Reticular structure for geotechnical applications and process for the realization of the same

Abstract

The present invention refers to a reticular structure (2) of plastic material for geotechnical applications comprising: first and second elements (3, 4) having an elongated conformation intersecting at nodes (5) to form meshes (6) and to define a uniplanar structure; a plurality of protuberances (7) emerging from at least one side of the reticular structure itself. The structure has first and second elements having respective cross-sectional area, the ratio of which is between 0.7 and 1.5.

Description

[0001] RETICULAR STRUCTURE FOR GEOTECHNICAL APPLICATIONS AND PROCESS FOR THE REALIZATION OF THE SAME

[0002] DESCRIPTION

[0003] FIELD OF THE INVENTION

[0004] The present invention relates to a reticular structure for geotechnical applications that can be used for soil containment and / or drainage. The reticular structure may also be used for the reinforcement and / or consolidation of soils, such as natural and artificial structures, for example, slopes, barrier walls, rockfall valleys, railroad ballasts, road bottoms and parking areas. The present invention also concerns a process of making said reticular structure and its use.

[0005] STATE OF THE ART

[0006] Geogrids are common in the geotechnical field for soil reinforcement, containment and / or consolidation.

[0007] Geogrids may be made by stretching (mono-directional or bi-directional) a starting semi-finished product consisting of a uniplanar slab having a constant thickness that is extruded and then drilled. Such geogrids have a uniplanar reticular structure having longitudinal and transverse elements which intersect at nodes. Such geogrids are, for example, described in the following patent applications / patents: US5419659A, US2004062615A1 , US3386876, US7407699B2, US6423394B1.

[0008] Alternatively, geogrids may be made by co-extruding a series of first and second elements joined together to define a monolithic grid. The co-extruded grid is then stretched along one or more directions to define a monostretched or bi-stretched reticular structure. Such co-extruded geogrids are, for example, described in the patent applications No. US4662946A and No. US5753337A.

[0009] The known geogrids are chemically inert and have excellent tensile strength in the direction of the stretched elements. In addition, the openings in the mesh defined by the reticular structure allow the soil to fit between the threadlike elements of the reticular structure, ensuring the formation of a reinforced composite material. In particular, geogrids are able to absorb stresses and redistribute them evenly in the soil ensuring greater static and dynamic strength of the entire reinforced structure.

[0010] However, the Applicant noted that the above-mentioned known geogrids are substantially lacking in drainage capacity. Therefore, geogrids made of sheet material having, on the one hand, a substantially flat surface suitable for accommodating a woven-nonwoven filter element and, on the other hand, having an irregular surface with a plurality of protuberances suitable for defining a sort of three-dimensional reticular structure with high drainage capacity were developed. Such geogrids is described, for example, in PCT patent application No. WO 2020 / 165726 A1 : such geogrid is defined by a rectangular mesh reticular structure with a first and a second set of elongated linked elements. The first and / or second strands have, throughout their development, a sort of rib suitable for defining a of three-dimensional structure with drainage capabilities. A further example is described in U.S. Patent No. US 5,891,549, which shows a co-extruded reticular structure with rectangular meshes defined by a first and a second set of elongated linked elements. The reticular structure has, on the one hand, a plurality of ribs each of which extends in height from a node of the reticular structure while longitudinally it is connected to at least one of the elongated elements. In fact, each rib defines a projecting part of the node and also constitutes a part of the elongated element: the ribs are suitable for defining a of three-dimensional structure with draining capabilities.

[0011] Although the reticular structures described in PCT Patent Application No. WO 2020 / 165726 A1 and U.S. Patent No. US 5,891,549 have good drainage capabilities, these are generally characterized by a hydraulic capacity strongly prevailing in one direction, particularly the direction of major sheet development. This characteristic may be a huge limitation of geogrid when applied on structures having different slope directions, e.g., parking lots, roads, structures dedicated to the collection of municipal solid waste.

[0012] An additional limitation of known drainage geogrids is the large contact surface area suitable for engaging the woven-nonwoven filter element, a condition that reduces the nominal permeability of the woven-nonwoven significantly.

[0013] Although the aforementioned drainage geogrids are used in the geotechnical filed, the Applicant noted that they are not devoid of drawbacks and therefore can be improved in some aspects.

[0014] SCOPE OF THE INVENTION

[0015] The scope of the present invention is therefore to solve at least one of the drawbacks and / or limitations of the previous solutions.

[0016] A first object of the present invention is to provide a reticular structure having excellent drainage capabilities in multiple directions. It is then an aim of the present invention to provide a reticular structure for geotechnical applications that can be easily installed, in particular capable of adapting to any ground arrangement while being installable by a common geogrid installation process, that is, without requiring special adjustments during the installation process. It is then the scope of the present invention to provide a reticular structure that is flexible in use and may be used for the reinforcement and / or consolidation of a wide range of structures.

[0017] It is also object of the present invention to provide a reticular structure having high mechanical strength, particularly capable of effectively reinforcing and consolidating soil. It is a further object of the invention to provide a reticular structure having a high capacity for interaction with the soil and simultaneously confining the soil, such that it is extremely effective in soil reinforcing action. A further object of the invention is to provide a simple reticular structure that can be manufactured with low production costs.

[0018] These purposes and others that will appear more from the following description are basically achieved by a reticular structure and a process of making the same in accordance with one or more of the attached claims.

[0019] SUMMARY

[0020] In an aspect, a reticular structure (2) is provided for geotechnical applications, said reticular structure (2) comprises: - a plurality of first elements (3) spaced apart and having an elongated conformation according to a first extension trajectory (T1),

[0021] - a plurality of second elements (4) spaced apart and having an elongated conformation according to a second extension trajectory (T2), transverse to the first extension trajectory (T1) of the first elements (3), wherein said first and second elements (3, 4) intersect at nodes (5) to form meshes (6).

[0022] In an aspect according to the preceding aspect, the reticular structure (2) comprises a plurality of protuberances (7) emerging from at least one side of the reticular structure itself. In an aspect according to the preceding aspect each protuberance (7) emerges from a respective node (5). In an aspect according to any one of the preceding two aspects the protuberances (7) are joined in a single piece to the nodes (5), optionally they are joined in a single piece to said first and second elements (3, 4). In an aspect according to any of the three preceding aspects the protuberances (7) only emerge from the nodes (5). In an aspect according to any of the four preceding aspects each protuberance (7) emerges directly from a respective node (5).

[0023] In an aspect according to any one of the preceding aspects the first and second elements (3, 4) lie substantially on only one ideal lying surface. In an aspect according to any one of the preceding aspects the first and second elements (3, 4) join at the nodes (5) to define a substantially uniplanar structure extending between a first and second surfaces (2a, 2b) opposite each other. In an aspect according to the preceding aspect, the distance between the first and second surfaces (2a, 2b) substantially defines the thickness of the uniplanar structure. In an aspect according to the preceding aspect the thickness of the uniplanar structure is between 1 and 4 mm, optionally between 1.5 and 2 mm.

[0024] In an aspect according to any one of the three preceding aspects the protuberances (7) emerge from at least one of said first and second surfaces (2a, 2b) of the uniplanar structure. In an aspect according to any of the four preceding aspects the protuberances (7) emerge from only one of said first and second surfaces (2a, 2b) of the uniplanar structure. In an aspect according to any one of the five preceding aspects each node (5) has, with respect to the ideal lying surface at the respective node (5), a prefixed size, wherein each protuberance (7) has a maximum size substantially equal to or less than the prefixed size of the node (5) from which the protuberance emerges; optionally said size of node (5) and protuberance (7) are defined with respect to the ideal lying surface at the respective node (5). In an aspect according to any one of the preceding six aspects each protuberance (7) does not protrude laterally relative to a surface size of the node (5) from which the protuberance (7) emerges. In an aspect according to any one of the preceding aspects each protuberance (7) is substantially laterally contained within a surface size of the node (5) from which the protuberance (7) emerges.

