Encapsulation system and method of installing a rock bolt

1. An encapsulation system for use in securing a rock bolt in a bore hole drilled into a rock face to be stabilised, said encapsulation system comprising at least two separate encapsulation mediums and one or more elongate cartridges containing said encapsulation mediums, each said cartridge having a frangible casing, said encapsulation mediums including:

a first encapsulation medium comprising a curable first resin formulation; and a second encapsulation medium comprising a curable second resin formulation;

wherein, following use in securing a rock bolt, said second resin formulation has a lower bond strength and/or a lower compressive strength than said first resin formulation.

2. The encapsulation system of claim 1 , wherein said second resin formulation has a longer curing time than said first resin formulation.

3. The encapsulation system of claim 1 , wherein said encapsulation system further comprises a third encapsulation medium comprising a curable third resin formulation;

wherein, following use in a securing a rock bolt, said second encapsulation medium has a lower bond strength and/or a lower compressive strength than said third resin formulation.

4. The encapsulation system of claim 3 , wherein said third resin formulation has a longer curing time than said first resin formulation.

5. The encapsulation system of claim 3 , wherein said one or more elongate cartridges comprises a first cartridge containing said first encapsulation medium, a second cartridge containing said second encapsulation medium and a third cartridge containing said third resin formulation.

6. The encapsulation system of claim 3 , wherein said encapsulation system comprises a single cartridge containing each of said encapsulation, and wherein said second encapsulation medium is located between said first and third encapsulation mediums; or wherein said encapsulation system comprises a single cartridge containing each of said encapsulation mediums, said casing having one or more constrictions formed along its length to define multiple regions along in an interior of said casing, and wherein said second encapsulation medium is located between said first and third encapsulation mediums.

7. The encapsulation system of claim 6 , wherein each said region contains one of said encapsulation mediums, wherein the casing has one constriction formed along its length defining a first region and a second region, and wherein the first encapsulation medium is contained in the first region, the third encapsulation medium is contained in the second region, and the second encapsulation medium is contained in both the first and second regions.

8. The encapsulation system of claim 3 , wherein said second resin formulation comprises an inert filler compound, and said first and third resin formulations comprise a curable component and a catalyst component.

9. The encapsulation system of claim 1 , wherein, said encapsulation system comprises a separate said cartridge containing each said encapsulation medium.

10. The encapsulation system of claim 1 , wherein said encapsulation system comprises a single cartridge containing each of said encapsulation mediums, said encapsulation mediums being arranged in longitudinal succession along an interior of said casing; or wherein said encapsulation system comprises a single cartridge containing each of said encapsulation mediums, said casing having one or more constrictions formed along its length to define multiple regions along in an interior of said casing.

11. The encapsulation system of claim 1 , wherein said first and second resin formulations comprises a curable component and a catalyst component.

12. A method of installing a rock bolt into a bore hole drilled into a rock face to be stabilised, said method comprising:

inserting an encapsulating system into the bore hole, said encapsulation system comprising at least two encapsulation mediums and one or more elongate cartridges containing said encapsulation mediums, each said cartridge having a frangible casing, said encapsulation mediums including a first encapsulation medium inserted into the bore hole followed by a second encapsulation medium, said first encapsulation medium comprising a curable first resin formulation;

inserting a rock bolt comprising an elongate load bearing element into the bore hole, thrusting said load being element through said encapsulating system towards a blind end of the bore hole and rotating said load bearing element so as to rupture said frangible casing of each said cartridge and mix each of said encapsulation mediums such that said first encapsulation medium encapsulates a leading portion of said load bearing element located adjacent a blind end of said borehole and said second encapsulating medium encapsulates an intermediate portion of said load bearing element extending between said leading portion of said load bearing element and a trailing portion of said load bearing element; and

curing said first resin formulation to secure leading portion of said load bearing element in said bore hole;

wherein, upon completion of said installation, said second encapsulation medium has a lower bond strength and/or a lower compressive strength than said first resin formulation.

13. The method of claim 12 , wherein said second encapsulation medium comprises a second resin formulation, said method further comprising curing said second resin formulation.

14. The method of claim 13 , wherein, said encapsulation system further comprises a third encapsulation medium comprising a curable third resin formulation, inserting said encapsulation system into the bore hole including inserting said third encapsulation medium into the bore hole after said second encapsulation medium, said third encapsulation medium at least partly encapsulating said trailing portion of said load-bearing element, said method further comprising curing said third resin formulation to secure said trailing portion of said load bearing element in said bore hole;

wherein upon completion of said installation, said second encapsulation medium has a lower bond strength and/or a lower compression strength than said third resin formulation.

15. The method of claim 14 , wherein said first resin formulation is fully cured prior to said third resin being fully cured.

16. The method of claim 14 , wherein said method further comprises, after curing of said first resin, tensioning said load bearing element, said load bearing element is tensioned prior to said third resin being fully cured.

17. The method of claim 13 , said method further comprises, after curing of said first resin, tensioning said load bearing element, wherein said load bearing element is tensioned prior to said second resin being fully cured.

18. The method of claim 12 , wherein, said method further comprises, after curing of said first resin, tensioning said load bearing element.

19. The method of claim 12 , wherein said encapsulation system comprises a separate said cartridge containing each said encapsulation medium, inserting said encapsulation system into said bore hole including inserting a first cartridge containing said first encapsulation medium into said bore hole, followed by inserting a second cartridge containing said second encapsulation medium into said bore hole; or wherein said encapsulation system comprises a single cartridge containing each of said encapsulation mediums, inserting said encapsulation system into said bore hole including inserting said cartridge into said bore hole with said first encapsulation medium leading.