Multi-axial integral geogrids and methods of making and using the same

Abstract

To provide a single layer multi-axial integral geogrid suitable for stabilizing an aggregate.SOLUTION: The single-layer, multi-axial, integral geogrid includes a plurality of interconnected oriented strands and a plurality of partially oriented junctions, wherein the oriented strands and the partially oriented junctions form a repeating pattern of outer hexagons having a series of openings. Oriented ribs extending inwardly from each of the outer hexagons support and surround the smaller inner hexagons having oriented strands to form 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 multi-axial integral geogrid and form additional triangular openings. The geogrid includes three different repeating geometric shapes. The inner hexagon can be moved up and down from the plane of the geogrid.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims the benefit of priority to U.S. Provisional Patent Application No. 63 / 043,627, filed June 24, 2020, U.S. Provisional Patent Application No. 63 / 154,209, filed February 26, 2021, and U.S. Provisional Patent Application No. 63 / 154,588, filed February 26, 2021. [Background technology]

[0002] The present invention relates generally to integral geogrids and other oriented grids used for reinforcing and stabilizing structures and buildings, and for other geotechnical purposes. More particularly, the invention relates to such integral geogrids having a single-layer multiaxial grid configuration. Integral geogrids have a high ability to engage, contain, and stabilize a wider variety of aggregates, along with other desirable properties disclosed herein, which, when combined, provide improved performance, greater economic benefits, and environmental advantages.

[0003] The present invention also relates to a method for making such a multiaxial integral geogrid.

[0004] Finally, the present invention relates to the use of such multiaxial integral geogrids for reinforcing and stabilizing soils and particulates, and to methods of such reinforcing and stabilizing.

[0005] For purposes of this invention, the term "integral geogrid" is intended to include integral geogrids and other integral geogrid structures made by orienting or stretching a polymeric starting material in a sheet or sheet-like form having the required thickness and having holes or recesses formed therein.

[0006] Polymer integral grid structures, e.g., integral geogrids, with mesh openings defined by various geometric patterns of substantially parallel oriented strands and their inter-connections have been fabricated for 35 years. These grids are fabricated by extruding a monolithic starting sheet with a predetermined pattern of holes or recesses, then subjecting the sheet to controlled uniaxial or biaxial stretching and orientation to produce highly oriented strands and partially oriented joints defined by the mesh openings formed by the holes or recesses. This uniaxial and biaxial stretching and orientation of the sheet results in strand tensile strength and modulus in the corresponding strand direction. It is also known that not only strand strength but also joint strength is important in the performance of these grid structures. These integrally oriented polymer grid structures can be used to retain or stabilize particulate material in any suitable form, such as soil, earth, sand, clay, gravel, or the like, in any suitable location, such as along the sides of roads or other cuts or fills, undersurfaces, or on skid surfaces.

[0007] Various hole shapes and patterns have been experimented with to achieve higher strength-to-weight ratios or faster processing rates during the fabrication process. Orientation is achieved under controlled temperature and strain rates. Some of the variables in this process include the polymer draw ratio, molecular weight, molecular weight distribution, and degree of branching or crosslinking.

[0008] The fabrication and use of such integral geogrids and other integral grid structures can be accomplished by well-known techniques, such as those described in detail in U.S. Patent No. 4,374,798 to Mercer, U.S. Patent No. 4,590,029 to Mercer, U.S. Patent No. 4,743,486 to Mercer and Martin, U.S. Patent No. 4,756,946 to Mercer, and U.S. Patent No. 5,419,659 to Mercer, in which a starting polymeric sheet material is first extruded and then die-cut to form the desired predetermined pattern of holes or recesses, and the die-cut sheet material is then stretched and oriented as needed to form the integral geogrid.

[0009] Such integral geogrids, known as uniaxial and biaxial integral geogrids (collectively "integral geogrids" or separately "uniaxial integral geogrids" or "biaxial integral geogrids"), were invented by Mercer in the late 1970s and have enjoyed tremendous commercial success over the past 35 years, completely revolutionizing the reinforcement technology of soils, road base layers and other civil structures made of granular aggregates or particulate materials.

[0010] Mercer discovered that an entirely new, substantially uniplanar, integral geogrid could be formed by starting with a relatively thick, preferably 1.5 mm (about 0.06 in) to 4.0 mm (about 0.16 in) thick polymer starting sheet bearing a pattern of holes or recesses centered on an imaginary substantially square or rectangular grid of rows and columns, and then stretching the starting sheet uniaxially or biaxially so that the strand orientation extends to the joints. As Mercer describes it, "uniplanar" means that all zones of the sheet material are generally symmetrical about the median plane of the sheet material. Mercer's geogrid addressed needs associated with use in civil and geotechnical engineering applications. High strength and stiffness of strands in one or two directions, and high integrity and stiffness of joints were required. The purpose is to make the geogrid strong and fit for purpose in civil and geotechnical applications, and to allow soil and aggregate particles to fall into and be trapped within the strands and joints.

[0011] In U.S. Patent Nos. 3,252,181, 3,317,951, 3,496,965, 4,470,942, 4,808,358, and 5,053,264, a starting material having the required pattern of holes or recesses is formed in conjunction with a cylindrical polymer extrusion, and substantial coplanarity is achieved by passing the extrudate over an expanding mandrel. The expanding cylinder is then longitudinally slit to produce a flat, substantially coplanar starting sheet.

[0012] Another integral geogrid is described in U.S. Patent No. 7,001,112 to Walsh (hereinafter the "Walsh '112 Patent"), assigned to Tensor International Limited, an affiliate of Tensor International Corporation (hereinafter "Tensor") of Atlanta, Georgia. The Walsh '112 Patent discloses oriented polymer integral geogrids, including biaxially oriented integral geogrids, in which oriented strands form triangular mesh openings with partially oriented joints at each corner and six highly oriented strands meeting at each joint (hereinafter sometimes referred to as "triaxial integral geogrids"). The triaxial integral geogrid of the Walsh '112 Patent has been commercialized by Tensor with great success. The geogrid of the Walsh '112 patent addressed the need to improve upon Mercer technology by adding strands in more than two directions with high strength and stiffness, and joints with high integrity and stiffness to better distribute and resist loads experienced during use, as well as by using triangular apertures to improve the geogrid's ability to contain and support soil or aggregates placed with the geogrid.

[0013] More recently, improved integral geogrids have been disclosed in U.S. Patent No. 9,556,580 to Walsh, U.S. Patent No. 10,024,002 to Walsh, and U.S. Patent No. 10,501,896 to Walsh, all of which are assigned to Tensor Technology, Inc., another affiliate of the assignee of this patent application. The aforementioned Walsh U.S. Patent Nos. 9,556,580, 10,024,002, and 10,501,896 disclose integral geogrids having what are known in the art as high aspect ratios, i.e., the ratio of thickness or height to width of the strand cross section is greater than 1.0. Hereinafter, these patents will be referred to as the High Aspect Ratio Patents, or Walsh HAR Patents. The high aspect ratio geogrids of the Walsh HAR Patents have also been commercialized by Tensor with great success.

[0014] The Walsh HAR patent teaches that multiaxial geogrids with high aspect ratio rib or strand cross sections and an appropriate ASM provide good performance when utilized as reinforcing or stabilizing elements in civil engineering structures such as roads and railways where one or more layers of the geogrid are employed as ground improvement or subgrade reinforcement. This disclosure of the Walsh HAR patent supersedes the prior art teaching that a maximum ASM was desirable.

[0015] The Walsh HAR patent demonstrates that for conventional multiaxial geogrids, the relationship between rib aspect ratio and traffic performance, as exemplified by the relationship between rib aspect ratio and rut depth shown in Walsh's Figure 5, is not linear. Changing the aspect ratio from 0.375 to 1.4 reduces rut ​​depth from 38 mm to 23 mm, while increasing it from 1.4 to 2.2 reduces rut ​​depth to 19 mm. While this improvement is significant, simply increasing the rib aspect ratio by increasing the thickness of the grid structure increases weight and product cost.

[0016] The Walsh HAR patent further refines the Walsh technology by adding strands in more than two directions with high strength and stiffness, and joints with high integrity and stiffness, and by carefully varying the dimensions and location of the tension strands, further improving the geogrid's ability to confining and support the soil or aggregate with which it is placed.

[0017] Yet another integral geogrid is disclosed in CN 102615818 A, which is directed to a plastic geogrid having a shape resembling a tortoiseshell pattern. While a "hexagonal within a hexagon" grid shape is disclosed, this shape does not have linearly continuous strands across either the length or width of the geogrid.

[0018] Thus, integral geogrids made from the conventional starting materials described above may generally exhibit satisfactory properties for engaging and stabilizing soil and other aggregates. However, the absence of linear strands extending continuously throughout the geogrid significantly compromises the structural integrity of the geogrid and limits the in-plane tensile properties of the geogrid and its usefulness in geosynthetic applications.

[0019] The present invention is intended to be applicable to all integral grids, regardless of the method of initiating sheet formation or orienting the starting material into an integral geogrid or grid structure. The subject matter of the above-mentioned U.S. Patent Nos. 3,252,181, 3,317,951, 3,496,965, 4,470,942, 4,808,358, 5,053,264, 7,001,112, 9,556,580, 10,024,002, and 10,501,896 is expressly incorporated by reference into this specification as if the disclosures were set forth herein in their entirety. These patents are cited by way of example only and are not to be construed as inclusive or exclusive of other techniques known in the art for making integral polymer grid materials.

[0020] When geosynthetics, including multiaxial geogrids, are used in road applications to resist the effects of vehicular traffic rutting, mechanisms to explain and / or predict their performance on granular materials such as soil and stone are still being developed. Research has shown that it is not possible to explain and / or predict the performance of geogrids in road applications based solely on the physical and / or mechanical performance of the geogrid. See, for example, Giroud, J.P. and Han, J., "Closure to 'Design Methods for Geogrid-Reinforced Unpaved Roads, I: Development of the Design Method,'" Journal of Geotechnical and Geoenvironmental Engineering, ASCE, Vol. 130, No. 8, pp. 775-786, August 2004; Webster, S.L., "Geogrid-Reinforced Subgrade for Flexible Pavements for Light Aircraft: Test Section Construction, Traffic Behavior, Laboratory Testing, and Design Criteria," Report DOT / FAA / RD-92, December 1992. Therefore, it is necessary to consider a composite matrix consisting of a geogrid and granular material that is both confined and restrained by the geogrid.

