[0069] Fig. 1 is schematic view of an example of a cellular confinement system according to the present disclosure,

[0070] Fig. 2a and 2b are schematic views of two adjacent strips of a cellular confinement system that are bonded to each other to form a cell according to an example of the present disclosure,

[0071] Fig. 3a is a schematic view of two strips bonded in the way illustrated by figure 2, and figure 3b is a schematic view of a transversal cross-section of a strip wherein reinforcements according to an example of the present disclosure are particularly visible,

[0072] Fig. 4 shows a more detailed schematic view of the cross section shown on figure 3b.

[0073] Fig. 5 shows a cross-section view of a particular example in which the reinforcements comprise a plurality of yarns obtained by twisting filaments of the reinforcement,

[0074] Fig. 6 shows a more detailed perspective view of twisted filaments constituting a yarn of a reinforcement,

[0075] Fig. 7 shows a cross-section partial view of a strip example in which a bonding primer is used, encircling a perimeter of the reinforcement,

[0076] Fig. 8 shows a schematic side view of a plurality of strips that are superimposed on top of each other in order to form a higher and deeper cellular confinement system according to an example of the present disclosure,

[0077] Fig. 9 shows a schematic view of the feeding process of reinforcements in the form of yarns prior to the coextrusion of a product which is then suited to be cut into a plurality of strips according to an example,

[0078] Fig. 10 shows a schematic view of the texturing, puncturing and cutting phases that may follow the coextrusion phase illustrated on figure 6 according to an example,

[0079] Fig. 11 shows a schematic view of an example of a bonding method using ultrasonic welding,

[0080] Fig. 12 shows a diagram of the manufacturing method of a cellular confinement system according to an example of the present disclosure.Description of Embodiments

[0081] Figure 1 shows an example of a cellular confinement system 1 according to the present disclosure. The cellular confinement system 1 comprises strips 10 arranged next to each other in a stack of strips 10. The stack comprises two end strips 10.1 , 10.2 defining the width of the cellular system, and a plurality of intermediate strips arranged between the two end strips 10.1 , 10.2. All of the strips are typically arranged in length side by side.

[0082] Each adjacent strips are attached together at local attachment areas 11 spaced along the length of the strips 10. Attachment areas 11 are spaced so that portions 12 of each strip 10 located between two local attachment areas 11 are allowed to bend or curl to conform the cellular confinement system 1 into an array of cells 13 for receiving filler material.

[0083] Any material is suitable to be used as filler material as long as it presents itself in a form that allows it to easily fill the volume offered by each cell. For example, filler material may be chosen among sand, soil, rock, gravel, construction waste, concrete or any other construction materials or locally available filler materials.

[0084] More particularly, such a configuration is obtained by the fact that each intermediate strip comprises a first side attached to a first adjacent strip at first local attachment areas, and a second side opposite to the first side attached to a second adjacent strip at second local attachment areas. As shown on figure 1 , the first and second local attachment areas 11.1 , 11.2 are arranged along the length of the strip in such a way that the second local attachment areas 11.2 are offset with respect to the first local attachment areas 11.1 along the longitudinal direction of the strips 10. The two end strips 10.1 , 10.2 are only attached to their respective adjacent strip on one side and limit the transversal boundaries of the cellular system 1 .

[0085] Such an offset of the first and second local attachment areas allows a pulling force exerted transversally for example on both end strips to expand the structure and to make the portions 12 to bend into cells 13.

[0086] In other words, the first and second local attachment areas 11.1 , 11 .2 are positioned alternately along the length of the intermediate strip 10.

[0087] Typically, second attachment areas 11 .2 are located approximately at the midpoint of the distance between two adjacent first local attachment areas 11 .1. In other examples, it is possible that the second attachment areas 11 .2 are located around any other region between two adjacent first attachment areas 11.1 provided their location allows expansion of the structure.

[0088] According to examples, and as shown on figure 1 , the stack of attached strips 10 forms an array of cells 13 that is regularly arranged on the entire area covered by the cellular system 1 . In other words, each cell 13 is substantially equal to the others in terms of dimensions such as depth, width and length.

