Experimental investigations of the creep-damage-rupture behaviour of rock salt

The creep-damage behaviour of rock salt, especially in the tertiary creep phase has been rarely investigated. The creep-damage-rupture characteristics of rock salt are studied in this paper by applying Wang's creep-damage model, the experimental results of the triaxial destructive creep-damage tests using quasi-static loading on rock salt specimens are presented, complete creep-damage curves are obtained, and the evolution laws of deformation and damage of rock salt in the primary (transitional), secondary (steady-state) and tertiary (accelerating) phases are deduced. The long-term behaviour of dilatancy of rock salt is investigated according to the dilatancy boundary theory and an approximate long-term dilatancy boundary range is obtained. Finally, the long-term strength of rock salt is evaluated for the test samples. The used model proves to conform well to the test data, including in the tertiary creep-damage phase; it can be suitable for the assessment of collapse, cracking, rupture and other long-term failures, and hence for theoretical basis of design in the underground engineering of gas and oil storage cavern, nuclear waste disposal and other facilities in salt deposit.