Classifications of properties influencing the drillability of rocks, based on the NTNU/SINTEF test method: Fid-Bau Portal

Classifications of properties influencing the drillability of rocks, based on the NTNU/SINTEF test method

Dahl, Filip / Bruland, Amund / Jakobsen, Pål Drevland / Nilsen, Bjørn / Grøv, Eivind

Highlights ► Rock type can only be an indicator of rock properties. ► Classifications based on statistical analysis of recorded test results. ► Correlations and comparisons of different rock drillability test methods. ► Classifications of rock properties constitute an important aid and guideline.

Abstract The demand for representative rock property parameters related to planning of underground excavations is increasing, as these parameters constitute fundamental input for obtaining the most reliable cost and time estimates. The Brittleness Value (S 20), Sievers’ J-Value (SJ), Abrasion Value (AV) and Abrasion Value Cutter Steel (AVS) have been used extensively at NTNU/SINTEF since the 1960s in connection with drillability testing of rock samples. Nearly 3200 samples originating from projects in 50 countries have so far been tested, and the method and associated prognosis model are internationally recognised for giving reliable estimates of time and cost for tunnelling. A classification of the NTNU/SINTEF drillability indices Drilling Rate Index™ (DRI), Bit Wear Index™ (BWI) and Cutter Life Index™ (CLI) has been available since 1998, but until now no official classification has been available for the individual tests used to calculate these indices. In this paper, classifications of the NTNU/SINTEF drillability test methods Brittleness Value (S 20), Sievers’ J-Value (SJ), Abrasion Value (AV) and Abrasion Value Cutter Steel (AVS) tests will be described in detail. The presented classifications of the individual tests are based on statistical analysis and evaluations of the existing test results recorded in the NTNU/SINTEF database.