EFFECTS OF ROCK AND GEOMETRICAL PROPERTIES ON THE PRODUCTION AND COST OF MUCK PILING AT OBAJANA QUARRY, NIGERIA

Abstract

Rock Samples were obtained from two pits currently being exploited at Obajana, for the purpose of investigating the effects of rock and geometrical properties on the production and cost of muck piling at Obajana quarry. The rock samples were tested for uniaxial compressive strength and tensile strength using 1100 kN compression machine and point load tester respectively. Hardness and density were determined using Schmidt hammer and density bottle respectively. The result of uniaxial compressive strength obtained for pit 1 at location 11A, 11B, 12A, 12B,13A, 13B, 14A,14B,15A and 15B are 27.8 MPa, 35.2 MPa, 43.6 MPa, 47.0 MPa, 43.5 MPa, 50.0 MPa, 47.6 MPa, 56.1 MPa, 53.9 MPa and 54.5 MPa respectively. While that of pit 2 at location 21A, 21B, 22A, 22B, 23A and 23B are 25.3 MPa, 28.7 MPa, 44.9 MPa, 44.3 MPa, 56.7 MPa and 58.4 MPa respectively. It was found that location 14B and 23B has the highest uniaxial compressive strength value in pit 1 and pit 2 respectively. The density obtained for three locations in Pit 2 varies from 2.45 g/cm3 to 2.63 g/cm3. Blasthole diameter, burden, spacing and charge length were measured on the field while drilling and charging operations was progressing as follows: 145mm, 3m to 4m, 4m to 6.5m and 75% of the hole depth respectively. Average cycle time during dry and rainy season are 16 minutes and 20 minutes respectively. Also, the cost of loading during the dry and rainy season were recorded during extraction loading operation. Cost of loading obtained from pit 1 for the five benches during dry and rainy season are ₦19.15, ₦19.90, ₦20.10, ₦20.17, ₦22.0 and ₦22.45, ₦23.00, ₦23.65, ₦24.25, ₦25.80/tones respectively. Whereas, in pit 2 the result for the three benches for both seasons are ₦19.15, ₦19.80, ₦20.00 and ₦22.45, ₦22.74, ₦23.10/tonnes respectively. The determined rock properties were subjected to statistical analysis using SPSS,. The determined rock properties are the dependent variables while the geometrical properties are the independent variables. The mathematical models generated from the analysis shows that the results of UCS values increases as the pit advance downward. Moreover, as UCS value increases, cost of muck piling increases as well. In mining operations the cost of production increases as the mines advance, suggesting that all mining operators should bear this in mind to avoid liquidation