  Renewable hydrogen storage in salt caverns requires fast injection and
production rates to cope with the imbalance between energy production and
consumption. Such operational conditions raise concerns about the mechanical
stability of salt caverns. Choosing an appropriate constitutive model for salt
mechanics is an important step in investigating this issue, and many
constitutive models with several parameters have been presented in the
literature. However, a robust calibration strategy to reliably determine which
model and which parameter set represent the given rock, based on stress-strain
data, remains an unsolved challenge. For the first time in the community, we
present a multi-step strategy to determine a single parameter set based on many
deformation datasets for salt rocks. Towards this end, we first develop a
comprehensive constitutive model able to capture all relevant nonlinear
deformation physics of transient, reverse, and steady-state creep. The
determination of the single set of representative material parameters is
achieved by framing the calibration process as an optimization problem, for
which the global PSO algorithm is employed. Dynamic data integration is
achieved by a multi-step calibration strategy for a situation where experiments
are included one at a time, as they become available. Additionally, our
calibration strategy is made flexible to account for mild heterogeneity between
rock samples, resulting in a single set of parameters that is representative of
the deformation datasets. As a rigorous mathematical analysis and the lack of
relevant experimental datasets, we consider a wide range of synthetic
experimental data, inspired by the existing sparse relevant data in the
literature. The results of our performance analyses show that the proposed
calibration strategy is robust and accuracy is improved as more experiments are
included for calibration.
