Study on Creep Properties of Salt Rock with Impurities During Triaxial Creep Test

In order to study creep characteristics of salt rock with impurities, the triaxial loading tests about two salt rock with different impurity content were carried out on large-scale programmable rheometer of Sichuan University. The results showed that the failure pattern and mechanical parameters of salt rock are different as the change of confining pressure or content of impurities. The destructional form of salt rock change from shear to drum type when the confining pressure increase. The steady-state creep rate of each sample grows exponentially with the deviatoric stress when confining pressure and impurity content is the same. As the confining pressure increasing, the creep rate is depressed, but the long-term strength is increased when deviatoric stress and impurity content is the same. The steady-state creep rate of low-impurity(ω=2.1%) is higher than high-impurity(ω=46.8%) when deviatoric stress and confining pressure is the same. Volume strain experiences three periods of pressure dense period, quiet period, and dilatation period. The volume strain of salt rock with high impurities inferior to the low impurity. A fractional unsteady creep damage model was established by introducing the relationship between insolubles impurity content and stress sensitivity constant to constitutive equation of creep. The reasonability of this model was proved by comparing the theory model with experimental data. © 2017, Editorial Department of Advanced Engineering Sciences. All right reserved.