Strain localization, bifurcation and plastic instability phenomena play important roles as precursors of failure of geomaterials. In geomechanics, it has been recognized that stiff soils such as overconsolidated or cemented soils are progressively strained and reach failure with shear banding and that a strain-softening phenomenon in the stress-strain relation is observed on a macroscopic level. The proper modelling of strain localization and bifurcation phenomena and its role in deformation and progressive can be very significant in such engineering problems as slope stability,...