Analysis of compressed air storage caverns in rock salt considering thermo-mechanical cyclic loading

Exploring the material response of rock salt subjected to the variable thermo-mechanical loading is essential for engineering design of compressed air energy storage (CAES) caverns. Accurate design of salt caverns requires adequate numerical simulations which take into account the most important processes affecting the development of stresses and strains. To fulfill this objective, this paper presents a two-step simulation to analyze the thermo-mechanical behavior of rock salt in the vicinity of CAES caverns. In the first step, the changes in air temperature and pressure resulted from injection and withdrawal processes are estimated using an analytical thermodynamic model. Then, in the second step, the temperature and pressure variations obtained from the analytical model are utilized as the boundary condition for a finite element model of CAES cavern. An elasto-viscoplastic creep model is employed to describe the material behavior of rock salt. In the numerical section, a computational model to simulate the thermo-mechanical behavior of rock salt around the cavern is presented. Finally, the stability and long-term serviceability of the simulated cavern are evaluated considering two extreme loading scenarios: (1) low-pressure working condition and (2) high-temperature operation. Obtained results show that both stability and serviceability of the cavern are highly affected by the internal operating pressure. Dilatancy, damage propagation, tensile failure and increasing the rate of cavern closure are the unfavorable consequences of low-pressure working condition. Similarly, the increased creep rate due to the elevated temperature accelerates the volume convergence and subsequently endangers the serviceability of the system.