Thermo-mechanical evolution of damage accumulation and macroscopic dilatancy in rock salt: Implications for salt cavern gas storage

Understanding the thermo-mechanical response of rock salt at high temperatures is important for the stability assessment of deep salt cavern gas storage. Uniaxial compression tests with synchronous acoustic emission (AE) monitoring were conducted on rock salt at 40–110 °C. The mechanical response, energy evolution, and AE characteristics were analyzed during the pre- and post-dilatancy stages. An AE-based damage variable was defined using cumulative AE counts, and its evolution was characterized using a normalized Weibull function. A distinct temperature-dependent transition in damage–dilatancy behavior is observed. At 40–80 °C, damage activity is concentrated predominantly in the post-dilatancy stage, with pre-dilatancy AE counts accounting for only 10.4% of the total pre-peak counts on average. By contrast, at 90–110 °C, the pre-dilatancy proportion increases to 54.2%, while the total strain energy density and dissipated energy density at the dilatancy point exceed 40% of their respective peak values. Low-frequency AE signals also become dominant during the pre-dilatancy stage. The normalized Weibull function can effectively characterize the pre-peak evolution of the AE-based damage variable in rock salt. These results indicate that substantial inelastic deformation and damage can accumulate while the specimen remains macroscopically compacted at high temperatures, revealing increasing damage–dilatancy decoupling. Tensile cracks remain dominant throughout the temperature range, indicating that temperature primarily redistributes crack activity across loading stages and alters its accumulation path without fundamentally changing the dominant crack type. These findings provide useful insights into the stability and safe operation of deep salt cavern energy storage.