[0021] Existing prior art geogrids have been developed with the goal of optimizing the relationship between granular material size and geogrid opening size, and with the goal of achieving a high degree of "strike-through" or "pass-through," i.e., allowing much of the aggregate gradation to fall into the geogrid openings so that the granular material can abut against the side walls of the confining ribs. See, e.g., Mercer U.S. Patent No. 5,419,659, col. 21, lines 32-43; Walsh HAR Patent No. 10,501,896, col. 1, lines 51-64 and col. 4, line 62 - col. 5, line 11; "Geosynthetic Design & Construction Guidelines - Reference Manual - NHI Course No. 132013," U.S. Department of Transportation Federal Highway Administration Publication No. FHWA NHI-07-092, August 28, 2008; and "Use of Geogrid for Strengthening and Reducing the Roadway Structural Sections," NDOT Research Report, Report No. 327-12-803, January 2016. In the Walsh HAR patent and other prior art, the single size of the openings corresponded to a relatively large granular particle size, with the intention that each particle would be completely contained. See the Walsh HAR patent approach shown in the photo below.

[0022] [Table 1]

[0023] Therefore, for optimal performance, the optimum aggregate particle size range was limited by the geogrid structure opening size selected for each geogrid application.

[0024] As roads and other public infrastructure age and their performance declines, there is an increasing need to replace and upgrade these assets. At the same time, materials traditionally used in the construction of roads and other public infrastructure continue to rise in cost and become scarce due to the environmental impact of mining high-quality natural aggregates, particularly. This has resulted in an increasing need to use materials that are more readily available and less environmentally burdensome to procure. Typically, these materials differ in their properties from traditional materials and often exhibit lower performance.

[0025] Thus, there is a commercial and environmental need for geogrid materials that can facilitate improved performance and economics while reducing the environmental impact on public infrastructure such as roads. Thus, there is a need for integral geogrids having shapes that can engage, confine, and stabilize a wider variety and quality of aggregate than shapes associated with traditional geogrids, including shapes that include continuous strands in at least two directions, while at the same time providing varying degrees of localized out-of-plane stiffness in addition to other desirable properties not available in current integral geogrids. Summary of the Invention

[0026] To achieve an integral geogrid having a shape capable of engaging, confining, and stabilizing a wider variety and quality of aggregate than those associated with prior geogrid structures, including continuous strands in at least two directions while simultaneously providing varying degrees of localized out-of-plane and in-plane stiffness and other desired properties, the present invention provides a single-layer multiaxial grid having a repeating shape composed of openings of different shapes and sizes formed from ribs having different lengths, heights, and widths, where the ribs preferably have an aspect ratio greater than 1.0. Some ribs extend laterally and diagonally in a continuous linear manner across the grid, while other strands are interrupted to provide localized compliance zones.

[0027] More specifically, the multiaxial geogrid according to the present invention combines the following features: Ribs with different widths and depths, preferably maintaining a high aspect ratio Different opening shapes and sizes to suit various granular materials Repeated geometry that better confines granular material by increasing the number of oriented ribs per unit area Repeated geometry that better confines granular material by increasing the number of angles formed between oriented ribs per unit area Repeated geometry with different angles formed between oriented ribs per unit area for better containment of granular material Integral joints for easy load distribution Stabilizing, strong-axis strands that run continuously in multiple directions throughout the geogrid for optimal load distribution Locally modifiable in-plane and out-of-plane stiffness.

[0028] In a preferred embodiment, the present invention employs a repeating pattern of interconnected oriented strands and partially oriented joints. The oriented strands and partially oriented joints form a repeating pattern of outer hexagons. Each of the outer hexagons supports and surrounds a smaller inner hexagon, defining three differently shaped openings in the single-layer multiaxial integral geogrid. To provide additional strength and stability, the shapes of the outer hexagons also form or define a plurality of linear strands, or strong axis strands or ribs, that extend continuously throughout the multiaxial integral geogrid without crossing into other outer hexagons. This makes the geogrid suitable for stabilizing aggregates. It should be understood that the continuous linear strands are comprised of oriented strands and partially oriented joints that define the outer hexagons and are aligned in the same line or strand direction. The continuous linear strands of the outer hexagons also form triangular openings between adjacent outer hexagons. These are repeated throughout the geogrid and are not interrupted by additional strands or ribs.

[0029] Formed in this manner, the inner hexagon is comprised of six oriented strands that define hexagonal openings unobstructed by additional strands or ribs. The inner hexagon is supported by six oriented connecting strands that extend from the partially oriented junctions of the outer hexagon to each corner of the inner hexagon, forming oriented tri-nodes. Tri-nodes have a much higher level of orientation than partially oriented junctions and tend to be fully oriented. The six oriented strands and six supporting oriented connecting strands that make up the inner hexagon, together with adjacent oriented strands of the outer hexagon, form six trapezoidal openings. None of the trapezoidal openings are obstructed by additional strands or ribs.

[0030] The configuration described in the previous paragraph also creates a structure in which the inner hexagons are suspended or floating relative to the outer hexagonal structure. This allows the inner hexagons to "float" or flex or deform upward or downward relative to the major plane of the geogrid and relative to the continuous linear strands of oriented strands and partially oriented joints that define the outer hexagons. Thus, the floating inner hexagons enhance the geogrid's ability to engage, confine, and stabilize aggregate during placement and compaction.

[0031] The above-described geogrid structure is sometimes referred to hereinafter as "floating hexagons repeating within a hexagonal pattern" or simply "floating hexagons within a hexagonal pattern."

[0032] According to one embodiment of the present invention, the starting material for manufacturing a multiaxial integral geogrid comprises a polymer sheet having holes or recesses that, when the starting material is biaxially stretched, provide openings of various shapes.

[0033] According to another embodiment of the present invention, the multiaxial integral geogrid includes floating hexagons that repeat within a hexagonal pattern.

[0034] According to another embodiment of the present invention, a soil structure includes a mass of particulate material that is reinforced and stabilized by embedding therein a multiaxial integral geogrid made from a polymer starting sheet having floating hexagons that repeat in a hexagonal pattern.

[0035] In accordance with yet another embodiment of the present invention, a method for manufacturing a starting material for a multiaxial integral geogrid includes providing a polymer sheet and providing holes or recesses therein to form a multiaxial integral geogrid having floating hexagons that repeat within a hexagonal pattern of interconnected oriented strands and openings.

[0036] In accordance with another embodiment of the present invention, a method for manufacturing a multiaxial integral geogrid includes the steps of providing a polymer sheet, providing holes or recesses therein, and biaxially stretching the polymer sheet with holes or recesses to provide a plurality of interconnected oriented strands with various shaped openings in the form of floating hexagons that repeat within a hexagonal pattern.

[0037] And according to yet another embodiment of the present invention, a method for strengthening a mass of particulate material includes embedding within the mass of particulate material a multiaxial integral geogrid having floating hexagons repeating in a hexagonal pattern made from a polymer sheet suitable for use in stabilizing the mass of particulate material.

[0038]

[0006] Accordingly, an object of the present invention is to provide a starting material for fabricating a multiaxial integral geogrid having repeated floating hexagons within a hexagonal pattern. The starting material includes a polymer sheet having holes or recesses. When the starting material is biaxially stretched, the holes or recesses provide openings.

[0039] Another object of the present invention is to provide a multiaxial integral geogrid suitable for stabilizing and strengthening aggregates, the multiaxial integral geogrid including repeated floating hexagons within a hexagonal pattern fabricated from a polymer sheet and having linear strands that extend continuously throughout the multiaxial integral geogrid. A related object of the present invention is to provide a geometry that can engage, confine, and stabilize a wider variety and quality of aggregate than those associated with prior geogrid structures, while providing varying degrees of localized out-of-plane and in-plane stiffness, and a variety of other desired properties.

[0040] It is yet another object of the present invention to provide an earth structure comprising a mass of particulate material, the mass of particulate material being reinforced and stabilized by embedding therein six multiaxial integral geogrids made from polymer sheets having floating hexagons repeating in a rectangular pattern.

[0041] It is yet another object of the present invention to provide a method of manufacturing a starting material for a multiaxial integral geogrid, the method comprising the steps of providing a polymer sheet and providing holes or recesses therein to form a multiaxial integral geogrid having floating hexagons that repeat within a hexagonal pattern of interconnected oriented strands and openings.

[0042] Another object of the present invention is to provide a method for manufacturing an integral geogrid, comprising the steps of providing a polymer sheet, providing holes or recesses therein, and biaxially stretching the polymer sheet with the holes or recesses to provide a plurality of interconnected oriented strands with a series of openings, including linear strands that extend continuously throughout the multiaxial integral geogrid, and floating hexagons that repeat within the hexagonal pattern of interconnected oriented strands and openings, including linear strands that extend continuously throughout the multiaxial integral geogrid. This method may employ known geogrid manufacturing methods described in the aforementioned U.S. Patents 4,374,798; 4,590,029; 4,743,486; 5,419,659; 7,001,112; 9,556,580; 10,024,002; and 10,501,896, as well as other patents.

[0043] The numerous advantages associated with the multiaxial integral geogrid of the present invention are diverse in nature. The repeated floating hexagons within the hexagonal pattern of interconnected oriented strands and openings allow the multiaxial integral geogrid to better accommodate aggregates of various sizes, i.e., by varying the limiting opening dimensions. While prior commercially available integral geogrid structures typically have one basic structure and one limited size, the multiaxial integral geogrid of the present invention utilizes three different basic shapes—in this example, hexagons, trapezoids, and triangles—defined and connected by oriented strands or ribs of various shapes and sizes. This allows the multiaxial integral geogrid of the present invention to better accommodate the commonly occurring variety of angles, orientations, and sizes of aggregate distributed throughout the geogrid.

[0044] Furthermore, the multiaxial integral geogrid of the present invention is better suited to stabilizing a wide variety of aggregates by providing a wide distribution of aperture sizes. This results in an improved ability to engage, confine, and stabilize aggregates with a wide variety of properties compared to the generally single-size triangular or rectangular shapes found in prior multiaxial integral geogrids. The multiaxial integral geogrid pattern of the present invention has unobstructed, open interior hexagons combined with larger perimeter hexagons, providing optimal aggregate containment and lateral restraint. Further distribution of aperture sizes is achieved through repeated trapezoidal and triangular shaped apertures.

[0045] Additionally, the multiaxial integral geogrid of the present invention provides a higher aspect ratio for all strands compared to the aspect ratios of prior integral geogrids. The higher aspect ratio of the present invention increases interlocking of the aggregate, allowing the multiaxial integral geogrid of the present invention to better accommodate a variety of aggregate aspect ratios.

[0046] Due to the repeated floating hexagons within the specialized rectangular pattern of interconnected oriented strands and openings, the multiaxial integral geogrids of the present invention are also characterized by an increased number and type of strand elements compared to prior integral geogrids. The multiaxial integral geogrids of the present invention also have more oriented tensile elements but fewer partially oriented joints. As a result, the multiaxial integral geogrids of the present invention are characterized by varying degrees of out-of-plane and in-plane local stiffness.

