MULTI-AXIAL INTEGRAL GEOGRID AND METHODS OF MAKING AND USING SAME

Abstract

A monolayer multi-axial integral geogrid suitable for stabilizing aggregate includes a plurality of interconnected oriented strands and partially oriented junctions forming a repeating pattern of outer hexagons having an array of openings therein. Oriented ribs extending inwardly from each of said outer hexagons support and surround a smaller inner hexagon having oriented strands thus forming a plurality of trapezoidal openings and a single hexagonal opening. The oriented strands and partially oriented junctions of the outer hexagons form a plurality of linear strong axis strands that extend continuously throughout the entirety of the geogrid and form additional triangular openings. The geogrid thus includes three different repeating geometric shapes. The inner hexagons preferably also can move up and down, out of the plane of the geogrid. The multi-axial integral geogrid thus provides a geometry that can better engage with, confine and stabilize a greater variety and quality of aggregates.

Claims

1. A multi-axial integral geogrid comprising: a plurality of interconnected oriented strands and partially oriented junctions forming a repeating pattern of outer hexagons having an array of openings therein, supporting ribs extending inwardly from each of said outer hexagons to support inside said outer hexagon a smaller inner hexagon having oriented strands and tri-nodes, said outer hexagons, said supporting ribs and said inner hexagons defining three different geometric configurations which are repeating throughout an entirety of the geogrid, said oriented strands and said partially oriented junctions of said outer hexagons defining a plurality of linear strands that extend continuously throughout the entirety of the geogrid, and said geogrid having a thickness of from about 3 mm to about 9 mm.

2. The multi-axial integral geogrid according to claim 1, wherein the smaller inner hexagon can deflect up and down out of a plane of the geogrid during compaction of the aggregate.

3. The multi-axial integral geogrid according to claim 2, wherein the smaller inner hexagon can deflect up and down out of the plane of the geogrid up to about 33% of the thickness of the partially oriented junctions.

4. The multi-axial integral geogrid according to claim 1, wherein the oriented strands have an aspect ratio of greater than about 1.5.

5. The multi-axial integral geogrid according to claim 1, wherein the three different geometric configurations are hexagonal, trapezoidal and triangular shapes.

6. The multi-axial integral geogrid according to claim 1, wherein there are three continuous linear strands that extend continuously throughout the entirety of the geogrid, which strands are separated from each other by about 120°.

7. The multi-axial integral geogrid according to claim 1, wherein the geogrid is a monolayer.

8. (canceled)

9. (canceled)

10. (canceled)

11. (canceled)

12. (canceled)

13. A method of making a multi-axial integral geogrid, comprising: providing a polymer sheet; providing a patterned plurality of holes or depressions in the polymer sheet; and biaxially orienting the polymer sheet having the patterned plurality of holes or depressions therein to provide a plurality of interconnected oriented strands and partially oriented junctions forming a repeating pattern of outer hexagons having an array of openings therein, each of said outer hexagons supporting and surrounding inside said outer hexagon a smaller inner hexagon having oriented strands, and tri-nodes, said outer hexagons, said supporting ribs and said inner hexagons defining three different configurations which are repeating throughout an entirety of the multi-axial geogrid, and said oriented strands and said partially oriented junctions of said outer hexagons defining a plurality of linear strands that extend continuously throughout the entirety of the geogrid, and said geogrid having a thickness of from about 3 mm to about 9 mm.

14. The method according to claim 13, wherein the polymer sheet has an initial thickness of from about 3 mm to about 10 mm.

15. The method according to claim 13, wherein the three different geometric configurations are repeating hexagonal, trapezoidal and triangular shapes.

16. (canceled)

17. (canceled)

18. (canceled)

19. (canceled)

20. The multi-axial integral geogrid according to claim 24, wherein the inner geometric shape is flexible or not flexible within the outer hexagon.

21. A reinforced and stabilized composite soil structure comprising: a mass of particulate material; and a multi-axial integral geogrid embedded in and engaging with said particulate material and having a plurality of interconnected oriented strands and partially oriented junctions forming a repeating pattern of outer hexagons having an array of openings therein, each of said outer hexagons supporting and surrounding a smaller inner hexagon having oriented strands and tri-nodes, said outer hexagons, said supporting ribs and said inner hexagons defining three different geometric configurations which are repeating throughout an entirety of the multi-axial geogrid, said oriented strands and said partially oriented junctions of said outer hexagons defining a plurality of linear strands that extend continuously throughout an entirety of the geogrid, and said geogrid having a thickness of from about 3 mm to about 9 mm.

22. The multi-axial integral geogrid according claim 21, wherein the openings provide a range of interaction with granular materials of varying particles size of at least 200 mm.sup.2.

23. The multi-axial integral geogrid according to claim 2, wherein the smaller inner hexagon can deflect up and down out of the plane of the geogrid in an area of compliance on the order of about 50% to about 75%.

24. A multi-axial integral geogrid comprising: a plurality of interconnected oriented strands and partially oriented junctions forming a repeating pattern of outer hexagons having an array of openings there, each of said outer hexagons supporting, by oriented ribs, a smaller oriented inner geometric configuration, said oriented strands, said partially oriented junctions, said oriented ribs and said smaller oriented inner geometric configurations forming at least three different geometric configurations which are repeating throughout an entirety of the multi-axial geogrid, said oriented strands and said partially oriented junctions of said outer hexagons defining a plurality of linear strands that extend continuously throughout the entirety of the geogrid, and said geogrid having a thickness of from about 3 mm to 9 mm.

25. The multi-axial integral geogrid according to claim 24, wherein said three different geometric configurations are a hexagon, a trapezoid, and a triangle.

26. (canceled)

27. (canceled)

28. The multi-axial integral geogrid according to claim 24, wherein said smaller oriented inner geometric configuration can deflect up and down out of a plane of said geogrid.

29. The multi-axial integral geogrid according to claim 24, wherein the oriented strands have an aspect ratio of greater than about 1.5.

30. The multi-axial integral geogrid according to claim 24, wherein there are three continuous linear strands that extend continuously throughout the entirety of the multi-axial integral geogrid, which strands are separated from each other by about 120°.

31. The multi-axial integral geogrid according to claim 1, wherein said plurality of linear strands extend continuously throughout the entirety of the geogrid without intersecting said inside of the outer hexagons.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0057] FIG. 1 is a plan view of an integral geogrid according to the prior art Walsh '112 patent.

[0058] FIG. 2 is a plan view of a multi-axial integral geogrid according to a preferred embodiment of the present invention.

[0059] FIG. 3 is a top perspective view of a starting sheet material having holes or depressions formed therein for forming the multi-axial integral geogrid shown in FIG. 2.

[0060] FIG. 3A is a plan view of a possible size and spacing for the holes shown in the starting sheet material of FIG. 3.

[0061] FIG. 4 is a perspective view of the multi-axial integral geogrid shown in FIG. 2.

[0062] FIG. 5 is an enlarged perspective view of the multi-axial integral geogrid shown in FIG. 4 rotated counter clockwise about 30 degrees.

[0063] FIG. 5A is an enlarged side schematic drawing illustrating a partial section of Rib A and adjoining junctions of an outer hexagon (see FIG. 13) which form or define a part of a strong axis strand of the multi-axial integral geogrid shown in FIG. 5.

[0064] FIG. 5B is an enlarged side schematic drawing illustrating a partial section of Ribs B and D and adjacent tri-nodes of an inner hexagon (see FIG. 13) of the multi-axial integral geogrid shown in FIG. 5.

[0065] FIG. 6 is a partial plan view that illustrates structural limitations of the prior art integral geogrid shown in FIG. 1.

[0066] FIG. 7 is a partial plan view that illustrates structural attributes of the multi-axial integral geogrid of the present invention shown in FIG. 2.

[0067] FIG. 8 is a graph that illustrates the range of distribution of individual aperture area in a prior art integral geogrid of the type shown in FIG. 1.

[0068] FIG. 9 is a graph that illustrates the range of distribution of individual aperture area in another prior art integral geogrid of the type shown in FIG. 1.

[0069] FIG. 10 is a graph that illustrates an enhanced range of distribution of individual aperture area that may be attainable with the multi-axial integral geogrid of the present invention shown in FIG. 2.

[0070] FIG. 11 is a partial plan view that illustrates the in-plane rotational stiffness of the prior art integral geogrid shown in FIG. 1.

