Boulder Blasting 



There are three ways in which boulders can be blasted. These are 

 known as "Mudcapping," "Snakeholing," and "Blockholing." "Mud- 

 capping" and "Snakeholing" are the easier and quicker methods, but 

 require more dynamite. It is almost impossible to shatter large round 

 boulders of hard rock by either of these methods, without using an 

 excessive quantity of explosives. 



Mudcapping 



When blasting boulders by mudcapping them (also called "doby 

 shooting" or "blistering") the charge of dynamite is packed closely 

 against the surface on the top or side of the boulder, covered with mud 

 and exploded. The charge should be placed on the spot which would be 

 struck with a sledge if the boulder were small enough to be broken in 

 that way, and should be packed in a solid mass by removing the paper 

 cartridge shells, but not spreading the contents over the surface of the 

 boulder any more than absolutely necessary. When working with bare 

 hands, it is a good plan to cover the dynamite with the original paper 

 wrappers of the cartridges to prevent absorption of nitroglycerin by the 

 pores. This paper also protects the dynamite against the water in the 

 mudcap. A blasting cap crimped on to fuse should be placed in the 

 middle of the charge, and the whole covered with six inches of damp clay 

 or sand. The idea is to get the mass of explosive in direct contact with 

 the boulder and exclude all air cushions. The mud or damp sand should 

 be pressed firmly over the mass of dynamite, care being taken not to 

 cover the outer end of the fuse. If the boulder is deeply imbedded in the 

 ground, it is best, before blasting, to dig away or loosen some of the 

 earth surrounding it. 



Blockholing 



This is the most economical way to use dynamite in breaking up 

 boulders, although it takes some time and labor to drill the one or more 

 necessary holes in the boulder. The holes in large boulders should be an 

 inch or more in diameter, while three-quarters or seven-eighths of an 

 inch will answer for the smaller ones. 



A boulder weighing from eight to ten tons can be well broken by 

 drilling a one-inch hole in it near the center from two to three feet deep 

 as the shape and grain of the rock may demand, and exploding in the hole 

 four to five one and one-quarter by eight-inch cartridges of Red Cross 

 Extra Dynamite 40%. The dynamite should be poured out of the paper 

 shells and packed down into the hole with a stick. When it is all in place 

 a hole is made in it with a sharp stick and the blasting cap, crimped to the 

 necessary length of fuse, is pushed down into this hole and held in posi- 

 tion by carefully packing any clay tamping there is room for about the 

 fuse. 



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