Estimating the strength parameters of a chosen rock failure criterion is crucial for rational stability analyses. However, the grid search algorithm applied to true triaxial test data presents challenges that hinder its widespread adoption. This study introduces a novel generalized procedure for approximating the strength parameters of the modified Lade and spatial mobilized plane failure criteria using conventional triaxial tests. By clarifying the theoretical basis for estimating three-dimensional failure criterion parameters at two extreme stress states, the proposed method was validated against the grid search algorithm using true triaxial compression (TTC), conventional triaxial compression (CTC), and reduced triaxial extension (RTE) test data from three different rock types. The results indicate that parameter approximation from CTC and RTE test data depends on the consistency between the actual CTC and RTE strength relationships and the predictions of the selected failure criterion. Notably, the RTE strength parameters estimated using the generalized procedure align more closely with the TTC strength trend when the strength relationship between the two extreme stress states is properly considered. Overall, the generalized procedure yields strength parameters with a lower misfit when the selected rock failure criterion closely matches the rock's characteristics. This research offers valuable guidelines for estimating 3D failure criterion parameters using conventional triaxial tests.
He et al. (Sun,) studied this question.