Abstract：Fatigue damage will be generated in rock foundation or slope under long-term dynamic loads. The rock and concrete belong to brittle materials. The attenuation laws for fatigue damage of rock and concrete are similar to certain extent，but there are some essential differences in deformation and damage of rock and concrete. Furthermore，the evolutionary processes for the fatigue damage of rock and concrete are different due to the differences of weathering degree，components and their contents. The histories of real-time ultrasonic wave velocity variations of sandstone specimen during cyclic compressive loading tests are researched. Results show that the attenuation of the transverse ultrasonic wave velocity follows inverse S-shaped line，which can be divided into three phases：initial fast attenuation phase，steady attenuation phase and rapid attenuation close to failure. The durations of the three phases are about 10%，85% and 5% of fatigue life，respectively. Comparing with concrete materials，the attenuation amplitude of the ultrasonic wave velocity at the end of the second stage is little，and the cyclic times in the third phase are less in particular compared with fatigue life. A damage variable is defined based on the transverse ultrasonic wave velocity and used to describe the growth law of sandstones fatigue damage. The fatigue tests on the different sandstones indicate that the transverse ultrasonic wave velocities of the sandstone containing gravel and siltstone all attenuate obviously. The attenuation speed rates of the transverse ultrasonic wave velocity of the slightly weathered sandstone are greater evidently than that of the strongly weathered sandstone during the fatigue damage. The results may offer theoretical references for the fatigue health diagnosis of similar rock foundation and slope.
