Poster: Effect of confining pressure on plastic flow of salt at 125°C

Abstract

The microphysics of crystal plastic flow of rocksalt have been studied to ascertain which dislocation mechanism controls creep at temperatures in the range 100-200 oC. This information is essential to reliably constrain extrapolation of laboratory flow laws to in-situ stresses and strain rates. For constant strain rate experiments on NaCl, microphysical models predict that climb-controlled creep should display a positive de-pendence of flow stress on confining pressure, at pressures where microcrack dilatancy is suppressed. By con-trast, cross-slip control should exhibit a negative dependence or virtually no dependence on confining pres-sure. Rigorous experimentation using confining pressures well above those encountered in salt in nature is required to test which of these models might apply. We tested polycrystalline sodium chloride samples at pressures in the range 50-600 MPa at 125 oC. The results revealed that the strength of the salt increased with pressure, pointing to climb control.