EVALUATION OF FRAGMENTATION SIZE DISTRIBUTION OF SELECTED ROCKS BREAKAGES IN IKERE-EKITI, EKITI STATE NIGERIA USING PREDICTIVE MODELS

Abstract

The primary purpose of blasting is to achieve optimum rock fragment size distribution as it is closely related to economics of the operation considering some factors that influences the outcome. Over the years, several analytical and numerical techniques, for example, Kuz Ram, Modified Kuz Raz and digital image processing had been developed to forecast and analyze fragment size distribution. In this research, the evaluation of fragmentation size distribution in MAC and KOPEK quarries were investigated for the purpose of establishing a model for the selected quarries. Intact rock properties, discontinuity parameters and blasting parameters were assessed at different blast locations in the selected quarries. Samples were collected for determination of physical (dry density) and mechanical (uniaxial compressive strength and Young modulus) properties. The uniaxial compressive strengths vary from 66.68 to 68.32 MPa and 130.64 to 131.76 MPa for MAC and KOPEK quarries respectively. Dry density results vary from 2.61 to 2.71 g/cm3 for MAC and 2.64 to 2.72 g/cm3 for KOPEK. The Young moduli vary from 42.82 to 43.23 GPa and 54.90 to 55.11 GPa for MAC and KOPEK quarries respectively. The results of the rock properties and their classification of the rock mass considered show that they fall under hard rock with moderate strength to high strength. Fragment sizes were predicted using the rock properties, geo- mechanical and controllable blast parameters. Comparative performance of Kuz Ram, Modified Kuz Ram and Split- Desktop image processing was evaluated to determine the most suitable model to predict blast results in the selected quarries. It was established from regression analysis between the existing models and image analysis results that modified Kuz Ram is the best predictive model as it is closer to 1 with R square values of 0.9967 and 0.9875 against 0.7941and 0.7796 of Kuz Ram. From the regression investigation of the effects of rock properties on mean fragment size, it was established that the mean fragment size increases with increase in uniaxial compressive strength, dry density and Young modulus. It can be concluded that uniaxial compressive strength and dry density has greater effects on mean fragments size distribution in the selected quarries.