Investigation on the Deformation and Strength Characteristics of Rock Salt Under Different Confining Pressures

The deformation and strength characteristics of rock salt is significant for the safety of hydrocarbon energy (oil, gas) storage in salt caverns. To overcome the problem of determining the peak strength by simultaneously considering the dilatancy characteristics of salt rock, compression experiments were carried out on Pingdingshan salt rock under different confining pressures. The results shew that the uniaxial experiment of salt rock presented a brittle failure, but the presence of impurities improved the strength of samples. After the confining stress reached a "Transition confining pressure"—6.55 MPa, which was determined by using a chart method, the strength of salt rock increased greatly and behaved a strong strain hardening phenomenon. An empirical method to determine the "transition confining pressure" was put forward, and it was also suggested that the minimum operating pressure in a gas storage salt cavern should be higher than this value. The experiments under different confining pressures indicated that the higher the confining pressure was, the more hysteretic the dilatancy occurred. Based on this result, a method to determine the peak strength of salt rock based on a certain axial strain value (6%) or the initial point of dilatancy was proposed. Then the peak strength of the salt rock samples in this study was calculated to verify the feasibility of this method. This study provided the determination methods for the "transition confining pressure" and the peak strength for salt rock, which was a reference for the evaluation and operation of the gas storage salt caverns.