[0047] The multiaxial geometry of the present invention imparts greater overall in-plane rotational stiffness to the integral geogrid, while the shorter strand length increases the rotational stiffness of the integral geogrid relative to that of prior integral geogrids. Thus, the multiaxial integral geogrid is characterized by compliance, i.e., initial resilience or flexibility, which results in good compression and high density, while possessing greater final horizontal aggregate geogrid composite stiffness as a result of the initial resilience.

[0048] And the multiaxial integral geogrid of the present invention has more confinement elements, or strands, that concentrically resist aggregate movement. For the same hexagonal size, the multiaxial integral geogrid of the present invention has twice as many confinement elements to resist radial load movement during compression and traffic as a conventional triaxial integral geogrid.

[0049] In summary, due to the repeated floating hexagons within the hexagonal pattern of interconnecting oriented strands and openings, the preferred multiaxial integral geogrids of the present invention have a greater number and type of strand elements and containment angles, or "knoks," as well as suspended internal hexagons for restraint of up and down out-of-plane movement. These features result in more opportunities for conformance and containment of aggregate while maintaining the overall structural integrity of the integral geogrid. Furthermore, by including linear strands of connecting oriented strands (or ribs) and partially oriented joints that run continuously throughout the multiaxial integral geogrid, the multiaxial geogrids of the present invention possess high strength and stability as aggregate reinforcement.

[0050] These objects and advantages, as well as others that will become apparent hereinafter, reside in the details of structure and operation set forth below. Reference is made to the accompanying drawings, which form a part hereof, in which like parts are designated by like reference numerals throughout, and which are intended to illustrate the invention, but are not necessarily drawn to scale. [Brief explanation of the drawings]

[0051] [Figure 1] FIG. 1 is a plan view of an integral geogrid according to the prior art Walsh '112 patent. [Figure 2] FIG. 2 is a plan view of a multiaxial integral geogrid according to a preferred embodiment of the present invention. [Figure 3] FIG. 3 is a top perspective view of the starting sheet material with holes or recesses formed therein for forming the multiaxial integral geogrid shown in FIG. [Figure 3A] FIG. 3A is a plan view of possible sizes and spacings of holes shown in the starting sheet material of FIG. [Figure 4] FIG. 4 is a perspective view of the multiaxial integral geogrid shown in FIG. [Figure 5] FIG. 5 is an enlarged perspective view of the multiaxial integral geogrid shown in FIG. 4 rotated approximately 30 degrees counterclockwise. [Figure 5A] FIG. 5A is an enlarged side schematic view showing a partial cross section of Rib A and adjacent joints of the outer hexagons (see FIG. 13) that form or define a portion of the strong axis strands of the multiaxial integral geogrid shown in FIG. [Figure 5B] FIG. 5B is an enlarged side schematic view showing partial cross sections of Rib B and Rib D and adjacent three-node points of the inner hexagon (see FIG. 13) of the multiaxial integral geogrid shown in FIG. [Figure 6] FIG. 6 is a partial plan view illustrating the structural limitations of the prior art integral geogrid shown in FIG. [Figure 7] FIG. 7 is a partial plan view illustrating the structural characteristics of the multiaxial integral geogrid of the present invention shown in FIG. [Figure 8] FIG. 8 is a graph showing the range of individual opening areas in prior art integral geogrids of the type shown in FIG. [Figure 9] FIG. 9 is a graph showing the range of individual opening areas in another prior art integral geogrid of the type shown in FIG. [Figure 10] FIG. 10 is a graph illustrating the favorable range of individual opening areas that may be achievable with the multiaxial integral geogrid of the present invention shown in FIG. [Figure 11] FIG. 11 is a partial plan view illustrating the in-plane rotational stiffness of the prior art integral geogrid shown in FIG. [Figure 12] FIG. 12 is a partial plan view illustrating the good in-plane rotational stiffness that may be achievable with the multiaxial integral geogrid of the present invention shown in FIG. [Figure 13] FIG. 13 is a partial plan view showing various strand lengths of the multiaxial integral geogrid of the present invention shown in FIG. [Figure 14] FIG. 14 is a partial plan view showing a single confining interior angle of the prior art integral geogrid shown in FIG. [Figure 15] FIG. 15 is a partial plan view showing two types of confinement interior angles of the multiaxial integral geogrid of the present invention shown in FIG. [Figure 16] FIG. 16 is a partial plan view showing six containment elements at specific distances of the prior art integral geogrid shown in FIG. [Figure 17] FIG. 17 is a partial plan view showing 12 containment elements at a specific distance of the multiaxial integral geogrid shown in FIG. [Figure 18] FIG. 18 is a partial plan view of the prior art integral geogrid shown in FIG. 1, showing 18 angled knucks, all of which are at the same angle. [Figure 19] FIG. 19 is a partial plan view showing 30 angle knucks with different angles of the multiaxial integral geogrid of the present invention shown in FIG. [Figure 20] FIG. 20 is a partial perspective view showing the floating nature of the inner hexagon of the multiaxial integral geogrid of the present invention shown in FIG. [Figure 21] FIG. 21 is a partial plan view showing localized zones of low compliance associated with individual strands or ribs of the prior art integral geogrid shown in FIG. [Figure 22] FIG. 22 is a partial plan view of the multiaxial integral geogrid of the present invention shown in FIG. 2, illustrating the localized zones of low compliance associated with individual strands or ribs in the outer hexagons and the repeated zones of high elastic compliance in the inner hexagons. [Figure 23A] FIG. 23A is a series of three (3) photographs showing the test box, granular material, and TriAx® geogrid used in the retention tests whose results are reported in Table D below. [Figure 23B] FIG. 23B is a series of three (3) photographs of the test box, granular material, and a sample of the present invention identified as Lab79 used in the retention tests whose results are set forth in Table D below. [Figure 24] FIG. 24 is a graph plotting rib aspect ratio against surface deformation after 10,000 passes in multiple traffic tests as detailed in Table E below. [Figure 25A] FIG. 25A illustrates how the large opening size of prior art geogrids causes selected aggregate particles to "fall" into the open spaces of the openings. [Figure 25B] FIG. 25B illustrates how the geogrid of the present invention, in contrast to prior art geogrids, serves to hold the aggregate along the top surface of the geogrid. [Figure 26A] FIG. 26A is a box plot showing the results of retention testing of the TriAx® geogrid shown in the photograph of FIG. 23A. [Figure 26B] FIG. 26B is a box plot showing the results of retention testing of the geogrid of the present invention shown in the photograph of FIG. 23B. [Figure 27] Figure 27 is a copy of Figures 6 and 7 showing the nominally identical hexagonal "Across the Flat" (A / F) dimensions for the sample used in Test 2 (rut) and the results reported in Table E. [Figure 28] FIG. 28 is another copy of FIGS. 6 and 7 showing the dimensions for each opening of the sample used in Test 2 (ruts) and the results reported in Table E. [Figure 29A] FIG. 29A is a schematic diagram illustrating the limited out-of-plane upward movement of an inner hexagon within an outer hexagon in accordance with the present invention. [Figure 29B] FIG. 29B is a schematic diagram illustrating the limited out-of-plane downward movement of an inner hexagon within an outer hexagon in accordance with the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0052] Only the preferred embodiment of the invention will be described in detail; it being understood that the invention is not limited in scope to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings.

[0053] Additionally, in describing preferred embodiments for purposes of this specification, including the appended claims, certain terminology will be used for the sake of clarity. Each term is intended to have its broadest meaning as understood by one of ordinary skill in the art and includes all technical equivalents that operate in a similar manner to accomplish a similar purpose. As used herein, the terms "oriented," "oriented," and "highly oriented" as applied to the strands of the outer hexagon and the strands or ribs of the inner hexagon and the three-node joints, and "partially oriented" or "partially oriented" as applied to the joints of the outer hexagon, shall have the meanings familiar to those skilled in the art in the context of geogrids over the past many years. For example, the term "partially oriented" as applied to the joints of the outer hexagon is readily apparent in that the joints are significantly larger and thicker when compared to the strands of the outer hexagon and the strands or ribs of the inner hexagon and the three-node joints, as shown in the present drawings.

[0054] Thus, the level of orientation in a geogrid can be observed by examining the geogrid to determine the degree to which its thickness has been reduced or increased by the stretching or orientation process from the corresponding thickness of the starting sheet, as well as by striations that are observable in the geogrid by visual (naked eye) inspection or scanning electron microscopy. Such terminology is not intended to require measurement of striations at a molecular level, such as by microscopic examination of polymer molecule orientation.

[0055] And for purposes of this specification, including the appended claims, when the term "about" is used in the specification and claims to modify a size, dimension, portion, shape, construction, parameter, proportion, quantity, characteristic, and other numerical value, it is meant to encompass plus or minus 10% of the stated value.

[0056] Also, for purposes of this specification, including the appended claims, the terms "aperture" and "opening" are used interchangeably herein and are meant to describe any of a plurality of open spaces located in the strands or ribs of a multiaxial integral geogrid.

[0057] The present invention relates to a multiaxial integral geogrid structure fabricated from polymer sheets as starting materials. According to a preferred embodiment of the invention, the polymer sheet starting material is substantially flat, preferably uniplanar or substantially uniplanar.

[0058] The present invention is based on the fact that a starting sheet with a selected pattern of holes or recesses and a polymer sheet that when converted into a multiaxial integral geogrid via an oven stretching process produces a finished product with unique properties relative to previous uniaxial, biaxial and triaxial geogrids.

[0059] Figure 1 is a plan view of a prior art integral geogrid, namely, the triaxial integral geogrid of the Walsh '112 patent. As shown in Figure 1, the triaxial integral geogrid 200 has a repeating triangular shape 210. The triaxial integral geogrid 200 includes a plurality of oriented strands 205 interconnected by partially oriented joints 235. Six triangular openings 210 surround each joint 235, forming a repeating hexagonal shape.

[0060] Figure 2 shows a plan view of a single-layer multiaxial integral geogrid 100 in accordance with a preferred embodiment of the present invention. The multiaxial integral geogrid 100 includes linear strands that extend continuously throughout the multiaxial integral geogrid, with a plurality of interconnected oriented strands having a series of openings therein and floating hexagons that repeat within the hexagonal pattern of interconnected oriented strands and openings. More specifically, the multiaxial integral geogrid 100 includes a repeating pattern of floating interior hexagons 130 within each exterior hexagon 110. The exterior hexagons 110 include a plurality of externally oriented strands or ribs 120 interconnected by partially oriented joints 115. The interior hexagons 130 include a plurality of oriented connecting strands 145 and 150 interconnected by tri-nodes 135 and enclose a hexagonal central opening 170. The outer hexagons 110 connect to the smaller inner hexagons 130 with a plurality of support strands or ribs 140 and 160 that define a plurality of trapezoidal shaped openings 180. In the center of each pattern of three adjacent outer hexagons 110 is a triangular shaped opening 190. As shown, the joints 115 are much larger than the tri-nodes 135.

