The use of digital image processing in monitoring shear band development

A new technique involving sample preparation, video imaging, and image analysis has been developed to observe the kinematics of shear bands when geomaterials are subjected to a general state of combined stress. The technique provides an effective, low-cost, and non-invasive way to monitor the development and measure the deformations inside and outside the shear bands. Its capabilities are demonstrated through a series of drained tests in which thin hollow cylinders of sand are subjected to combinations of hydrostatic, axial, and torsional stresses. It is shown that the deformation within the shear band is different from the global one and the one in its vicinity. For sand specimens with the same configuration, density, and confining pressure, the initiation, orientation, and thickness of shear bands depend on the loading path.