Stability analysis of the pillars between bedded salt cavern gas storages by cusp catastrophe model

The failure of pillars between bedded salt cavern gas storages can be seen as processes that the deformations of pillars convert from continuous gradual change system to catastrophe state, which are typical nonlinear catastrophe problems. In the paper, the cusp catastrophe model is proposed to obtain the stability factors of pillars. It can overcome the shortages of traditional strength reduction finite element method (SR FEM) and greatly improve the accuracy of stability factors obtained by numerical simulations. The influences of cavern depth, gas pressure, pillar width, and time on the stability factors are studied. Y-1 and Y-2 salt cavern gas storages, located at Jiangsu province of China, were simulated as examples. The stability factors of pillars between Y-1 and Y-2 were evaluated, and the running parameters were recommended to ensure the pillars stability. The results showed that the cusp catastrophe model has high practicability and can precisely predict the stability factors. The stability factors are equidirectional with the increase of gas pressure and pillar width, but reverse to the increase of cavern depth and time. The stability factors of pillars between Y-1 and Y-2 are small for narrow widths, which are influenced greatly by gas pressure, time, pressure difference, and gas production rate. In order to ensure the safety of pillars, the lowest gas pressure, safe running time, max. pressure difference and max. gas production rate of Y-1 and Y-2 were recommended as 7 MPa, 5 years, 3 MPa, and 0.50 MPa/d, respectively.