A Discrete Element Simulation Method for Self-Healing of Salt Rock Damage

Salt rock, owing to its excellent rheological and self-healing properties, has been widely applied in underground gas storage. However, a numerical method capable of systematically simulating the entire damage–healing process of salt rock is still lacking, which limits the in-depth understanding of fracture evolution mechanisms and the long-term stability of storage caverns. To overcome this limitation, this study improves the parallel bond model within the framework of the Discrete Element Method (DEM) by incorporating a stress-driven healing criterion and a healing-equivalent stress coupling algorithm, thereby enabling the complete simulation of crack initiation, propagation, and closure in salt rock. The results show that the proposed method effectively captures healing effects: under uniaxial compression and tension, the number of cracks decreased by approximately 27% and 23%, with strength recovery of 110.7% and 7%, respectively. Moreover, the reconstruction of particle contact chains closely corresponds to the crystal-bridge phenomena observed in experiments, verifying the model’s reliability in reproducing macroscopic mechanical responses. In addition, the healing process exhibits a temporal characteristic in which crack closure occurs earlier than volumetric strain reduction, indicating an evolution pattern of “structural closure first, macroscopic densification later.” This study not only fills the gap in DEM-based simulation of salt rock damage–healing processes but also provides theoretical support for long-term stability evaluation and operational optimization of underground salt cavern storage.