solid column explosive charge method for blasting rock

Abstract

A solid column explosive charge method for blasting rock includes a hollow gas-filled core component arranged collinearly in concentrically spaced relation within a vertical borehole, the core component being seated upon a first layer of particulate explosive material, and a first annular portion of the particulate explosive material being arranged concentrically about the core component. The first layer and the first annular portion are in engagement to define a continuous explosive column. A plurality of core components together with associated layers and annular portions of the explosive charge may be arranged in a continuous vertical column, the total volume of the core components being from 10 percent to 25 percent of the volume of the explosive column. A top layer of inert fill material is arranged above the core component to close the upper end of the bore opening.

1 . A method for blasting rock for surface coal mining and the like, comprising: 
 (a) drilling in the rock a vertical bore hole having a given diameter of from about 6″ to about 13″ and a generally vertical axis extending to a depth of from about 10 feet to about 200 feet;    (b) depositing into said bore hole a bottom layer ( 6 ) of inert backfill material;    (c) depositing into said bore hole above said layer of backfill material a first layer ( 8   a ) of a particulate explosive charge;    (d) folding a cardboard blank having a plurality of panels ( 30   a ) and flaps ( 30   b ) to define a closed air-filled core component ( 30 ), said core component having a length of from between 3 feet to 6 feet,    (e) inserting said core component into said bore hole in seated engagement with said first layer of particulate explosive charge, said core component having a cross-sectional dimension that is less than that of said bore hole diameter;    (f) depositing into said bore hole about the entire length of said core component a second layer ( 8   b ) of said particulate explosive charge, said second layer being in direct engagement with said first layer, thereby to define a continuous explosive column containing said core component, the volume of said core component being about 10 percent to 25 percent of the volume of said continuous explosive column;    (g) depositing into said bore hole above said core component a top stem of inert material; and    (h) detonating said particulate explosive charge.    
   
   
       2 . A method for blasting rock as defined in  claim 1 , and further including, prior to said top stem depositing step: 
 (i) depositing in said bore hole above said second layer a third layer ( 8   c ) of said particulate explosive charge;    (j) inserting into said bore hole a second one of said hollow gas-filled core components, said second core component having a cross-sectional transverse dimension that is less than said bore hole diameter; and    (k) depositing into said bore hole about said second core component a fourth layer ( 8   d ) of said particulate explosive charge, said fourth layer being in engagement with said third layer, thereby to define a continuous explosive column containing said core components in spaced collinearly arranged relation, the sum of the volumes of said core components being 10 percent to 25 percent of that of said continuous explosive column    
   
   
       3 . A method for blasting rock as defined in  claim 2 , and further including: 
 (l) depositing into said bore hole above said second core component and in direct contact with said fourth layer a fifth layer ( 8   c ) of said particulate explosive charge, thereby to define a continuous explosive column between said first and said fifth explosive layers.    
   
   
       4 . A method for blasting rock as defined in  claim 1 , and further including 
 (i) introducing into said first layer a booster firing cap for detonating said continuous explosive column.