The experiments of the secondary rock blasting by the shaped explosive charge was performed at the Kamaishi iron mine (Iwate pref.) and the Kamioka lead-zinc mine (Gifu pref.). Shaped charges with the conical cavity were used at the Kamaishi mine but the hemispherical liners were used at the Kqimioka mine. Explosives used in the work were Carlit powder which were detonated by No. 6 detonaters with fuses.
Both results indicate approximately the same result and powder consumption has been estimated to 0.8-0.9 Kilogramms per one cubic metsrs of boulders. The explosive saving of about 50% was obtaiined against the ordinary mud capping method.
Within the limits of the tests it appears that shaped charges will prove useful for secondary breakage of boulders in large underground stopes.
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