[0025] In an aspect according to any one of the preceding aspects each protuberance (7) extends in height along a direction, transverse to the first extension trajectory (T1) and the second extension trajectory (T2). In an aspect according to the preceding aspect each protuberance (7) extends, along its respective direction, from a base (7a) to a top (7b) opposite the base (7a). In an aspect according to the preceding aspect the base (7a) of the protuberance (7) is joined in a single piece to a respective node (5). In an aspect according to any one of the preceding aspects each protuberance (7) has a height (H) defined as the maximum distance between the base (7a) and the top (7b) of the same protuberance (7). In an aspect according to the preceding aspect the height (H) of each protuberance (7) is greater than 4 mm, optionally between 5 and 40 mm, even more optionally between 5 and 30 mm. In an aspect according to any one of the two preceding aspects the ratio between the height of a protuberance (7) and the thickness of the uniplanar structure is greater than 2, optionally between 3 and 5.

[0026] In an aspect according to any one of the preceding aspects, each protuberance (7) has a shape that is basically rectangular parallelepiped or truncated pyramid or cylindrical.

[0027] In an aspect according to any one of the preceding aspects each protuberance (7) has a predetermined length (L1), optionally measured along the first extension trajectory (T1) of the first element (3) passing through the respective protuberance (7). In an aspect according to the preceding aspect the length (L1) of each protuberance (7) is less than the height (H) of the same protuberance (7). In an aspect according to any one of the two preceding aspects the ratio between the height (H) and the length (L1) of a protuberance (7) is greater than 1, optionally is between 2 and 5, even more optionally is between 2.5 and 4.

[0028] In an aspect according to any one of the preceding aspects each protuberance (7) has a predetermined width (L2), optionally measured along the second extension trajectory (T2) of the second element (4) passing through the respective protuberance (7). In an aspect according to the preceding aspect, the width (L2) of each protuberance (7) is less than the height (H) of the same protuberance (7). In an aspect according to any one of the two preceding aspects, the ratio between the height (H) and the width (L2) of a protuberance (7) is greater than 1, optionally is between 2 and 5, even more optionally is between 2.5 and 4. In an aspect according to any one of the preceding aspects, the ratio of the length (L1) to the width (L2) of a protuberance (7) is between 0.8 and 1.2, still more optionally between 0.9 and 1.1.

[0029] In an aspect according to any one of the preceding aspects each protuberance (7) has, for a preponderant part of its height extension, a substantially constant section. In an aspect according to any one of the preceding aspects each protuberance (7) has, for at least 80% of its height extension, a substantially constant section. In an aspect according to any one of the preceding aspects each protuberance (7) has, at least for 90% of its height extension, a substantially constant section.

[0030] In an aspect according to any one of the preceding aspects each protuberance (7) has, for a predominant part of its height extension, a section between 1 .5 and 25 mm2, optionally between 4 and 9 mm2.

[0031] In an aspect according to any one of the preceding aspects the protuberances (7) are substantially identical to each other, optionally they are substantially identical to each other in shape and size.

[0032] In an aspect according to any one of the preceding aspects, the minimum distance (D72) between two immediately adjacent protuberances (7) emerging from two respective nodes (5) connected by a tract of a first element (3) is equal to or less than a distance (D2) between two second elements. In an aspect according to any one of the preceding aspects, the ratio of the minimum distance (D72) between two immediately adjacent protuberances (7) emerging from two respective nodes (5) connected by a tract of a first element (3) to a distance (D2) between two second elements is greater than or equal to 1, optionally being between 1 and 1.2. In an aspect according to any one of the preceding aspects, the minimum distance between two protuberances (7) immediately adjacent to and emerging from two respective nodes (5) connected by a tract of a first element (3) is between 7 mm and 80 mm, optionally between 8 mm and 70 mm.

[0033] In an aspect according to any one of the preceding aspects, the minimum distance (D71) between two protuberances (7) immediately adjacent to and emerging from two respective nodes (5) connected by a tract of a second element (4) is equal to or less than a distance (D1) between two first elements. In an aspect according to any one of the preceding aspects, the ratio of the minimum distance (D71) between two immediately adjacent protuberances (7) emerging from two respective nodes (5) connected by a tract of a second element (4) to a distance (D1) between two first elements is greater than or equal to 1, optionally being between 1 and 1.2. In an aspect according to any one of the preceding aspects, the minimum distance between two protuberances (7) immediately adjacent to and emerging from two respective nodes (5) connected by a tract of a second element (4) is between 7 mm and 80 mm, optionally between 15 mm and 70 mm.

[0034] In an aspect according to any one of the preceding aspects the reticular structure (2) is at least partly made of plastic material. In an aspect according to any one of the preceding aspects the reticular structure (2) is entirely made of plastic material. In an aspect according to any one of the preceding aspects the first elements (3), second elements (4) and protuberances (7) are joined in a single piece to define a monolithic structure made of plastic material. In an aspect according to any one of the preceding aspects the reticular structure (2) consists only of the first elements (3), the second elements (4) and the protuberances (7).

[0035] In an aspect according to any of the preceding aspects the first elements (3) are identical in shape to the second elements (4). In an aspect according to any of the preceding aspects the first elements (3) are identical in size to the second elements (4). In an aspect according to any one of the preceding aspects the reticular structure (2) comprises meshes (6) having the shape of quadrilaterals. In an aspect according to any one of the preceding aspects the reticular structure (2) comprises meshes having a square or rectangular shape.

[0036] In an aspect according to the preceding aspect the first elements (3), at least at a centerline portion defined between two immediately consecutive nodes (5) and according to a plane orthogonal to the first extension trajectory (T1), has a section having a substantially circular or elliptical or rectangular or square outline. In an aspect according to any one of the preceding aspects each first element (3) has a full cross-section.

[0037] In an aspect according to any one of the preceding aspects each first element (3) has a predetermined crosssection, optionally said cross-section being defined according to a plane orthogonal to the first extension trajectory of the respective first element (3). In an aspect according to any one of the preceding aspects each first element (3) has, for a preponderant portion of a tract of said first element connecting two immediately consecutive nodes (5), a substantially constant cross-section. In an aspect according to any one of the preceding aspects each first element (3) has, for at least 80% of a tract of said first element connecting two immediately consecutive nodes (5), a substantially constant cross-section. In an aspect according to any one of the preceding aspects each first element (3) has, for at least 90% of a tract of said first element connecting two immediately consecutive nodes (5), a substantially constant cross section.

[0038] In an aspect according to any one of the preceding aspects said first elements (3) have a cross-sectional area, measured at a centerline portion defined between two immediately consecutive nodes, greater than 1 mm2, optionally between 2 mm2and 10 mm2.

[0039] In an aspect according to any one of the preceding aspects the first elements (3) are parallel to each other, optionally the first extension trajectories (T1) of the first elements (3) are parallel to each other. In an aspect according to any one of the preceding aspects the minimum distance (D1 ) between two immediately adjacent first elements (3) is between 7 mm and 80 mm, optionally between 15 mm and 70 mm. In an aspect according to any of the preceding aspects, the extension trajectory (T1), in use, is substantially straight.

[0040] In an aspect according to any one of the preceding aspects the first elements (3) are stretched along their development, wherein the stretching ratio of a first element (3) is defined as the ratio of a final length of the same first element once the stretching is carried out to the initial length of that first element before the stretching action. In an aspect according to the preceding aspect, the first elements (3) have a stretching ratio greater than 3, optionally between 3 and 8, plus optionally between 4 and 7, the stretching ratio of the first elements is defined as the ratio between a final length of the first elements after a stretching action of the first elements and an initial length of the first elements before stretching.

[0041] In an aspect according to any one of the preceding aspects the first elements (3) have a thickness (S1 ). In an aspect according to the preceding aspect the thickness (S1 ) of each first element is measured orthogonally to the first extension trajectory (T1) of said first element (3) and transversely, optionally orthogonally, to the second extension trajectory (T2) of the second elements (4). In an aspect according to any one of the two preceding aspects, the thickness (S1) of the first elements is measured transversely, optionally orthogonally, to a lying surface of the uniplanar structure. In an aspect according to any of the three preceding aspects the thickness (S1) of each first element (3) is between 0.8 and 5 mm, optionally between 1 and 3 mm. In an aspect according to any one of the four preceding aspects the thickness (S1) of each first element (3) is measured at a centerline zone of a tract of the first element defined between two immediately consecutive nodes (5) along the first extension trajectory of the respective first element (3).

