ISRM Suggested Method for the Determination of Mode II Fracture Toughness

The suggested method for the determination of Mode II fracture toughness is reviewed. This so-called Mode II loading in fracture mechanics, the crack faces slide relative to each other and displacements of the crack surfaces are in the crack plane and perpendicular to the crack front. For any specimen preparation treatment appropriate high precision tools should be used. The specimens should be right circular cylinders having a height L to diameter D ratio of 1:1 and a diameter D equal to 50 mm. The minimum information on each specimen shall include dimensions, specimen preparation routines, special observations made during specimen preparation, moisture content, and macroscopic description of the surface. The report of each experiment should include source of specimen as precisely as possible; location and orientation. The shear stress at failure is reported to increase with confining pressure for various rock types.