[0089] In other examples, it is possible that the cellular arrangement 1 features zones with different cell 13 dimensions, for example in order to adapt to different conditions of the terrain or to receive different quantities of filler material. In such an arrangement, the attachment areas 11 locations and / or the width of the strips may be adapted to this end.

[0090] In examples, the strips may comprise apertures 23 suited for drainage of water out of the cells 13. Such apertures may typically be performed between two local attachment areas 1 1 .

[0091] Apertures 23 may be orifices, cuttings, or holes of any shape. In the show example, apertures 23 comprise 13 holes distributed in a four, five, four pattern. However, it is understood that this a non-limitating example and that apertures 23 may comprise any number of orifices, cutting or holes.

[0092] Figure 2 shows a more detailed view of two strip being attached together according to an example. As describe above, strips 10 are arranged lengthwise side by side and joined together at local attachment areas 11. When pulled transversally, the portions 12 of each strip between two adjacent local attachment areas 11 are free to bend apart from one another to form cells 13.

[0093] In examples, the local attachment areas 11 are linear, and extend along the width of the strip. As illustrated on figure 2A in dotted points, the local attachment areas 11 extend perpendicular to the elongation direction of the strip. Such a configuration may help obtain proper bending of the portions 12.

[0094] Assembly at local attachment areas 11 may be performed by any means known by the skilled person. For example, assembly may be achieved by welding, including thermal, hot air, hot plate, Infrared, ultrasonic, mechanical, laser, linear vibration, electromagnetic means.

[0095] In other examples or in combination with a welding technique, assembly may be performed with fasteners that may be provided in the local attachment areas 11 for connecting the strips to each other. For example, such fasteners may comprise hooks, staples, clips or any additional fixing part.

[0096] In other examples, the local attachment areas 11 may comprise yarns that are stitched for connecting the strips to each other. For example, the stitching yarns may be polymeric or co-polymeric stitching yarns.

[0097] Figures 3 and 4 are now described. In a cellular confinement system 1 according to the present disclosure, at least one strip 10 comprises a polymer matrix 20 and at least one reinforcement 21 embeddedwithin the polymer matrix 20 and extending over the entire length of the strip 10. Typically, each strip 10 of the whole cellular system 1 features at least one reinforcement 21.

[0098] These figures show a particular example of a rectangular cross section of the reinforcements, for the sake of clear explanation. However, each reinforcement can feature any shape of cross section, and the present invention is not limited to any particular shape.

[0099] A reinforcement 21 typically comprises at least one longitudinal side constituting its outer surface, and two end faces. In the example of figure 4, each reinforcement comprises four longitudinal sides 210, 211 , 212, 213, and two end faces 214 (one of them not being visible on the figure).

[0100] Each reinforcement 21 is embedded into the polymer matrix 20 so that all of its longitudinal sides are entirely covered by a thickness of the matrix 20 material. In other words, none of the reinforcement 21 sides are exposed to an exterior side of the polymer matrix, other than the two end surfaces, extending typically normally to the elongation direction of the reinforcement 21 .

[0101] As it is more visible on figure 4 showing a particular embodiment in which the reinforcements 21 present a substantially rectangular cross-section with four longitudinal sides 210, 211 , 212, 213, each of the longitudinal sides is entirely covered by the polymer matrix 20.

[0102] In this case, the terms “extending over the entire length” is used meaning that the at least one reinforcement 21 extends continuously from one longitudinal end to the other opposite end of the strip 10.

[0103] In examples, as represented on figure 3, reinforcements 21 may be arranged in two groups: a first group located near a top edge of the strip and a second group near a bottom edge of the strip. Each group can comprise one of more reinforcement 21. The strip 10 thus typically comprise a reinforced part, comprising at least one reinforcement, and a non-reinforced part, comprising plain matrix 20.

[0104] The thickness of the strip near the top edge, containing the first group of reinforcement 21 , and the thickness of the strip near the bottom edge containing the second group of reinforcement 21 may be equal, or greater than the thickness of the strip around an intermediate height of the strip which is free from reinforcement. Due to this difference of thickness, a groove extends in the axial direction of the strip in this area free from reinforcement. The groove may be on a single side of the strip, the other side being flat, as shown in figure 3. As a non-illustrated variant, this difference of thickness may create a groove on each side of the strip, in this aera free from reinforcement.