[0042] In an aspect according to any one of the five preceding aspects each first element (3) has a plurality of aligned tracts along its respective first extension trajectory, wherein each tract of a first element (3) is defined between two immediately consecutive nodes along the first extension trajectory of the respective first element (3), optionally each tract connects two immediately consecutive nodes. In an aspect according to the preceding aspect, the thickness of each tract of each first element (3), for a preponderant part of its extension defined between two immediately consecutive nodes (5), is substantially constant. In an aspect according to any one of the two preceding aspects the thickness of each tract of each first element (3), for at least 80% of its extension defined between two immediately consecutive nodes (5), is substantially constant. In an aspect according to any of the three preceding aspects the thickness of each tract of each first element (3), at least for 90% of its extension defined between two immediately consecutive nodes (5), is substantially constant. In an aspect according to any one of the preceding aspects the second elements (4) has, at least at a centerline portion defined between two immediately consecutive nodes (5) and according to a plane orthogonal to the second extension trajectory (T2), a section having a substantially circular or elliptical or rectangular or square outline. In an aspect according to any one of the preceding aspects each second element (4) has a full cross-section.

[0043] In an aspect according to any one of the preceding aspects each second element (4) has a predetermined cross-section, optionally said cross-section being defined according to a plane orthogonal to the second extension trajectory of the respective second element (4). In an aspect according to any one of the preceding aspects each second element (4) has, for a preponderant portion of a tract of said first element connecting two immediately consecutive nodes (5), a substantially constant cross-section. In an aspect according to any one of the preceding aspects each second element (4) has, for at least 80% of a tract of said second element connecting two immediately consecutive nodes (5), a substantially constant cross-section. In an aspect according to any one of the preceding aspects each second element (4) has, for at least 90% of a tract of said second element connecting two immediately consecutive nodes (5), a substantially constant cross-section.

[0044] In an aspect according to any one of the preceding aspects, the second elements (4) have a cross-sectional area, measured at a defined centerline portion between two immediately consecutive nodes, greater than 1 mm2, optionally between 2 mm2and 10 mm2.

[0045] In an aspect according to any one of the preceding aspects, the ratio between a cross-sectional area of a first element (3), measured at an intermediate portion between two immediately consecutive nodes (5), and a cross-sectional area of a second element (4), also measured at an intermediate portion between two immediately consecutive nodes (5), is between 0.7 and 1.5, optionally between 0.8 and 1.3.

[0046] In an aspect according to any one of the preceding aspects the second elements (4) are parallel to each other, optionally the second extension trajectories (T2) of the second elements are parallel to each other. In an aspect according to any of the preceding aspects the minimum distance (D2) between two immediately adjacent second elements (4) is between 7 mm and 80 mm, optionally between 15 mm and 70 mm. In an aspect according to any one of the preceding aspects, the second extension trajectory (T2) of the second elements (4) is substantially orthogonal to the first extension trajectory (T1) of the first elements (3).

[0047] In an aspect according to any one of the preceding aspects the second elements (4) are stretched along their development, wherein the stretching ratio of a second element (4) is defined as the ratio of a final length of the same second element once stretching is performed to the initial length of such second element (4) before the stretching action. In an aspect according to the preceding aspect the second elements (4) have a stretching ratio greater than 3, optionally between 3 and 8, plus optionally between 4 and 7, the stretching ratio of the second elements being defined as the ratio between a final length of the second elements after a stretching action of the second elements and an initial length of the second elements before stretching.

[0048] In an aspect according to any one of the preceding aspects the second elements (4) have a thickness (S2). In an aspect according to the preceding aspect the thickness (S2) of each second element is measured orthogonally to the second extension trajectory (T2) of said second element (4) and transversely, optionally orthogonally, to the first extension trajectory (T1) of the first elements (3). In an aspect according to any one of the two preceding aspects, the thickness (S2) of the second elements is measured transversely, optionally orthogonally, to a lying surface of the uniplanar structure. In an aspect according to any of the three preceding aspects the thickness (S2) of each second element (4) is between 0.8 and 5 mm, optionally between 1 and 3 mm. In an aspect according to any one of the four preceding aspects the thickness (S2) of each second element (4) is measured at a centerline zone of a tract of the second element connecting two immediately consecutive nodes (5).

[0049] In an aspect according to any one of the five preceding aspects each second element (4) has a plurality of aligned tracts along its respective second extension trajectory, wherein each tract of a second element (4) is defined between two immediately consecutive nodes along the second extension trajectory of the respective second element (4), optionally each tract connects two immediately consecutive nodes. In an aspect according to the preceding aspect, the thickness of each tract of each second element (4), for a preponderant part of its extension defined between two immediately consecutive nodes (5), is substantially constant. In an aspect according to any one of the two preceding aspects the thickness of each tract of each second element (4), for at least 80% of its extension defined between two immediately consecutive nodes (5), is substantially constant. In an aspect according to any one of the three preceding aspects the thickness of each tract of each second element (4), at least for 90% of its extension defined between two immediately consecutive nodes (5), is substantially constant.

[0050] In an aspect according to any one of the preceding aspects, the thickness (S1 , S2) of the first and second elements (3, 4) respectively is measured along one and the same direction. In an aspect according to any one of the preceding aspects the ratio of the thickness (S1) of a first element to the thickness of a second element (4) is between 0.7 and 1.5, optionally between 0.8 and 1.3.

[0051] In an aspect according to any one of the preceding aspects the ratio of the height of a protuberance (7) to the thickness (S1 ) of a first element (3) is greater than 3, optionally it is between 4 and 6. In an aspect according to any one of the preceding aspects the ratio of the height of a protuberance (7) to the thickness (S2) of a second element (4) is greater than 3, optionally it is between 4 and 6.

[0052] In an aspect according to any one of the preceding aspects, the first and second elements (3, 4) are obtained by stretching a reticular structure semifinished product having first and second precursor elements intersecting at nodes to define meshes. In an aspect according to the preceding aspect the reticular structure semifinished product is obtained by:

[0053] - a co-extrusion process, or

[0054] - extrusion of a full sheet subsequently cut.

[0055] In an aspect according to any one of the preceding aspects the reticular structure (2) comprises at least one filter element (18) engaged to at least one of said first and second elements (3, 4). In an aspect according to any one of the preceding aspects, the filter element (18) defines, in cooperation with each mesh (6) a seat configured to receive gravel and / or crushed stone. In an aspect according to any one of the preceding aspects the filter element (18) is constrained to the top (7b) of a plurality of protuberances (7). In an aspect according to any one of the preceding aspects the filter element (18) comprises a body made of sheet material, optionally having a flat structure. In an aspect according to any one of the three preceding aspects the filter element (18) comprises one or more sheets made of woven-nonwoven material.

[0056] In an aspect according to any one of the preceding aspects, the reticular structure (2) has a first draining transmissivity along a first direction parallel to an ideal lying plane of the reticular structure and a second draining transmissivity along a second direction parallel to an ideal lying plane of the reticular structure. In an aspect according to the preceding aspect, the ratio between the first and second draining transmissivity is between 0.6 and 1.4, optionally between 0.8 and 1.2, even more optionally between 0.9 and 1.1. In an aspect according to any one of the two preceding aspects said first direction along which the first drainage transmissivity is measured is at least partially parallel to the first extension trajectory (T1) of the first elements. In an aspect according to any one of the three preceding aspects said second direction along which the second draining transmissivity is measured is at least partly parallel to the second extension trajectory (T2) of the second elements. In an aspect according to any one of the four preceding aspects, the draining transmissivity of the reticular structure is substantially identical along two directions orthogonal to each other, optionally parallel to the ideal lying plane of the uniplanar structure. In an aspect according to any one of the five preceding aspects, the reticular structure has a substantially uniform drainage transmissivity at least according to two directions orthogonal to each other. In an aspect according to any one of the six preceding aspects, the reticular structure has a drainage transmissivity - in the first direction, for vertical pressures of 20 kPa and at unit hydraulic gradient at rigid upper and lower interfaces - equal to or greater than 3.0*103m2 / sec. In an aspect according to any one of the seven preceding aspects, the reticular structure has a drainage transmissivity - in the second direction, for vertical pressures equal to 20 kPa and at unit hydraulic gradient under conditions of stiff upper and lower interfaces - equal to or greater than 2*103m / sec2.

