Dynamic mechanical properties of jointed soft rock samples subjected to cyclic triaxial loading: a FEM-DEM-based study

Abstract

In order to investigate the fatigue behavior of jointed soft rock samples with different joint dip angles, cyclic triaxial tests under different stress amplitudes and confining pressures were numerically simulated using the combined finite-discrete element method (FEM-DEM). The dynamic strength and deformation rules were revealed, including the masing effect, the ratcheting effect, the volumetric strain properties and the failure modes influenced by joint dip angles. During the first hysteresis loop, the nonlinearity of the loading curve is much stronger than that in subsequent cycles, and the damage and deformation are almost the most, which demonstrates that the effect of stress history on soft jointed samples subjected to cyclic loading is great, especially the first loading cycle. When the applied static and dynamic maximum deviatoric stress are the same, the vertical compressive stress of the dynamic case is found to be lower than that of the static case, and the vertical tensile stress exists in some local position, which may be the reason why the cracks can increase and propagate gradually when the dynamic maximum stress is lower than the static strength.