Experimental investigation of linear damping characteristics on granite and red sandstone under dynamic cyclic loading

Damping is a significant dynamic characteristic used to describe rock vibration failures and plays an important role in various seismic engineering applications, specifically for evaluating stability of rock masses under forced vibration loading. In this paper, cyclic loading tests were carried out on sandstone and granite samples to study their damping characteristics. The effect of the selected influential indicators (stress level, strain amplitude and loading frequency) on the damping ratio and damping coefficient was studied. The damping parameters of sandstone and granite were calculated and the variability in the damping parameters as a function of stress level, frequency and strain amplitude were determined. The linear relationship between damping ratio, damping coefficient and strain amplitude was investigated. The results suggest that the relationship between the damping parameters and the strain amplitude could be expressed as a linear function. The influential indicators to the damping parameter of granite were sorted as follows: stress level > strain amplitude > frequency. The influential indicators of sandstone were sorted as follows: strain amplitude > stress level > frequency. Under a fixed-amplitude stress path, the damping ratio of granite was approximately 80% that of the sandstone and the damping coefficient is approximately 200% of that of the sandstone.