[0071] FIG. 12 is a partial plan view that illustrates the enhanced in-plane rotational stiffness that may be attainable with the multi-axial integral geogrid of the present invention shown in FIG. 2.

[0072] FIG. 13 is a partial plan view that illustrates the various strand lengths of the multi-axial integral geogrid of the present invention shown in FIG. 2.

[0073] FIG. 14 is a partial plan view that illustrates the sole internal angle of confinement of the prior art integral geogrid shown in FIG. 1.

[0074] FIG. 15 is a partial plan view that illustrates the two internal angles of confinement of the multi-axial integral geogrid of the present invention shown in FIG. 2.

[0075] FIG. 16 is a partial plan view that illustrates the six confinement elements in a specific distance of the prior art integral geogrid shown in FIG. 1.

[0076] FIG. 17 is a partial plan view that illustrates the twelve confinement elements in the same specific distance of the multi-axial integral geogrid shown in FIG. 2.

[0077] FIG. 18 is a partial plan view that illustrates the eighteen angular nooks, all of the same angle, of the prior art integral geogrid shown in FIG. 1.

[0078] FIG. 19 is a partial plan view that illustrates the thirty angular nooks, of varied angles, of the multi-axial integral geogrid of the present invention shown in FIG. 2.

[0079] FIG. 20 is a partial perspective view that illustrates the floating nature of the inner hexagon of the multi-axial integral geogrid of the present invention shown in FIG. 2.

[0080] FIG. 21 is a partial plan view that illustrates the localized zones of lower compliance associated with individual strands or ribs of the prior art integral geogrid shown in FIG. 1.

[0081] FIG. 22 is a partial plan view that illustrates the localized zones of lower compliance associated with individual strands or ribs of the outer hexagon, and the repeating zones of high resilient compliance of the inner hexagon, of the multi-axial integral geogrid of the present invention shown in FIG. 2.

[0082] FIG. 23A is a series of three (3) photographs showing the test box, granular material and TriAx® geogrid used in the retention test for which results are reported in Table D, set forth hereinafter.

[0083] FIG. 23B is a series of three (3) photographs showing the test box, granular material and a specimen of the present invention, identified as the Lab 79, used in the retention test for which results are reported in Table D, set forth hereinafter.

[0084] FIG. 24 is a chart which plots the Rib Aspect Ratio against Surface Deformation after 10,000 passes in the multiple trafficking tests reported in Table E, set forth hereinafter.

[0085] FIG. 25A is a drawing illustrating how the apertures of the prior art geogrids are large enough for the selected aggregate particles to physically “fall into” the open spaces of the apertures.

[0086] FIG. 25B is a drawing illustrating how the geogrids of the present invention serve to retain the aggregate along the upper surface of the geogrid, in contrast to prior art geogrids.

[0087] FIG. 26A is a box plot of the results of the retention test for the TriAx® geogrids as shown in the photographs of FIG. 23A.

[0088] FIG. 26B is a box plot of the results of the retention tests for geogrids of the present invention, as shown in the photographs of FIG. 23B.

[0089] FIG. 27 is a reproduction of FIGS. 6 and 7 illustrating the nominally same hexagon “across the flats” (A/F) dimensions for the samples used in TEST 2 (Rutting) and the results reported in Table E.

[0090] FIG. 28 is another reproduction of FIGS. 6 and 7 illustrating measurements for the respective apertures of the samples used in TEST 2 (Rutting) and the results reported in Table E.

[0091] FIG. 29A is a schematic drawing illustrating the restricted out of plane upward movement of the inner hexagon within the outer hexagon according to the present invention.

[0092] FIG. 29B is a schematic drawing illustrating the restricted out of plane downward movement of the inner hexagon within the outer hexagon according to the present invention.

[0093] FIG. 30 is a drawing illustrating the approach of the Walsh HAR patents of matching the single size of the geogrid apertures to a relatively large granular particle size.

[0094] FIG. 31 is a graph illustrating typical grading curves for traditional commonly used granular materials.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0095] Although only preferred embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its scope to the details of construction and arrangement of components set forth in the following description or illustrated in the drawings. As described hereinafter, the present invention is capable of other embodiments and of being practiced or carried out in various ways.

[0096] Also, for the purposes of this specification, including the appended claims, certain terminology will be resorted to for the sake of clarity in describing the preferred embodiments. It is intended that each term contemplates its broadest meaning as understood by those skilled in the art, and includes all technical equivalents which operate in a similar manner to accomplish a similar purpose. As used herein, the terms “oriented”, “orientation”, and “highly oriented” as applied to the strands of the outer hexagon and the strands or ribs and tri-nodes of the inner hexagon, as well as the term “partially oriented” or “partial orientation” as applied to the junctions of the outer hexagon shall have the meanings well known to those skilled in the art in connection with the geogrids over the past many years. For example, the term “partially oriented” as applied to the junctions of the outer hexagon is readily apparent when compared to the strands of the outer hexagon and the strands or ribs and tri-nodes of the inner hexagon in that the junctions are considerably larger and thicker, as illustrated in the drawings herein.

[0097] As such, the level of orientation in the geogrid is that which can be observed by examining the geogrid to determine the extent to which the thickness of the geogrid has been narrowed or thinned from the corresponding thickness of the starting sheet caused by the stretching or orientating process, as well as by the striations which can be observed in the geogrid by visual (naked eye) examination or scanning electron microscope. Such terms are not intended to require determination of striation on a molecular level, such as for example, by microscopic examination of orientation of the polymer molecules.

[0098] And, for the purposes of this specification, including the appended claims, the term “about” when modifying numbers expressing a number of sizes, dimensions, portions, shapes, formulations, parameters, percentages, quantities, characteristics and other numerical values used in the specification and claims, the term is meant to encompass the stated value plus or minus 10%.

[0099] In addition, for the purposes of this specification, including the appended claims, the terms “aperture” and “opening” are used interchangeably herein, and the terms are meant to describe any of the plurality of open spaces located within the strands or ribs of the multi-axial integral geogrid.

[0100] The present invention is directed to a multi-axial integral geogrid structure produced from a polymer sheet as the starting material. According to a preferred embodiment of the invention, the polymer sheet starting material is substantially flat, and preferably uniplanar or substantially uniplanar.

[0101] The invention is based on the fact that the polymer sheet, when converted to a multi-axial integral geogrid via a starting sheet having a selected pattern of holes or depressions and oven stretching process, produces a finished product that has unique characteristics relative to prior uniaxial, biaxial, and triaxial geogrids for purposes of soil and other aggregate reinforcement and stabilization, and other geotechnical applications.

[0102] FIG. 1 is a plan view of an integral geogrid according to the prior art, i.e., a triaxial integral geogrid according to the Walsh '112 patent. As shown in FIG. 1, the triaxial integral geogrid 200 has a repeating triangle 210 geometry. The triaxial integral geogrid 200 includes a plurality of oriented strands 205 interconnected by partially oriented junctions 235 wherein the six triangular openings 210 surrounding each junction 235 create a repeating hexagon geometry.

[0103] FIG. 2 is a plan view of a monolayer multi-axial integral geogrid 100 according to a preferred embodiment of the present invention. The multi-axial integral geogrid 100 includes a plurality of interconnected, oriented strands having an array of openings therein, a repeating floating hexagon within a hexagon pattern of the interconnected, oriented strands and the openings, and including linear strands that extend continuously throughout an entirety of the multi-axial integral geogrid. More specifically, multi-axial integral geogrid 100 includes a repeating pattern of floating inner hexagons 130 within each outer hexagon 110. The outer hexagon 110 includes a plurality of outer oriented strands or ribs 120 interconnected by partially oriented junctions 115. The inner hexagon 130 includes a plurality of oriented connecting strands 145 and 150 interconnected by tri-nodes 135, and encompasses a hexagon-shaped center opening 170. The outer hexagon 110 is connected to the smaller inner hexagon 130 by a plurality of supporting strands or ribs 140 and 160, which define a plurality of trapezoid-shaped openings 180. At the center of each pattern of three adjacent outer hexagons 110 is a triangular shaped opening 190. As shown, junctions 115 are much larger than tri-nodes 135.

