3.2.1.4 Ring Test
The ring test is similar in form to that of the Brazilian test, but differs by having an axial hole. This hole means that when the disc is compressed it fails in a tensile manner. The hole removes the stress concentrations at the loading surface. Hobbs [1963] suggested that a relationship between tensile and compressive strengths was present for massive laminated rocks. However, Hudson [1968] concluded that the tensile strength of the material increased as the diameter of the hole decreased. This suggests that results achieved are a factor of the experiment and not a property of the material.