New prediction method for maximum surface deformation in salt rock storage field considering different cavity geometries

The prediction and control of the surface subsidence above rock salt storage caverns is one of the key problems to ensure the long-term safely stable operation, which has been proved by in-situ monitoring data and catastrophe examples of the existing rock salt underground storage caverns. The salt stratum in China has characteristics as follows: thin salt layer and bedded sediment, which not only increases the damage extent of surface subsidence occurrence, but also directly influences our energy storage scale. Based on the Gaussian distribution theory and combined with convergence function, a new surface deformation prediction theory, transfer function method, is established, which is different from the probability integration method. On this basis, according to the salt strata characteristics in China, elliptic cavity, pear-shaped cavity and cylindrical cavity, which have the same volume, are chosen to compare the maximum surface deformation induced by the cavity completely converged. In addition, the superposition theory is employed to calculate the maximum subsidence in the field with different cavity layouts and different interval distances between cavities. The elliptic cavity is better than the other two kinds of cavities when the single cavity is completely converged. However, when considering to increase the distance between two cavities, the elliptic cavity will not be the best all the time. The research results will provide a reliable theory support for the surface deformation prediction, optimization of cavity shape and cavity layout and relative instruction about rock salt cavity construction in China.