Roof Stability Evaluation of Bedded Rock Salt Cavern Used as Underground Gas Storage

摘要

The cusp catastrophe model is proposed in the study to evaluate the roof stability factor of natural gas storage cavern in bedded rock salt, which can overcome the shortages of traditional Strength Reduction Finite Element (or difference) Method (SR FEM) that the failure criteria can not be precisely given. The proposed model can greatly improve the calculating precision and has clear physical and mathematical meanings. The numerical simulations of generic natural gas storage caverns in bedded rock salt located in Jiangsu province of China are carried out based on the proposed model to evaluate the stability factor of cavern roof. In addition, parameters are studied to investigate the stability factors as functions of the buried depth, roof span, roof salt thickness and roof salt Young's modulus, overlying non-salt thickness, overlying non-salt Young's modulus and gas pressure, etc. The examples show that the proposed model is precise and correct, which can meet the actual engineering demands. The stability factor of cavern roof is equidirectional with the increase of roof salt thickness, roof salt stiffness, overlying non-salt thickness, overlying non-salt stiffness and gas pressure, but reverse to the increase of buried depth and roof span. Our methods provide a new way to evaluate the roof stability factor of natural gas storage cavern in bedded rock salt.