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Use of notched boreholes for fracture controlled blasting in the ornamental stone quarries

Exadaktylos Georgios, Nomikos P., Gikas N., Tsoutrelis, C

Πλήρης Εγγραφή

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Περίληψη

The ornamental stone industry is continuously seeking new cost effective methods to improve present day techniques of: (a) diamond wire cutting; (b) dense drilling followed by mechanical wedging or light blasting and (c) jet cutting, for extracting primary blocks from the quarry face and for splitting and squaring them to appropriate commercial sizes. Among the techniques proposed and tested notching a borehole followed by wedging or decoupled blasting seems to be a commercially feasible technique provided that a suitable notching method becomes available. Notching can be used in soft non-abrasives stones such as marbles for splitting and squaring blocks and in hard and abrasive rocks (granites), where the diamond wire cutting technique can not be used effectively, for extraction from the bench face and for splitting and squaring. For marbles and many sandstones a detachable type notching tool fitted to a 7/8″ hexagon drill still can be used with a hand held or mechanically mounted rock drill in which the rotation mechanism has been removed. In granites and other abrasive rocks having fracture toughness values twice as big as those of marbles a two stage linear explosive (hybrid explosive) is proposed for extraction of the rock from the quarry face and for secondary treatment. Laboratory and field tests in 3 different types of marble blocks and in granite blocks in the laboratory proved the cost effectiveness of the proposed techniques, which are also environmentally friendly since they produce less dust and reduce noise duration in comparison to present day practice.

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