ABSTRACT:

Understanding the dynamic mechanical properties of jointed rocks is beneficial for the rational design and stability analysis of rock engineering projects. This study experimentally investigated the influences of joint geometrical parameters on the dynamic fatigue mechanism of jointed rock models using the synthetic materials with artificially intermittent joints. Our results revealed that the dynamic fatigue stress-strain curve of jointed rock is dominated by its static uniaxial curve; the terminal failure strain in dynamic fatigue curve is equal to the post-peak strain corresponding to the maximum cyclic stress in the static stress-strain curve. The studied four joint geometrical parameters significantly affect the dynamic properties, including the energy evolution, the damage variable and the crack coalescence pattern. The higher the geometrical parameter, the higher the fatigue damage accumulates in the first few cycles, and the lower the fatigue life. Two basic micro-cracks, i.e., tensile wing crack and shear crack, are observed in dynamic cyclic tests, which are controlled principally by joint dip angle and persistency. In general, shear cracks only occur in jointed rocks with high dip angle or high persistency, and these jointed rocks are associated with the low fatigue strength, the large damage variable and the low fatigue life.

1. INTRODUCTION
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