[0061] As evident from FIG. 2, another feature of the multiaxial integral geogrid of the present invention is the linearly continuous nature of the outer strands 120 of the repeating outer hexagonal pattern. That is, the oriented strands 120 are linearly continuous through the partially oriented joints 115 because they extend continuously throughout the multiaxial integral geogrid in three different directions spaced approximately 120° apart from one another, as 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 shape are possible after stretching if the punched starting sheet shape is correspondingly rotated appropriately. The linearly continuous nature of the strands 120 provides the multiaxial integral geogrid of the present invention with the required good strength and in-plane stiffness.

[0062] Figure 3 is a perspective view of a starting single-layer material sheet 300 having holes or recesses formed therein for forming the multiaxial integral geogrid shown in Figure 2. The single-layer starting sheet 300 used as starting material for a multiaxial integral geogrid according to the present invention is preferably punched through, although it may be possible to use recesses formed in the sheet instead. In accordance with an embodiment of the starting material having recesses formed in the sheet, recesses are provided on each side of the sheet, i.e., on both the top and bottom of the sheet.

[0063] The single layer starting sheet 300 contains a repeating pattern 310 of holes 320 and spacing 330 that, when oriented, provides the floating hexagons within the hexagonal pattern of the multiaxial integral geogrid shown in Figure 2. According to one possible embodiment of the invention, the diameter of the holes 320 is 3.68 mm, with spacing of holes 330 of a few millimeters as shown in Figure 3A.

[0064] Preferably, the total thickness of the single-layer material sheet 300 is about 3 mm to about 10 mm, and more preferably, the total thickness of the single-layer material sheet 300 is about 5 mm to about 8 mm.

[0065] Generally, the monolayer material sheet 300 is polymeric in nature. For example, the constituent materials can include high molecular weight polyolefins and a wide variety of polymers. Furthermore, the polymeric materials can be virgin stock or recycled materials, such as post-manufacturing or post-consumer recycled polymeric materials. According to a preferred embodiment of the present invention, the high molecular weight polyolefin is polypropylene.

[0066] Figure 4 is a perspective view of the multiaxial integral geogrid 100 shown in Figure 2, and Figure 5 is an enlarged perspective view of the multiaxial integral geogrid 100 shown in Figure 4. As is apparent from Figures 4 and 5, strands 120, 140, 145, 150, and 160 have what is known in the art as a high aspect ratio, i.e., a ratio of the thickness or height of the cross-section of the strand to the width of the cross-section of the strand greater than 1.0, in accordance with the aforementioned Walsh HAR patent, U.S. Patent Nos. 9,556,580, 10,024,002, and 10,501,896. While not absolutely required for the present invention, a high aspect ratio of the strands or ribs is preferred. In this manner, the multiaxial integral geogrid of the present invention improves the compatibility of the geogrid with the aggregate, resulting in improved aggregate interlocking, lateral restraint, and containment.

[0067] Figure 5A is an enlarged, schematic side view showing partial cross sections of Rib A and adjacent junctions of the outer hexagon (see Figure 13), which form or define a portion of one of three straight strong axis strands that run continuously throughout the geogrid of the present invention. These strong axis strands provide the strength and in-plane stability required for the geogrid as they engage, confine, and stabilize aggregate in civil engineering applications. Figure 5B is a similar enlarged, schematic side view showing partial cross sections of Rib B and Rib D and adjacent tri-nodes of the inner hexagon. Typical thicknesses of each of these components according to the present invention are set forth in Figures 5A and 5B.

[0068] Figure 6 is a partial plan view illustrating certain structural constraints of the prior art triaxial integral geogrid shown in Figure 1. The repeating geometric elements of conventional triaxial integral geogrid 200 have one basic aperture shape (triangle), one limited strand size, and a high ratio of joints to connecting strands (1 to 3). Therefore, conventional triaxial integral geogrid 200 offers only a single containment angle of 60° without any variation in either aperture shape or size.

[0069] Figure 7 is another plan view illustrating the structural attributes of the multiaxial integral geogrid 100 shown in Figure 2. Similarly, while the conventional triaxial integral geogrid 200 shown in Figure 1 has only one basic shape and one limited strand size, the multiaxial integral geogrid 100 utilizes three different basic opening shapes (hexagonal 110, trapezoidal 180, and triangular 190), various strand sizes, and two different confinement angles (60° and 120°). Furthermore, the multiaxial integral geogrid 100 contains only one junction for every six connecting strands and has three strands associated with each tri-node. This allows the multiaxial integral geogrid 100 to better accommodate a variety of aggregate angles and orientations distributed throughout the geogrid.

[0070] FIG. 8 is a graph showing the range of individual opening areas in a prior art triaxial integral geogrid 200 of the type shown in FIG. 1. More specifically, FIG. 8 shows the distribution of individual opening areas in a prior art triaxial integral geogrid 200 of the type shown in FIG. (R) TX160 (R) The distribution of individual opening areas associated with a commercially available triaxial integral geogrid from Tensor is shown in Figure 8. As is evident from Figure 8, the individual opening areas associated with conventional triaxial integral geogrids are relatively limited, with the distribution range of individual opening areas being approximately 775 mm. 2 ~about 850mm 2 , i.e., about 75 mm 2 Only a range is offered.

[0071] FIG. 9 is a graph showing the range of individual opening areas in another prior art triaxial integral geogrid 200 of the type shown in FIG. 1. More specifically, FIG. (R) TX130S (R) The distribution of individual opening areas associated with a commercially available triaxial integral geogrid from Tensor is shown in Figure 9. As is evident from Figure 9, the individual opening areas associated with this conventional triaxial integral geogrid are also relatively limited, with the distribution range of individual opening areas being approximately 475 mm. 2 ~about 550mm 2 , i.e., about 75 mm 2 Only a range is offered.

[0072] In contrast, Figure 10 is a graph illustrating the favorable individual opening area distribution range that can be achieved with the multiaxial integral geogrid 100 of the present invention shown in Figure 2. As is evident from Figure 10, the individual opening area distribution range associated with the multiaxial integral geogrid 100 is much greater than that provided by the triaxial integral geogrid. 2 ~approx. 800mm 2 The wider distribution of the individual opening areas of the granular material provides a more optimal interaction with granular materials of various particle sizes. 2 ~about 700mm 2 , or at least 200 mm 2 This is evident in the range of

[0073] Figure 11 is a plan view illustrating the in-plane rotational stiffness of the prior art triaxial integral geogrid 200 shown in Figure 1. As is apparent from Figure 11, the prior art integral geogrid 200 has partially oriented joints 235 connecting the oriented strands 205, each of which has approximately the same length.

[0074] In contrast, Figure 12 is a partial plan view illustrating the excellent in-plane rotational stiffness achievable with the multiaxial integral geogrid 100 of the present invention shown in Figure 2. Similarly, the multiaxial integral geogrid 100 includes preferred repeating floating hexagons in a hexagonal 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 joints 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 support or connector strands 140 and 160. Due to the short length of the oriented strands 140, 145, 150, and 160 relative to the length of strand 205, the multiaxial integral geogrid 100 has a high in-plane rotational stiffness.

[0075] FIG. 13 is a partial plan view showing various strands of the multiaxial integral geogrid shown in FIG. 2. The multiaxial integral geogrid 100 includes repeating floating hexagons in a hexagonal pattern with an outer hexagon 110 and a smaller inner hexagon 130. The outer hexagon 110 includes a plurality of oriented strands 120 (also designated "A" in FIG. 13) interconnected by partially oriented joints 115. The inner hexagon 130 includes a plurality of oriented strands 145 ("B") and 150 ("D") interconnected by oriented trinodes 135. The outer hexagon 110 is connected to the inner hexagon 130 by a plurality of oriented support strands 140 ("C") and 160 ("E"). (The data in Tables A, B, and E presented below employ the designations A, B, C, D, and E for the various strands.)

[0076] According to one embodiment of the present invention, four strands 150 (D) and two strands 160 (E) are the widest (largest lateral thickness), and four strands 140 (C) are the longest. All of these provide strength and stiffness. Two strands 145 (B) are the thinnest, which provides out-of-plane flexibility. Strands 120 (A) are TX160(R) These strands are representative of strands B, C, D, and E, which are neither the longest nor the widest, nor the strongest nor the most flexible. Therefore, they are neutral and incompatible without the presence of strands B, C, D, and E. Thus, Figure 13 illustrates the effect of several strand dimensions on strength and stiffness. Other embodiments and dimensional relationships will readily occur to those skilled in the art.

[0077] Table A shows the height, width, and aspect ratio of each of the various strands for an example multiaxial geogrid 100 of the present invention shown in Figure 13. While the values ​​shown in Table A are representative of heights, widths, and aspect ratios that may be associated with a multiaxial geogrid 100 of the present invention, they are presented for illustrative purposes and are not intended to limit the scope of the present invention.

[0078] [Table 2]

[0079] Table B shows a comparison of the aspect ratios associated with the various strands of the multiaxial integral geogrid 100 of the present invention to the aspect ratios of various commercially available triaxial integral geogrids commercialized by Tensor.

[0080] [Table 3]

[0081] As can be seen from Table B, the multiaxial integral geogrid 100 has a higher aspect ratio in all strands compared to each of the conventional triaxial integral geogrids. This higher aspect ratio, combined with other features of the geometry of the present invention, provides better performance than the Walsh HAR patent.

[0082] The broad scope and preferred parameters of the multiaxial geogrid according to the present invention as shown in Figures 13 and 15 are as follows:

[0083] Rib A has a height ranging from 1 mm to 4 mm, with a preferred range of 2 mm to 3 mm, with a preferred dimension of 2.86 mm. Rib A's width ranging from 0.75 mm to 3 mm, with a preferred range of 1 mm to 2 mm, with a preferred dimension of 1.6 mm. Rib A's length ranging from 30 mm to 45 mm, with a preferred range of 35 mm to 40 mm, with a preferred dimension of 37 mm. Rib A's aspect ratio ranging from 1:1 to 3:1, with a preferred range of 1.5:1 to 1.8:1, with a preferred value of 1.7:1.