[0104] As is evident from FIG. 2, another feature of the multi-axial integral geogrid of the present invention is the linearly continuous nature of the outer strands 120 of the repeating outer hexagon pattern. That is, the oriented strands 120 are linearly continuous, via partially oriented junctions 115, as they extend continuously throughout the entirety of the multi-axial integral geogrid in three different directions separated from each other by approximately 120°, and indicated by arrows 120A, 120B, and 120C in FIGS. 4 and 5. Those skilled in the art will appreciate that different orientations of the same basic geometry are possible after stretching, if an appropriate corresponding rotation of the punched starting sheet geometry is made. The linearly continuous nature of the strands 120 provides the necessary enhanced strength and in-plane stiffness to the multi-axial integral geogrid of the present invention.

[0105] FIG. 3 is a perspective view of a starting monolayer material sheet 300 having holes or depressions formed therein for forming the multi-axial integral geogrid shown in FIG. 2. The monolayer starting sheet 300 used as the starting material for a multi-axial integral geogrid according to the present invention is preferably through-punched, although it may be possible to use depressions formed therein instead. According to the embodiment of the starting material in which depressions are formed in the sheet, the depressions are provided on each side of the sheet, i.e., on both the top and the bottom of the sheet.

[0106] The monolayer starting sheet 300 includes a repeating pattern 310 of holes 320 and spacing 330 that when oriented provide the floating hexagon within a hexagon pattern of the multi-axial integral geogrid shown in FIG. 2. According to one possible embodiment of the present invention, the diameter of holes 320 is 3.68 mm, and the spacing of the holes 330 in millimeters is as shown in FIG. 3A.

[0107] Preferably, the overall thickness of the monolayer material sheet 300 is from about 3 mm to about 10 mm and, more preferably, the overall thickness of the monolayer material sheet 300 is from about 5 mm to about 8 mm.

[0108] And, in general, the monolayer material sheet 300 is polymeric in nature. For example, the material of construction may include high molecular weight polyolefins, and broad specification polymers. Further, the polymeric materials may be virgin stock, or may be recycled materials, such as, for example, post-industrial or post-consumer recycled polymeric materials. According to the preferred embodiment of the invention, the high molecular weight polyolefin is a polypropylene.

[0109] FIG. 4 is a perspective view of the multi-axial integral geogrid 100 shown in FIG. 2, and FIG. 5 is an enlarged perspective view of the multi-axial integral geogrid 100 shown in FIG. 4. As is evident from FIGS. 4 and 5, the strands 120, 140, 145, 150, and 160 have what is known to one skilled in the art as a high aspect ratio, i.e., a ratio of the thickness or height of the strand cross section to the width of the strand cross section that is greater than 1.0 in accordance with the aforesaid Walsh HAR patents, U.S. Pat. Nos. 9,556,580, 10,024,002, and 10,501,896. While not absolutely necessary for the present invention, a high aspect ratio for the strands or ribs is preferred. Thus, the multi-axial integral geogrid of the present invention provides enhanced compatibility between geogrid and aggregate, which results in improved interlock, lateral restraint, and confinement of the aggregate.

[0110] FIG. 5A is an enlarged side schematic drawing illustrating a partial section of Rib A and adjoining junctions of an outer hexagon (See FIG. 13) which form or define a part of one of three linear strong axis strands that extend continuously throughout the geogrids of the present invention. These strong axis strands provide the necessary strength and in-plane stability of the geogrids when engaging with, confining and stabilizing aggregate in civil engineering applications. FIG. 5B is a similar enlarged side schematic drawing illustrating a partial section of Ribs B and D and adjacent tri-nodes of an inner hexagon. Typical thicknesses for each of these components in accordance with the present invention are set forth in FIGS. 5A and 5B.

[0111] FIG. 6 is a partial plan view that illustrates certain structural limitations of the prior art triaxial integral geogrid shown in FIG. 1. The repeating geometric element of the conventional triaxial integral geogrid 200 has one basic opening shape—a triangle—one limiting strand dimension, and a high ratio of junctions to connecting strands, one to three. As such, the conventional triaxial integral geogrid 200 provides no variation in either opening shape or size and a single confinement angle of 60°.

[0112] FIG. 7 is another plan view that illustrates structural attributes of the multi-axial integral geogrid 100 as shown in FIG. 2. Again, while the prior triangular integral geogrid 200 shown in FIG. 1 has only one basic shape and one limiting strand dimension, the multi-axial integral geogrid 100 leverages three different basic opening shapes—a hexagon 110, a trapezoid 180, and a triangle 190—varying strand sizes, and two different internal confinement angles—60° and 120°. Further, the multi-axial integral geogrid 100 includes only one junction per six connecting strands, and has three strands associated with each tri-node. As such, the multi-axial integral geogrid 100 can better accommodate varying angles and orientation of aggregate as it is distributed across the geogrid.

[0113] FIG. 8 is a graph that illustrates the range of distribution of individual aperture area in a prior art triangular integral geogrid 200 of the type shown in FIG. 1. More specifically, FIG. 8 shows the distribution of individual aperture area associated with a triaxial integral geogrid commercially available from Tensar as a TriAx® TX160® geogrid. As is evident from FIG. 8, the individual aperture area associated with a conventional triaxial integral geogrid is relatively limited, providing a range of distribution of individual aperture area only from about 775 mm.sup.2 to about 850 mm.sup.2, or a range of only about 75 mm.sup.2.

[0114] FIG. 9 is a graph that illustrates the range of distribution of individual aperture area in another prior art triangular integral geogrid 200 of the type shown in FIG. 1. More specifically, FIG. 9 shows the distribution of individual aperture area associated with a triaxial integral geogrid commercially available from Tensar as a TriAx® TX130S® geogrid. As is evident from FIG. 9, the individual aperture area associated with this conventional triaxial integral geogrid is also relatively limited, providing a range of distribution of individual aperture area only from about 475 mm.sup.2 to about 550 mm.sup.2, or a range of only about 75 mm.sup.2.

[0115] In contrast, FIG. 10 is a graph that illustrates the enhanced range of distribution of individual aperture area that may be attainable with the multi-axial integral geogrid 100 of the present invention shown in FIG. 2. As is evident from FIG. 10, the range or distribution of individual aperture area associated with the multi-axial integral geogrid 100 is substantially greater than that provided by the triaxial integral geogrid, with the wider distribution of individual aperture area from about 475 mm.sup.2 to about 800 mm.sup.2 providing more optimal interaction with granular materials of varying particle size, and especially pronounced between from about 500 mm.sup.2 to about 700 mm.sup.2, or a range of at least 200 mm.sup.2.

[0116] FIG. 11 is a plan view that illustrates the in-plane rotational stiffness of the prior art triaxial integral geogrid 200 shown in FIG. 1. As is evident from FIG. 11, the prior art integral geogrid 200 has a partially oriented junction 235 that connects oriented strands 205, with each of the strands 205 having approximately the same length.

[0117] In contrast, FIG. 12 is a partial plan view that illustrates the enhanced in-plane rotational stiffness that may be attainable with the multi-axial integral geogrid 100 of the present invention shown in FIG. 2. Again, the multi-axial integral geogrid 100 includes the preferred repeating floating hexagon within a hexagon pattern having an outer hexagon 110 and a smaller inner hexagon 130. The outer hexagon 110 includes a plurality of oriented strands 120 interconnected by partially oriented junctions 115. The inner hexagon 130 includes a plurality of oriented strands 145 and 150 interconnected by tri-nodes 135. The outer hexagon 110 is connected to the inner hexagon 130 by a plurality of oriented supporting or connecting strands 140 and 160. By virtue of the shorter length of oriented strands 140, 145, 150, and 160 relative to the length of strands 205, the multi-axial integral geogrid 100 has increased in-plane rotational stiffness.

[0118] FIG. 13 is a partial plan view that illustrates the various strands of the multi-axial integral geogrid shown in FIG. 2. The multi-axial integral geogrid 100 includes a repeating floating hexagon within a hexagon pattern having an outer hexagon 110 and a smaller inner hexagon 130. The outer hexagon 110 includes a plurality of oriented strands 120 (also designated by “A” in FIG. 13) interconnected by partially oriented junctions 115. The inner hexagon 130 includes a plurality of oriented strands 145 (“B”) and 150 (“D”) interconnected by oriented tri-nodes 135. The outer hexagon 110 is connected to the inner hexagon 130 by a plurality of oriented supporting strands 140 (“C”) and 160 (“E”). (The designations A, B, C, D, and E for the various strands are employed in the data of Tables A, B and E, presented hereinafter.)

