Pillar safety in shallow salt caverns by using numerical simulations

Problems such as low recovery rates and frequent accidents occur in rock salt solution mining areas in China. Reasonable design parameters are essential for improving the economic benefits of solution mining areas and the safety of underground caverns. The long-term stability of salt caverns under different pillar widths was analyzed by considering the inclined shallow-buried deep salt layer with a buried depth of 300-400 m in the Huasu solution mining area, Anhui Province, China, as the research object. Physical and mechanical tests of the rock core were performed to obtain the corresponding mechanical parameters, and a three-dimensional geological model was established. The stability calculation was performed using FLAC3D software, and the safe spacing between the two adjacent cavities in the shallow buried salt layer was optimized to improve the recovery rate. The results demonstrate that when the pillar width is 1.2 times the cavity diameter, the plastic zone between the two cavities does not penetrate, and there is no dilatancy failure near the surrounding rock of the cavity. With an increase in the pillar width, the displacement around the cavity and the volume shrinkage rate gradually increases. Secondly, when the volume of brine accounts for 100 % of the cavity volume, it is beneficial to improve the stability of the cavity. A comparison with the simulation results of cavities with various salt dip angles demonstrates that the salt dip angle increases the risk of cavity instability, and the influence of the salt dip angle on cavity stability should be considered in the actual construction process. The results of this study are significant for ensuring the safety of shallow-buried salt cavern operations and the improvement of the recovery rate.