Prediction of the plastic zone radius around a circular opening in the rock mass is an important problem in a wide variety of mining, tunneling and geotechnical engineering projects. A large number of analytical solutions for determining the plastic zone radius in axisymmetric opening problem have been presented by conside-ring different models of material behavior with the different failure criteria, like the linear Mohr–Coulomb (M–C) and nonlinear Hoek–Brown (H–B) criteria. In this paper, based on the two different failure criteria, M-C and H-B, the plastic zone radius around a circular tunnel is determined and compared with the actual field data obtain-ed from several tunnels in Iran. The results show that in some sections of tunnels, the difference of the corresponding plastic zone radii obtained from Mohr-Coulomb and Hoek-Brown criteria increases with increasing in situ stresses. Comparison of the analytical results and the experimental data illustrates that the non-linear failure criterion estimates the plastic zone radius with a better accuracy.
Determination of the plastic zone radius is an important problem in geotechnical, petroleum and mining engineering such as the design of tunnels, boreholes and mine shafts. A large number of analytical solutions for this axisymmetric opening problem have been presented by considering different yield criteria, like the linear Mohr–Coulomb (M–C) and nonlinear Hoek–Brown (H–B) criteria (Wang 1996). According to Fig.1 elasto-plastic analysis of circular openings in an infinite medium subject to a hydrostatic in situ stress has been of special interest and numerous contributions that have been made to obtain closed-form solutions for this problem. Brown et al. (2003, 2008) presented solutions for the elastic perfectly plastic and elastic–brittle–plastic analyses of circular openings in Hoek–Brown media.
