The assessment of rock brittleness effect on their drillability

The brittleness is an important rock property and effective in rock excavation. Recognition of the relationship between drillability and brittleness will increase performance the rock excavations. In this study, the number of 16 samples has been studied rock mechanical properties of granite, granodiorite, dolomite, hornfels and marble in the area of Glass water conveyance tunnel project in the margin of Naghadeh city. The number of 16 brittleness indices were calculated with stress-strain curve, modulus and rocks strength properties. In addition, Sievers’ J-miniature drill test and the brittleness test are carried out and DRI values were calculated. The statistical relationships between the brittleness indices and the drilling rate index are showed a strong correlation between B3 brittleness index (R2= 0.76 and RMSE= 1.02 coefficients) and B4 brittleness index (R2= 0.79 and RMSE= 0.95 respectively) with rocks drilling rate index. The statistical relationships are compared with study former between the brittleness indices and the drilling rate index of rocks. The Precision and accuracy of relationships are confirmed with relationships former. In addition, a model was presented with multiple regression analysis. It can use for the assessment of rock drillability.