Multi-axial grid or mesh structures with high aspect ratio ribs
A multi-axial geogrid possesses a series of interconnected strands or ribs that are arranged along at least two different axes within the plane of the structure. The strands or ribs have an aspect ratio, defined as the ratio of the thickness to width, of greater than 1.0, thickness being the direction normal to the plane of the structure. The geogrid can be manufactured by modifying the process parameters in order to create high aspect ratio ribs, using any of the various known methods for producing geogrids. A reinforced civil engineering structure, and method therefor, is formed by embedding in soil one or more horizontal layers of geogrid having high aspect ratio ribs. The reinforced structure shows improved rutting performance when subjected to vehicular traffic.
1 . A multi-axial grid or mesh structure comprising a generally uniform array of substantially straight oriented transverse strands or ribs interconnected by junctions extending transversely across said grid or mesh structure in spaced apart rows and a plurality of substantially straight oriented connecting strands or ribs interconnecting said junctions in adjacent rows to form apertures or openings between adjacent oriented strands or ribs and junctions, said strands or ribs having an aspect ratio greater than 1.0.
2 . The grid or mesh structure of claim 1 wherein the grid or mesh structure is an integral geogrid.
3 . The grid or mesh structure of claim 1 wherein the grid or mesh structure is a triangular geogrid, and said aspect ratio is between 1.0 and about 2.5, and preferably between about 1.4 and about 2.2.
4 . The grid or mesh structure of claim 1 wherein the grid or mesh structure is a rectangular geogrid, and said aspect ratio is in the range between 1.0 and about 4.0.
5 . The grid or mesh structure of claim 4 , wherein the grid or mesh structure has an aperture stability modulus greater than about 0.3 Nm/degree at 20 kg-cm of applied torque, and preferably greater than about 0.45 Nm/degree at 20 kg-com of applied torque.
6 . A method of strengthening a particulate material, comprising embedding in the particulate material the multi-axial geogrid of claim 2 .
7 . A geoengineering construction comprising a mass of particulate material strengthened by embedding therein a multi-axial geogrid as claimed in claim 2 .
8 . The grid or mesh structure of claim 1 wherein the grid or mesh structure is a series of parallel strands or ribs intersected at junctions with a second series of parallel strands or ribs that are essentially perpendicular to the first series of parallel strands or ribs.
9 . The grid or mesh structure of claim 8 wherein the grid or mesh structure is an integral geogrid having generally rectangular apertures or openings.
10 . The grid or mesh structure of claim 1 wherein the grid or mesh structure has three or more series of parallel strands or ribs intersecting each other at junctions such that the angles of the intersecting strands or ribs at the junction are angles not equal to 90°.
11 . The grid or mesh structure of claim 10 wherein the grid or mesh structure has three series of parallel strands or ribs intersecting each other at the junctions at angles of about 60° to form generally equilateral triangular apertures or openings.
12 . The grid or mesh structure of claim 1 wherein the ribs have a concave cross-section at or near their center.
13 . A method of retaining a particulate material, comprising embedding a grid or mesh structure as claimed in claim 1 in the particulate material so that the particulate material is at least partially interlocked in said apertures or openings.
14 . A method of making a biaxially oriented plastic material integral geogrid, comprising:
providing a plastics sheet starting material having a selected thickness and having holes of a selected dimension and arranged in a selected configuration array of substantially identical shape and size;
applying a stretch in a first direction to stretch out strand forming zones between adjacent holes on sides of each configuration to form oriented strands from such zones;
applying a stretch in a second direction substantially at right angles to said first direction to stretch out strand forming zones between adjacent holes on the side of the selected configuration to form oriented strands from the latter zones; and
the thickness of the sheet starting material, the size of the holes and the hole configuration are each selected to produce oriented strands having an aspect ratio greater than 1.0.
15 . A geoengineering construction comprising a mass of particulate material strengthened by embedding therein a biaxially oriented plastics material geogrid produced in accordance with the method of claim 14 .
16 . A method of strengthening a particulate material, comprising embedding in the particulate material the biaxially oriented plastics material geogrid made in accordance with the method of claim 14 , the particulate material at least partially interlocked in apertures between said oriented strands.