Blasting

Abstract

In blasting rock, a drill hole ( 12 ) is charged with spaced, composite layers ( 20 ), ( 30, 40 ) at different levels between an open mouth ( 14 ) and a blind bottom ( 16 ). Each composite layer is supported on a plug ( 22, 32, 42 ). Flowable plunger material ( 24, 34, 44 ), e.g. drill cuttings, is supported on the respective plug followed by blast material ( 26, 36, 46 ), topped by a further layer of plunger material ( 28, 38, 48 ). The plunger material ( 48 ) at the top, is in the form of tamping. The composite layers are spaced respectively from one another and optionally, from the bottom ( 16 ). Initiators ( 27, 37, 47 ) can be actuated by means of a controller to initiate the blasting material to displace the layers of plunger material at speed to collide, e.g. with the bottom and with one another to concentrate enemy at the collision sites.

1 . A method of charging and blasting a drill hole extending between a mouth thereof at a surface, and a blind end or bottom thereof remote from the mouth, the method comprising: 
 charging the drill hole which comprises 
 providing in the drill hole at a relatively low level toward said bottom a lower layer of a blasting substance, and a lower layer of a plunger material proximately above the lower layer of blasting substance;  
 providing in the drill hole at a relatively high level remote from said bottom a higher layer of a plunger material, spaced a predetermined distance above said lower layer of plunger material to form a spacing, and proximately above said higher layer of plunger material, a higher layer of a blasting substance;  
 placing initiators in association with the respective layers of blasting substances and connecting the initiators to a controller for actuating the initiators at predetermined time interval; and  
   blasting the charged drill hole which comprises 
 actuating the initiators by means of the controller, thereby propelling the lower layer of plunger material by means of the lower layer of blasting substance into said spacing, and propelling the higher layer of plunger material by means of the higher layer of blasting substance into said spacing thereby causing the lower layer of plunger material and the higher layer of plunger material to impinge upon each other, and causing conversion of kinetic energy associated with the propelled layers of plunger material into pressure or shock waves to effect destruction of rock in the surrounding material.  
   
   
   
       2 . A method as claimed in  claim 1 , in which the spacing between opposing surfaces of respectively said lower layer of plunger material and said higher layer of plunger material is between about 0.5 m and about 3 m.  
   
   
       3 . A method as claimed in  claim 1  in which the respective layers of plunger material are flowable material allowing placement in the drill hole at the respective desired positions.  
   
   
       4 . A method as claims in  claim 1 , further comprising tamping the drill hole proximate its mouth.  
   
   
       5 . A method as claimed in  claim 1  in which said relatively lower level is spatially adjacent the bottom of the drill hole end spaced above the bottom by a predetermined distance.  
   
   
       6 . A method as claimed in  claim 5  in which the spacing between said relatively low level and the bottom is between about 0.5 m and about 3 m.  
   
   
       7 . A method as claimed in  claim 5 , wherein said charging step further comprises supporting in each respective case the layer of plunger material and the layer of blasting substance on a plug capable of being positioned in the drill hole at a predetermined level.  
   
   
       8 . A method as claims in  claim 5 , wherein said charging step further comprises providing plunger material below the lower layer of blasting substance to provide a lower composite layer, providing plunger material above the higher layer of blasting substance to provide a higher composite layer, and providing one or more further composite layers of blasting substance and plunger material in the drill hole, with spacings in-between, in series along the drill hole.  
   
   
       9 . A method as claimed in  claim 1 , in which the lower layer of blasting substance is positioned proximate and is supported on the bottom of the drill hole.  
   
   
       10 . A method as claimed in  claim 1  wherein said actuating step further comprises actuating the initiators at time intervals to initiate the respective blasting substances simultaneously.  
   
   
       11 . A method as claimed in  claim 10  wherein said actuating step further comprises actuating the initiators in a way selected from electrically, electronically, or pyrotechnically.  
   
   
       12 . A method of mining comprising carrying out the method of  claim 1  on each of an array of drill holes.  
   
   
       13 . A charged drill hole extending between a mouth thereof at a surface, and a blind end or bottom thereof remote from the mouth, comprising within the drill hole, 
 a lower layer of a blasting substance at a relatively low level toward said bottom, and a lower layer of plunger material proximately above the lower layer of blasting substance,    a higher layer of plunger material at a relatively high level remote from said bottom, and spaced a predetermined distance above said lower layer of plunger material such as to form a spacing therebetween, and proximately above said higher layer of plunger material, a higher layer of a blasting substance;    initiators placed in association with the respectively layers of blasting substances and having connectors for connection to a controller for actuating the initiators at predetermined time intervals,    wherein the lower and higher layers of plunger material oppose each other spatially, each layer of plunger material being backed by a layer of blasting substance, such that, in use, on actuation of the layers of blasting substance the layers of plunger material are propelled toward each other, to impinge upon each other and to convert kinetic energy associated with the propelled layers of plunger material into pressure or shock waves to destruct surrounding material.    
   
   
       14 . A charged drill hole as claimed in  claim 13  in which the spacing between opposing surfaces of respectively said lower layer and said higher layer of plunger material is between about 0.5 m and about 3 m.  
   
   
       15 . A charged drill hole as claimed in  claim 13  in which the respective layers of plunger material are flowable material allowing placement in the drill hole at the respective desired positions.  
   
   
       16 . A charged drill holes as claimed in  claim 13 , further comprising tamping material closing the drill hole proximate its mouth.  
   
   
       17 . A charged drill hole as claimed in  claim 13  in which said relatively low level is spatially adjacent a bottom of the drill hole and spaced above the bottom by a predetermined distance.  
   
   
       18 . A charged drill hole as claimed in  claim 17  in which the spacing is between about 0.5 m and about 3 m.  
   
   
       19 . A charged drill hole as claimed in  claim 17  in which in each respective case, the layer of plunger material and the layer of blasting substance is supported on a plug positioned in the drill hole at a predetermined level.  
   
   
       20 . A charged drill hole as claimed in  claim 17 , further comprising plunger material provided below the lower layer of blasting substance to form a lower composite layer, plunger material provided above the higher layer of blasting substance to form a higher composite layer, and one or more further composite layers of blasting substance and plunger material, with spacings in-between, in series along the drill hole.  
   
   
       21 . A charged drill hole as claimed in  claim 13 , in which the lower layer of blasting substance in proximate the bottom and is supported on the bottom.  
   
   
       22 . A blasting operation comprising an array of blast holes each in accordance with  claim 13.