[0119] According to one embodiment of the invention, the four strands 150 (D) and the two strands 160 (E) are the widest (thickest side-to-side) and the four strands 140 (C) are the tallest, all of which provides for strength and stiffness. The two strands 145 (B) are the thinnest, which provides for out-of-plane flexibility. The strands 120 (A) are representative of TX160® strands, and these strands are neither the tallest nor the widest, neither the strongest nor the most flexible, and as such they are middle ground and inadaptable without the presence of strands B, C, D, and E. Thus, FIG. 13 illustrates the impact of multiple strand dimensions on strength and stiffness. Other embodiments and dimensional relationships will readily occur to those skilled in the art.

[0120] Table A presents the height, width, and aspect ratio of each of the various strands for one example of the multi-axial geogrid 100 of the present invention as illustrated in FIG. 13. While the values presented in Table A are representative of the height, width, and aspect ratio that may be associated with the multi-axial geogrid 100 of the present invention, they are presented for purposes of illustration, without intending to be limiting of the scope of the invention.

TABLE-US-00001 TABLE A Strand Height (mm) Width (mm) Aspect Ratio A 2.86 1.12 2.55 B 2.05 1.10 1.86 C 3.16 1.11 2.84 D 3.13 1.32 2.37 E 2.63 1.29 2.03

[0121] Table B presents a comparison of aspect ratios associated with the various strands of the multi-axial integral geogrid 100 of the present invention with the aspect ratio of various commercial triaxial integral geogrids commercialized by Tensar.

TABLE-US-00002 TABLE B Strand Invention TX160 ® TX180 ™ TX130S ® A 2.55 1.47 1.62 1.85 B 1.86 — — — C 2.84 — — — D 2.37 — — — E 2.03 — — — Average rib 2.33 1.47 1.62 1.85 aspect ratio

[0122] As is evident from Table B, the multi-axial integral geogrid 100 has a higher aspect ratio on all strands compared to each of the conventional triaxial integral geogrids. Combined with the other features of the present invention's geometry, this higher aspect ratio provides better performance than the triaxial geogrids of the Walsh HAR patents.

[0123] Broad ranges and preferred parameters for the multi-axial geogrid according to the present invention as shown in FIGS. 13 and 15 are as follows.

[0124] Rib A has a height within a broad range of from 1 mm to 4 mm, a preferred range of from 2 mm to 3 mm, and a preferred dimension of 2.86 mm. The Rib A width has a broad range of from 0.75 mm to 3 mm, a preferred range of from 1 mm to 2 mm, and a preferred dimension of 1.6 mm. The Rib A length has a broad range of from 30 mm to 45 mm, a preferred range of from 35 mm to 40 mm, and a preferred dimension of 37 mm. The Rib A aspect ratio has a broad range of from 1:1 to 3:1, a preferred range of from 1.5:1 to 1.8:1, and a preferred value of 1.7:1.

[0125] The Rib B height has a broad range of from 1 mm to 3 mm, a preferred range of from 1.5 mm to 2.5 mm, and a preferred dimension of 1.6 mm. The Rib B width has a broad range of from 0.75 mm to 3.5 mm, a preferred range of from 1 mm to 3 mm, and a preferred dimension of 1.8 mm. The Rib B length has a broad range of from 15 mm to 25 mm, a preferred range of from 18 mm to 22 mm, and a preferred dimension of 21 mm. The Rib B aspect ratio has a broad range of from 0.75:1 to 2:1, a preferred range of from 1.2:1 to 1.4:1, and a preferred value of 1.3:1.

[0126] The Rib C height has a broad range of from 1 mm to 4 mm, a preferred range of from 2 mm to 3 mm, and a preferred dimension of 2.7 mm. The Rib C width has a broad range of from 0.75 mm to 3.5 mm, a preferred range of from 1 mm to 2.5 mm, and a preferred dimension of 1.6 mm. The Rib C length has a broad range of from 15 mm to 30 mm, a preferred range of from 20 mm to 25 mm, and a preferred dimension of 23 mm. The Rib C aspect ratio has a broad range of from 1:1 to 3:1, a preferred range of from 1.5:1 to 2.5:1, and a preferred value of 1.7:1.

[0127] The Rib D height has a broad range of from 1.5 mm to 4 mm, a preferred range of from 2 mm to 3.5 mm, and a preferred dimension of 2.3 mm. The Rib D width has a broad range of from 1 mm to 4 mm, a preferred range of from 1.5 mm to 2.5 mm, and a preferred dimension of 1.5 mm. The Rib D length has a broad range of from 10 mm to 30 mm, a preferred range of from 15 mm to 25 mm, and a preferred dimension of 18 mm. The Rib D aspect ratio has a broad range of from 1:1 to 3:1, a preferred range of from 1.4:1 to 1.7:1, and a preferred value of 1.6:1.

[0128] The Rib E height has a broad range of from 1 mm to 4 mm, a preferred range of from 1.5 mm to 3.0 mm, and a preferred dimension of 1.9 mm. The Rib E width has a broad range of from 0.75 mm to 3.5 mm, a preferred range of from 1 mm to 3 mm, and a preferred dimension of 1.7 mm. The Rib E length has a broad range of from 15 mm to 30 mm, a preferred range of from 20 mm to 25 mm, and a preferred dimension of 22 mm. The Rib E aspect ratio has a broad range of from 0.75:1 to 2:1, a preferred range of from 1:1 to 1.5:1, and a preferred value of 1.3:1.

[0129] And, as shown in FIG. 5A, the outer hexagon 110 of the multi-axial integral geogrid 100 has a partially oriented junction 115 thickness (dimension “TO2”) having a broad range of from 3 mm to 9 mm, a preferred range of from 4.5 mm to 7.5 mm, and a preferred dimension of about 5.6 mm, and a strand or rib 120 thickness (dimension “TO1”) having a broad range of from 1 mm to 5 mm, a preferred range of from 1.5 mm to 3.5 mm, and a preferred dimension of about 2.8 mm.

[0130] In addition, as shown in FIG. 5B, the inner hexagon 130 of the integral geogrid 100 has a tri-node 135 thickness (dimension “TI1”) and a strand or rib 145 thickness (also dimension “TI1”) and a strand or rib 150 thickness (also dimension “TI1”) having a broad range of from 1 mm to 5 mm, and a preferred range of from 1.5 mm to 3.5 mm.

[0131] According to one preferred embodiment of the multi-axial integral geogrid shown in FIG. 13, the “across the flats” dimension, i.e., the distance from one junction 115 of the outer hexagon (see FIG. 15) to the opposite junction 115 of the outer hexagon, is about 80 mm. And, for the same embodiment, the across the flats dimension, i.e., the distance from one tri-node 135 of the inner hexagon (see FIG. 15) to the opposite tri-node 135 of the inner hexagon, is about 33 mm.

[0132] The punch size/diameter has a broad range of from 2 mm to 7 mm, a preferred range of from 3 mm to 5 mm, and a preferred dimension of 3.68 mm. The major pitch in the first stretch direction has a broad range of from 5 mm to 9 mm, a preferred range of from 6 mm to 8 mm, and preferred dimension of 6.7088 mm. The minor pitch in the first stretch direction has a broad range of from 1 mm to 4 mm, a preferred range of from 2 mm to 3 mm, and a preferred dimension of 2.58 mm. The second major/minor pitch in the first stretch direction has a broad range of from 4 mm to 8 mm, a preferred range of from 5 mm to 7 mm, and a preferred dimension of 5.934 mm. The major pitch in the second stretch direction has a broad range of from 4 mm to 8 mm, a preferred range of from 5 mm to 7 mm, and a preferred dimension of 6.192 mm.

[0133] FIG. 14 is a partial plan view that illustrates the sole internal angle of confinement of the prior art triangular integral geogrid 200 shown in FIG. 1. As is evident, the integral geogrid 200 has a single internal angle of confinement, i.e., an angle of about 60°. That is, about each junction 235, the integral geogrid 200 has a total of six 60° angles of confinement. And, the integral geogrid 200 has a total of eighteen 60° confinement angles within the boundaries of a single hexagon. (The designation A shown in FIG. 14 is for the strand/rib of the prior art TriAx® geogrids employed in the data of Table E, presented hereinafter.)

