Rheology of synthetic rocksalt : with emphasis on the influence of deformation history and geometry on the flow behaviour

Abstract

The present study consists of an experimental investigation into the deformation behaviour of synthetic polycrystalline rocksalt (NaCl) in uniaxial compression and in simple shear. While there exists an extensive body of experimental work regarding the deformation behaviour of synthetic and natural rocksalt in compression, a number of important questions remains unanswered. In particular, though recognized that deformation history and geometry can strongly influence rheological behaviour and microstructural and texture development via so-called "memory' effects", such effects have not been systematically investigated. In addition, there still is widespread disagreement in the literature regarding the detailed dislocation creep mechanisms, rate-controlling processes and microstructural processes operating in polycrystalline NaC!. This study aims at helping to resolve these questions. However, special attention is given to the influence of deformation geometry/history on the mechanical behaviour of rocksalt and to testing the validity of the assumptions underlying methods normally used to generalize experimentally obtained (axi-symmetric) flow laws, where stress and strain rate are treated as scalars, into forms suitable for 3-dimensional numerical modelling, where these quantities are treated as tensors. The results not only provide insight into the influence of deformation geometry and/or history on the deformation behaviour of NaC!, but allow general principles to be distilled that are also relevant to the effects of deformation geometry and history on the deformation behaviour of other rock-forming minerals.