Linear Mohr-Coulomb criterion with tension cut-off cannot consider the nonlinear yielding characteristics of rocks at high stresses.According to Hoek-Brown criterion

the linear Mohr-Coulomb criterion was modified as a nonlinear criterion in the compressive region.Three kinds of principal stress criteria of rockbursts were introduced to assess the distribution and evolution of weak

moderate and serious rockbursts in the surrounding rock of a circular tunnel

respectively.In numerical simulation

a circular tunnel is excavated after the plane strain model has reached a static equilibrium state.Rock obeys an elastic-brittle-plastic constitutive model.It is found that the number of elements occurring serious rockburst is less than that of elements occurring weak rockbursts.Regions where weak rockbursts occur are very similar to plastic zones and zones with high shear strain increments.According to Barton criterion

the area of serious rockburst zones is larger and serious rockbursts in tension predominate.The numbers of elements occurring moderate and weak rockbursts based on Tao′s criterion are greater than those based on Gu and Tao′s criterion.For rockbursts in shear

serious rockbursts occur within the surrounding rock

while weak rockbursts can occur at the surface of the tunnel.