Rock strength determination from scratch tests

This paper provides compelling experimental evidence that the unconfined compressive strength of rocks can be reliably assessed from scratch tests performed with a sharp cutter, and at depth of cut small enough to prevent any significant chipping of the rock. The paper describes the model used to interpret the experimental results, the test methodology, and the Rock Strength Device that was developed to perform scratch tests under kinematically controlled conditions. It concludes with a summary of an extensive experimental campaign involving the testing of several hundred rocks to compare strength data from conventional uniaxial compression experiments and from scratch tests.