[0057] In an aspect a process of making a reticular structure (2) according to any one of the preceding aspects is provided. In an aspect according to the preceding aspect, the process comprises the steps of:

[0058] - forming a plurality of elongated first and second elements, extending along respective transverse extension trajectories, optionally orthogonal to each other, the first and second elements intersecting at nodes to form meshes,

[0059] - forming a plurality of protuberances (7) emerging from at least one side of the reticular structure (2).

[0060] In an aspect according to the preceding aspect the plurality of first and second elements and the plurality of protuberances (7) are joined in a single piece to form a single solid body and obtained by extrusion of plastic material.

[0061] In an aspect according to any one of the two preceding aspects, the process comprises the sub-steps of:

[0062] - forming a reticular structure semifinished product comprising a plurality of first and second precursor elements that intersect at nodes to form meshes,

[0063] - stretching said semi-finished product along the development of the first and / or second precursor elements so as to define said first and second elements (3, 4) of the reticular structure. In an aspect according to any one of the preceding aspects of process said semi-finished product is continuously obtained by a co-extrusion process. In an aspect according to any one of the preceding aspects of process the step of stretching said semi-finished product is performed along at least one direction substantially parallel to one between the extension trajectory of the first precursor elements and the second precursor elements to define a stretched reticular structure. In an aspect according to any one of the preceding aspects, the process comprises, following the stretching step, constraining the filter element (18) to the first and / or second elements (3, 4). In an aspect according to any one of the preceding aspects, the filter element (18) is constrained to the first and / or second elements by a rolling process.

[0064] In an aspect a use of the reticular structure (2) according to any one of the preceding aspects is provided, said use comprising a process for consolidation and / or reinforcement of: soils or natural or artificial structures. In an aspect according to the preceding aspects, the reticular structure (2) according to any one of the preceding aspects is used in a process for the consolidation and / or reinforcement of at least one of: slopes, green walls, block walls, sound barriers, rockfall valleys, railroad embankments, road bottoms, and parking areas.

[0065] In an aspect a natural or artificial structure is provided, said structure comprising:

[0066] - a lower layer of soil,

[0067] - a middle layer made for a preponderant wall of gravel and / or crushed stone,

[0068] - an exposed surface layer, wherein the intermediate layer is interposed between the lower layer and the exposed surface layer,

[0069] - at least one reticular structure (2) in accordance with any one of the preceding aspects, said reticular structure being arranged at least partially in the intermediate layer.

[0070] In an aspect according to any one of the preceding aspects the intermediate layer comprises the gravel and / or crushed stone of the intermediate layer have a grain size of 2 mm or more, optionally between 5 mm and 30 mm. In an aspect according to any one of the preceding aspects at least part of the gravel and / or crushed stone of the intermediate layer is engaged within the meshes (6) of the reticular structure (2).

[0071] In an aspect according to any one of the preceding aspects the lower layer comprises soil having a grain size smaller than a grain size of the gravel and / or crushed stone of the middle layer. In an aspect according to any one of the preceding aspects the lower layer comprises at least one of: sand, silt, clay. In an aspect according to any one of the preceding aspects the reticular structure (2) comprises the at least one filter element (18) facing the lower layer. In an aspect according to any one of the preceding aspects, the filter element (18) is configured to prevent the material comprising the bottom layer from reaching the meshes (6) of the reticular structure (2).

[0072] BRIEF DESCRIPTION OF THE DRAWINGS

[0073] Certain embodiments and aspects of the invention will be described below with reference to the accompanying drawings, provided for illustrative purposes only and therefore not limiting wherein:

[0074] - Figure 1 is a perspective view of a reticular structure in accordance with the present invention;

[0075] - Figure 2 is a top view of the reticular structure of Figure 1 ; - Figure 3 is a detail view of the reticular structure of Figure 2;

[0076] - Figure 4 is a side view of a reticular structure in accordance with the present invention;

[0077] - Figure 5 is a cross-section view, according to the V-V tract, of the reticular structure of Figure 4;

[0078] - Figure 6 is a cross-section view, according to track VI-VI, of the reticular structure of Figure 4;

[0079] - Figure 7 is a further perspective view of a reticular structure in accordance with the present invention;

[0080] - Figure 8 schematically shows the steps of a manufacturing process of a reticular structure;

[0081] - Figure 9 is a schematic view of a flow chamber or permeameter during a test condition of a sample of a reticular structure in accordance with the present invention.

[0082] DEFINITIONS AND CONVENTIONS

[0083] In this description corresponding parts illustrated in the various figures are shown with the same numerical references. The figures may illustrate the subject matter of the invention by representations that are not to scale; therefore, parts and components illustrated in the figures related to the subject matter of the invention may relate only to schematic representations.

[0084] In the description and in the claims, the term machine direction (MD) refers to the handling of a starting semifinished product formed by an extrusion station and proceeding along an advance path through a cooling station, optionally a stretching station, and then to a collection station.

[0085] The term "transmissivity" or "draining transmissivity" of the reticular structure refers to its ability to allow water flow through it.

[0086] To determine the drainage transmissivity of the reticular structure, the following steps may be followed:

[0087] - Sample preparation: Cut a sample of reticular structure (see reference 2 in Figure 9) having dimensions of at least 300 mm x 300 mm (these dimensions refer to the length and width of the reticular structure, for example, measured along the first extension trajectory of the first elements and along the second extension trajectory of the second elements, respectively);

[0088] - Test apparatus: Employ a flow chamber or permeameter (see reference 200 in Figure 9 designed to measure the transmissivity of geotechnical materials. These instruments allow a constant pressure difference to be applied across the sample and measure the flow of water through it (see Figure 9);

[0089] - Test conditions: Set a pressure difference AH (head difference) across the sample equal to a unit gradient with respect to the length of the sample and water temperature equal to 20 °C. The pressure difference AH is given by the difference of the pressures P1 and P2 present in the water containers as schematized in Figure 9;

[0090] - Test process: Place the sample in the test apparatus and apply a vertical load (see PV reference in Figure 9) of 20 kPa. Measure the water flow through the sample at a specific time interval;

[0091] - Calculations: Calculate the drainage transmissivity T of the reticular structure sample. Drainage transmissivity may be calculated using Darcy's equation:

[0092] T= (Q * L) / (A *AH) Where:

[0093] T is the drainage transmissivity of the geogrid (m2 / s)

[0094] Q is the flow rate of water through the sample (m3 / s)

[0095] L is the thickness of the specimen (m). The thickness is a maximum thickness of the reticular structure that comprises a thickness of the uniplanar structure defined by first and second elements to which the height of the protuberance is added A is the cross-sectional area of the sample (m2) AH is the pressure difference across the sample (m)

[0096] The drainage transmissivity test may be carried out according to ISO 12958 regulation.

[0097] DETAILED DESCRIPTION

[0098] Reticular structure

[0099] A reticular structure for geotechnical applications, such as the reinforcement and / or consolidation of soils, such as slopes, green walls, block walls, soundproof barriers, rockfall valleys, railroad embankments, road bottoms, and parking areas, has been collectively referred to as 2.

[0100] The reticular structure 2 comprises a plurality of first elements 3 spaced apart and parallel to each other; the first elements 3 are interconnected to a plurality of second elements 4 also spaced apart and parallel to each other: the plurality of second elements 4 are placed transversely, optionally orthogonally, to the first elements 3. In detail, each of the first elements 3 extends along the entire reticular structure 2 and is formed by a plurality of portions aligned along the same line. Similarly, each of said second elements 4 also extends along the entire reticular structure 2, transversely to the first elements 3, and is formed by a plurality of portions aligned along the same line: each of the first elements 3 is intersected by a plurality of second elements 4, and each of the second elements 4 is intersected by a plurality of first elements 3 at nodes 5 to form meshes 6.

