Penetration rate and fabric anisotropy

An extensive investigation of roller disc cutter penetration into anisotropic rocks reported by Sanio (1985) was designed to simulate as far as possible the cutter process illustrated in Figure 23 . The author used 7 rock types [slate, gneiss, sandstone(s) and limestone] with varying degrees of anisotropy. He found that his experimental results correlated best with the anisotropic tensile strength of these rocks. The ratio of the point load index on 50 mm diameter core ( I 50 ⊥/ I 50 ∥) for perpendicular and parallel loading correlated directly with the variable cutter penetration achieved ( P 0 / P 90 ) where the subscripts 0° and 90° refer to the angle β in Figure 23 .