Abstract
Natural discontinuities as well as mechanical properties are the difficult-to-control parameters that significantly influence the fragmentation of marble after blasting. In Central Africa, the Bidzar quarry is the only one producing marble, plagued for decades by block fragmentation problems, requiring multiple blasts that cause huge costs and environmental problems. The objective of this study is to predict the fragmentation of the Bidzar rock quarry and to improve its geological and mechanical knowledge using the Kuz–Ram method. Thus, blastability as a function of the dip of the discontinuity planes as well as fragmentation as a function of the powder factor, compressive strength and drilling mesh were studied. The results obtained show that, the rock quarry is heterogeneous, consisting mainly of fissured marble of medium hardness. Its dip is about 85°, its rock factor is 10.455 and it is class III, with a difficult blastability of 0.2654 kg/m3. The marble from the Bidzar quarry is of excellent quality with an RQD of 93%.The fractures and discontinuity planes are spaced and of class ES2. The density of the fractures and discontinuity planes is low and of class ID2.The rock quarry is intercepted by a network of discontinuity planes marked by three families of direction, major (N30–40E, N40–50E, N160–170E), secondary (N10–20E, N50–60E, N80–90E, N140–150E, N150–160E, N170–180E) and minority (N00–10E, N20–30E, N40–50E, N70–80E, N100–110E, N110–120E, N120–130E, N130–140E). Finally, the variation in fragmentation intensity is caused by differences in the dips of the blasting planes, their compressive strength, and the variation in the drilling mesh.
Highlights
The fragmentation of boulders by blasting has always been an important aspect of mining and is the subject of numerous studies (Sang Ho Cho et al, 2004; Gheibie et al, 2009; Stjepan et al, 2011; Biessikirski et al, 2019; Shaib et al, 2020)
Firing with the 4.5 m × 4.5 m drilling mesh results in Rosin-Rammler slopes (X/Xc) greater than 1 for dipping firing planes (70°, 75°, 60°) and less than 1 for dipping firing planes (86°, 85°, 90°, 82°) (Table 4 to 6). These results show that the Rosin-Rammler slope (X/Xc) increases as the dip of the firing planes and the drilling mesh decreases
The aim of this work was to predict the fragmentation of the Bidzar marble considering the effect of natural discontinuities and mechanical properties using the Kuz-Ram method, while enhancing the information on the said quarry
Summary
The fragmentation of boulders by blasting has always been an important aspect of mining and is the subject of numerous studies (Sang Ho Cho et al, 2004; Gheibie et al, 2009; Stjepan et al, 2011; Biessikirski et al, 2019; Shaib et al, 2020). The size of the fragments obtained should not exceed the opening of the crushing plant for efficient operation (Jug et al, 2017; Shaib et al, 2020). The presence of large blocks requires secondary fragmentation to further reduce the material pulled to acceptable sizes, thereby increasing production costs (Rustan, 1990; De Lile, 2012; Mohammad et al, 2018; Yahyaoui et al, 2018; Agyei et al, 2019). Knowledge of the properties of the rock matrix is important in modelling a blast. These properties (natural discontinuities and physicomechanical characteristics) are fundamental for the optimisation of fragmentation and constitute the uncontrollable parameters of a blast (Adebayo et al, 2007; Akbari et al, 2015; Jug et al, 2017; Behrouz, 2018)
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