[0134] FIG. 15 is a partial plan view that illustrates the two different internal angles of confinement of the multi-axial integral geogrid 100 of the present invention shown in FIG. 2. Advantageously, by virtue of the geometry having inner hexagon 130 supported within outer hexagon 110, and the five different strand types A, B, C, D, and E, the multi-axial integral geogrid 100 has a combination of 60° and 120° internal angles. That is, about junction 115 there are six 60° angles of confinement, and about tri-nodes 135 there are three 120° angles of confinement. And, the multi-axial integral geogrid 100 has a total of thirty confinement angles within the boundaries of a single outer hexagon 110. Thus, across its range of apertures, the multi-axial integral geogrid 100 provides two angles of confinement, leading to enhanced aggregate confinement.

[0135] Table C below presents a comparison of node orientation, tensile element orientation, open area, and average aperture open area that may be attainable with the multi-axial integral geogrid 100 of the present invention with those features of various prior art triaxial integral geogrids.

TABLE-US-00003 TABLE C Invention TX160 ® TX130S ® Partially oriented 384 480 720 junctions per m.sup.2 (measured and extrapolated) Oriented tensile 2224 1424 2336 elements per m.sup.2 (measured and extrapolated) Angles of 5713 3015 5096 confinement per m.sup.2 Open Area 85% 85% 87%

[0136] As evident from Table C, when compared to TX160®, the multi-axial integral geogrid 100 of the present invention has 20% less partially oriented junctions 115 and 56% more oriented tensile elements 120, 140, 145, 150, 160 per square meter, thus providing both a significantly higher number of physical elements for aggregate particles to bear against, be confined by and interact with per unit area, and providing a significantly lower number of physical elements per unit area, i.e., partially oriented junctions, that contribute less to the geogrid's ability to engage, confine and stabilize the aggregate. Further, when compared to TX130S®, the multi-axial integral geogrid 100 of the present invention has 47% less partially oriented junctions 115 per square meter, and nearly the same amount of oriented tensile elements 120, 140, 145, 150, 160 per square meter, but a higher number of angles of confinement. These features thus provide a high number of physical elements for aggregate particles to bear against, be combined by and interact with per unit area, but with a significantly lower number of physical elements per unit area that contribute less to the geogrid's ability to engage and stabilize the aggregate.

[0137] FIG. 16 is a partial plan view that illustrates the six confinement elements in a specific distance of the prior art triangular integral geogrid 200 shown in FIG. 1. Per FIG. 16, the prior art integral geogrid 200 has six bearing elements, i.e., the six strands 205 that surround junction 235.

[0138] FIG. 17 is a partial plan view that illustrates the twelve confinement elements in the same specific distance of the multi-axial integral geogrid 100 of the present invention shown in FIG. 2. As is evident from FIG. 17, the multi-axial integral geogrid 100 has twelve bearing (confining) elements, i.e., the six strands 120 that form outer hexagon 110, and the six strands that form inner hexagon 130, i.e., the two strands 145 and the four strands 150. That is, in a like-for-like hexagon size with similar “across the flats” distance, the multi-axial integral geogrid 100 provides twice as many confinement elements to bear against radial loading motion during compaction and trafficking. Thus, the multi-axial integral geogrid 100 provides twice as many elements that provide concentric-like resistance to aggregate movement.

[0139] FIG. 18 is a partial plan view that illustrates the eighteen angular nooks, all of the same angle, of the prior art integral geogrid 200 shown in FIG. 1. As noted above, the integral geogrid 200 has a single internal angle of confinement, i.e., an angle of about 60°. That is, about each junction 235, the integral geogrid 200 has a total of six 60° angles of confinement, or nooks. And, the integral geogrid 200 has a total of eighteen 60° confinement angles or nooks within the boundaries of a single hexagon.

[0140] FIG. 19 is a partial plan view that illustrates the thirty angular nooks, of varied angles, of the multi-axial integral geogrid 100 of the present invention shown in FIG. 2. As noted above, by virtue of the geometry having inner hexagon 130 supported within outer hexagon 110, and the five different strand types A, B, C, D, and E, the multi-axial integral geogrid 100 has a combination of 60° and 120° internal angles. That is, about each junction 115 there are six 60° angles of confinement or nooks, and about each tri-node 135 there are three 120° angles of confinement or nooks. And, the multi-axial integral geogrid 100 has a total of thirty confinement angles or nooks within the boundaries of a single outer hexagon 110. Thus, across its range of apertures, the multi-axial integral geogrid 100 provides thirty independent (or unique) confinement angles or nooks, with two different internal angles of confinement, this combination of features leading to enhanced aggregate confinement.

[0141] FIG. 20 is a partial perspective view that illustrates the preferred floating nature of the inner hexagon 130 of the multi-axial integral geogrid of the present invention shown in FIG. 2. The invention incorporates a resilient (or suspended) and adaptable inner hexagon 130, which better accommodates aggregate during compaction by varying “out of plane” stiffness. The floating inner hexagon is relatively movable in the vertical Z-axis dimension and as such allows a meaningful degree of compliance or deflection during compaction.

[0142] In a preferred embodiment of the invention, this vertical compliance or deflection of the inner hexagon 130 can be as much as about 33% of the greatest thickness of the surrounding outer hexagon 110. In other words, if the thickness of the partially oriented junctions (which is the thickest component of the outer hexagon) is 6 mm, the out of plane compliance, or deflection, of the floating inner hexagon 140 can be as much as about 2 mm. This resilient (or suspended) compliance extends over the entire area bounded by each outer hexagon 110, the outer hexagon having a lesser degree of vertical compliance. It has been surprisingly discovered that this enhanced resilient (or suspended) compliance or deflection of the inner hexagon enhances the ability of the geogrid 100 of the present invention to interlock with the aggregate.

[0143] As shown in FIG. 29A, the inner hexagon 130 of integral geogrid 100 is capable of flexing (i.e., floating or deforming) upwardly, i.e., outwardly away from the plane of the outer hexagon 110, to an extent that a distance “D” is equal to about 33% of the overall thickness of the surrounding outer hexagon 110 (with the overall thickness of outer hexagon 110 being essentially the thickness of junctions 115). Correspondingly, as shown in FIG. 29B, the inner hexagon 130 of integral geogrid 100 is capable of flexing (i.e., floating or deforming) downwardly, i.e., outwardly away from the plane of the outer hexagon 110, to an extent that a distance “D” is equal to about 33% of the overall thickness of the surrounding outer hexagon 110.

[0144] Moreover, the tendency for this resilient (or suspended) and adaptable inner hexagon 130 to sit above the subgrade and even to deflect further vertically upward if the subgrade is uneven provides the opportunity for improved lateral restraint and impedes aggregate from rolling over the strands 140, 145, 150, 160 when subjected to repeated loading, with the outer hexagon 110 creating a second ring of confinement for aggregate to have to pass over. A conventional prior art multi-axial geogrid, like geogrid 200, lacks this level of resilient (or suspended) compliance, and as such provides only one level of confinement.

[0145] FIG. 21 is a partial plan view that illustrates the localized zones of lower compliance associated with individual strands or ribs 205 of the prior art integral geogrid 200 shown in FIG. 1. That is, because the individual strands or ribs 205 connect the partially oriented junctions 235, the prior art integral geogrid 200 has numerous localized zones of lower compliance, and thus minimal resiliency.

[0146] FIG. 22 is a partial plan view that illustrates the localized zones of lower compliance associated with individual strands or ribs 120 of the outer hexagon 110, and the repeating zones of high resilient compliance of the inner hexagon 130, of the multi-axial integral geogrid 100 of the present invention shown in FIG. 2. By virtue of the ability of the floating inner hexagon 130 to deflect vertically within outer hexagon 110, the multi-axial geogrid 100 has a repeating zone of high resilient compliance within each of the corresponding outer hexagons 110.

[0147] To repeat, as illustrated in FIG. 21, a conventional prior art tri-axial geogrid lacks the level of compliance over such a large area that characterizes the multi-axial integral geogrid of the present invention. As such, any compliance associated with the prior art triaxial geogrid is restricted to individual ribs which are constrained by the junctions located at either end. In contrast, per unit area, the geogrid of the present invention has an area of significant vertical resilient (or suspended) compliance in the order of about 50% to about 75% as shown in FIG. 22. This contrasts with a conventional prior art multi-axial geogrid, as shown in FIG. 21, which has no such zones of significant vertical compliance.

