Rock Brittleness Index of Gneiss Rock Selected From Quarries in Kwara State, Nigeria
W.A, S.A and Bello
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Abstract: This research examines the brittleness index in some gneiss rock samples collected from four different quarries in Kwara State, Nigeria. The gneiss samples were tested in the laboratory to determine chemical and mineral compositions using X-ray fluorescence (XRF) spectrometer and atomic absorption spectrophotometer (AAS). Schmidt rebound hammer (L type) was used to estimate compressive strength of the rock samples. The average gneiss silica contentis72.1 %.The average uniaxial compressive strength and tensile strength are 138.5 MPa and 5.81 MPa respectively, classified as extremely high and very high strength. The average density of the rock is 2.6 g/cm3. The result of statistical correlation indicates the dominant factors (uniaxial compressive strength and density) affecting the brittle nature of the rock samples having high coefficient of correlation. The relationship between the strength parameter, area under the line C – T of the graph falls within the range of 285.78 – 462. 65MPa. The rock brittleness concept value obtained from the graph was within 96.62 – 136.68MPa. The brittleness index of the selected quarries serves as a reference for the selection of drill bits and drilling equipment in accordance to the nature of the rock within the basement complex.