A method of blasting an open cast blast hole

Abstract

The invention provides a method of Wasting an open cast blast hole the method including placing one or more explosive charge in the blast hole, stemming the blast hole with stemming material above said one or more explosive charge, placing a propellant powder cartridge into the stemming material so that there is a layer of stemming material between the propellant powder cartridge and the explosive charge which is closest to the open end of the blast hole, and initiating the propellant powder charge with an igniter, or a detonator, or a fuse head, or any electronic initiation system.

1 . A method of blasting an open cast blast hole, the method including:
 placing one or more explosive charge in the blast hole;   stemming the blast hole with stemming material above said one or more explosive charge;   placing a propellant powder cartridge into the stemming material so that there is a layer of stemming material between the propellant powder cartridge and the explosive charge which is closest to the open end of the blast hole; and   initiating the propellant powder charge with an igniter, or a detonator, or a fuse head, or any electronic initiation system.   
     
     
         2 . A method as claimed in  claim 1 , wherein the explosive in the blast hole is initiated by a detonator having a delay of from 350 ms to 20 000 ms, and the propellant powder charge initiation system includes a delay time which is at least 25 ms shorter than that of the detonator in the same blast hole. 
     
     
         3 . A method as claimed in  claim 2 , wherein the propellant powder charge initiation system delay is from 25 ms to 19 975 ms. 
     
     
         4 . A method as claimed in  claim 1 , wherein in a blast hole, starting from the bottom end thereof, there are alternating explosive layers and stemming material layers with the propellant powder cartridge being located below the stemming material layer at the blast hole opening. 
     
     
         5 .- 8 . (canceled) 
     
     
         9 . A method as claimed in  claim 2 , wherein in a blast hole, starting from the bottom end thereof, there are alternating explosive layers and stemming material layers with the propellant powder cartridge being located below the stemming material layer at the blast hole opening. 
     
     
         10 . A method as claimed in  claim 3 , wherein in a blast hole, starting from the bottom end thereof, there are alternating explosive layers and stemming material layers with the propellant powder cartridge being located below the stemming material layer at the blast hole opening. 
     
     
         11 . An initiation method for a propellant powder cartridge in which an igniter having a delay time of 400 ms difference with that of an explosive charge is placed in a same hole below the propellant powder cartridge.