A novel soil strength criterion is proposed based on the shear stress ratio on a new spatially mobilized plane, where the cube root of principal stresses is constant. The strength failure surface depicted in the principal stress space by this criterion was smoothly conical, with a curved triangle shape on the octahedral plane. A comparative analysis of the strength failure surfaces of the Mohr-Coulomb (M-C), the Drucker-Prager (D-P), the Matsuoka-Nakai (M-N), the Lade-Duncan (L-D), the new criteria, and the shear strength laws of different criteria with parameter b on the π plane showed that the L-D criterion and the new spatially mobilized plane strength criterion were comparable, which revealed the physical essence of the L-D criterion. Comparing the new strength criterion with the measured results of true triaxial tests of 4 kinds of intact loess under conditions of consolidation and drain, the strength law of loess could be described by the new strength criterion under complex stress conditions, and the rationality and reliability of the strength criterion were verified by the correspondence between the criterion and experimental values.
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