The rock stregnth device: a scratching apparatus to determine rock properties

The present paper presents a portable apparatus, the Rock Strength Device (RSD), and the methodology to assess mechanical properties of cohesive granular material from 'partially-destructive' scratching tests with rectangular cutters (the material surface is just scratched at shallow depth). A correlation between the intrinsic specific energy (measured in the scratch test) and the uniaxial compressive strength has been built on more than 200 rock samples, and a correlation between the friction angle at the wear flat/rock interface and the internal friction angle of the material is given for 20 different rocks. The test provides also a 'continuous' log of the material properties along the groove with a wide range of practical applications.