Cumulative deformation and non-coaxial characteristics of fiber and cement-modified iron tailings under the rotation of principal stress

In order to study the deformation characteristics of fiber and cement-modified iron tailings (FCIT) under traffic loads, the cumulative deformation, stress–strain paths, cyclic stiffness, and non-coaxial characteristics of FCIT under the coupling of different cyclic stress ratios (CSR) and torsional shear stress ratios (η) were analyzed by using a heart-shaped stress path. The results indicate that: 1) The cumulative strain and torsional shear strain of FCIT under the rotation of the principal stress vary with CSR and η. The established empirical formula for the cumulative strain can be used to calculate the cumulative deformation of FCIT under different principal stress rotations based on the results of cyclic triaxial tests. 2) The difference between shear stiffness and positive deviation stiffness is the inherent mechanism that induces the non-coaxial characteristics of FCIT, that is, shear stiffness is subjected to torsional shear stress more than positive deviation stiffness is subjected to axial stress. 3) The non-coaxial characteristics of FCIT gradually weaken with the increase of axial force and torsional shear force, while the non-coaxial angle between the direction of strain increment and the direction of stress decreases.