Assessment of using borehole‐closure data to determine the constitutive behavior of salt

Borehole closure data have often been used to determine the constitutive behaviour of rock salt. This is an inverse problem and analysis of the data is confused by the fact that borehole closure is a structural response that does not uniquely determine constitutive behaviour since both the stress and deformation depend on the constitutive behaviour. This application brief assesses the conclusion of a recent study that the transient power law, ϵ = K τ m t n , which includes no term to account for steady‐state deformation, is a better constitutive model for salt than are models that account for steady‐state straining, and that an empirical model developed from the borehole closure data could be extrapolated to give conservative predictions of long‐term closure of single or widely spaced openings.