Scaling in Multiaxial Compressive Fracture

Size effect studies under multiaxial-compressive loading are experimentally challenging as they involve three-dimensional scaling, notably if cubical specimens are considered in poly-axial testing. Laboratory experiments using model openings such as scaled hollow cylinders are suited for such an investigation. The hollow cylinder geometry lends itself for providing permutations of various multiaxial states of stress around its inner-hole depending on the stress path applied to its external boundaries. They are also advantageous in terms of specimen boundary restraint and load application procedure since radial pressures are applied using a fluid pressure along the circumference of the cylinder, which is almost unrestrained. This test geometry is frequentely used as a model test for stability studies of underground tunnels and deep boreholes.