Investigation on the cyclic shear properties of steel-crushed red mudstone particles interface

The cyclic shear characteristics between the structure and soil are critical to the bearing capacity of an infrastructure. In this study, the cyclic shear behavior of the interface between rough steel and crushed red mudstone particles under constant normal load (CNL) and constant normal stiffness (CNS) boundary conditions are investigated using an improved large-scale cyclic shear apparatus. Under the two normal boundary conditions, the variation rule of the interface shear stress with shear displacement is similar, and the interface generally exhibits softening behavior during cyclic shear. Nevertheless, the interface shear strength and deformation values are not equal for the two boundary conditions, i.e., under the CNL boundary condition, higher interface shear strengths are usually obtained, and more significant normal densification behavior is exhibited compared to the CNS boundary condition. The peak shear strength of the interface has a linear relationship with the normal stress, which conforms to the Mohr-Coulomb failure criterion. Additionally, the influence of water content on the interface deformation and cyclic shear strength under the above boundary conditions are explored. The water content does not change the interface volumetric response pattern but is reflected in the magnitude. Regarding interface shear strength, the interface softening phenomenon is more significant with increased water content. The interface shear strength of the initial and residual states is analyzed, while the relationship between the interface shear strength parameters and water content is established.