[0148] In one aspect of the present invention, the geogrid 100 represents a horizontal mechanically stabilizing geogrid. The repeating pattern of outer hexagons 110 including a plurality of outer oriented strands or ribs 120 interconnected by partially oriented junctions 115 comprise strong axis strands which extend continuously in a linear path throughout the geogrid as indicated by lines 120A, 120B, and 120C in FIG. 4. As will be noted from FIG. 4, the strong axis strands formed by outer oriented strand or ribs 120 interconnected by partially oriented junctions 115, as indicated by lines 120A, 120B and 120C in the FIG. 4, extend continuously throughout the entirety of the geogrid without intersecting inside an outer hexagon. This feature provides the necessary strength and stability for the geogrids of the present invention. In another aspect, the ribs 140, 160 which extend inwardly from the partially oriented junctions 115 and connect with the tri-nodes 135 of the floating inner hexagon 145, or other geometric configuration described hereinafter, which is supported by such ribs comprise “engineered discontinuities” or “floating engineered discontinuities”.

[0149] The invention also relates to a method of making the above-described multi-axial integral geogrid 100. The method includes providing a polymer sheet 300; providing a patterned plurality of holes or depressions 310 in the polymer sheet 300; and orienting the polymer sheet 300 having the patterned plurality of holes or depressions 310 therein to provide a plurality of interconnected, oriented strands 120, 140, 145, 150, and 160 having an array of openings 170, 180, and 190 therein, a repeating floating hexagon 130 within an outer hexagon 110 pattern of the interconnected, oriented strands and the openings, including three linear strands that extend continuously throughout the entirety of the multi-axial integral geogrid 100.

[0150] In general, once the polymer sheet 300 has been prepared with holes or depressions, the multi-axial integral geogrid 100 can be produced from the sheet 300 according to the methods described in the above-identified prior art patents and known to those skilled in the art.

[0151] As indicated above, the hexagonal geometric shape of the outer hexagon 110 and smaller inner hexagon 130 are a preferred embodiment for providing the floating geometric configuration of the present invention. However, other geometric shapes are possible within the scope of the present invention. For example, the geometric shapes could be rectangular or square with four supporting or connecting strands connecting each inner corner of the outer rectangle or square to the corresponding outer corner of the smaller inner rectangle or square. Or, the geometric shapes could be triangular with only three supporting or connecting strands between adjacent inner corners of the outer triangle and outer corners of the smaller inner triangle. Other polygon shapes are also contemplated within the scope of the present invention.

[0152] In the rectangular or square embodiment of the present invention, described in the preceding paragraph, there would preferably be two linear strands defined by interconnected oriented strands and partially oriented junctions that extend continuously throughout the entirety of the geogrid for each outer rectangle or square, such continuous strands extending at an angle of approximately 90° from each other. In the triangular embodiment, there would preferably be three such linear strands for each outer triangle which extend from each other by approximately 120°, similar to linear strands 120 of the preferred hexagon embodiment described in detail herein.

[0153] Also, different geometric shapes could be possible without departing from the present invention. For example, the inner geometric shape could be a circular ring supported within the preferred outer hexagon shape with six supporting strands similar to the preferred embodiment disclosed herein. Thus, it is intended that the geometric shapes of the outer repeating structure and the inner or interior floating structure not be limited to identical geometric forms.

[0154] As described above and illustrated in the accompanying drawings, the geogrid embodiments disclosed herein comprise a monolayer structure; therefore, the composition of the starting sheet 300 illustrated in and described in the connection with FIG. 3 is comprised of a single polymer or copolymer.

[0155] While the preferred embodiment of the integral geogrid 100 has been described above with the outer hexagons 110 surrounding and supporting smaller floating inner hexagons 130, the present invention also contemplates that the outer hexagons 110 can surround and support smaller inner hexagons 130 which do not float or flex (deform), but rather remain in the plane of the geogrid. Therefore, in accordance with the present invention, the integral geogrids 100 shown in FIGS. 2, 4 and 5, and made with the starting sheet material shown in FIG. 3, can be made to have smaller inner hexagons which do not float or flex. Thus, the repeating hexagon within a hexagon pattern of the present invention is the same whether the inner hexagon 130 is able to float or not.

[0156] Lastly, it is clearly preferred that each of the outer hexagons 110 of the multi-axial integral geogrid 100 include the floating hexagon 130 within its interior thereof as disclosed in this application. On the other hand, it is possible by changing some individual punch patterns, or otherwise, to produce a multi-axial integral geogrid in which the hexagons 130 are surrounded and supported in only a portion of the outer hexagons 110, and the other outer hexagons support a different interior structure, such as included in the prior art, without departing from the scope and intent of the present invention. So long as such modified integral geogrid includes one or more outer hexagons 110 which surround and support a floating or non-floating smaller inner hexagon 130, and define the requisite arrays of substantially parallel linear strands that extend continuously throughout the entirety of the geogrid, i.e., strong axis strands in accordance with the disclosure contained herein, it is presently believed that such modified integral geogrid falls within the scope of the present invention.

[0157] As indicated in the “Related Art” section above, prior art geogrids utilize the concept of having apertures that are large enough to cause most of the aggregate particles to physically “fall into” the open space of the apertures. The geogrid then provides benefit by laterally constraining these particles as/when load is applied from above. As load is applied from above, the aggregate particles try to move down and out (laterally), and the geogrid prevents both from happening. As such, the fundamental premise of the prior art geogrids is that the aggregate particles need to “strike through” or “penetrate” the apertures. This strike through concept of the prior art is confirmed by the Walsh HAR patents whereby the high aspect ratio concept of tall/thin ribs to promote “confinement” provides even better resistance to the lateral spreading of the aggregate.

[0158] In contrast, the present invention has converted every other junction along the non-continuous strands into an open hexagon or other open geometric configuration. This unique configuration generates at least two meaningful changes. First, the present invention has created an aperture structure where a junction was present thereby introducing a “confining element” where there was a “non-confining element”. In the preferred embodiment, the aperture formed by the inner hexagon includes the creation of six ribs that form the hexagon, and these ribs are now available to interact with and support the aggregate, whereas the replaced junction is only a “point of connection” for the geogrid itself. Second, the present invention has reduced the aperture size for the six (6) trapezoidal apertures shown in FIGS. 2 and 17, as compared to the triangular apertures of the triaxial geogrids shown in FIGS. 1 and 16, to better retain and confine a wider range of aggregate sizes and quality.

[0159] As such, it has been surprisingly discovered that the “goal” of an improved geogrid in accordance with the present invention is not to have most the aggregate particles fall into the apertures, as previously embodied in the prior art. Rather, as demonstrated by the test results reported hereinafter, the geogrid configurations of the present invention create more functional elements in the geogrid per unit area than with the prior art structures (see Table C above), and it is a goal of the present invention not to have particles fall through the apertures but rather to have more of the aggregate particles partially penetrate into more apertures. This surprisingly new interaction between the geogrid and the aggregate particles to be confined therein for the present invention versus the prior art is illustrated by the comparative drawings of FIGS. 25A and 25B.

[0160] The foregoing surprising discoveries are demonstrated by the following tests and results therefrom.

TEST METHODS FOR EXAMPLES

Test 1—Retention

[0161] The performance of a multi-axial geogrid for improving interaction with a granular material was evaluated using a small scale test to simulate granular material being “cascaded” onto the geogrid following the installation methods outlined in published guidance (e.g., “Tensar Installation Guideline IG/TriAx,” Oct. 19, 2020). This small scale test comprises an open box on which a specimen of geogrid approximately 350 mm×350 mm is clamped above the open box. Then 2 kg of granular material graded to between 20 mm and 40 mm particle size is cascaded across the geogrid by a “brushing” action. A 20 mm to 40 mm particle grading is experimentally representative of a grading commonly used in constructing civil engineering structures, while removing excess variability associated with smaller or larger particle sizes. For each test, measurement is taken of the amount of granular material “captured” by the geogrid and the amount of granular material falling through the geogrid into the box below. A comparison is made of the two results. A geogrid better designed to “capture” the granular material will retain more granular material on the geogrid and allow much less material to fall into the open box beneath the geogrid specimen. Typical comparison is made on the basis of 10 repeated tests for each geogrid type, using the same 2 kg batch of granular material.

