Abstract: Discontinuous cyclic loading/unloading fatigue tests were conducted on salt rock to investigate the evolution laws of mechanic characteristics (i.e., deformation and elastic constants) at different time intervals by using a multifunctional testing machine. The results show that compared with the residual deformation in the normal loading/unloading circle, residual deformation in circle after interval is greater than that in circle before interval. The behavior of the radial and volumetric residual deformation follows the same rule as that of axial deformation. Modulus of elasticity in circles after interval is larger than that in circles before interval generally, while Poisson’s ratio does not change obviously with interval which shows a similar upward trend before and after the time intervals. Interval accelerates the accumulation of residual deformation. The longer the interval is, the faster the residual deformation accumulates during fatigue process, and the shorter the fatigue life of salt rock. The interval without applied stress is beneficial to regression of crystal lattice under the function of residual stress and to generating new slip planes. Less energy consumption is caused when the crystal lattice returns to its initial position corresponding to previous peak stress value. Salt rock samples break more easily and have shorter fatigue life at the macro level.

Key words: salt rock, interval, fatigue, dislocation