[0084] The height of Rib B ranges from 1 mm to 3 mm, with a preferred range of 1.5 mm to 2.5 mm, and a preferred dimension of 1.6 mm. The width of Rib B ranges from 0.75 mm to 3.5 mm, with a preferred range of 1 mm to 3 mm, and a preferred dimension of 1.8 mm. The length of Rib B ranges from 15 mm to 25 mm, with a preferred range of 18 mm to 22 mm, and a preferred dimension of 21 mm. The aspect ratio of Rib B ranges from 0.75:1 to 2:1, with a preferred range of 1.2:1 to 1.4:1, and a preferred value of 1.3:1.

[0085] The height of the rib C ranges widely from 1 mm to 4 mm, with a preferred range of 2 mm to 3 mm, and a preferred dimension of 2.7 mm. The width of the rib C ranges widely from 0.75 mm to 3.5 mm, with a preferred range of 1 mm to 2.5 mm, and a preferred dimension of 1.6 mm. The length of the rib C ranges widely from 15 mm to 30 mm, with a preferred range of 20 mm to 25 mm, and a preferred dimension of 23 mm. The aspect ratio of the rib C ranges widely from 1:1 to 3:1, with a preferred range of 1.5:1 to 2.5:1, and a preferred value of 1.7:1.

[0086] The height of the rib D ranges widely from 1.5 mm to 4 mm, with a preferred range of 2 mm to 3.5 mm, and a preferred dimension of 2.3 mm. The width of the rib D ranges widely from 1 mm to 4 mm, with a preferred range of 1.5 mm to 2.5 mm, and a preferred dimension of 1.5 mm. The length of the rib D ranges widely from 10 mm to 30 mm, with a preferred range of 15 mm to 25 mm, and a preferred dimension of 18 mm. The aspect ratio of the rib D ranges widely from 1:1 to 3:1, with a preferred range of 1.4:1 to 1.7:1, and a preferred value of 1.6:1.

[0087] The height of Rib E ranges from 1 mm to 4 mm, with a preferred range of 1.5 mm to 3.0 mm, and a preferred dimension of 1.9 mm. The width of Rib E ranges from 0.75 mm to 3.5 mm, with a preferred range of 1 mm to 3 mm, and a preferred dimension of 1.7 mm. The length of Rib E ranges from 15 mm to 30 mm, with a preferred range of 20 mm to 25 mm, and a preferred dimension of 22 mm. The aspect ratio of Rib E ranges from 0.75:1 to 2:1, with a preferred range of 1:1 to 1.5:1, and a preferred value of 1.3:1.

[0088] As shown in FIG. 5A, the outer hexagon 110 of the multiaxial integral geogrid 100 has a partially oriented joint 115 thickness (dimension "TO2") in a wide range of 3 mm to 9 mm, with a preferred range of 4.5 mm to 7.5 mm, with a preferred dimension of approximately 5.6 mm, and a strand or rib 120 thickness (dimension "TO1") in a wide range of 1 mm to 5 mm, with a preferred range of 1.5 mm to 3.5 mm, with a preferred dimension of approximately 2.8 mm.

[0089] Also, as shown in FIG. 5B, the inner hexagon 130 of the integral geogrid 100 has a three-node 135 thickness (dimension "TI1"), a strand or rib 145 thickness (also dimension "TI1"), and a strand or rib 150 thickness (also dimension "TI1") in a wide range of 1 mm to 5 mm, with a preferred range of 1.5 mm to 3.5 mm.

[0090] According to one preferred embodiment of the multiaxial integral geogrid shown in Figure 13, the "across the flats" dimension, i.e., the distance from one junction 115 of the outer hexagon (see Figure 15) to the opposing junction 115 of the outer hexagon, is approximately 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 Figure 15) to the opposing tri-node 135 of the inner hexagon, is approximately 33 mm.

[0091] The punch size / diameter ranges from 2 mm to 7 mm, with a preferred range of 3 mm to 5 mm, and has a preferred dimension of 3.68 mm. The long pitch in the first stretching direction ranges from 5 mm to 9 mm, with a preferred range of 6 mm to 8 mm, and has a preferred dimension of 6.7088 mm. The short pitch in the first stretching direction ranges from 1 mm to 4 mm, with a preferred range of 2 mm to 3 mm, and has a preferred dimension of 2.58 mm. The second long / short pitch in the first stretching direction ranges from 4 mm to 8 mm, with a preferred range of 5 mm to 7 mm, and has a preferred dimension of 5.934 mm. The long pitch in the second stretching direction ranges from 4 mm to 8 mm, with a preferred range of 5 mm to 7 mm, and has a preferred dimension of 6.192 mm.

[0092] FIG. 14 is a partial plan view showing a single interior confinement angle of the prior art triangular integral geogrid 200 shown in FIG. 1. As can be seen, the integral geogrid 200 has a single interior confinement angle, i.e., an angle of approximately 60°. That is, for each joint 235, the integral geogrid 200 has a total of six confinement angles. And, the integral geogrid 200 has a total of eighteen 60° confinement angles within the perimeter of a single hexagon. (The designation A shown in FIG. 14 refers to the prior art TriAx integral geogrid employed in the data in Table E presented below.) (R) (vs. geogrid strands / ribs).

[0093] Figure 15 is a partial plan view illustrating two different interior confinement angles for the multiaxial integral geogrid 100 of the present invention shown in Figure 2. Advantageously, with its configuration of an interior hexagon 130 supported within an exterior hexagon 110 and five different strand types A, B, C, D, and E, the multiaxial integral geogrid 100 has a combination of 60° and 120° interior angles. That is, there are six 60° confinement angles at the joints 115 and three 120° confinement angles at the tri-junctions 135. Thus, the multiaxial integral geogrid 100 has a total of 30 confinement angles within the confines of a single exterior hexagon 110. In this way, the multiaxial integral geogrid 100 provides improved aggregate containment by providing two confinement angles throughout the extent of its opening.

[0094] Table C below compares the node orientation, tension element orientation, open area, and average aperture open area achievable with the multiaxial integral geogrid 100 of the present invention with the characteristics of various prior art triaxial integral geogrids.

[0095] [Table 4]

[0096] As is clear from Table C, the TX160 (R) In comparison, the multiaxial integral geogrid 100 of the present invention has 20% fewer partially oriented joints 115 and 56% more oriented tension elements 120, 140, 145, 150, 160 per square meter. Thus, there are significantly more physical elements per unit area for abutting, confining, and interacting aggregate particles, and significantly fewer physical elements per unit area, i.e., partially oriented joints, which contribute less to the geogrid's ability to engage, confining, and stabilize the aggregate. Furthermore, the TX130S (R)In comparison, the multiaxial integral geogrid 100 of the present invention has 47% fewer partially oriented joints 115 per square meter, and approximately the same amount of oriented tension elements 120, 140, 145, 150, 160 per square meter, but a higher number of confinement angles. These features result in a higher number of physical elements per unit area for abutting, confining, and interacting aggregate particles, but significantly fewer physical elements per unit area, i.e., partially oriented joints, which contribute less to the geogrid's ability to engage, confine, and stabilize the aggregate.

[0097] Figure 16 is a partial plan view showing six containment elements at a particular distance of the prior art triangular integral geogrid 200 shown in Figure 1. Referring to Figure 16, the prior art integral geogrid 200 has six abutment elements, i.e., six strands 205 surrounding a joint 235.

[0098] Figure 17 is a partial plan view showing 12 confinement elements at the same specific distance for the multiaxial integral geogrid 100 of the present invention shown in Figure 2. As is apparent from Figure 17, the multiaxial integral geogrid 100 has 12 abutting (confining) elements: six strands 120 forming the outer hexagon 110 and six strands forming the inner hexagon 130: two strands 145 and four strands 150. In other words, for a similar hexagon size with a similar "across the flat" distance, the multiaxial integral geogrid 100 provides twice as many confinement elements to resist radial load movement during compression and traffic. Thus, the multiaxial integral geogrid 100 provides twice as many elements providing concentric resistance to aggregate movement.

[0099] Figure 18 is a partial plan view of the prior art integral geogrid shown in Figure 1, showing 18 angled nooks, all of which are the same angle. As discussed above, integral geogrid 200 has a single confining interior angle, i.e., an angle of approximately 60°. That is, for each joint 235, integral geogrid 200 has a total of six 60° confining angles, or nooks. And integral geogrid 200 has a total of eighteen 60° confining angles, or nooks, within a single hexagonal boundary.

[0100] Figure 19 is a partial plan view of the multiaxial integral geogrid of the present invention shown in Figure 2, showing 30 angled nooks with different angles. As described above, with its geometry having an inner hexagon 130 supported within an outer hexagon 110, and five different strand types A, B, C, D, and E, the multiaxial integral geogrid 100 has a combination of 60° and 120° interior angles. That is, there are six 60° confinement angles or nooks at each joint 115 and three 120° confinement angles or nooks at each tri-junction 135. Thus, the multiaxial integral geogrid 100 has a total of 30 confinement angles or nooks within the confines of a single outer hexagon 110. In this way, the multiaxial integral geogrid 100 provides 30 independent (or unique) confinement angles or nooks with two different interior confinement angles throughout the extent of its opening. This combination of features results in better aggregate containment.

[0101] Figure 20 is a partial perspective view illustrating the favorable floating nature of the inner hexagons 130 of the multiaxial integral geogrid of the present invention shown in Figure 2. The present invention incorporates elastic (i.e., suspended) conformable inner hexagons 130 to better conform to the aggregate during compression by varying the "out-of-plane" stiffness. The floating inner hexagons are relatively mobile in the vertical Z-axis dimension, allowing a significant degree of compliance or deflection during compression.

[0102] In a preferred embodiment of the present invention, this vertical compliance or deflection of the inner hexagons 130 can be equal to about 33% of the maximum thickness of the surrounding outer hexagons 110. In other words, if the thickness of the partially oriented joint (which is the thickest component of the outer hexagon) is 6 mm, the out-of-plane compliance or deflection of the floating inner hexagons 140 can be equal to about 2 mm. This elastic (i.e., suspended) compliance is spread throughout the area bounded by each outer hexagon 110, and the degree of vertical compliance of the outer hexagons is small. Surprisingly, it has been found that this good stiff (suspended) compliance or deflection of the inner hexagons improves the ability of the geogrids 100 of the present invention to interlock with aggregate.

[0103] As shown in Figure 29A, the inner hexagons 130 of the integral geogrid 100 can deflect (i.e., float or deform) upward, i.e., outward, away from the plane of the outer hexagon 110, to an extent that the distance "D" is equal to about 33% of the total thickness of the surrounding outer hexagon 110 (the total thickness of the outer hexagon 110 being essentially the thickness of the joints 115). Correspondingly, as shown in Figure 29B, the inner hexagons 130 of the integral geogrid 100 can deflect (i.e., float or deform) downward, i.e., outward, away from the plane of the outer hexagon 110, to an extent that the distance "D" is equal to about 33% of the total thickness of the surrounding outer hexagon 110.

