Application of new twin-shear unified strength criterion to frozen soil

A new twin-shear unified strength criterion is proposed in this study. This criterion reveals the relationship among single-shear, twin-shear, and triple-shear strength criteria. All known linear and nonlinear strength criteria-such as Huber-von Mises, Drucker-Prager, Mohr-Coulomb, Tresca, and twin-shear series-are special cases of the new twin-shear unified strength criterion. The proposed unified strength criterion was employed to study the strength characteristics in the compressed meridional plane (where the stress Lode angle, theta(sigma) = - 30 degrees) of frozen soil, based on the soil's nonlinear and asymmetric properties. In the criterion, beta and C, which denote the relationship between the shear stress tau and normal stress sigma on the twin-shear stress acting plane, are deemed variable; they vary with the change in normal stress sigma or mean stress p. Through a comparison of results, we found that the results obtained with the proposed strength criterion were in good agreement with the results of tests on frozen soil. On this basis, expressions for the cohesive force and the internal friction angle of frozen soil were derived and discussed.