Fracture angle of Hoek–Brown materials

Abstract

The fracture angle (defined as the angle between the normal vector of the fracture plane and the first principal stress) of Mohr–Coulomb is 45°+ ϕ/2, which plays a crucial role in soil mechanics. However, for the non-linear Hoek–Brown criterion, the fracture angle cannot be derived as easily as Mohr–Coulomb. Based on the physical evidence that there is no parallel plastic strain in the shear zone, the fracture angle of Hoek–Brown materials, is derived as tan−11+m2s+mσ3/σc. The experimental data of marble and granite and numerical results demonstrate that the obtained theoretical fracture angles agree well with the experimental and numerical fracture angles.