[0104] Additionally, the ability of the elastic (i.e., suspended) conformable inner hexagons 130 to rest on the subgrade and further deflect vertically upward if the subgrade is uneven provides an opportunity for improved lateral restraint and prevents aggregate from rolling over the strands 140, 145, 150, 160 under cyclic loading because the outer hexagons 110 form a second containment ring through which the aggregate must pass. Conventional prior art multiaxial geogrids, such as geogrid 200, lack this level of elastic (i.e., suspended) compliance and therefore only provide one level of containment.

[0105] Figure 21 is a partial plan view illustrating local zones of low compliance associated with individual strands or ribs of the prior art prior art integral geogrid 200 shown in Figure 1. That is, because the individual strands or ribs 205 connect at partially oriented joints 235, the prior art integral geogrid 200 has many local zones of low compliance and therefore minimal resilience.

[0106] Figure 22 is a partial plan view of the multiaxial integral geogrid of the present invention shown in Figure 2, illustrating localized zones of low compliance associated with individual strands or ribs of the outer hexagons 110 and repeated zones of high elastic compliance in the inner hexagons 130. Due to the ability of the floating inner hexagons 130 to deflect vertically within the outer hexagons 110, the multiaxial geogrid 100 has repeated zones of high elastic compliance within each of the corresponding outer hexagons 110.

[0107] Again, as shown in Figure 21, conventional prior art triaxial geogrids lack the level of compliance over such a large area that characterizes the multiaxial integral geogrid of the present invention. Therefore, the compliance associated with prior art triaxial geogrids is limited to individual ribs that are constrained by joints at either end. In contrast, the geogrids of the present invention have zones of significant vertical elastic (or suspended) compliance per unit area, on the order of about 50% to about 75%, as shown in Figure 22. This is in contrast to the conventional prior art multiaxial geogrid shown in Figure 21, which does not have such zones of significant vertical compliance.

[0108] In one embodiment of the present invention, geogrid 100 exhibits horizontal mechanical stability. The repeating pattern of exterior hexagons 110, including a plurality of outwardly oriented strands or ribs 120 interconnected by partially oriented joints 115, provides strong-axis strands that extend continuously in straight paths throughout the geogrid, as shown by lines 120A, 120B, and 120C in FIG. 4. As noted in FIG. 4, the strong-axis strands formed by the outwardly oriented strands or ribs 120 interconnected by partially oriented joints 115 extend throughout the geogrid without crossing the interior of the exterior hexagons, as shown by lines 120A, 120B, and 120C in FIG. 4. This feature provides the necessary strength and stability for the geogrids of the present invention. In another aspect, the ribs 140, 160 extending inward from the partially oriented joint 115 and connecting to the three-node 135 of the floating inner hexagon 145, or other geometric configurations described below supported by such ribs, comprise an "engineering discontinuity" or "floating engineering discontinuity."

[0109] The present invention also relates to a method of manufacturing the above-described multiaxial integral geogrid 100. The method includes the steps of providing a polymer sheet 300, providing the polymer sheet 300 with a plurality of patterned holes or depressions 310, and orienting the polymer sheet 300 with the plurality of patterned holes or depressions 310, thereby providing a plurality of interconnected oriented strands 120, 140, 145, 150, and 160 with a series of openings 170, 180, and 190, and repeating floating hexagons 130 within the outer hexagon 110 pattern of interconnected oriented strands and openings, comprising three types of linear strands that extend continuously throughout the multiaxial integral geogrid 100.

[0110] Generally, once the polymer sheet 300 having holes or recesses is prepared, the multiaxial integral geogrid 100 can be fabricated from the sheet 300 according to the prior art patents mentioned above and methods known to those skilled in the art.

[0111] As noted above, the hexagonal geometry of the outer hexagon 110 and the smaller inner hexagon 130 is a preferred embodiment for providing the floating geometry of the present invention. However, other geometries are possible within the scope of the present invention. For example, the geometric shape may be a rectangle or square with four support 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. Alternatively, the geometric shape may be a triangle with only three support or connecting strands between adjacent inner corners of the outer triangle and the outer corner of the smaller inner triangle. Other polygonal shapes are also contemplated within the scope of the present invention.

[0112] In the rectangular or square embodiments of the invention described in the previous paragraph, there may preferably be two linear strands defined by interconnected oriented strands and partially oriented joints extending continuously throughout the geogrid for each outer rectangle or square. Such continuous strands extend at approximately 90° angles from each other. In triangular embodiments, there may preferably be three such linear strands extending at approximately 120° from each other for each outer triangle, similar to the linear strands 120 of the preferred hexagonal embodiment described in detail herein.

[0113] Also, different geometries are possible without departing from the invention. For example, the inner geometric shape can be a circular ring supported within a preferred outer hexagonal shape having six support strands similar to the preferred embodiment disclosed herein. Thus, it is intended that the outer repeating structure and the inner or internal floating structure are not limited to identical geometries.

[0114] As discussed above and illustrated in the accompanying drawings, the geogrid embodiments disclosed herein comprise a single layer construction. Accordingly, the composition of the starting sheet 300 shown and described with respect to Figure 3 is comprised of a single polymer or copolymer.

[0115] While a preferred embodiment of an integral geogrid 100 having outer hexagons 110 surrounding and supporting small, floating inner hexagons 130 has been described, the present invention also contemplates that the outer hexagons 110 may surround and support small inner hexagons 130 that remain within the plane of the geogrid without floating or sagging (deforming). Thus, in accordance with the present invention, the integral geogrids 100 shown in Figures 2, 4, and 5, fabricated from the starting sheet material shown in Figure 3, may be fabricated with small inner hexagons that do not float or sag. Thus, the repeating hexagons within the hexagonal patterns of the present invention are the same whether or not the inner hexagons 130 are allowed to float.

[0116] Finally, it is clearly preferred that each of the outer hexagons 110 of the multiaxial integral geogrid 100 include floating hexagons 130 therein, as disclosed herein. However, by modifying some individual punch patterns or otherwise, it is possible to create a multiaxial integral geogrid in which hexagons 130 are surrounded and supported by only a portion of the outer hexagons 110, while other outer hexagons support other interior structures within the prior art, without departing from the scope and spirit of the present invention. It is presently believed that such modified integral geogrids are within the scope of the present invention, so long as they include one or more outer hexagons 110 surrounding and supporting smaller inner hexagons 130, floating or non-floating, that define the required series of substantially parallel linear strands extending continuously throughout the geogrid, i.e., strong axis strands, in accordance with the disclosure contained herein.

[0117] As noted in the "Background" section above, prior art geogrids utilize the concept of having openings large enough that the majority of aggregate particles physically "fall" into the open space of the openings. The geogrid then benefits by laterally constraining these particles when a load is applied from above. As the load is applied from above, the aggregate particles tend to move downward and outward (laterally), and the geogrid prevents both. Thus, the basic premise of prior art geogrids is that the aggregate particles must "slide through" or "pass through" the openings. This prior art "pass through" concept is confirmed by the Walsh HAR patent, where the high aspect ratio concept of long / thin ribs that promote "confinement" provides even better resistance to lateral spreading of the aggregate.

[0118] In contrast, the present invention converts all other joints along the discontinuous strands into open hexagons or other open geometric configurations. This unique configuration results in at least two significant changes. First, the present invention creates an open structure where joints previously existed, thereby introducing "confinement elements" where "unconfined elements" previously existed. In a preferred embodiment, the openings created by the inner hexagons result in six ribs forming the hexagon. These ribs are now available to interact with and support the aggregate, while the replaced joints become merely "connection points" for the geogrid itself. Second, the present invention reduces the opening size for the six (6) trapezoidal openings shown in Figures 2 and 17 compared to the triangular openings of the triaxial geogrid shown in Figures 1 and 16, thereby better retaining and confining a wide range of aggregate sizes and qualities.

[0119] Thus, it has been surprisingly discovered that the "goal" of the improved geogrids of the present invention is not to have most of the aggregate particles fall through the openings, as embodied in the prior art. Rather, as demonstrated by the test results described below, the geogrid structure of the present invention creates more functional elements per unit area in the geogrid than the prior art structure (see Table C above). And the goal of the present invention is not to have particles fall through the openings, but rather to have more aggregate particles partially pass through more of the openings. This surprising new interaction between the geogrid and the aggregate particles to be trapped therein is illustrated by the comparative illustrations of the present invention versus the prior art in Figures 25A and 52B.

[0120] These surprising findings are substantiated by the following tests and their results.

[0121] Test method example Test 1 - Retention The ability of multiaxial geogrids to improve interaction with granular materials was evaluated using small-scale tests simulating granular material "cascaded" onto the geogrid, following installation methods outlined in published guidance (e.g., "Tensar Installation Guideline IG / TriAx," October 19, 2020). The small-scale test consisted of an open box into which a geogrid specimen, approximately 350 mm x 350 mm, was clamped. Two kilograms of granular material, graded to a particle size of 20 mm to 40 mm, was then cascaded across the geogrid using a "brushing" motion. The 20 mm to 40 mm particle size grading is empirically representative of gradings commonly used in civil engineering construction, eliminating excessive variability associated with smaller or larger particle sizes. For each test, the amount of granular material "captured" by the geogrid and the amount of granular material that passed through the geogrid and fell into the box below were measured. The two results were then compared. A geogrid better designed to "trap" granular material will retain more of the granular material on the geogrid, and much less of the material will fall into the open box below the geogrid specimen. A typical comparison is based on 10 replicate tests for each geogrid type using the same 2 kg load of granular material.

[0122] Test 2 - Rut The ability of multiaxial geogrid to resist rutting due to vehicle traffic was evaluated using a small-scale test simulating established field tests, such as those described in Webster, S.L., "Geogrid-Reinforced Subbase for Light Aircraft Flexible Pavements: Test Section Construction, Traffic Laboratory Test Performance, and Design Criteria" (Report DOT / FAA / RD-92, December 1992). This small-scale test, designed to replicate the results of established field tests of multiaxial geogrid traffic performance, included a test section consisting of a clay subbase, a single geogrid layer, and a compacted granular base. The test section was subjected to a single weighted wheel load. The wheel traversed the test section along a single horizontal path, constantly reversing direction from end to end. Control tests without geogrid would rapidly fail under such testing. For example, deep ruts would form after fewer than 1,000 wheel passes on an unreinforced test section. By using a properly designed multiaxial geogrid as reinforcement, the rut depth can be reduced for a given number of wheel passes compared to an unreinforced test section. This reduction in rut depth impacts the lifespan of civil engineering structures, which can be increased by up to 50 times compared to unreinforced structures. Thus, roads and other civil engineering structures reinforced according to the present invention will have a longer lifespan but require less maintenance.

