Strength criterion effect on elasto-plastic solution of deep tunnels considering strain softening characteristics

In order to explore the effect of strength criterion on the stability of the surrounding rock of strain softening tunnel, the expressions of the common strength criteria in the analysis of the tunnel surrounding rock were summarized, and the unified equation of common strength criteria was proposed. Combined with the strain softening model and non-associated flow rule, the calculation method of the stress field, plastic zone and displacement of the surrounding rock of the tunnel was derived. The results show that the strength criterion effect of the surrounding rock in strain softening tunnel is significant. The calculation results of the inner corner circumscribed circle DP(Drucker-Prager) criterion, inscribed circle DP criterion, equivalent area circle DP criterion, matching circle DP criterion and Mohr-Coulomb criterion are generally conservative. The calculation results of unified strength theory with parameter b=1 and external corner circumscribed circle DP criterion are relatively dangerous. Without considering dilatancy characteristics can result in dangerous calculation results. In engineering applications, the Mogi-Coulomb criterion or unified strength theory with parameter b=1/2 should be preferentially adopted, and the dilatancy characteristics of surrounding rock should be considered reasonably to reveal the stability of surrounding rocks. © 2020, Central South University Press. All right reserved.