[0101] The reticular structure 2 defines a monolithic, i.e., one-piece, grid (net). The reticular structure 2 is made at least in part (optionally entirely) of plastic material, for example, it is made using one or more of the following polymers: polyethylene, high-density polyethylene (HDPE), polypropylene, or a polyolefin blend.

[0102] In detail, the first 3 elements have an elongated conformation according to a first T1 extension trajectory. As shown, for example, in Figures 1 and 2, the T1 trajectories are parallel to each other to define a plurality of first elements 3 parallel to each other. The first extension trajectories T1 may be substantially rectilinear, at least under a use condition of the reticular structure; the possibility of making a reticular structure 2 having the first extension trajectories developed along trajectories that are at least partially arcuate is not excluded.

[0103] As mentioned above, the first elements 3 are spaced apart, particularly spaced by tracts of the second elements. Quantitatively, the minimum distance D1 (Figure 3) between two immediately adjacent first elements 3 may be between 7 mm and 80 mm, optionally between 15 mm and 70 mm. The first elements 3 have, at least at a portion of the centerline defined between two immediately consecutive nodes 5 and orthogonally to the first extension trajectory T1, a section having substantially circular or elliptical or rectangular or square outline.

[0104] As shown from the attached figures, the first elements 3 may have a substantially constant section in the tract connecting two immediately consecutive nodes 5. In detail, as visible, the first elements have a slight deformation at the node to define a kind of connection with the second elements 4. In fact, at least for 80% (optionally for 90%) of the extension of a tract of a first element 3 connecting two immediately consecutive nodes 5, said tract of the first element 3 exhibits an optionally full cross-section that is substantially constant. For example, said first element 3 has a cross-sectional area, measured at a defined portion of the centerline between two immediately consecutive nodes 5, greater than 1 mm2, optionally between 2 and 10 mm2.

[0105] In more detail, the first elements 3 have a thickness S1 (Figure 6), measured orthogonally to the first extension trajectory T1 of said first element 3 and transversely, optionally orthogonally, to the second extension trajectory T2 of the second elements 4. In fact, the thickness S1 of the first elements is measured transversely, optionally orthogonally, to a laying surface of the uniplanar structure . Quantitatively, the S1 thickness of each first element 3 may be between 0.8 and 5 mm, optionally between 1 and 3 mm.

[0106] In greater detail still, each first element 3 has a plurality of aligned tracts along its respective first extension trajectory: each tract of a first element 3 is defined between two immediately consecutive nodes along the first extension trajectory of the respective first element 3 (each tract, in fact, connects two immediately consecutive nodes). The thickness of each tract of each first element 3, for a preponderant part of its extension defined between two immediately consecutive nodes 5, is substantially constant; in particular, the thickness of each tract of each first element 3, for at least 80% (optionally at least 90%) of its extension defined between two immediately consecutive nodes 5, is substantially constant.

[0107] The first elements 3 may be stretched along their development. For example, the stretching ratio, that is, the ratio of the length of the first elements after stretching to the length of the first elements before stretching is greater than 2, optionally between 3 and 10, even more optionally between 4 and 8.

[0108] As for second elements 4, on the other hand, they also have an elongated conformation according to a second extension trajectory T2, which is transverse, optionally orthogonal to the first extension trajectory T1. As shown in the attached figures, the trajectories T2 are parallel to each other to define a plurality of second elements 4 parallel to each other. The second extension trajectories T2 may also be substantially rectilinear, at least under a use condition of the reticular structure 2; the possibility of making a reticular structure 2 having the second T2 extension trajectories developed along trajectories that are at least partially arcuate is not excluded.

[0109] As mentioned above, second elements 4 are spaced apart, particularly spaced by tracts of the first elements. Quantitatively, the minimum distance D2 (Figure 3) between two immediately adjacent second elements 4 may be between 7 mm and 80 mm, optionally between 15 mm and 70 mm. The distance D2 between second elements 4 may be substantially similar to the distance D1 between first elements 3; however, the possibility of providing a reticular structure 2 with meshes having a rectangular shape wherein the distance of second elements 4 is different from the distance between first elements is not excluded. For example, the ratio between the distance D1 between first elements 3 and the distance D2 between second elements may be between 0.3 and 5, optionally between 0.5 and 4, even more optionally between 0.5 and 3.

[0110] The second elements 4 have, at least at a portion of the centerline defined between two immediately consecutive nodes 5 and orthogonally to the second extension trajectory T2, a section having substantially a circular or elliptical or rectangular or square outline.

[0111] As shown from the attached figures, the second elements 4 may have a substantially constant section in the tract connecting two immediately consecutive nodes 5. In detail, as visible, the second elements also have a slight deformation in correspondence of the node to define a kind of connection with the first elements 3. In fact, for at least 80% (optionally 90%) of the extension of a tract of a second element 4 connecting two immediately consecutive nodes 5, said tract of the second element 4 exhibits an optionally full, substantially constant cross section. For example, said second element 4 has a cross-sectional area, measured at a defined centerline portion between two immediately consecutive nodes 5, greater than 1 mm2, optionally between 2 mm2and 10 mm2.

[0112] In more detail, the second elements 4 have a thickness S2 (Figures 5 and 6), measured orthogonally to the second extension trajectory T2 of said second element 4 and transversely, optionally orthogonally, to the first extension trajectory T1 of the first elements 3. In fact, the thickness S2 of the second elements is measured transversely, optionally orthogonally, to a uniplanar structure bedding surface. Quantitatively, the S2 thickness of each second element 4 may be between 0.8 mm and 5 mm, optionally between 1 mm and 3 mm.

[0113] In greater detail still, each second element 4 has a plurality of aligned tracts along its respective second extension trajectory: each tract of a second element 4 is defined between two immediately consecutive nodes along the second extension trajectory of the respective second element 4 (each tract, in fact, connects two immediately consecutive nodes). The thickness of each tract of each second element 4, for a preponderant part of its extension defined between two immediately consecutive nodes 5, is substantially constant; in particular, the thickness of each tract of each second element 4, for at least 80% (optionally at least 90%) of its extension defined between two immediately consecutive nodes 5, is substantially constant.

[0114] The thickness S1 , S2 of first and second elements 3, 4, respectively, is measured along the same direction. The ratio between the thickness S1 of a first element and the thickness S2 of a second element 4 is 0.7 to 1 .5, optionally 0.8 to 1.3. As a matter of fact, the first and second elements 3, 4, in addition to extending along a same lying surface to define the uniplanar structure, have substantially a similar cross-section and thickness; this feature, as will be better described later, in addition to equalizing the mechanical characteristics in the two directions of extension, improves the draining capabilities of the reticular structure 2.

[0115] The second elements 4 may be stretched along their development. For example, the stretching ratio, that is, the ratio of the length of second elements 4 after stretching to the length of second elements 4 before stretching is greater than 2, optionally between 3 and 10, even more optionally between 4 and 8.

[0116] In fact, the reticular structure 2 may be stretched along only one direction of extension of the first or second elements to define a mono-stretched reticular structure 2. Alternatively, the reticular structure 2 may be stretched along two directions, specifically along the development of the first and second elements 3, 4 to define a bi-stretched reticular structure. The stretching ratio, that is, the ratio of the length of the elements (first elements and / or second elements) after stretching to the length of the elements before stretching is greater than 2, optionally between 3 and 10, even more optionally between 4 and 8.

[0117] The first and second elements 3, 4 may be substantially identical to each other, optionally in shape and / or size. In the attached figures, a reticular structure has been illustrated in a non-limiting way, having first elements that are substantially identical to each other in shape and size and which are substantially identical in shape and size to the second elements.

[0118] Of course, first and second elements may differ in shape and size. For example, the ratio between a cross- sectional area of a first element 3, measured at an intermediate portion between two immediately consecutive nodes 5, and a cross-sectional area of a second element 4, also measured at an intermediate portion between two immediately consecutive nodes 5, may be between 0.5 and 3, optionally between 0.7 and 2.

