Influence of fracture stiffness on local stress redistributions

A fracture has a certain deformability which is quantified by its stiffness. It depends among others on the filling material and roughness. The fracture stiffness allows a limited movement in normal and in shear direction, before tensile or shear failure occurs. A Brazilian tensile test on a sample with one inclined diametrical discontinuity is modelled using 2D distinct element code UDEC to investigate the effect of the stiffness of the discontinuity on the stress distribution. It is observed that the stress distribution deviates considerably from the classical elastic stress distribution in a homogeneous sample. It is also noted that the fracture stiffness affects the external failure load and the position of the start of the shear failure of the discontinuity. The softer a fracture behaves, the larger its effect becomes. The characteristics of the discontinuity have also an effect on the occurrence of new fractures in the intact material.