[0105] Adjacent strips having such grooves may be attached at local attachment area 1 1 , by joining only the upper parts near the top edge of the adjacent strips containing the first group of reinforcement 21 , and the lower parts near the bottom edge of the adjacent strips containing the second group of reinforcement 21 , thus without joining the aera of adjacent strips free from reinforcement around an intermediate height of the strip where the groove extends, as shown in non-limitative example of figure 3-A. The groove(s) thus creates a drainage passage through the local area 11 allowing water to flow from one cell to an adjacent cell obtained by the two adjacent strips.

[0106] Drainage apertures 30 may be arranged in the intermediate aera of the height of strip which is free from reinforcement, typically in the non-reinforced part of the strip 10. Each drainage aperture 30 comprises a plurality of drainage hole 31 passing through a thickness of the strip 10.

[0107] In the non-limiting example shown on figure 3, the strip 10 comprises six reinforcement 21 arranged in two separate groups of three reinforcements 21. Each group being respectively located in a bottom part that is closer to the ground and on a top part of the strip 10. In this example, the strip 10 comprises a middle part on which are arranged apertures 30. The reinforcements 21 may thus be advantageously arranged away from the apertures 30, here the reinforcements 21 are arranged below and above the apertures 30.

[0108] In other examples, any number of strips ofthe cellular confinement system 1 may comprise any number of reinforcements 21. In examples, the reinforcements 21 may be arranged parallel to each other, oriented along the length of the strip 10. In cases wherein the local attachment areas 11 are linear along the width of the strip, the reinforcements 21 may thus extend perpendicular to the local attachment areas 1 1 .

[0109] In examples, reinforcements 21 are provided in a number in a range of 4 to 12 per strips.

[0110] The non-limiting example of figure 3B illustrates reinforcements 21 arranged on top of each other, stacked along the width of the strip 10. In other examples, two or more reinforcements 21 may be stacked along the thickness of the strip 10 (non-illustrated). More generally speaking, any other configuration is possible provided the at least one reinforcement 21 is oriented along the length of the strip 10.

[0111] In examples, reinforcements 21 may feature a constant cross-sectional shape. In other words, the shape and dimensions of the transversal cross-section of a reinforcement 21 may be substantially invariant along the entire length of the strip 10. This allows an identical and constant performance of the reinforcement along the entire length of the strip 10.

[0112] In examples, the strips 10 may feature a width that is in a range of 50 to 300mm.

[0113] In examples, the reinforcement 21 may have a cross-sectional area in a range of 0,3mm2to 12mm2, preferably of 0,87mm2to 7,2mm2. In the case of a rectangular cross-section reinforcement 21 , it can feature a height h in a range of 3 to 10mm, preferably in a range of 5.8mm to 6mm. In examples, reinforcement 21 can feature a thickness e in a range of 0,1 mm to 2mm, preferably of 0,15mm to 1 ,2mm.

[0114] In particular examples, the value ofthe cross-section area of a reinforcement 21 may be invariant along the length of the strip.

[0115] In examples, every reinforcement 21 of the strip may feature the same cross-sectional shape and dimensions. On the non-limiting example of figure 4, reinforcements 21 each feature the same rectangular cross-sectional shape.

[0116] In examples, reinforcements 21 may be spaced from each other with a gap d in a range of 0,5mm to 3mm, preferably of 1 mm to 1 ,25mm.

[0117] In other examples, the cross-sectional shape of two reinforcements 21 may differ in dimensions and in shape.

[0118] In reference to figure 4, reinforcements 21 comprise a plurality of filaments 22, visible as dots on the figure, arranged alongside of each other another.

[0119] In another example that will be described hereafter in reference to figure 5, each reinforcement may comprise one or more yarns obtained by twisting filaments together in the manner of a rope.

[0120] In examples, each reinforcement 21 can comprise a plurality of unitary filaments 22 so as to form a multi-filament assembly. In this case, each reinforcement 21 is obtained by extrusion of a plurality of filaments.

[0121] A particular embodiment of a reinforced part of a strip is depicted in figure 5.

