The effect of varying stress intervals on fatigue of rock salt

Abstract

The surrounding rock of underground energy storage salt caverns is subjected to periodic loading with stress intervals during actual operation. To study the fatigue behavior of rock salt with such stress intervals, one conventional fatigue test and three fatigue tests with multi-step varying stress intervals (MVSIs) were conducted. The results show that the circumferential deformation first decreases and eventually becomes similar to the axial deformation in fatigue tests with MVSIs, as the interval duration increases. Both the dissipated energy and the spacing between the loading and unloading curves of a single cycle first decreased, then remained constant, and finally increased sharply as the stress interval increased. When the stress intervals corresponded to the elastic phase of loading (between 20% and 40% of the uniaxial compressive strength), the rock salt was subjected to the minimum damage. Based on the Bauschinger effect and dislocation internal friction theory, the micromechanism of rock salt fatigue was further explained.