An automated machine for pure shear deformation of analogue materials in plane strain

A plane strain, pure shear rig has been developed for the deformation of rock-analogue materials under tightly controlled experimental conditions. Shortening of up to 42% is possible, with constant natural strain rates and a predetermined confining side stress ( σ₃). Differential stress, side stress, temperature and strain rate are recorded during the experiments, allowing rheological calibration under exactly the same conditions used in the applied studies of mechanical instabilities (folds, boudinage, etc.). The relatively large specimen size, three-piece side plate design and the extensive use of low-friction facing materials in contact with the model result in boundary conditions which closely approximate plane strain, pure shear.