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    Dominant rock properties affecting the penetration rate of percussive drills
    (Elsevier BV, 2003) Kahraman S.; Bilgin N.; Feridunoglu C.
    Percussive blast hole drills were observed in eight rock types at an open pit mine and three motorway sites. The net penetration rates of the drills were calculated from the performance measurements. Rock samples were collected from the drilling locations and the physical and mechanical properties of the rocks were determined both in the field and in the laboratory. The penetration rates were correlated with the rock properties. The uniaxial compressive strength, the Brazilian tensile strength, the point load strength and the Schmidt hammer value exhibit strong correlations with the penetration rate. Impact strength shows a fairly good correlation with penetration rate. Weak correlations between penetration rate and both elastic modulus and natural density were found. Any significant correlation between penetration rate and P-wave velocity was not found. It was concluded that, among the rock properties adopted in this study, the uniaxial compressive strength, the Brazilian tensile strength, the point load strength and the Schmidt hammer value are the dominant rock properties effecting the penetration rate of percussive drills. Theoretical specific energy as defined by different research workers is proved also to be well correlated with penetration rate of percussive drills which verifies basic theoretical works on the subject. In addition, the point load and the Schmidt hammer test can practically be used in the field as a predictive tool for the estimation of penetration rate. © 2003 Elsevier Ltd. All rights reserved.
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    Prediction of the penetration rate of rotary blast hole drills using a new drillability index
    (2000) Kahraman S.; Balci C.; Yazici S.; Bilgin N.
    Rotary blast hole drills were observed in several formations at different open pit mines and quarries. Rock samples were collected as near as possible to drilling locations and mechanical and physical properties of the total 22 rock samples were determined. Indentation tests were carried out on the block samples from the same formations. A new drillability index for the prediction of the penetration rates of rotary blast hole drills and the mechanical and physical properties of the rock formations was defined from force-indentation curves of indentation tests. A penetration rate model for rotary for blast hole drills was developed using this drillability index. It was seen that the model was valid for the formations having uniaxial compressive strength over 40 MPa and especially for carbonaceous rocks. The drillability index exhibits a significant correlation with the proportionality constant k defined in the model. It is also seen that significant correlations exist between the drillability index and rock properties suggesting that the proposed model may be used universally to estimate the penetration rate of rotary blast hole drills. (C) 2000 Elsevier Science Ltd. All rights reserved.