Abstract: In the process of long-term operation of salt cavern storage, the surface subsidence prediction is important for the storage safety assessment. So far, there is no analytical model based on the theory of mechanics. The problem of the surface subsidence above salt cavern storage is similar to the one of boundary deformation of the sphere cavern with shrinkage force in the elastic half infinite space. By using the spherically symmetric displacement of the sphere cavern with shrinkage force in the elastic infinite space, the elastic analytical solution of the surface subsidence in integral form is derived with the principle of superposition. The surface subsidence is caused by the sphere cavern under a certain internal pressure in the half infinite space. Then, regarding volume deformation as elasticity and distortion as viscoelasticity Maxwell with the correspondence principle, the elastic analytical solution is transformed to be a viscoelastic analytical solution in integral form in space-time domain by Laplace transformation. In comparison with the results of numerical simulation, the accuracy of the elastic model is verified. Finally, the viscoelastic model is applied to predictive analysis of the surface subsidence in a salt cavern storage, and is compared with the observation data in cavern site, demonstrating the new model to be effective in predicting the surface subsidence and its development trend of the salt cavern storage. Therefore, the model can be expected to provide a theoretical method for subsidence prediction of salt cavern storage.

Key words: salt rock, energy storage, surface subsidence, prediction, viscoelastic model