Investigating the Effect of Fracture on Rock Fragmentation Efficiency: A case study of Kopec Granite Quarries, South Western, Nigeria

Abstract

Investigating the effects of fracture on rock fragmentation efficiency in selected quarries in South Western, Nigeria is imperative for economical operation. In data collection for fracture characterization, both scanline and window mapping with the aid of compass clinometers were used. AutoCAD model was utilized to generate the in-situ block size model. The blast efficiency was determined using standard methods. From the fracture characterization carried out on the selected sites, it was observed that two main joints are predominant in Kopec Ikere, Kopec Ibadan as well as Kopec Ife granites. Two main joints with random are predominant in Kopec Ikole. The results of empirical estimation of average in-situ bock size distribution using joint spacing, block volume and volumetric joint count methods, all agreed that Kopec Ikere is having the biggest average in-situ block size with Kopec Ife having the smallest average in-situ block size. The results of numerical modelling also agreed with the results of empirical estimation with Kopec Ikere having biggest average block size and Kopec Ife being the smallest. The results of rock mass classification shows that all the rocks under consideration falls between very good to good rock. The results of the Schmidt hammer test shows that the rock under consideration have uniaxial compressive strength of 130MPa. The results of blast efficiency obtained for the selected sites show that Kopec Ikere with lowest fracture index is having the lowest blast efficiency while Kopec Ife with highest fracture Index is having highest blast efficiency. From the correlation of measured variables, it was observed that there is a good correlation between blast efficiency and average fracture index. It was observed that blast efficiency increases with increase in fracture index. Good correlation was observed between blast efficiency and RMR. It was observed that blast efficiency decreases with increase in RMR value. Similarly, blast efficiency decreases with increase in GSI value.