[0119] The first and second elements 3, 4 lie substantially on a single ideal lying surface. In detail, the first and second elements 3, 4 join at nodes 5 to define a substantially uniplanar structure extending between opposite first and second surfaces 2a, 2b (Figure 4). The first and second surfaces 2a, 2b basically define the thickness of the uniplanar structure which may be between 1 mm and 4 mm, optionally between 1 .5 mm and 2 mm.

[0120] In the embodiments shown in the attached figures, the meshes 6 of the reticular structure 2 are basically square. Of course, the possibility of making meshes having a different shape, for example, rectangular, triangular or rhomboidal, is not excluded. As the distances between the first and second elements vary, the size of the 6 meshes varies, and they may have a through area between 400 mm2and 6,400 mm2.

[0121] As shown from the attached figures, the reticular structure 2 comprises a plurality of protuberances 7 that emerge from at least one side of the reticular structure itself. In particular, protuberances 7 emerge from the uniplanar structure defined by the first and second elements to define a reticular structure having a certain three-dimensionality. The protuberances 7 emerges from at least one between the first and second surfaces 2a, 2b. In the attached figures, a reticular structure 2 having a plurality of protuberances emerging only from the second surface 2b has been illustrated in a non-limiting way; of course, the possibility of defining a reticular structure wherein the plurality of protuberances 7 emerge from the first surface 2a alone or from both surfaces 2a, 2b of the uniplanar structure, is not excluded.

[0122] In more detail and as visible, for example, from Figures 1 and 2, each protuberance 7 emerges from a respective node 5: protuberances 7 are joined in a single piece to nodes 5 and then joined in a single piece to first and second elements 3, 4. In greater detail, protuberances 7 emerge directly and only from nodes 5, without going to the tracts of the first and second elements immediately outside the node 5. Node 5 means the part of intersection and union of the first and second elements.

[0123] Again, as shown in Figures 1 and 2, each node 5 has, with respect to the ideal lying surface at the respective node 5, a predetermined size, which is greater than a lateral size defined by the protuberance 7 emerging from the same node 5. In other words, each protuberance 7 has a predetermined maximum size that is substantially equal to or less than the predetermined size of the node 5 from which the protuberance emerges. These sizes are substantially defined with respect to the ideal lying surface at the respective node 5. In fact, the size of the node is understood to be the surface size in view along a direction orthogonal to the uniplanar structure while the size of protuberance 7 is understood to be the lateral size always understood to be the size defined by protuberance 7 always in view along a direction orthogonal to the uniplanar structure.

[0124] In other words, each protuberance 7 does not protrude laterally from a surface size of the node 5 from which protuberance 7 emerges or is laterally contained within a surface size of node 5 from which the protuberance itself emerges.

[0125] In detail, each protuberance 7 extends in height along one direction, transverse to the first extension trajectory T1 and the second extension trajectory T2, from a base 7a to a top 7b opposite the base 7a: the base 7a of the protuberance 7 is joined in a single piece to a respective node 5, optionally occupying only part of the surface of that node.

[0126] In more detail still, each protuberance 7 has a height H (see, for example, Figure 5), defined as the maximum distance between the base 7a and the top 7b of the same protuberance 7, greater than 4 mm, optionally between 5 and 40 mm, even more optionally between 5 and 30 mm. The height of each protuberance 7 is greater than the thickness of the first and second elements 3, 4 (especially the thickness of the uniplanar structure); in fact, the ratio between the height of a protuberance 7 and the thickness of the uniplanar structure is greater than 2, optionally it is between 3 and 5. The thickness of the uniplanar structure and the height of the protuberances 7 define the overall thickness of the reticular structure 2, which may be greater than 1 mm, optionally between 2 mm and 5 mm. In detail, the ratio between the height of a protuberance 7 and the thickness S1 of a first element 3 may be greater than 3, optionally ranging between 4 and 6, whereas the ratio between the height of a protuberance 7 and the thickness S2 of a second element 4 is greater than 3, optionally ranging between 4 and 6.

[0127] Each protuberance 7 may have a substantially rectangular parallelepiped shape or a truncated pyramid shape or a cylindrical shape. In the attached figures, protuberances 7 having a substantially cylindrical shape have been illustrated in a non-limiting way. In fact, the shape of each protuberance 7 is such as to define substantially the same lateral size according to directions transverse (optionally orthogonal) to each other, with respect to a plane orthogonal to the direction of the height extension of the protuberance itself.

[0128] In fact, each protuberance 7 has a predetermined L1 length (Figure 3), optionally measured along the first extension trajectory T1 of the first element 3 passing through the respective protuberance 7, which may be substantially identical to a predetermined L2 width of the same protuberance, optionally measured along the second extension trajectory T2 of the second element 4 passing through the respective protuberance 7; for example, the ratio between length L1 and width L2 of a protuberance 7 may be between 0.8 and 1.2, even more optionally between 0.9 and 1.1.

[0129] Protuberances 7 may also have a substantially elongated conformation along the height. In fact, the length L1 and width L2 of each protuberance may be less than the height H of the same protuberance 7. For example, the ratio between the height H and the length L1 of a protuberance 7 may be greater than 1, optionally comprised between 2 and 5, even more optionally comprised between 2.5 and 4. Equally, the ratio between the height H and the width L2 of a protuberance 7 is greater than 1, optionally is between 2 and 5, even more optionally between 2.5 and 4.

[0130] Additionally, each protuberance 7 may have, for a preponderant part of its height extension, a substantially constant section. In detail, each protuberance 7 may present, for at least 80% (optionally at least 90%) of its height extension, a substantially constant section. For example, each protuberance 7 may have, for a preponderant part of its height extension (e.g., at least 80 percent or at least 90 percent of its height extension), a cross section between 1.5 mm2and 25 mm2, optionally between 4 mm2and 9 mm2.

[0131] The protuberances 7 may be substantially identical to each other, optionally both in shape and size, as for example shown in a non-limiting way in the attached figures; however, making different protuberances from each other is not excluded.

[0132] As described above, protuberances 7 are made to occupy only the surface of the respective node 5. In other words, the minimum distance D72 between two protuberances 7 immediately adjacent to and emerging from two respective nodes 5 connected by a tract of a first element 3 is equal to or less than the distance D2 between two second elements 4. Specifically, the ratio between the minimum D72 distance between two immediately adjacent protuberances 7 emerging from two respective nodes 5 connected by a tract of a first element 3 and the D2 distance between two second elements may be greater than or equal to 1, optionally it is between 1 and 1.2. Quantitatively, the minimum D72 distance between two immediately adjacent protuberances 7 emerging from two respective nodes 5 connected by a tract of a first element 3 may be between 7 mm and 80 mm, optionally between 15 mm and 70 mm.

[0133] Equally, the minimum distance D71 between two immediately adjacent protuberances 7 emerging from two respective nodes 5 connected by a tract of a second element 4 may be equal to or less than the distance D1 between two first elements. Specifically, the ratio between the minimum distance D71 between two immediately adjacent protuberances 7 emerging from two respective nodes 5 connected by a tract of a second element 4 and the distance D1 between two first elements may be greater than or equal to 1, optionally it is between 1 and 1 .2. Quantitatively, the minimum distance between two immediately adjacent protuberances 7 emerging from two respective nodes 5 connected by a tract of a second element 4 may be between 7 mm and 80 mm, optionally between 15 mm and 70 mm.

[0134] As described above, protuberances 7 may emerge only from one of the surfaces 2a, 2b of the reticular structure. It is useful to note that the illustrated reticular structure 2 has, in a non-limiting way, a plurality of protuberances 7 emerging only from the second surface 2b of the reticular structure 2 which then has a first surface 2a that is substantially smooth, optionally flat, i.e., without protuberance or ridges; on the other hand, the protuberances 7 give the structure a certain three-dimensionality and draining capabilities.

[0135] As can be seen from Figures 4-6, reticular structure 2 may comprise at least one filter element 18. The filter element may be optionally fixed (welded, bonded, or laminated) to a plurality of protuberances 7 which distance said filter element 18 from the first and second elements (Figures 4 to 6). In fact, the filter element 18 is engaged at the top of a plurality of protuberances 7. The possibility of engaging filter element 18 directly to the first and second elements, i.e., the first smooth surface 2a of reticular structure 2, is not excluded.

