Empirical Analysis of Blast Design Parameters and Fragmentation Outcomes at Granite Quarries in South West Nigeria

Optimising blast fragmentation is central to reducing downstream crushing costs and improving quarry productivity, yet the relationship between blast design parameters and fragmentation outcomes at Nigerian granite quarries has not been empirically established. This study analyses the empirical relationship between blast design parameters and rock fragmentation outcomes at seven granite quarries in Ogun, Ondo, and Oyo states in South West Nigeria. A field experimental design was employed, measuring blast outcomes across 42 monitored blast events. Input parameters recorded include burden, spacing, hole depth, stemming length, explosive type, and initiation sequence. Post-blast fragmentation was measured using digital image analysis with Split-Desktop software applied to muck pile photographs. Regression analysis was used to develop site-specific empirical models relating design parameters to mean fragment size and the proportion of oversize material. Results indicate that the burden-to-spacing ratio and stemming length are the most statistically significant predictors of fragmentation quality, explaining 68 percent of variance in mean fragment size across the sample. The study develops quarry-specific Kuz-Ram model calibration factors and demonstrates that implementing design recommendations reduces oversize proportions by an average of 31 percent. These findings provide actionable blast design guidelines for quarry engineers and advance the empirical basis for blast optimisation in the Nigerian granite sector. Keywords: blast design, fragmentation, granite quarry, South West Nigeria, Kuz-Ram model.