Evaluating the Relationship between Strength Properties and their Ratios in some Selected Granitic Outcrops

Abstract

This paper evaluates the variations in the characteristics properties of some granitic rocks and their relationships with uniaxial compressive strength (UCS). Twenty rock samples were selected from different locations in order to determine their rebound hardness number (RN), porosity (n), specific gravity (GS), modulus of elasticity (E), rock mass rating (RMR) and blastability index (BI). The UCS and other rock properties were coordinated such that each of the properties or their ratios is compared individually with UCS. Regression statistics was used to predict UCS from the variables and the results when compared with measured UCS shows that 94 percent of the predicted UCS was explained by the measured UCS. The relationship between UCS and other parameters show that UCS increases linearly with RMR and RN with R2 values of 0.92 and 0.84 respectively while it reduces in value with n at R2 value of 0.78 but a weak relationship was observed with GS and BI with R2 value of 0.42 and 0.33 respectively. Ratios of E/UCS, RMR/BI and UCS/GS were also evaluated and their relationships shows that the correlation coefficient of RMR/BI and E/UCS, UCS/GS and E/UCS and, RMR/BI and UCS/GS are 0.86, 0.92 and 0.74 respectively. The blastability index which relate the strength of rocks with fragmentation ability using explosive have no linear relationship with other strength parameters.