Modified Hoek–Brown criterion for nonlinear strength of frozen soil

The strength of frozen soil presents obvious nonlinearity, which makes many theoretical criteria unable to accurately predict failure. The Hoek–Brown criterion, which is one of the most widely used strength criteria in geotechnical engineering, could predict the strength of frozen soil subjected to low confining pressure. For high values of confining pressure, the predicted results do not agree well with experimental data. In the present study, the criterion was modified by incorporating a new parameter to account for the nonlinearity of frozen soil under high confining pressures. The parameter and instantaneous friction angle for the nonlinear failure envelope were also analyzed. To describe the failure mechanism of frozen soil under complicated stress state, the deviatoric section of strength criterion for frozen soil, in which the Mohr–Coulomb criterion forms the low bound, and the Drucker–Prager criterion forms the upper bound, was obtained, and a united strength criterion was established to take the effect of intermediate principal stress on strength behavior into account. The strength criterion could well reflect the nonlinear strength characteristic of frozen soil under the influence of pressure melting and crushing phenomena.