[0136] As schematized in Figure 4, the filter element 18, in cooperation with each mesh 6 - defined by first and second elements 3, 4 - define cells configured to receive and engage gravel and / or crushed stone for soil reinforcement and / or consolidation. In fact, the filter element 18 allows the gravel or crushed stone to be engaged with the first and second elements and protrusions in such a way that the reticular structure 2 may provide, in cooperation with the gravel and crushed stone, soil reinforcement / consolidation. It is useful to clarify how gravel and / or crushed stone, in soil consolidation and reinforcement works, play an important role. In fact, gravel and / or crushed stone are "noble" materials, very often found in natural and / or artificial structures to be reinforced, placed immediately below the surface soil layer: thanks to their mechanical and natural drainage characteristics compared to the soil, gravel and / or crushed stone allow for soil consolidation and / or reinforcement, ensuring a longer life to the natural and / or artificial structure.

[0137] With the introduction of reticular structure 2, the latter is able to cooperate the gravel and / or crushed stone layer to further improve the holding characteristics of the soil thus increasing its consolidation and reinforcement. In detail, reticular structure 2 may be placed in a layer of gravel and / or crushed stone or at the base of said layer and at the interface between it and a lower layer characterized by less noble material with greater variability (fine materials having reduced grain size, such as sand and clay).

[0138] Under such a condition, the filter element 18 may be used to prevent subgrade material (e.g., fine soil, sand, or clay) from migrating into the gravel or crushed stone and reducing its mechanical properties. Filter element 18 may also be used to allow selective passage of materials through the reticular structure 2. For example, the filter element 18 may be configured to allow water to pass through the soil to ensure proper drainage conditions.

[0139] Filter element 18 may comprises a sheet material body, optionally having a substantially flat structure. In detail, the filter element 18 comprises one or more sheets of woven-nonwoven material.

[0140] The reticular structure 2 described above (monolithic plastic structure) may have a specific weight between 100 g / m2and 500 g / m2and a specific tensile strength, along the first and / or second stretched elements (the first and / or second elements 3, 4), greater than 5 KN / m, optionally between 8 KN / m and 20 KN / m, even more optionally between 10 KN / m and 15 KN / m. Specific tensile strength is measured by the method set forth in ASTM D6637.

[0141] The presence of protrusions 7, which, as described above, have a predetermined height development , allow to define a reticular structure having, in addition, a considerable compressive strength. In fact, protrusions 7 are configured to allow the reticular structure 2, upon the action of a compressive pressure equal to 200 kPa and having a direction parallel to the direction of extension of protrusions 7, to maintain a residual thickness of the reticular structure equal to at least 80% of the original thickness (thickness of the reticular structure before the application of compression), after an application time equal to 1 hour.

[0142] The presence and structure of the protuberances 7 which, as described above, extend from the uniplanar structure by occupying only the space defined by the nodes allows the definition of a reticular structure 2 with excellent draining capabilities. In particular, the structure of protuberances 7 makes it possible to provide a reticular structure 2 having similar and excellent draining capabilities at least along two directions orthogonal to each other. In fact, the draining structure 2 has a first draining transmissivity along a first direction parallel to an ideal lying plane of the reticular structure (e.g., said first direction may be substantially parallel to the first elements 3) and a second draining transmissivity along a second direction parallel to an ideal lying plane of the reticular structure (e.g., said second direction may be substantially parallel to the second elements 4). All things being equal, the ratio between the first and second drainage transmissivity is between 0.6 and 1.4, optionally between 0.8 and 1.2, even more optionally between 0.9 and 1.1. In fact, the drainage transmissivity of reticular structure 2 is not substantially different in the two directions orthogonal to each other. In still other words, reticular structure 2 is characterized by substantially uniform drainage transmissivity at least according to two directions orthogonal to each other.

[0143] Quantitatively, reticular structure 2 has a drainage transmissivity - in the first direction, for vertical pressures equal to 20 kPa and optionally under conditions of stiff upper and lower interfaces - equal to or greater than 3.0*1 O'3m2 / sec. The reticular structure 2 has a drainage transmissivity - in the second direction, for vertical pressures equal to 20 kPa and optionally under conditions of stiff upper and lower interfaces - equal to or greater than 2.0*103m / sec.2

[0144] Manufacturing process

[0145] It is also an object of the present invention a process of making a reticular structure 2 in accordance with the description above.

[0146] The process involves the formation of first and second precursor elements 3, 4 by a coextrusion process (simultaneous extrusion of first and second precursor elements 3, 4). The coextrusion process, represented schematically in Figure 8, involves the simultaneous extrusion of first and second precursor elements by an extrusion head 100; the first precursor elements are longitudinal elements that extend along the direction of advancement of the plastic material exiting the head 100 while the second precursor elements are elements transverse to the first precursor elements: first and second precursor elements are joined together at nodes to form a monolithic integral body.

[0147] The first precursor elements exiting the extrusion head have a plurality of protuberances emerging from the nodes: the protuberances are joined in a single piece to the nodes and thus define, together with the first and second elements, the monolithic integral body.

[0148] The reticular structure exiting the extrusion head may be in the form of a cylindrical lattice. For example, the process may involve a step of cutting the cylindrical lattice (cutting station 101 in Figure 8) and opening in plane of it.

[0149] Subsequent to the formation of the monolithic integral body, the latter may undergo a stretching process along the development of the first and / or second elements to define a mono-stretched or bi-stretched reticular structure. A first longitudinal stretching station 102 i.e., along a machine direction (direction of advancement MD of the reticular structure) and a second transverse stretching station (direction orthogonal TD to the machine direction MD) are schematized, in a non-limiting way, in Figure 8.

[0150] Following the stretching step, the process may include a step of laminating the stretched structure with the filter element 18 in such a way that the latter is constrained to the protuberances 7 or directly to the first and second elements.

[0151] At the end of the stretching phase, the reticular structure 2 may be wound in a roll around an axis that is substantially parallel to the second extension trajectory of the second elements (e.g., according to an axis parallel to the direction TD shown in Figure 8). In fact, the characteristics of the reticular structure 2 allows it to be wound in a roll, for example, to facilitate transport.

[0152] The reticular structure is then cut transversely to the first elements according to a predetermined length, measured in the direction of the first elements or longitudinal elements to define said reticular structure 2.

[0153] Different manufacturing systems may be used to make the reticular structure. For example, it is possible to start from a flat extrusion head to make a sheet with protuberances 7 on at least one face, which will then drilled and stretched.

[0154] ADVANTAGES

[0155] The reticular structure 2 object of the present invention has considerable advantages over solutions in the known art. In fact, the reticular structure 2 has protuberances 7 that substantially occupy only the size of the respective node 5 allow the reticular structure to present excellent drainage capabilities, in particular to present a high drainage capacity in two directions orthogonal to each other.

[0156] The uniformity of the drainage capacities of the reticular structure at least in two transverse directions may also be improved by the presence of first and second elements lying on a single surface and having similar dimensions; this feature, in addition to unifying the mechanical strength of the reticular structure, contributes to improve and uniform the drainage capacities at least in two transverse directions.

[0157] Drainage capacity is important in geotechnical applications, where reticular structures (e.g., geogrids) are used to reinforce soil and manage drainage.

Claims

CLAIMS1. Reticular structure (2) of plastic material for geotechnical applications, said reticular structure (2) comprising: a plurality of first elements (3) spaced apart and having an elongated conformation according to a first extension trajectory (T1), wherein each first element (3) has a predetermined cross section defined according to a plane orthogonal to the first extension trajectory of the respective first element (3), a plurality of second elements (4) spaced from each other and having an elongated conformation according to a second extension trajectory (T2) transverse to the first extension trajectory (T1) of the first elements (3), wherein each second element (4) has a predetermined cross section defined according to a plane orthogonal to the second extension trajectory of the respective second element (4), wherein said first and second elements (3, 4) intersect at nodes (5) to form meshes (6) and substantially define a uniplanar structure extending between a first and second surfaces (2a, 2b) opposite each other, wherein the reticular structure (2) comprises a plurality of protuberances (7) emerging from at least one side of the reticular structure itself, characterized by the fact that the ratio between a cross-sectional area of a first element (3), measured at an intermediate portion between two immediately consecutive nodes (5), and a cross-sectional area of a second element (4), also measured at an intermediate portion between two immediately consecutive nodes (5), is between 0.7 and 1.5.