Test 2—Rutting

[0162] The performance of a multi-axial geogrid for resisting rutting due to vehicle traffic was evaluated using a small scale test to simulate well-established field tests such as the one described in Webster, S. L.; “Geogrid Reinforced Base Course for Flexible Pavements for Light Aircraft: Test Section Construction, Behavior Under Traffic, Laboratory Tests, and Design Criterial,” Report DOT/FAA/RD-92, December 1992. The small scale test was designed to reproduce the results of well-established field tests for traffic performance of multi-axial geogrids and comprises a test section consisting of an underlying clay subgrade, a single layer of geogrid, and a compacted granular sub base. The test section is subjected to the load of a single weighted wheel. The wheel traverses the test section along a single horizontal path, constantly reversing direction from one end of the test section to the other. A control test with no geogrid present will fail rapidly under such testing. For example, after 1000 passes or less of the wheel on an unreinforced test section, a deep rut will be formed. By using properly designed multi-axial geogrids as reinforcement, decreased amounts of rutting depth will occur for a given number of wheel passes compared to the unreinforced test section. This decreased rut depth has an impact on the lifetime of the civil engineering structure and can extend this lifetime by factors of up to 50 times that of an unreinforced structure. Hence, a roadway or other civil engineering structure reinforced in accordance with the present invention will have increased longevity and decreased maintenance requirements.

[0163] The aforesaid small scale test used in connection with the present invention is the same small scale test as described in the Walsh HAR patents (See U.S. Pat. No. 10,501,896, at col. 10, lines 43-67) and which generated the data reported therein.

Example—Test 1 (Retention)

[0164] The performance of a multi-axial geogrid for improving interaction with a granular material was evaluated using a small scale test to simulate granular material being “cascaded” onto the geogrid following the installation methods outlined in published guidance.

[0165] A sample of a commercially available prior art TriAx® geogrid (see FIG. 23A) had a 2000 g batch of granular material, graded between 20 mm and 40 mm particle size, cascaded across its surface. The material falling through the geogrid into the box below was weighed, as was the material retained upon the geogrid. This test was repeated 10 times for the same specimen and the same 2000 g batch of granular material was used in each repetition.

[0166] This experiment was then repeated for a specimen of the present invention, identified as Lab 79 (see FIG. 23B). Lab 79 was made from the same sheet material recipe as the prior art TriAx® geogrid already tested. The same 2000 g batch of granular material was used for assessing Lab 79 that was used to assess the prior art TriAx® geogrid.

[0167] The results are shown in Table D below:

TABLE-US-00004 TABLE D Mass of Granular Material Mass of Granular Material Passing Through Geogrid, grams Retained on Geogrid, grams Prior Art Invention Prior Art Invention TriAx ® Lab 79 TriAx ® Lab 79 1732 47 268 1953 1659 136 341 1864 1698 68 302 1932 1702 98 298 1902 1814 42 186 1958 1758 103 242 1897 1690 53 310 1947 1682 79 318 1921 1712 76 288 1924 1770 73 230 1927 86% passed 4% passed Retained 14% Retained 96% through through on average on average on average on average

[0168] The results shown in Table D above indicate that the combined effect of all the geometrical elements of the multiaxial geogrid of the present invention greatly improve its ability to interact with the same granular material when compared to the prior art multi-axial geogrid. While the prior art geogrid only retained or captured 14% of the material cascaded across its surface with the remaining 86% falling through the geogrid, the geogrid of the present invention captures 96% of the granular material, with only 4% falling through. This very large improvement in the ability of the geogrids according to the present invention to interact with granular material is beneficial in improving resistance to rutting in trafficking testing.

[0169] The test results reported in Table D are also shown in the Box Plots shown in FIGS. 26A and 26B. As can be seen in FIG. 26A, a very large proportion of the 2000 g batch of granular material, as indicated by the test plots at 501, passed through the TriAx® geogrid, and only a small proportion, as indicated by the plot test at 502, was retained on the geogrid. In dramatic contrast, as shown in FIG. 26B, only a small proportion of the same 2000 g batch of granular material passed through the geogrid of the present invention, as indicated by the test plots at 503, whereas almost all of the aggregate was retained, as indicated by the test plot at 504.

[0170] In accordance with the present invention, it has been surprisingly discovered that the ability of the geogrid “to retain” the aggregate in a standard retention test is a better predictor than the “strike through/penetration” concept employed by the prior art. More specifically, it is believed at the present time that for any particular aggregate a retention by the geogrid of at least 50% in the aforedescribed retention test should predict an effective geogrid in a composite structure comprising that tested geogrid and tested aggregate. More preferably, the retention test should show greater than 75% retention, and more preferably at least 90% or more.

Example—Test 2 (Rutting)

[0171] The performance of a multi-axial geogrid for resisting rutting due to vehicle traffic was evaluated using a small scale test to simulate well-established field tests.

[0172] Trafficking tests were carried out for the specimens shown in Table E below. This table shows data for eight (8) tests of the preferred floating hexagon within a hexagon geometry that is the subject of the present invention, and eighteen (18) tests for the prior art Walsh HAR patents geometry. The specimens were made from these same polymer material (polypropylene), the same punch pattern (except an additional punch was utilized for the specimens of the present invention in order to form the inner hexagon, and a range of similar starting sheet thickness, that produced geogrid samples having nominally the same hexagon across the flats (A/F) dimension, as illustrated in FIG. 27, which are duplicates of the prior Walsh HAR patents geogrid shown in FIG. 6 (prior art) and the geogrid of the present invention shown in FIG. 7. FIG. 6 (prior art) and 7 are reproduced again in FIG. 28 to set forth the dimensions of the apertures within the respective outer hexagons. In the FIG. 6 (prior art) samples, Dimensions A, B, and C=33 mm+/−3 mm, and in the invention samples: Dimension A=35 mm+/−3 mm; Dimension B=24 mm+/−3 mm; and Dimension C=30 mm+/−3 mm. The prior art specimens have rib aspect ratios that exceed well beyond those of the specimens that are made in accordance with the present invention. In Table E, Rib A shown in FIGS. 13 and 14 is used for comparison.

TABLE-US-00005 TABLE E Starting Av. surface Final Sheet Actual Rib Actual Rib defm. For last Final pattern Aperture size thickness width height Rib aspect 500 passes description (mm AF) (mm) (mm) (mm) ratio (mm) Invention 80 4.6 1.23 1.77 1.45 29.9 Invention 80 4.6 1.23 1.77 1.45 38.6 Invention 80 4.6 1.23 1.77 1.45 39.5 Invention 81 5.45 1.14 1.75 1.57 30.5 Invention 76 6.3 1.07 2.82 2.63 22.1 Invention 76 6.3 1.07 2.82 2.63 28.3 Invention 77 6.3 1.14 2.8 2.47 22.1 Invention 80 7.5 1.49 2.94 2.12 26.9 Prior Art 77 3 2.54 0.72 0.28 48.3 Multi-axial Prior Art 80 3 1.08 0.87 0.81 51.9 Multi-axial Prior Art 80 4.55 1.06 1.56 1.47 41.0 Multi-axial Prior Art 80 4.55 1.06 1.56 1.47 43.2 Multi-axial Prior Art 80 4.55 0.73 1.74 2.38 46.4 Multi-axial Prior Art 80 4.55 0.66 1.97 2.98 41.7 Multi-axial Prior Art 81 4.55 1.06 1.56 1.47 42.9 Multi-axial Prior Art 81 4.55 1.06 1.56 1.47 46.1 Multi-axial Prior Art 81 4.55 1.62 1.39 0.86 43.7 Multi-axial Prior Art 79 6.3 0.69 2.82 4.09 49.9 Multi-axial Prior Art 80 6.3 0.72 2.68 3.72 37.2 Multi-axial Prior Art 80 6.45 1.3 2.1 1.62 37.7 Multi-axial Prior Art 79 7.5 0.78 3.44 4.41 39.2 Multi-axial Prior Art 80 8.5 1.51 3.52 2.33 41.7 Multi-axial Prior Art 80 8.5 1.07 2.94 2.75 39.5 Multi-axial Prior Art 80 8.5 1.19 3.51 2.95 39.0 Multi-axial Prior Art 80 8.5 0.66 4.13 6.26 39.2 Multi-axial Prior Art 82 8.5 1.13 3.91 3.46 40.2 Multi-axial

[0173] The data in Table E can be used to plot Rib Aspect Ratio against Surface Deformation after 10,000 passes, as an indicator of performance in terms of resistance to rutting. The foregoing plot is presented in the FIG. 24 of the drawings, where specimens of the present invention are identified as “InterAx”.

