Mechanical characteristics of sandstone under both static pre-stress and cyclic loading

To study the fatigue properties of rock under high geo-stress, a novel uniaxial fatigue stress path test was conducted on ZTR-203 testing machine. The high static pre-stress was first applied on the cylindrical sandstone and the cyclic dynamic disturbance with different amplitudes and frequencies was applied until rock failure. The result shows that the strain evolution of the sandstone under small-amplitude cyclic loading can be divided into three stages: transient damage stage, steady-state stage and accelerated failure stage. Under a high static stress (σ_min ≥ 70% σ_ucs), the damage of the sandstone increases with an increase of cyclic loading magnitude. The fatigue life of the sandstone decreases with an increase of the frequency. The damage energy of the sandstone is smaller under cyclic dynamic disturbance than that under uniaxial compression, which implies that the cyclic disturbance may cause damage in the sandstone and accelerate micro-fracturing, thus resulting in reduction in the energy needed for rock disintegration.