Based on triaxial compression test

this paper presents the analysis of strain variation characteristics at five stages during triaxial compression test and defines compression-dilatancy boundary as the point of maximum compression.According to the development of fracture in rock salt sample

this paper analyzes the feature quantity which leads to the change of strain of rock salt and comes to the conclusion that the change of strain is consistent with the change of porosity in triaxial compression test.Based on the conclusion

the damage variable is defined as the change of porosity of rock salt.Then strain variation of rock salt in triaxial compression test is analyzed.And variation of rock salt porosity is obtained in different damage states.This formulation quantitatively describes the relationship between damage of rock salt and volume strain.Based on the study above

formulation between rock salt damage and volume strain

which can provide a basis for the following study of the law of gas permeability in different damage states and the construction of energy storage can be obtained.The conclusion provides a theoretical basis for the safe operation of engineering.