Blast Induced Ore Movement Prediction Using Rock Strength Parameters – A Case Study

Abstract

Blasting causes movement of rocks and so can be a nuisance in gold mines as it leads to ore loss or dilution. Auriferous ore at Golden Star Wassa Limited, Akyempim mine which is found in the Birimian Supergroup in Ghana is no exception to problems relating to blast movement. The ore comprises of altered mafic and felsic-metavolcanic rocks, diorite, feldspar porphyry, and phyllite. To track the ore after blasting in SAK-1 Pit, blast monitors measure the extent of blast induced movements which were parallel to strike and down dip of the orebody. Hence, graphs plotted from data collected in benches at 6 metres intervals were used to derive equations which relate movement of rock fragments, of diverse sizes up to boulders. These equations indicate that blast induced movement is dependent on rock structure - whether foliated or massive. Other parameters were rock density which is a controlling factor to the extent of movement and uniaxial compressive strength which influences breakage. Deductions show that at Akyempim mine, foliated rocks may have higher movement than massive rocks and so the equations should be used to plan adjustment of ore boundaries before blasting.

Keywords: Blast induced, Ore movement, Prediction, Birimian, Ghana