Intensification of blasting of different quality rock masses using explosive charges with cumulative effect

In terms of Dzheroi–Sardara phosphorites (Uzbekistan), the article describes theoretical studies and experimental tests in Tashkura open pit mine, based on which the method and technology of intensified blasting in different quality rock masses are recommended. To characterize the process of controlled drilling-and-blasting in different quality, stratified, complex-structure rock masses and mineral deposits, an emphasis is laid on determination of physical properties of rock fragmentation depending on the specific structure and strength of rocks. The authors describe the structure scheme of blasting where the basic (in use) pattern is added by shortcut borehole drilling within the limits of hard bands (partings) with special explosive charges having hollows at the bottom; explosive charges in the main blastholes are decoupled using inert material. Blast energy control is implemented using a special sequence of short-delay non-electrical firing. Parameters of efficient drilling-and-blasting in different quality rock masses are determined, specifying the lengths of decoupled columns of the main explosive charges, useful length of shortcut boreholes and weight of the shortcut hole charges depending on powder factor and thickness of hard partings. The comparison of blasts on the reference and test sites shows that the recommended drilling-and-blasting method and technology ensure reduction in average size of blast rock fragments, in yield of large fragments, as well as in powder factor and amount of drilling. The developed and commercially introduced method of different quality rock blasting using decoupled and shortcut charges with cumulative effect has allowed uniform fragmentation of rock mass along the bench height owing to controlled utilization of blast energy in hard bands, with blasthole pattern larger by 23%, powder factor reduced by 20% and blasthole drilling costs improved by 15%.

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