Abstract: In order to study the discontinuous fatigue failure evolution process of surrounding rock of underground salt cavern gas storage under intermittent cyclic loads of injection and production, triaxial interval fatigue tests on deep salt rock from Pakistan was carried out, and the effects of confining pressure and stress level on the interval fatigue of salt rock under triaxial condition were analyzed. The results show that: Compared with uniaxial interval fatigue, confining pressure not only improves the compressive strength of salt rock specimens, but also increases the fatigue life of salt rock. The higher confining pressure results in a more significant increase in range. In triaxial interval fatigue tests, the residual strain of the stress cycles after intervals is larger than that before the interval, which is consistent with the results from uniaxial interval fatigue tests. However, the increase of confining pressure will lead to a decrease in the residual strain accumulation and the residual deformation difference between the cycles before and after the interval. With the increase of stress level, the residual strain and the difference of residual strain before and after time interval both show an increasing trend.

Key words: salt rock, interval fatigue, confining pressure, cyclic loading