Applications of NTNU/SINTEF Drillability Indices in Hard Rock Tunneling

Drillability indices, i.e., the Drilling Rate Index (TM) (DRI), Bit Wear Index (TM) (BWI), Cutter Life Index (TM) (CLI), and Vickers Hardness Number Rock (VHNR), are indirect measures of rock drillability. These indices are recognized as providing practical characterization of rock properties used in the Norwegian University of Science and Technology (NTNU) time and cost prediction models available for hard rock tunneling and surface excavation. The tests form the foundation of various hard rock equipment capacity and performance prediction methods. In this paper, application of the tests for tunnel boring machine (TBM) and drill and blast (D&B) tunneling is investigated and the impact of the indices on excavation time and costs is presented.