[0122] In this example, each reinforcement 21 comprises a plurality of yarns 24 obtained by grouping together a plurality of filaments 22.

[0123] In this figure, filaments 22 are represented only on one yarn 24 for the sake of clarity. It is however implied that each yarn 24 does indeed comprise twisted filaments 22.

[0124] In this example, yarns 24 feature a substantially circular cross section. In particular, each yarn 24 can present a thickness (corresponding to a diameter in case of a circular yarn section) roughly ranging between a sixth and half of a thickness of the strip 10.

[0125] In this example, each reinforcement comprises between six and seven yarns 24 agglomerated together in two rows of three to four yarns 24.

[0126] It is now referred to figure 6. It is schematically shown hereby a particular embodiment in which a bonding primer 23 is present between a reinforcement 21 and the matrix 20.

[0127] In fact, the bonding primer 23 is here represented fully encircling the reinforcement 21 inside the matrix 20. However, it may be applied around the reinforcement so as to only partially cover an outer surface of the reinforcement 21 .

[0128] For schematic purposes, the figure only illustrates a partial cross-section of a strip 10, picturing a particular longitudinal point of the length of the strip 10. However, it may be preferable that the bonding primer 23 is not present along the entire length of the reinforcement 21 .

[0129] In fact, in non-represented examples, the bonding primer 23 may be applied punctually along the length of the reinforcement 21 , in one or several occurrences. In other words, each reinforcement 21 can comprise a longitudinal succession of portions alternatively comprising and not comprising a bonding primer 23.

[0130] A more detailed view of the particular example of figure 5 is represented on figure 7.

[0131] In this case, the reinforcement 21 comprises yarns 24 formed by twisting a plurality of filaments 22 together along a longitudinal direction L of the reinforcement. The outer surface of each yarn 24 thus presents an edge that extends at least partially transversally to the elongation direction of the reinforcement, thus helping prevent translation of the reinforcement 21 along the sheath constituted by the polymer matrix 20.

[0132] In reference to figure 8, according to examples, it is possible to obtain different values of width with a unique base product that is the strip 10. In the non-limiting illustrated example, a larger coextruder width isused in order to obtain a wider strip, in which there are three alternations of reinforced and non-reinforced parts featuring apertures 30.

[0133] The matrix 20 of the strip 10 may comprise the following materials: Linear low-density polyethylene (LLDPE), Medium-density polyethylene (MDPE), high-density polyethylene (HDPE) or high impact polystyrene (HIPS). Some examples of characteristics for these materials are represented in the chart below:

[0134]

[0135] In examples, the creep modulus for the matrix 20 of the strip may be in a range of 100 to 2000 MPa when measured at 25°C. and of the young modulus of the matrix 20 may be in a range of 200 to 2400 MPa.

[0136] In examples, reinforcements 21 may be of a different material than the matrix 20. Advantageously, the reinforcement 21 material may be chosen to have a greater tensile resistance than the matrix 20. The tensile resistance being influenced by the creep modulus and by the young modulus.

[0137] For instance, the material of the reinforcement 21 may feature a greater creep modulus and / or a greater young modulus than the material of the matrix 20.

[0138] For instance, reinforcements 21 may comprise any combination of the following materials: High Tenacity Polyethylene Terephthalate (PET), polyvinyl alcohol (PVA), Poly (p-phenylene terephthalamide) PPTA, Polyamide-imide (PAI), Poly (paraphenylene benzobisoxazole) (PBO), Poly Amide (PA) , or non- polymeric materials such as steel. Some examples of characteristics for these materials are represented in the chart below:

[0139]

[0140] For instance, it may be advantageous to choose a material for the reinforcement 21 that features a high creep resistance, and high Young modulus, in order to obtain a strip that is capable of withstanding the heavy loads of civil applications and prevent material deformation during its service life.

[0141] According to examples, the creep modulus of reinforcements 21 may be in a range of 01 GPa to 30 GPa when measured at 25°C and / or the young modulus of the reinforcements 21 may be in a range of 01 GPa to 210 GPa.

[0142] The cross-section area (surface) of the matrix 20 may be typically larger than the sum of the cross sections of reinforcements 21 , as for example shown in figure 3B. The sum of the cross sections of reinforcements 21 may represent less than 40% of the cross-section area of the matrix 20, for example less than 30% of the cross section of the matrix 20.

