ABSTRACT
The steady-state creep rate of salt is typically described using only the maximum and minimum principal stresses and is generally considered to be independent of the intermediate principal stress; thus, the steady-state creep rate of salt is expected to be the same under both compressive and extensile states of stress. However, little experimental evidence has been obtained regarding the transient nature of salt under alternating states of stress between triaxial compression and triaxial extension; i.e. alternating Lode angles. Multistage creep tests were performed to investigate the time-dependent behavior of salt at two Lode angles. The data show that Lode angle does not affect the steady-state strain rate of salt; however, each time the Lode angle was changed, a significant transient response was observed. This transient response to changes in Lode angle is not predicted by constitutive models commonly used to evaluate natural gas storage caverns.
