Long-Term Stability Analysis of Pillars in Salt Cavern Storage Based on the Salt Rock Dilatancy Boundary Evaluation Method

Using deep salt caverns for underground energy storage is a globally recognized method of energy storage. The safety of gas storage and the utilization rate of salt mine formation resources are related to the pillar design of salt cavern gas storage. Existing theoretical research on the pillar design of salt cavern gas storage prioritizes universality. This may affect the accuracy of regional research. In this study, triaxial mechanical tests are conducted on salt rock under varying confining pressures. Moreover, a linear dilatancy limit equation is fitted according to the stress state at the dilatancy point. Based on the dilatancy failure mechanism of salt rock pillars, considering the influence of the cavern parameters of the salt rock and internal pressure during gas storage operation, the criteria for pillar failure were improved, and a theoretical method for pillar stability evaluation that is suitable for the Jintan area was established. Through the comparison of numerical simulation and theoretical results under different working conditions, the influence laws on pillar stability in terms of pillar width, cavern air pressure and salt hole depth were obtained, and the accuracy of the theoretical method for pillar stability evaluation was verified. Using the pillar stability analysis method to calculate the actual working conditions of a gas storage cavern in Jintan, the minimum operating pressure obtained was in line with the field working conditions. This method can provide a reference for future pillar design of salt caverns for gas storage in the Jintan area.