[0123] The small-scale study described above and used in connection with the present invention is the same small-scale study described in the Walsh HAR patent (see U.S. Pat. No. 10,501,896, column 10, lines 43-67) that generated the data set forth therein.

[0124] Example - Test 1 (Retentiveness) The ability of multiaxial geogrids to improve interaction with granular materials was evaluated using small-scale tests simulating granular material "cascaded" onto the geogrid, following installation methods outlined in published guidance.

[0125] Commercially available prior art TriAx (R)A geogrid sample (see Figure 23A) was cascaded over its surface with 2000 g of granular material graded to a particle size of 20 mm to 40 mm. The weight of the material that fell through the geogrid into a box below was measured, as well as the weight of the material retained on the geogrid. This test was repeated 10 times on the same specimen, each time using the same 2000 g of granular material.

[0126] This test was then repeated on a test specimen of the present invention identified as Lab79 (see Figure 23B). Lab79 was a prior art TriAx® test specimen that had already been tested. (R) Manufactured from the same sheet material recipe as the geogrid. (R) The same 2000g portion of granular material used in the geogrid evaluation was used in the Lab79 evaluation.

[0127] The results are shown in Table D below.

[0128] [Table 5]

[0129] The results, shown in Table D above, demonstrate that the combined effect of all of the geometric elements of the multiaxial geogrid of the present invention significantly improves its ability to interact with the same granular material compared to a prior art multiaxial geogrid. The prior art geogrid retained or captured only 14% of the material that cascaded across its surface, with the remaining 86% falling through the geogrid, while the geogrid of the present invention captured 96% of the granular material, with only 4% falling through. This vast improvement in the ability of the geogrid of the present invention to interact with granular material is beneficial for improving rutting resistance in traffic inspections.

[0130] The test results reported in Table D are also presented in the box plots shown in Figures 26A and 26B. As can be seen in Figure 26A, a significantly larger percentage of the 2000g portion of granular material was found to be in the TriAx® granules, as shown in the test plot at 501. (R) The aggregate passed through the geogrid, with only a small percentage being retained on the geogrid, as shown in the test plot at 502. Conversely, as shown in Figure 26B, only a small percentage of the same 2000g of granular material passed through the geogrid of the present invention, as shown in the test plot at 503, with almost all of the aggregate being retained, as shown in the test plot at 504.

[0131] In accordance with the present invention, it has surprisingly been discovered that the ability of a geogrid to "retain" aggregate in a standard retention test is a better predictor than the "pass-through" concept employed by the prior art. More specifically, it is currently believed that for any particular aggregate, a geogrid retention of at least 50% in the above-described retention test should predict an effective geogrid in a composite structure comprising the tested geogrid and the tested aggregate. More preferably, the retention test should demonstrate greater than 75% retention, and even more preferably at least 90% or greater.

[0132] Example - Test 2 (rut) The performance of multiaxial geogrids to resist rutting caused by vehicular traffic was evaluated using small-scale tests that mimic established field tests.

[0133] Traffic tests were conducted on the specimens shown in Table E below. The table presents data for eight (8) tests on the preferred floating hexagons within the hexagonal geometry of the subject invention and eighteen (18) tests on the geometry of the prior art Walsh HAR patent. The specimens were manufactured from the same polymer material (polypropylene). The same die-cut pattern (except that an additional die-cut was utilized for the inventive specimens to form the inner hexagons) and a similar range of starting sheet thicknesses produced geogrid samples having nominally identical hexagons across the flat (A / F) dimensions, as shown in Figure 27, a copy of the prior Walsh HAR patent shown in Figure 6 (Prior Art), and the inventive geogrid shown in Figure 7. Figures 6 (Prior Art) and 7 are reproduced in Figure 28 to indicate the dimensions of the openings within each outer hexagon. In the sample of Figure 6 (Prior Art), dimensions A, B, and C = 33 mm ± 3 mm. For the inventive sample, dimension A = 35 mm ± 3 mm, dimension B = 24 mm ± 3 mm, and dimension C = 30 mm ± 3 mm. The aspect ratio of the ribs in the prior art specimens significantly exceeds that of the specimens produced according to the present invention. In Table E, Rib A shown in Figures 13 and 14 is used for comparison.

[0134] [Table 6]

[0135] Using the data in Table E, one can plot the aspect ratio of the ribs against the surface deformation after 10,000 passes as an indication of performance in terms of resistance to rutting. Such a plot is shown in Figure 24 of the drawings, where the specimen of the present invention is identified as "InterAx."

[0136] As is evident from Figure 24, the prior art multiaxial geogrid exhibited behavior similar to that shown in Figure 5 of the prior art Walsh HAR patent. The improvement in performance of the prior art geogrid tends to level off as the rib aspect ratio increases. A rib aspect ratio of 1 limits the surface deformation to around 45 mm, while increasing the aspect ratio to 2 reduces the deformation to 42 mm. Increasing the aspect ratio to 5 limits the deformation to 40 mm.

[0137] For geogrid specimens fabricated according to the preferred geometry that is the subject of this invention, an aspect ratio of 1.4 limits deformation to 30 mm from 40 mm, and an aspect ratio increase to 2.6 limits deformation to 22 mm from 28 mm. This test data demonstrates the substantial improvement of the present invention over the prior art geogrids of the Walsh HAR patent in its suitability for stabilizing and reinforcing aggregates in civil engineering applications.

[0138] As can be seen from the above, the geogrid of the present invention offers significant improvements over prior art geogrids due to the unique structure and operation of the floating hexagons within the hexagonal structure to engage, confine, and stabilize aggregate in geotechnical applications.

[0139] More specifically, existing commercially available prior art geogrids, regardless of fabrication method, have utilized one basic repeating shape and size of the apertures / openings formed between the oriented ribs / strands and their joints and nodes. Shapes such as rectangles, squares, and triangles have been utilized. The use of one basic repeating shape of apertures also means that the angle formed between two adjacent ribs at an intersecting joint or node is always the same throughout the geogrid.

[0140] Furthermore, existing prior art geogrids, regardless of fabrication method, have continuous ribs that repeat in the main direction. In products with square or rectangular openings, such as the Mercer patent mentioned above, these ribs may extend orthogonally, typically at 0° and 90° relative to the machine direction. In products with triangular openings, such as the Walsh '112 patent, these ribs will depend on the shape of the triangle. In a typical equilateral triangle, these ribs will extend at angles of 30°, 90°, and 150° relative to the machine direction.

[0141] Furthermore, existing commercially available prior art geogrids, again regardless of fabrication method, typically have ribs with roughly the same cross-sectional area and aspect ratio regardless of the direction in which they extend.

[0142] These similarities in the characteristics of prior art geogrids mean that the product properties that may enhance the performance of the geogrid as part of a composite matrix composed of geogrid and granular material are broadly similar throughout the body of the geogrid. These properties mentioned in the prior art may include (but are not limited to) aperture stability coefficient, geogrid in-plane and out-of-plane stiffness, rib in-plane and out-of-plane bending stiffness, aperture open area, aperture shape, and rib aspect ratio.

[0143] Thus, in accordance with the present invention, it has been discovered that the performance of a geogrid in a composite matrix can be improved if the geogrid is more variable, both in its repeating shape and in its individual characteristics, and can better integrate with the granular materials that make up the other components of the composite matrix. Most of the granular materials employed as components of a composite matrix are not uniform in shape or size, but are "graded" into size ranges, e.g., 20-40 mm, 10-63 mm, 20-70 mm, etc. Typical grading curves for commonly used granular materials are shown in the "Typical Aggregate Grading Curves" table below.

[0144] [Table 7]

[0145] As traditional granular materials become increasingly scarce and expensive, a wider variety of granular materials is becoming commonplace for use in construction. This is driven by a strong need to minimize the environmental impacts associated with the quarrying of traditional high-quality natural aggregates. For example, the energy and environmental impacts of quarrying natural aggregates, pressure to close quarry operations, the impacts of transporting quarried material to site, and the desire to use locally available granular and recycled materials.

[0146] Thus, it has been surprisingly discovered that the multiaxial geogrid of the present invention performs better than prior art commercially available geogrids in combination with the aforementioned lower quality and diverse granular materials, as well as with conventional well-graded granular materials. The geogrid construction of the present invention surpasses existing prior art geogrids and no longer follows the same "increasing returns" rule present in the high aspect ratio prior art geogrids of the Walsh HAR patent. While the size of the openings relative to the aggregate intended for a particular application must be optimized in prior commercially available geogrids, the opening shapes, sizes, and interior angles were all identical within the macro- and micro-levels of each differently constructed geogrid. Furthermore, geogrids based on repeating equilateral triangular patterns tend to perform better than those based on rectangular or square openings. In contrast, according to the present invention, the multiaxial geogrid has a repeating shape of openings of different shapes and sizes, multiple confinement angles, and is formed from ribs of different lengths, heights, and widths. The ribs preferably have an aspect ratio greater than 1.0, with some of the ribs, i.e., the strong axis strands, extending continuously across the grid in a linear manner in the transverse and diagonal directions, while other strands are interrupted to provide localized compliance zones, i.e., engineering discontinuities.

[0147] More specifically, it has been surprisingly discovered that, through the novel geometries and aperture / opening sizes and shapes, the present invention achieves two improvements in the containment and stabilization of diverse aggregates. First, by having apertures / openings of different sizes and shapes, the geogrids of the present invention are able to better match "natural" mineral aggregates sourced from quarries or mining methods, which have a wide variety of sizes and shapes due to their procurement and processing methods. Second, the geogrids of the present invention are better suited to and stabilize "non-natural" aggregate substitutes, such as recycled concrete and glass, which tend to have different physical properties than natural aggregates. While prior art geogrids are designed for natural aggregates, the shapes of the present invention are able to perfectly engage, contain, and stabilize both natural and non-natural aggregates.

[0148] In addition to the above, in addition to the performance improvements obtained with geogrids produced in accordance with the present invention, there are also savings in construction materials, time savings for construction of geotechnical matrices embodying the geogrids of the present invention, and carbon dioxide equivalent (CO2e) savings. https: / / www.sustainablebusinesstoolkit.com / difference-between-co2-and-co2e / It has also been found that the cost savings (see, e.g., U.S. Pat. No. 6,139,499) should be expected relative to the costs encountered with prior art commercially available geogrids, such as those made in accordance with the Mercer and Walsh HAR patents. According to current estimates, and when comparing geogrids having similar physical characteristics other than the Walsh HAR example with high aspect ratio ribs with examples of the present invention having the preferred geometries described herein and in accordance with the present invention, the cost savings achieved with geogrids made in accordance with the present invention can be as much as 10% to 40% relative to the cost of using geogrids made in accordance with the aforementioned prior art patents, as shown in Table F below.

