Effect of loading frequency on the deformation behaviours of sandstones subjected to cyclic loads and its underlying mechanism

To explore the mechanism of frequency on the evolution of deformation parameters, triaxial compression tests under multi-level loading were carried out at different frequencies. The results show that increasing the frequency by reducing the duration of loading cycles can inhibit the development of primary and new fractures in a rock in the compaction and plastic stages, thus hardening the rock and improving the strength. The increase in frequency induced by an excessive increase in loading cycles causes the rock more compact. The cumulant of irreversible deformation greatly increased to degrade the strength. Additionally, loading cycles plays a more important role.