2. Reticular structure according to claim 1 , wherein each first element (3) has, for at least 80% of a tract of said first element connecting two immediately consecutive nodes (5), a substantially constant cross section, wherein each second element (4) has, for at least 80% of a tract of said second element connecting two immediately consecutive nodes (5), a substantially constant cross section.

3. Reticular structure according to any one of the preceding claims, wherein the first elements (3) have a thickness (S1), optionally measured orthogonally to the first extension trajectory (T1) of said first element (3) and transversely to the second extension trajectory (T2) of the second elements (4), wherein the second elements (4) have a thickness (S2), optionally measured orthogonally to the second extension trajectory (T2) of said second element (4) and transversely to the first extension trajectory (T1) of the first elements (3), wherein the ratio between the thickness (S1) of a first element and the thickness (S2) of a second element (4) is between 0.7 and 1.5, optionally between 0.8 and 1.3.

4. Reticular structure according to any one of the preceding claims, wherein each protuberance (7) emerges from a respective node (5).

5. Reticular structure according to any one of the preceding claims, wherein each protuberance (7) is substantially laterally contained within a surface size of the node (5) from which the protuberance (7) itself emerges.

6. Reticular structure according to any one of the preceding claims, wherein protuberances (7) emerge from at least one of the first and second surfaces (2a, 2b) of the uniplanar structure.

7. Reticular structure according to any one of the preceding claims, wherein each protuberance (7) extends along a direction from a base (7a) to a top (7b) opposite the base (7a), wherein the base (7a) of the protuberance (7) is joined in a single piece to a respective node (5), optionally, the extension direction of each protuberance (7) is transverse to the first extension trajectory (T1) and the second extension trajectory (T2).

8. Reticular structure according to the preceding claim, wherein each protuberance (7) has a height (H) defined by the maximum distance between the base (7a) and the top (7b) of the same protuberance (7), wherein the height (H) of each protuberance (7) is more than 4 mm, optionally between 5 mm and 40 mm, even more optionally between 5 mm and 30 mm.

9. Reticular structure according to the preceding claim, wherein the ratio between the height (H) of a protuberance (7), optionally of each protuberance, and the thickness of the uniplanar structure is greater than 2, optionally is between 3 and 5.

10. Reticular structure according to any one of the preceding claims, wherein each protuberance (7) has a substantially rectangular parallelepiped or a truncated pyramid shape.11 . Reticular structure according to any one of the preceding claims, wherein each protuberance (7) has a predetermined length (L1), optionally measured along the first extension trajectory (T1) of the first element (3) passing through the respective protuberance (7), wherein each protuberance (7) has a predetermined width (L2), optionally measured along the second extension trajectory (T2) of the second element (4) passing through the respective protuberance (7), wherein the ratio between the length (L1) to the width (L2) of a prominence (7) is between 0.8 and 1.2, even more optionally between 0.9 and 1.1.

12. Reticular structure according to any one of the preceding claims, wherein each protuberance (7) has, for at least 80% of its height extension, a substantially constant section.

13. Reticular structure according to any one of the preceding claims, wherein the minimum distance between two protuberances (7) immediately adjacent to and emerging from two respective nodes (5) connected by a tract of a first element (3) is equal to or less than the distance between two second elements.

14. Reticular structure according to any one of the preceding claims, wherein the ratio between the minimum distance between two immediately adjacent protuberances (7) emerging from two respective nodes (5) connected by a tract of a first element (3), and the distance between two second elements is greater than or equal to 1, optionally between 1 and 1.2.

15. Reticular structure according to any one of the preceding claims, wherein the minimum distance between two protuberances (7) immediately adjacent to and emerging from two respective nodes (5) connected by a tract of a second element (4) is equal to or less than the distance between two first elements.

16. Reticular structure according to any one of the preceding claims, wherein the ratio between the minimum distance between two immediately adjacent protuberances (7) emerging from two respective nodes (5) connected by a tract of a second element (4), and the distance between two first elements is greater than or equal to 1, optionally between 1 and 1.2.

17. Reticular structure according to any one of the preceding claims, wherein protuberances (7) only emerge from nodes (5).

18. Reticular structure according to any one of the preceding claims, wherein the first and second elements (3, 4) lie substantially on a single ideal lying surface, wherein each node (5) has, with respect to the ideal lying surface at the respective node (5), a predetermined size, wherein each protuberance (7) has a maximum size substantially equal to or less than the predetermined size of the node (5) from which the protuberance emerges, optionally said sizes of the node (5) and protuberance (7) are defined with respect to the ideal lying surface at the respective node (5).

19. Reticular structure according to any one of the preceding claims, wherein the ratio between a minimum distance (D72) between two protuberances (7) immediately adjacent to and emerging from two respective nodes (5) connected by a tract of a first element (3), and a distance (D2) between two second elements is greater than or equal to 1, optionally being between 1 and 1.2.

20. Reticular structure according to any one of the preceding claims, wherein the ratio between a minimum distance (D71) between two protuberances (7) immediately adjacent to and emerging from two respective nodes (5) connected by a tract of a second element (4), and a distance (D1) between two first elements is greater than or equal to 1, optionally being between 1 and 1.2.

21. Reticular structure according to any one of the preceding claims, wherein the first elements (3) are stretched along their development, wherein the first elements (3) have a stretching ratio greater than 3, optionally between 3 and 8, more optionally between 4 and 7, optionally the stretching ratio of the first elements is defined as the ratio between a final length of the first elements after a stretching action of the first elements and an initial length of the first elements before stretching.

22. Reticular structure according to any one of the preceding claims, wherein the second elements (4) are stretched along their development, wherein the second elements (4) have a stretching ratio greater than 3, optionally between 3 and 8, plus optionally between 4 and 7, optionally the stretching ratio of the second elements is defined as the ratio between a final length of the second elements after a stretching action of the second elements and an initial length of the second elements before stretching.

23. Reticular structure (2) of plastic material for geotechnical applications, said reticular structure (2) comprising: a plurality of first elements (3) spaced apart and having an elongated conformation according to a first extension trajectory (T1), a plurality of second elements (4) spaced apart and having an elongated conformation according to a second extension trajectory (T2), transverse to the first extension trajectory (T1) of the first elements (3), wherein said first and second elements (3, 4) intersect at nodes (5) to form meshes (6) and to define a substantially uniplanar structure extending between a first and second surfaces (2a, 2b) opposite each other, wherein the first and second elements (3, 4) lie substantially on a single ideal lying surface, wherein the reticular structure (2) comprises a plurality of protuberances (7) emerging from at least one side of the reticular structure itself, characterized by the fact that each node (5) has, with respect to the ideal lying surface and at the respective node (5), a predetermined size, wherein each protuberance (7) has a maximum size substantially equal to or less than the predetermined size of the node (5) from which the protuberance emerges.

24. Reticular structure according to the preceding claim, wherein the protuberances (7) emerge only from nodes (5).

25. Reticular structure according to claim 23 or 24, wherein the ratio between a height (H) of a protuberance (7), optionally of each protuberance, to the thickness of the uniplanar structure is more than 2, optionally is between 3 and 5.

26. Process of making a reticular structure (2) in accordance with any one of the preceding claims, wherein the process comprises the steps of:- forming the plurality of elongated first and second elements and extending along respective transverse extension trajectories, optionally orthogonal to each other, the first and second elements intersecting at nodes to form meshes,- form the plurality of protuberances (7) that emerge from at least one side of the reticular structure (2), wherein the plurality of first and second elements and the plurality of protuberances (7) are joined in a single piece to form a single solid body and obtained by extrusion of plastic material.

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