A unified acoustic emission model for stiffened and damaged siltstone under cyclic thermal and mechanical loading of an energy storage system

To understand and quantify fatigue in siltstone, uniaxial cyclic loading was applied on siltstone specimens along with acoustic emission (AE) monitoring. The specimens were pre-treated with cyclic temperatures up to 200 °C, 400 °C, and 600 °C, respectively. The upper limit of cyclic stress was 40% and 60% of the average uniaxial compressive strength of the specimens. The results show that the fatigue behaviour of siltstone can be classified into stiffened and damaged categories. An increase in the cyclic temperature leads to a decrease in the fatigue threshold. The AE cumulative ringing count was recorded during the experiment. A unified model was derived with high accuracy to describe both the stiffened and damaged behaviour of siltstone under post-thermal cyclic loading.