Creep properties of salt rock and its nonlinear constitutive model.

In order to study the creep property of salt rock, triaxial compression creep tests with step loading axial stress to salt rock specimens were carried out on the RLW-2000 rock rheology testing machine. The test results show that the instantaneous strain, creep strain and creep velocity of salt rock increase gradually with the increasing of axial stress, meanwhile, the duration of the primary creep stage gradually extend. And isochronous stress-strain curves of salt rock indicate that the creep process of salt rock has nonlinear characteristic, and the nonlinear degree is related to creep time and stress level. Based on nonlinear rheological theory, a new nonlinear viscosity component with a variable viscosity coefficient was proposed, and the viscosity coefficient of which was time and stress-dependent. Then, by using this proposed nonlinear component to replace the conventional viscous components in Burgers model, a nonlinear vis-coelasticity creep model, which was named MBurgers model and can describe the nonlinear creep property of salt rock was established. According to triaxial compression creep test results of salt rock, the parameters of MBurgers model were in versed by using curve fitting method. And the theoretical curves accord well with the test curves, which indicates that the MBurgers model can describe the creep property of salt rock. [ABSTRACT FROM AUTHOR]