Research on the Mechanical Behavior of Interlayer-Salt Rock Interface in Salt Cavern Gas Storage Under Storage-Release Cycle

The interlayer-salt rock interface in the surrounding rock of salt caverns is the main channel for gas leakage during long-term operation of salt cavern gas storage (SCGS). To ensure the long-term safe operation of SCGS containing interlayered salt caverns, this study establishes a standard pear-shaped cavity numerical model and uses interface elements to simulate the interlayer-salt rock interface. Through a 30-year operating cycle simulation, the effects of key parameters such as minimum operating pressure, interlayer dip angle, and interlayer thickness on cavity deformation, plastic zone distribution, interface shear stress, and interface fracture development were studied, clarifying the mechanical behavior of the interlayer-salt rock interface in salt cavern gas storage facilities under storage-release cycles. The research results show that a lower minimum operating pressure significantly enhances the creep and interface slip of salt rock, leading to an increase in interface shear stress, fracture propagation, and cavity shrinkage. An increase in the dip angle of the interlayer raises the proportion of tangential stress at the interface, inducing intense shear concentration and an increase in the volume of shear failure. However, thickening the interlayer can improve the interface compliance, significantly weaken the shear effect, and suppress interface fracture. Moreover, the overall stability of the cavity is jointly controlled by three factors. Higher operating pressure, moderate dip angle, and reasonable interlayer thickness all contribute to reducing the volume of the plastic zone, decreasing the contraction rate, and enhancing long-term safety. This study reveals the mechanical influence of the interface between the interlayer and salt rock during the storage and release cycle of the cavity and its impact on the stability of the cavity and interlayer. It provides a theoretical basis for the design optimization and operation management of salt cavern gas storage facilities with interlayers.