ISRM Suggested Method for Determining the Abrasivity of Rock by the CERCHAR Abrasivity Test

Rock abrasivity plays an important role in characterizing a rock material for excavation purposes. Abrasion can be defined as the wearing or tearing away of particles from the surface, i.e. it is a process causing removal or displacement of material at a solid surface, which will lead to wear, especially on tools that are used in mining, drilling, and tunneling applications. The CERCHAR Abrasivity Test is a method to determine an index called CERCHAR Abrasivity Index (CAI) for the rock’s abrasivity. The test was originally developed by the Laboratoire du Centre d’Etudes et Recherches des Charbonnages (CERCHAR) de France for coal mining applications (Cerchar 1986). Two standards exist for this test method: the French standard AFNOR NF P 94-430-1 (2000) and ASTM D7625-10 (2010). The test is widely used in research and practice. There are essentially two designs of testing apparatus: the original design as developed at the CERCHAR Centre (Valantin 1973) and a modified design as reported by West (1989). While the designs are similar there are some important differences as well as ambiguities in test conditions that include equipment actuation, material properties of the stylus and sample preparation as summarized by Plinninger et al. (2003).