Abstract
Dimension stone quarry is believed to be type of mining operation that always result to low recovery since what is expected from the extracting operation is a cubical block with no fracture. It is noticed that majority of the damage in the natural blocks are always from poor extraction method. In aggregate quarry, series of work have been done on powder factor that gives economical blasting. In this research work, breaking factor is used in place of powder factor since breaking is required not powder. The aim of this research work is to establish a standard breaking factor for bench blasting in dimension quarries that will improve recovery.Two cases were considered. In case 1, gun powder is used for basal cutting. Of the seven patterns considered, pattern3 gives highest recovery (70%) with breaking factor of 23.15g/m3 (i.e. 5kg of Gun powder for (6 by 6 by 6) m bench design). In the case 2, dynacord is used for basal cutting. Of the four patterns considered, pattern 2 gives highest recovery (55%) with breaking factor of 15g/m3 ( i.e. 3.24kg of explosive for (6 by 6 by 6) m bench design.Keywords: Extracting, powder factor, aggregate, recovery, breaking factor
Highlights
Dimension stone production is relatively new development in the quarrying industries in Nigeria
In superficial deposits blocks are extracted from isolated boulders some of which were probably transported over a long distance by denudation or weathered from the parent rock mass
It is observed from the field that the spacing of 40cm is often used when gun powder is used for basal cutting while the spacing of 20cm is used for a situation where dynacord are used
Summary
Dimension stone production is relatively new development in the quarrying industries in Nigeria. Getting a block out of massive or boulder rock requires experience as small mistakes may result in a lot of waste. Dimension blocks can be obtained from either a superficial deposits or massive deposits. In superficial deposits blocks are extracted from isolated boulders some of which were probably transported over a long distance by denudation or weathered from the parent rock mass. This type of deposit forms a convenient source of building stone. Examples are in cliffs of the Isle of Portland and Penmaenmaws in Wales (Bezzant, 1980)
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