Elastic Strain Energy–Based Modified Mohr–Coulomb Strength Criterion

To address the Mohr–Coulomb (M-C) strength criterion’s inadequate consideration of intermediate principal stress effects on rock strength, this study establishes an energy-based strength criterion grounded in the fundamental mechanism of elastic strain energy release driving rock damage. By analyzing the intrinsic relationship between directional elastic strain energy release and the contributions of principal stresses to strength, the proposed criterion quantitatively integrates intermediate and minimum principal stress influences. Validation via true triaxial test data from three distinct lithologies demonstrates (1) high predictive accuracy for rock strength (mean error <7%); (2) enhanced material strength utilization compared to the M-C criterion; and (3) mitigation of Singh B criterion errors caused by intermediate principal stress overestimation. Weighting coefficients for minimum principal stress consistently exceed 0.5 across stress levels, confirming its dominance over intermediate principal stress in governing strength. Inheriting the M-C criterion’s advantages of mathematical simplicity and parameter clarity, this model overcomes the neglect of intermediate principal stress, offering critical insights for characterizing rock strength evolution under complex stress states and informing geotechnical engineering design.