[0143] Reinforcements 21 may thus be configured to limit the axial deformation of the strips, without significantly increasing the pulling force exerted transversally for example on both end strips to expand the structure and to make the portions 12 to bend into cells 13.

[0144] Figure 9 to 12 illustrate examples of a manufacturing method for producing strips 10 and assembling them into a cellular confinement system 1 according to the present disclosure. The principle is to co-extrude both the matrix 20 and the reinforcement(s) 21 embedded within the matrix 20 in a single operation. The coextrusion process ensures a continuous an uninterrupted extension of the reinforcement along the entire length of the strip 10.

[0145] Figure 9 shows phases 100 and 101 according to an example of the disclosed method.

[0146] Reinforcements 21 are first extruded and fed 100 by one or more creels, for example depending on the number of reinforcements 21 embedded at once within the matrix 20. Typically, a plurality of filaments 22 are extruded and grouped together into reinforcements 21 .

[0147] In examples, filaments 22 are twisted into yarns 24 before being grouped together into reinforcements 21.

[0148] Phase 101 consists in co-extruding 101 both a matrix 20 of polymeric material and reinforcements 21 fed by the creels in order to produce a strip-shaped co-extruded product 200, the reinforcements 21 being thus directly embedded within the polymer matrix 20.

[0149] Thanks to this method, the reinforcements 21 extend continuously along the co-extruded product 200.

[0150] Figure 10 then shows an example of additional operations to achieve manufacturing of strips 10.

[0151] The method may further comprise texturing 102 at least one side of the co-extruded product 200 or the strips 10.

[0152] For example, such a treatment may be performed by embossing wheels placed right after the coextrusion of the product 200. The freshly extruded product 200 may go through the embossing wheel with a predetermined amount of load on the wheels, and then go through a cooling tank where the sheath becomes hard and features embossments on its final shape. Such a texturing treatment may be useful for improving frictional resistance and interlock between cells 13 of the cellular system 1.

[0153] The method may further comprise puncturing 103 the co-extruded product 200 or the strips 10 to form apertures 23. For example, such apertures are located between the first local attachment areas 11.1 and the second local attachment areas 11 .2.

[0154] The texturing 102 or puncturing 103 is performed either on the extruded product 200 of on the strips 10 depending on whether they occur before of after a cutting 104 phase of the extruded product.

[0155] The co-extruded product 200 is cut 104 into strips 10 of desired lengths, either before or after texturing 102 or puncturing 103 phases.

[0156] The strips 10 are then assembled 105 to configure the cellular confinement system 1 . As described before, the strips may be assembled as a stack of strips 10 including two end strips and a plurality of intermediate strips between the two end strips, wherein each intermediate strip has a first side attached to an adjacent strip of the stack at first local attachment areas 11.1 spaced apart along the strips and an opposite second side attached to another adjacent strip of the stack at second local attachment areas 11 .2 spaced apart along the strips, wherein the second local attachment areas 11 .2 are offset with respect to the first local attachment areas 11 .1 along the longitudinal direction of the strips, so that portions(12 of each strip 10 located between two first local attachment areas 11.1 or between two second local attachment areas 1 1 .2 are allowed to bend to conform the cellular confinement system 1 into an array of cells 13 for receiving filler material.

[0157] Such an assembling phase 105 may comprise a welding process, for which a non-limiting example is illustrated on figure 11 . On such an example, two strips 10 are brought stack one onto the other under welding heads 14 that are able to translate vertically closer to the strips 10 to perform the welding and to elevate away from the strips 10. In this example, there are two welding heads 14 that are thus able to perform two spaced welding points at once, resulting in two local attachment areas 11 .

[0158] The method may further comprise coating the strips 10 or the extruded product 200 with a protective layer, for example to prevent UV deterioration of the material. The extruded product 200 or the strips may further be impregnated with additives for enhanced performances.