[0149] [Table 8]

[0150] As noted above, Table F compares a conventional "geogrid-free" structure, a biaxial geogrid structure commercialized by Tenser under the original Mercer U.S. Patent No. 4,374,798, a triaxial geogrid structure commercialized by Tenser under the Walsh HAR patent, and the projected use of the present invention. For relative comparison, the typical aggregate layer thickness for each comparative geogrid is listed. Calculations are based on "lane kilometers," a standard construction industry measure at least in the UK and Europe. The term "tonne" refers to a metric ton (equal to 2,200 pounds).

[0151] The above description and drawings should be considered illustrative of the principles of the present invention. The present invention can be configured in a variety of sizes and is not limited to the precise shape of a preferred hexagon within a hexagonal 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 construction and operation described and illustrated. Rather, all suitable modifications and equivalents may be used that fall within the scope of the invention.

Claims

1. 1. A multiaxial integral geogrid comprising a plurality of interconnecting oriented strands and a plurality of partially oriented joints, the oriented strands and the partially oriented joints forming a repeating pattern of an exterior hexagon having a series of openings; each of said outer hexagons supports and surrounds a smaller inner hexagon having oriented strands; A multiaxial integral geogrid, wherein the oriented strands and the partially oriented joints of the outer hexagon define a plurality of linear strands that extend continuously throughout the entire multiaxial integral geogrid.

2. 2. The multiaxial integral geogrid of claim 1, wherein a plurality of said linear strands extend continuously throughout said multiaxial integral geogrid without crossing the interior of an outer hexagon.

3. 3. The multiaxial integral geogrid according to claim 1 or 2, wherein the oriented strands are biaxially oriented.

4. 4. The multiaxial integral geogrid of claim 1, 2 or 3, wherein the smaller internal hexagons are deflectable above or below the plane of the geogrid during compaction of the aggregate.

5. 5. The multiaxial integral geogrid of claim 4, wherein the smaller internal hexagons are deflectable up to about 33% of the thickness of the partially oriented joints above or below the plane of the geogrid during compaction of the aggregate.

6. The multiaxial integral geogrid of any one of claims 1 to 5, wherein the oriented multiaxial integral geogrid exhibits a high individual opening area distribution and stiffness relative to the individual opening area distribution, strength, and stiffness of a triaxial integral geogrid.

7. 7. The multiaxial integral geogrid of any one of claims 1 to 6, wherein the oriented strands form openings having repeating hexagonal, trapezoidal, and triangular shapes.

8. 8. The multiaxial integral geogrid of any one of claims 1 to 7, wherein there are three continuous strong axis strands extending continuously throughout the multiaxial integral geogrid, the strands being spaced apart at approximately 120° from each other.

9. The multiaxial integral geogrid according to any one of claims 1 to 8, wherein the geogrid is a single layer.

10. 10. The multiaxial integral geogrid of any one of claims 1 to 9, wherein the geogrid has a thickness of about 3 mm to about 9 mm.

11. 11. The multiaxial integral geogrid of claim 10, wherein the geogrid has a thickness of about 4 mm to about 7 mm.

12. The opening is at least 200 mm ２ 8. The multiaxial integral geogrid of claim 7, wherein the multiaxial integral geogrid provides a range of interaction with granular materials having different particle sizes.

13. A multiaxial integral geogrid according to one of the preceding claims, wherein the oriented strands have an aspect ratio of at least 1.0, preferably greater than 1.

86.

14. 5. The multiaxial integral geogrid of claim 4, wherein said smaller inner hexagons are deflectable up and down by an amount that is 33% of the total thickness of the surrounding outer hexagons.

15. 5. The multiaxial integral geogrid of claim 4, wherein the smaller internal hexagons are capable of deflecting above and below the plane of the geogrid during compression of the aggregate in a compliance region on the order of about 50% to about 75%.

16. A starting material for manufacturing a multiaxial integral geogrid comprising a polymer sheet, the polymer sheet has a pattern of holes or recesses that provide three differently shaped openings and a plurality of linear strands; When the sheet is biaxially stretched, the linear strands extend continuously throughout the multiaxial geogrid starting material.

17. 17. The starting material of claim 16, wherein when the sheet is biaxially stretched, the pattern of holes or recesses provides repeating hexagons formed from oriented strands within a hexagonal pattern of openings.

18. 18. The starting material of claim 16 or 17, wherein the three differently shaped openings are repeating hexagonal shapes, trapezoidal shapes, and triangular shapes.

19. 19. The starting material of claim 16, 17 or 18, wherein the polymer sheet has an initial thickness of about 3 mm to about 10 mm.

20. 20. The starting material of claim 19, wherein the polymer sheet has an initial thickness of about 5 mm to about 8 mm.

21. The starting material according to claim 16, wherein the multiaxial geogrid is as defined in any one of claims 1 to 15.

22. 1. A method for manufacturing a multiaxial integral geogrid, comprising: providing a polymer sheet; providing a plurality of patterned holes or recesses in the polymer sheet; orienting the polymer sheet having the patterned holes or recesses to provide a plurality of interconnecting oriented strands and partially oriented joints, wherein the oriented strands and partially oriented joints form a repeating pattern of outer hexagons with a series of openings, each of which supports and surrounds a smaller inner hexagon with oriented strands inside the outer hexagon, and the oriented strands and partially oriented joints of the outer hexagons form a plurality of linear strands that extend continuously throughout the multiaxial integral geogrid.

23. 1. A method for manufacturing a multiaxial integral geogrid, comprising: providing a polymer sheet; providing a plurality of patterned holes or recesses in the polymer sheet; orienting the polymer sheet having the patterned holes or recesses to provide a plurality of interconnecting oriented strands and partially oriented joints, wherein the oriented strands and partially oriented joints form a repeating pattern of outer hexagons having a series of openings, each of the outer hexagons supporting and surrounding a smaller inner hexagon having oriented strands, the oriented strands and partially oriented joints of the outer hexagons defining a plurality of linear strands extending continuously throughout the multiaxial integral geogrid.

24. 24. The method of claim 22 or 23, wherein the polymer sheet having the patterned plurality of holes or recesses is oriented by biaxial stretching.

25. The method of any one of claims 22 to 24, wherein the polymer sheet has an initial thickness of from about 3 mm to about 10 mm.

26. 26. The method of claim 25, wherein the polymer sheet has an initial thickness of about 5 mm to about 8 mm.

27. The method of any one of claims 22 to 26, wherein the openings have repeating hexagonal, trapezoidal and triangular shapes.

28. 24. The method according to claim 22 or 23, wherein the multiaxial geogrid is as defined in any one of claims 1 to 15.

29. biaxially stretching a starting material, which is a polymer sheet having a plurality of patterned holes or recesses, to provide a multiaxial integral geogrid, the multiaxial integral geogrid having a plurality of interconnecting oriented strands and a plurality of partially oriented joints, the oriented strands and the partially oriented joints forming a repeating pattern of outer hexagons having a series of openings, each outer hexagon supporting and surrounding a smaller inner hexagon having oriented strands, the oriented strands and the partially oriented joints of the outer hexagons defining a plurality of linear strands extending continuously throughout the multiaxial integral geogrid; and embedding said multiaxial integral geogrid in a mass of particulate material.

30. 30. The method of claim 29, wherein a plurality of said linear strands extend continuously throughout said multiaxial integral geogrid without crossing the interior of an outer hexagon.

31. 31. The method of claim 29 or 30, wherein the openings have repeating hexagonal, trapezoidal, and triangular shapes.

32. 31. The method according to claim 29 or 30, wherein the multiaxial geogrid is as defined in any one of claims 1 to 15.

33. 1. A multiaxial integral geogrid comprising a plurality of interconnecting oriented strands and a plurality of partially oriented joints, the oriented strands and the partially oriented joints forming a repeating pattern of a selected outer geometric shape having a series of openings; each of the outer geometric shapes supports and surrounds a smaller inner geometric shape having oriented strands, the inner geometric shapes being the same as or different from the outer geometric shapes; A multiaxial integral geogrid, wherein the oriented strands and partially oriented joints of the outer geometry form at least two sets of substantially parallel linear strands that extend continuously throughout the entire multiaxial geogrid.

34. 34. The multiaxial integral geogrid of claim 33, wherein said exterior geometric shape and said interior geometric shape are identical, said shapes being selected from the group consisting of a triangle, a rectangle, a square, and a hexagon.

35. 35. The multiaxial integral geogrid of claim 33 or 34, wherein the inner geometric shape is flexible or inflexible within the outer geometric shape.

36. a mass of particulate material; a multiaxial integral geogrid embedded in and engaged with the particulate material, the multiaxial integral geogrid having a plurality of interconnecting oriented strands and a plurality of partially oriented joints, the oriented strands and the partially oriented joints forming a repeating pattern of an exterior hexagon with a series of openings; each of said outer hexagons supports and surrounds a smaller inner hexagon having oriented strands; A reinforced stabilized composite soil structure, wherein the oriented strands and the partially oriented joints of the outer hexagon form a plurality of linear strands that extend continuously throughout the entire multiaxial integral geogrid.

37. 1. A multiaxial integral geogrid comprising a plurality of interconnecting oriented strands and a plurality of partially oriented joints, the oriented strands and the partially oriented joints forming a repeating pattern of an exterior hexagon having a series of openings; each of said outer hexagons supports a compact, oriented inner geometric configuration by means of an oriented rib; the oriented strands, the partially oriented joints, the oriented ribs, and the small oriented interior geometries form at least three different geometric configurations that are repeated throughout the multiaxial geogrid; A multiaxial integral geogrid, wherein the oriented strands and the partially oriented joints of the outer hexagon define a plurality of linear strands that extend continuously throughout the entire multiaxial integral geogrid.

38. 38. The multiaxial integral geogrid of claim 37, wherein said three different geometric configurations are hexagonal, trapezoidal, and triangular.

39. 1. A method for determining the performance of a particular geogrid in relation to a particular aggregate, comprising: conducting a standardized retention test using the geogrid and a quantity of the aggregate; and determining whether the geogrid captured at least about 50% of the aggregate during the test.

40. 40. The method of claim 39, wherein the determination of capture is at least 75%, preferably greater than 90%.

41. 41. The method of claim 39 or 40, wherein the geogrid is a multiaxial geogrid as defined in any one of claims 1 to 15.

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