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A method of blasting plural layers of material in a blastfield that reduces the amount of mechanical excavation required to expose a lower layer of material. The method includes using rows of equally spaced blastholes that pass through all of the layers and additional intermediate rows of blastholes

A method of blasting plural layers of material in a blastfield that reduces the amount of mechanical excavation required to expose a lower layer of material. The method includes using rows of equally spaced blastholes that pass through all of the layers and additional intermediate rows of blastholes that pass down only through the top layer. Each blasthole is capped with stemming material and includes one or more decks of explosive material and detonators, which air decks or inert stemming separating adjacent explosive decks. The detonators in layer are detonated first in order from row rearwards to throw a substantial amount of the blast material from the layer forwardly of free face onto the floor. In the same blasting cycle and within seconds of the throw blast, explosives materials in layers are detonated in a stand-up blast in which material in layers are broken up but otherwise are minimally displace or thrown forwardly.

대표청구항 ▼

1. In open cut mining for recoverable mineral, a method of blasting plural layers of material in a blast field including a first body of material comprising at least a first layer of material and a second body of material comprising at least a second layer of material over the first body of material

1. In open cut mining for recoverable mineral, a method of blasting plural layers of material in a blast field including a first body of material comprising at least a first layer of material and a second body of material comprising at least a second layer of material over the first body of material, the method comprising: drilling rows of blastholes through the second body of material and, for at least a plurality of the blastholes, at least into the first body of material,loading the blastholes with explosives, in which at least a plurality of the blastholes that extend into the first body of material are loaded with a respective deck of explosives in each of the first and second bodies of material, andfiring the explosives in the first and second bodies of material in a single cycle of drilling, loading and blasting at least the first and second bodies of material and configuring delay times of detonators of the explosives in the first and second bodies of material in a manner to subject the second body of material to a blast of different design compared to the blast of the first body of material and to produce a different blast outcome in the second body of material compared to that in the first body of material,wherein configuring delay times of the detonators of the explosives in the first and second bodies of material in each blasthole to produce the blast of different design comprises providing in said at least a plurality of the blastholes having a respective deck of explosives in each of the first and second bodies of material at least one of 1), between adjacent rows, different inter-row blasthole delay times of the detonators for the explosives in the second body of material relative to the detonators for the explosives in the first body of material, wherein the different inter-row blasthole delay times comprise, for at least two blastholes in adjacent rows having a respective deck of explosive in each of the first and second bodies of material, a first delay time between initiation of a deck of explosive in the second body of material in one blasthole in one row and initiation of a deck of explosive in the second body of material in an adjacent blasthole in any adjacent row which is different from a second delay time between initiation of a deck of explosive in the first body of material in the one blasthole and initiation of a deck of explosive in the first body of material in the adjacent blasthole or 2), in any one row, different inter-hole blasthole delay times of the detonators for the explosives in the second body of material relative to the detonators for the explosives in the first body of material, wherein the different inter-hole blasthole delay times comprise, for at least two blastholes in the same row having a respective deck of explosive in each of the first and second bodies of material, a first delay time between initiation of a deck of explosive in the second body of material in one blasthole in the row and initiation of a deck of explosive in the second body of material in another blasthole in the same row which is different from a second delay time between initiation of a deck of explosive in the first body of material in the one blasthole in the row and initiation of a deck of explosive in the first body of material in the other blasthole in the same row. 2. A method of blasting according to claim 1, wherein blasting is of plural strata of material in which the first body of material comprises at least a first stratum of material and the second body of material comprises at least a stratum of overburden over the first body of material. 3. A method of blasting according to claim 1, wherein the blasts of different design in the first and second bodies of material achieve differential fragmentation between the two bodies of material. 4. A method of blasting according to claim 2, wherein the second body of material consists essentially of the stratum of overburden. 5. A method of blasting according to claim 4, wherein the explosives in the second body of material are spaced from the bottom of the second body of material. 6. A method of blasting according to claim 1, wherein the explosives in the second body of material in each of at least some of the blastholes are provided as a main column of explosives and as a further deck of explosives spaced from and beneath the main column, said further deck of explosives being smaller than the main column of explosives. 7. A method of blasting according to claim 6, wherein the further deck of explosives is fired on a different delay to the main column. 8. A method of blasting according to claim 2, wherein the first body of material comprises at least two strata of recoverable mineral and at least one stratum of interburden therebetween. 9. A method of blasting according to claim 8, wherein the explosives in the first body of material are disposed only in the at least one stratum of interburden. 10. A method of blasting according to claim 9, wherein the explosives in the interburden are spaced from the strata of recoverable mineral. 11. A method of blasting according to claim 10, wherein the blastholes are not drilled into the lowermost strata of recoverable mineral in the first body of material. 12. A method of blasting according to claim 9, wherein the explosives in the interburden in each of at least some of the blastholes are provided as a main column of explosives and as a further deck of explosives spaced from and beneath the main column, said further deck of explosives being smaller than the main column of explosives. 13. A method of blasting according to claim 12, wherein the further deck of explosives is fired on a different delay to the main column. 14. A method of blasting according to claim 1, wherein not all of the blastholes in the second body of material extend into the first body of material. 15. A method of blasting according to claim 14, wherein at least some of the blastholes only in the second body of material do not extend to the bottom of the second body of material. 16. A method of blasting according to claim 2, wherein a third body of material is disposed between the first and second bodies of material, the third body of material comprising at least one stratum of burden or recoverable mineral, and wherein the third body of material is subjected to a blast in said single cycle of different design to the blast to which at least one of the first or second body of material is subjected in said single cycle. 17. A method of blasting according to claim 1, wherein the explosives in blastholes in the first body of material are initiated from the back of the blast, i.e. remote from the location of the free face, towards the front of the blast, i.e. adjacent the location of the free face. 18. A method of blasting according to claim 1, wherein the explosives in blastholes in one or both of the first and second bodies of material have an initiation point remote from edges of the blast field. 19. A method of blasting according to claim 1, wherein the blast in said one or both of the first and second bodies of material proceeds in multiple directions from said initiation point. 20. A method of blasting according to claim 1, wherein the blast field has a free face at the level of the second body of material and wherein the explosives in blastholes in the second body of material adjacent the back of the blast, i.e. remote from the location of the free face, are initiated before the explosives in blastholes in the second body of material further forward, i.e. closer to the location of the free face. 21. A method of blasting according to claim 1, wherein in said single cycle the blast in the first body of material is initiated after initiation of the blast in the second body of material. 22. A method of blasting according to claim 21, wherein the delay between initiation of the blast in the second body of material and initiation of the blast in the first body of material is about 40 seconds or less. 23. A method of blasting according to claim 22, wherein said delay is in the range of about 500 to 25000 ms. 24. A method of blasting according to claim 1, wherein in said single cycle the blast in the first body of material is initiated before initiation of the blast in the second body of material. 25. A method of blasting according to claim 1, wherein the explosives in the blast field are initiated by an electronic detonator delay system. 26. A method of blasting according to claim 1, wherein said loading and blasting in said single cycle are preceded by blast-hole logging to determine the location of any stratum of recoverable mineral in each blasthole. 27. A method of blasting according to claim 26, wherein the blasthole logging comprises gamma-ray logging. 28. A method of blasting according to claim 1, wherein the blast in the second body of material and the blast in the first body of material have additional different blast design features selected from one or more of blasthole pattern, explosive type, explosive density, blast-hole loading configuration, explosive mass, powder factor, stemming and buffering. 29. A method of blasting according to claim 2, wherein said first stratum of material is recoverable mineral.