Claims

Claims

1. A cellular confinement system (1) for soil stabilization, comprising strips (10) arranged next to each other, wherein adjacent strips (10) are attached together at local attachment areas (11) spaced along the strips (10), wherein portions (12) of each strip (10) located between two local attachment areas (11) are allowed to bend to conform the cellular confinement system (1) into an array of cells (13) for receiving filler material, wherein each strip (10) comprises a polymer matrix (20) and at least one reinforcement (21) embedded within the polymer matrix (20) and extending over the entire length of the strip (10), each reinforcement (21) being obtained by grouping a plurality of filaments (22) together, the reinforcement (21) being pretensioned so that a residual force is conserved in the reinforcement (21) once it is embedded into the polymer matrix (20).

2. The cellular confinement system (1) according to claim 1 wherein said residual force is substantially equal or superior to 5% of the tensile strength of the reinforcement (21).

3. The cellular confinement system (1) according to claim 1 or 2, comprising a bonding primer (23) between the reinforcement (21) and the polymer matrix (20), the bonding primer (23) being suited to adhere both to the reinforcement (21) material and to the polymer matrix (20) material.

4. The cellular confinement system (1) according to any one of the preceding claims, wherein filaments (22) of the at least one reinforcement (21) are twisted around an elongation direction of the reinforcement (21) into one or more yarns (24) forming the reinforcement (21).

5. The cellular confinement system (1) according to any one of the preceding claims, wherein a crosssection of each filaments (22) of the at least one reinforcement features a substantially constant dimension and shape along the entire length of said reinforcement (21).

6. The cellular confinement system (1) according to any one of the preceding claims, wherein the reinforcements (21) have a cross-sectional area in a range of 0,87mm2to 7,2mm2.

7. The cellular confinement system (1) according to any one of the preceding claims, wherein each reinforcement (21) comprises PET filaments (22).

8. The cellular confinement system (1) according to any one of the preceding claims, wherein the reinforcements (21) comprise metallic filaments (22).

9. The cellular confinement system (1) according to any one of the preceding claims, wherein the strips have apertures (30) between the local attachment areas.

10. The cellular confinement system (1) according to any one of the preceding claims, wherein the strips comprise fasteners to attach them to each other.

11. The cellular confinement system (1) according to any one of the preceding claims, wherein local attachment areas comprise stitching yarns, the strips being stitched together by the stitching yarns at local attachment areas or local attachment areas comprise welding points obtained by ultrasonic welding.

12. The cellular confinement system (1) according to the preceding claim, wherein the local attachment areas comprise a polymeric cover to protect the stitching yarns.

13. A method for manufacturing a cellular confinement system (1), the method comprising: co-extruding (101) polymeric material and a plurality of filaments into groups forming at least one reinforcement (21) to form a strip-shaped co-extruded product (200) having a polymer matrix (20), wherein the reinforcements (21) are embedded within the polymer matrix (20) and extend continuously along the co-extruded product (200), and wherein the reinforcements (21) are pretensioned before coextrusion with the polymer matrix (20) so that a residual force is conserved in the reinforcement (21) once it is embedded into the polymer matrix (20); cutting (104) the co-extruded product (200) into strips (10); and assembling (105) the strips (10) to configure the cellular confinement system (1) as a stack of strips including two end strips and a plurality of intermediate strips between the two end strips, wherein each intermediate strip has a first side attached to an adjacent strip of the stack at first local attachment areas (11.1) spaced apart along the strips and an opposite second side attached to another adjacent strip of the stack at second local attachment areas (1 1.2) spaced apart along the strips, wherein the second local attachment areas (11 .2) are offset with respect to the first local attachment areas (11.1) along the longitudinal direction of the strips, wherein portions (12) of each strip (10) located between two first local attachment areas (1 1.1) or between two second local attachment areas (11 .2) are allowed to bend to conform the cellular confinement system (1) into an array of cells (13) for receiving filler material.

14. The method according to claim 13, comprising diving each reinforcement (21) into a bonding primer before co-extrusion of said reinforcement (21) with the polymer matrix (20), said bonding primer being suited to adhere both to the reinforcement (21) material and to the polymer matrix (20) material.

15. The method according to any of claims 13 or 14, comprising twisting filaments (22) of the at least one reinforcement (21) around an elongation direction of the reinforcement (21) into one or more yarns (24), prior to co-extrusion of the reinforcement with the polymer matrix (20).

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