Abstract: Large-scale laminar-ring simple shear test and large-scale triaxial test of soil-rock mixture(SRM) were carried out. The stress state of samples in simple shear was analyzed according to the joint test law of granular material and sand in simple shear. The differences in the strength properties of SRM under simple shear and triaxial compression were then explored. Results reveal that: (i) With the same minimum principal stress, the rate of maximum principal stress in simple shear is lower and changes in a smaller range, and the peak value of principal stress ratio is lower, which means the ultimate Mohr's circle of stress is smaller. (ii) The secant shear modulus under simple shear is anisotropic, and the secant shear modulus in horizontal direction is constantly lower than that under triaxial compression, but such difference shortens with the decrease of non-coaxiality degree between principal stress axes and principal strain axes. (iii) For the samples used, the shear strength indices of Mohr-Coulomb strength criterion obtained under simple shear are significantly lower than those under triaxial compression, and in particular, the internal friction angle is about 9.5% lower. Preliminary investigation shows that the rotation of principal stress axes and non-coaxiality in simple shear are important reasons for the differences of strength properties of SRM.

Key words: soil-rock mixture, strength properties, large-scale simple shear test, large-scale triaxial test, rotation of principal stress axes, non-coaxiality