Shear bands in plane strain compression of loose sand

Experimental results are presented which characterize the behaviour of a loose, fine-grained, water-saturated sand tested under globally undrained and drained conditions in a plane strain apparatus. The objective of this investigation is to provide insight into the phenomenon of shear banding in loose sand. Together with local measurements of boundary forces and deformations, stereophotogrammetry Is used to investigate the progression of strain localization in plane strain compression. Typical results and findings concerning the evolution of non-homegeneous deformation are presented in detail. Shear banding occurred in both undrained and drained experiments on loose masonry sand. In general, temporary modes of strain localization, observed during macroscopically 'uniform' deformations of a specimen, gave way to a single, persistent shear band. A clear pattern of onset of the formation of the persistent shear band, mobilization of the maximum effective friction and complete formation of the band was observed in all tests. The stress state when the localization begins is very close to, yet precedes that corresponding to the maximum mobilized friction. The persistent shear bands evolve with changing width and orientation.