Polymer sheet, method of installing and producing same

1. A polymer sheet adapted to attach to a ceiling of a geological cavity and provide protective cover, the sheet comprising:

a webbing portion defining a plurality of primary openings; and

two margin portions extending along opposite edges of the sheet on either side of the webbing portion along a length of the sheet, each margin portion defining a plurality of secondary openings, wherein the margin portions are angled relative to the webbing portion,

wherein the sheet is shaped such that the margin portions are angled out of a webbing plane defined by the webbing portion and the sheet defines elongate creases between the webbing portion and each margin portion,

wherein the elongate creases form an obtuse angle between the webbing portion and either of the margin portions in a range of 140° to 160°.

2. The sheet of claim 1 , wherein the margin portions are angled out of the webbing plane in opposite directions on either side of the webbing plane.

3. A polymer sheet adapted to attach to a ceiling of a geological cavity and provide protective cover, the sheet comprising:

a webbing portion defining a plurality of primary openings; and

two margin portions extending along opposite edges of the sheet on either side of the webbing portion along a length of the sheet, each margin portion defining a plurality of secondary openings, wherein the margin portions are angled relative to the webbing portion,

wherein the sheet comprises a plurality of webbing portions and adjacent webbing portions are separated by a wider web portion extending between the margin portions,

wherein the dimension of the wider web portion is greater than the largest dimension of the openings.

4. The sheet of claim 3 , wherein the sheet is shaped such that the margin portions are angled out of a webbing plane defined by the webbing portion and the sheet defines elongate creases between the webbing portion and each margin portion.

5. The sheet according to claim 3 , wherein the secondary openings defined by the two margin portions are arranged in a regular array.

6. The sheet according to claim 5 , wherein the regular array of secondary openings in each margin portion is the same so that, when either one of the margin portions and a margin portion on an identical but separate sheet are overlapping, at least two of the secondary openings are aligned.

7. The sheet according to claim 3 , wherein a separation between the secondary openings is greater than a separation between primary openings.

8. The sheet according to claim 3 , wherein the sheet is a self-supporting structure and is flexible.

9. A method of installing protective covering on a ceiling of a geological cavity comprising:

positioning a first polymer sheet according to claim 3 near or on the ceiling; and

attaching a first portion of the first polymer sheet to the ceiling, wherein the attaching comprises using fasteners to attach the first portion to the ceiling, and a first section of each fastener is attached to the ceiling while a second section of each fastener passes through either a primary or secondary opening defined by the first polymer sheet.

10. The method of claim 9 , further comprising attaching a second portion of the first polymer sheet to the ceiling, the first portion is near a first end of the first polymer sheet and the second portion is near a second end opposite the first end along the length of the first polymer sheet.

11. The method according to claim 9 , further comprising:

positioning a second polymer sheet according to claim 1 such that: the second polymer sheet partially overlaps the first polymer sheet, and at least one of the primary or secondary openings in the second polymer sheet is aligned with a primary or secondary opening in the first polymer sheet; and

attaching at least one portion of the second polymer sheet to the ceiling.

12. The method according to claim 11 , wherein attaching the at least one portion of the second polymer sheet comprises using the same fasteners used to attach the first or second portion of the first polymer sheet to the ceiling, and the second section of the fasteners pass through aligned openings in the first and second polymer sheet.

13. A method of producing a polymer sheet adapted to attach to a ceiling of a geological cavity and provide protective cover, the method comprising:

extruding a polymer material into a sheet with a length and a width, wherein the sheet comprises a plurality of webbing portions;

forming a plurality of primary openings in at least one of the webbing portions and forming a plurality of secondary openings in each of a first and second margin portion,

wherein the first and second margin portion extend along opposite edges of the sheet on either side of the webbing portions along the length of the sheet,

wherein adjacent webbing portions are separated by a wider web portion extending between the margin portions, and

wherein the dimension of the wide web portion is greater than the largest dimension of the openings; and

shaping the sheet such that the first and second margin portion are angled relative to the webbing portions.

14. The method according to claim 13 , wherein the sheet is shaped such that the margin portions are angled out of a webbing plane defined by the webbing portions and the sheet defines elongate creases between the webbing portions and each of the first and second margin portions.

15. The method of claim 14 , wherein the sheet is shaped such that the first margin portion is angled out of the webbing plane in a first direction and the second margin portion is angled out of the webbing plane in a second direction on the other side of the webbing plane.

16. The method according to claim 13 , wherein the plurality of secondary openings are formed in a regular array, and the regular array of secondary openings in the first margin portion is formed to be the same as the regular array of secondary openings in the second margin portion so that, when either of the first or second margin portion and a margin portion on an identical but separate sheet are overlapping, at least two of the secondary openings are aligned.

17. The method according to claim 13 , wherein a separation between the secondary openings is greater than a separation between primary openings.

18. A polymer sheet adapted to attach to a ceiling of a geological cavity and provide protective cover, the sheet comprising:

a plurality of webbing portions located adjacent to each other, each webbing portion defining a plurality of primary openings, wherein a first separation divides adjacent primary openings; and

two margin portions extending along opposite edges of the sheet on either side of the webbing portions along a length of the sheet, each margin portion defining a plurality of secondary openings, wherein adjacent webbing portions are separated by a wider web portion extending between the margin portions, and wherein the dimension of the wider web portion is greater than the largest dimension of the first separation between the primary openings.

19. The sheet according to claim 18 , wherein a second separation between the secondary openings is greater than the first separation.

20. A method of producing a polymer sheet adapted to attach to a ceiling of a geological cavity and provide protective cover, the method comprising:

extruding a polymer material into a sheet with a length and a width, wherein each sheet comprises a plurality of webbing portions located adjacent to each other;

forming a plurality of primary openings in a webbing portion and a plurality of secondary openings in each of a first and second margin portion, wherein the first and second margin portion extend along opposite edges of the sheet on either side of the webbing portion along the length of the sheet;

wherein a first separation divides adjacent primary openings, wherein adjacent webbing portions are separated by a wider web portion extending between the margin portions, and wherein the dimension of the wider web portion is greater than the largest dimension of the first separation between the primary openings.