Abstract: In order to understand the strain hardening and damage self-healing properties of salt rock, the mechanics test, porosity and permeability tests and nuclear magnetic test were performed. The mechanical properties, permeability, porosity and pore size distribution under strain hardening and damage self-healing conditions were investigated after being maintained at room temperature and confining pressure. The results show that: (1) Strain hardening of damaged salt rock weakens the plasticity of rock samples, decreases the peak strain under secondary loading, and increases the elastic modulus. With the maintenance at room temperature or confining pressure, the salt rock self-healing occurs, and the plasticity gradually recovers, while the peak strain increases and the elastic modulus decreases under secondary loading. (2) The stress–strain curves of intact and damaged salt rocks almost have no compacting stage, while the stress–strain curves of intact and damaged salt rocks show obvious compacting stage after long-term maintenance at room temperature and confining pressure. (3) The permeability and porosity of the intact salt rock are very low, and the permeability of the damaged salt rock is two orders of magnitude higher than that of the intact salt rock. With the increase of the maintenance time at room temperature, the permeability and the porosity decrease slowly. The permeability of damaged rock after being maintained at confining pressure is restored to the same order of magnitude as that of intact rock. (4) After being maintained at room temperature and confining pressure, part of the middle pores and large pores healed into small pores and middle pores. (5) Slow self-healing of damaged salt rock occurs when the salt rock is maintained at room temperature, and the confining pressure can greatly improve the speed of self-healing of damaged salt rock. (6) The damage self-healing of salt rock can be divided into rapid recovery stage and slow recovery stage in the later stage.

Key words: self-healing, strain hardening, porosity and permeability, nuclear magnetic resonance (NMR)