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 und rained and drained conditions in a plane strain apparatus. The objecti ve of this investigation is to provide insight into the phenomenon of shear banding in loose sand. Together with local measurements of bound ary forces and deformations, stereophotogrammetry Is used to investiga te the progression of strain localization in plane strain compression. Typical results and findings concerning the evolution of non-homegene ous deformation are presented in detail. Shear banding occurred in bot h undrained and drained experiments on loose masonry sand. In general, temporary modes of strain localization, observed during macroscopical ly 'uniform' deformations of a specimen, gave way to a single, persist ent shear band. A clear pattern of onset of the formation of the persi stent shear band, mobilization of the maximum effective friction and c omplete formation of the band was observed in all tests. The stress st ate when the localization begins is very close to, yet precedes that c orresponding to the maximum mobilized friction. The persistent shear b ands evolve with changing width and orientation.