Cuttability assessment using the Drilling Rate Index (DRI)

For given geological conditions, cuttability or performance prediction can be expressed by specific cutting force (SFC), specific normal force (SFN), specific energy (SE), and pick wear rate. These parameters are difficult to determine. For this reason researchers try to assess these parameters indirectly by rock mechanical parameters. The Drilling Rate Index (DRI) is the most important input parameter of a commonly used performance prediction model for tunnel boring machines. However, little research has been seen in the literature about assessing cuttability indirectly by DRI. In this study, different types of rock and ore samples were subjected to a small-scale rock cutting test, the Cerchar abrasivity test, the Sievers J miniature drill test, and the brittleness ( S 20 ) test. With the aid of the Sievers and brittleness test results, the DRI parameter was determined. SFC, SFN, and SE, which are the output parameters of small scale rock cutting tests, and the Cerchar abrasivity index values were correlated with Sievers J ( S j ) value and DRI. It was seen that SFC, SFN, SE and CAI parameters slightly decreased with increasing Sievers J value and DRI. With these results, it can be stated that DRI and S j could be an alternative to other mechanical rock parameters for assessing cuttability.