[0174] As evident from FIG. 24, the prior art multiaxial geogrids exhibited similar behavior to that shown in the FIG. 5 of the prior art Walsh HAR patents. There is tendency for the improvement in performance of the prior art geogrid to level off as the rib aspect ratio increases. While a rib aspect ratio of 1 limits surface deformation to around 45 mm surface deformation, an increase in aspect ratio to 2 reduces deformation to 42 mm. It takes an increase of aspect ratio to 5 to limit deformation to 40 mm.

[0175] For the geogrid specimens made according to the preferred geometry that is the subject of the present invention, an aspect ratio of 1.4 limits deformation to between 40 mm and 30 mm, while an increase in aspect ratio to 2.6 limits deformation to between 28 mm and 22 mm. This test data demonstrate the substantial improvement of the present invention over the geogrid of the prior art Walsh HAR patents in the suitability of the present invention to stabilize and strengthen aggregate in civil engineering applications.

[0176] As evident from the foregoing, the geogrids of the present invention offer significant improvement over prior art geogrids by reason of the unique structure and operation of the floating hexagon within a hexagon configuration to engage with, confine and strengthen aggregate in geotechnical applications.

[0177] More specifically, existing commercial prior art geogrids, irrespective of the manufacturing method, have utilized one basic repeating shape and size of aperture opening formed between the oriented ribs/strands and their junctions and nodes. Shapes such as rectangles, square, and triangles have been utilized. The use of one basic repeating shape of aperture also means that the angle formed between two adjacent ribs at an intersecting junction or node has always been the same throughout the geogrid.

[0178] Further, existing prior art geogrids, irrespective of the manufacturing method, have repeating continuous ribs in the primary directions. In a product with square or rectangular apertures, such as in the aforementioned Mercer patents, these ribs would be orthogonal and would typically run at 0° and 90° to the machine direction. In a product with triangular apertures, such as in the Walsh '112 patent, these ribs would be dependent on the form of the triangle. In a typical equilateral triangle these ribs would run at 30°, 90° and 150° to the machine direction.

[0179] Still further, existing commercial prior art geogrids, also irrespective of the manufacturing method, typically have ribs of roughly the same cross sectional area and aspect ratio, irrespective of the direction in which they run.

[0180] These similarities in features of prior art geogrids mean that the properties of the products which allow the geogrid to improve the performance of the geogrid as part of the composite matrix comprising geogrid and granular material are broadly similar throughout the body of the geogrid. These properties referred to in prior art would include (but not exclusively) aperture stability modulus, in-plane and out-of-plane stiffness of the geogrid, rib flexural stiffness in and out of plane, aperture open area, aperture shape, and rib aspect ratio.

[0181] Therefore, in accordance with the present invention, it was discovered that the performance of a geogrid in a composite matrix could be improved if the geogrid were more variable in both its repeating geometry as well as its individual features to better integrate with the granular materials that comprise the other component of the composite matrix. The majority of granular material employed as a component of the composite matrix are not uniform in shape or size, but are “graded” with ranges of size, e.g., 20 to 40 mm, 10 to 63 mm, 20 to 70 mm, etc. Typical grading curves for traditional commonly used granular materials are shown in the “Typical Aggregate Grading Curves” graph presented in FIG. 31.

[0182] As traditional granular materials become more scarce and more expensive, a wider range of variability in the granular materials being utilized in construction is becoming more prevalent. This prevalence is driven to a large extent by the need to minimize the environmental impacts associated with quarrying of traditional high quality natural aggregates, for example energy and environmental impact of quarrying natural aggregates, pressure to close quarrying activities, impact of transporting quarried materials to site, greater desire to utilize locally available granular materials or recycled materials.

[0183] As such, it has been surprisingly discovered that the multi-axial geogrids of the present invention perform better in conjunction with the aforementioned poorer quality and more varied granular materials, and they also perform better with traditional well graded granular material, than prior art commercial geogrids. The geogrid configuration of the present invention out performs existing prior art geogrids and is no longer subject to the same “diminishing returns” rule that exist with the high aspect ratio prior art geogrid of Walsh HAR patents. While the size of the aperture in relation to the intended aggregate in a particular application has to be optimized in prior commercial geogrids, the aperture shape, size and internal angle have all been the same within the macro and micro level of each differently configured geogrid, with a tendency for geogrids based upon a repeating equilateral triangle pattern performing better than those based on rectangular or square openings. In contrast, according to the present invention, the multi-axial geogrid has a repeating geometry comprised of different shapes and sizes of apertures, plural angles of confinement, and formed from ribs of different lengths, heights and widths, in which the ribs preferably have an aspect ratio greater than 1.0; and with some of the ribs, i.e., strong axis strands, extending continuously in a linear fashion transversely and diagonally across the grid while other strands are interrupted to provide zones of local compliance, i.e. engineered discontinuities.

[0184] More specifically, with the new geometry and aperture/opening sizes and shapes, it has been surprisingly discovered that the present invention accomplishes two improvements in the containment and stabilization of a greater variety of aggregate. First, by having apertures/openings of different sizes and shapes, the geogrids of the present invention are better able to match with “natural” mineral aggregates that are sourced from quarries or mining methods of various sizes and shapes due to how they are sourced and processed. Second, the geogrids of the present invention better accommodate and stabilize “non-natural” aggregate alternatives, such as recycled concrete and glass which tend to have different physical properties from natural aggregates. While prior art geogrids have been configured for natural aggregates, the geometry of the present invention is able to successfully engage with, confine and stabilize both natural and non-natural aggregates.

[0185] Further to the foregoing, it has also been discovered in addition to the performance improvement obtained by the geogrids made in accordance with the present invention, that there should be projected savings in construction material costs, saving in time for construction of the geotechnical matrix embodying the geogrids of the present invention, as well as savings in the carbon dioxide equivalent (CO2e), (see https://www.sustainablebusinesstoolkit.com/difference-between-co2-and-co2e/) over the costs encountered with prior art commercial geogrids such as those made in accordance with the Mercer patents and the Walsh HAR patents. According to present estimates, and comparing geogrids of similar physical properties other than the Walsh HAR examples having high-aspect ratio ribs, and the examples of the present invention having the preferred geometry described in accordance with the present invention set forth herein, the cost savings achieved by geogrids made in accordance with the present invention can be as much as 10% up to 40% or more over the cost of using geogrids made in accordance with aforesaid prior art patents, as shown in Table F below.

TABLE-US-00006 TABLE F Conventional Walsh Construction, Mercer HAR Present No Geogrid Patent Patents Invention Aggregate 600 mm 450 mm 375 mm 325 mm Layer Thickness Cost/lane £55,356 £46,392 £41,160 £38,172 km Time/lane 4.3 days 3.3 days 2.8 days 2.4 days km Carbon/ 232 176 147 128 lane km Tonnes Tonnes Tonnes Tonnes CO2e CO2e CO2e CO2e
As indicated above, Table F compares conventional “no geogrid” construction, Tensar's commercialized biaxial geogrid construction according to the original Mercer U.S. Pat. No. 4,374,798, Tensar's commercialized triaxial geogrid construction that falls under the Walsh HAR patents, and a projection for utilization of the present invention. The standard thicknesses of the aggregate layer for each of the comparative geogrids is set forth for the relative comparison. The calculations are based on “lane km”, which is a standard construction industry measure, at least in the United Kingdom and Europe. The “reference to “Tonne,” refers to metric ton (equal to 2,200 lbs).

[0186] The foregoing descriptions and drawings should be considered as illustrative of the principles of the invention. The invention may be configured in a variety of sizes and is not limited to the exact shape of the preferred hexagon within a hexagon embodiment. Further, since numerous modifications and changes may readily occur to those skilled in the art, it is not desired to limit the invention to the exact configurations and operation described and shown. Rather, all suitable modifications and equivalents may be resorted to, falling within this scope of the invention.