Field observations indicate that failure in soft rock is often associated with a slip surface or shear band, where deformation is concentrated in a narrow zone; displacements occur with decreasing stress within the shear band, whereas outside the band the material appears to be intact. In examining the propagation of the shear band, it is useful to establish the relation between shear stress and slip displacement. This was accomplished within a laboratory setting with a plane-strain compression ...
A new apparatus for determining the constitutive response of rock and concrete, named the University of Minnesota Plane-Strain Apparatus, was designed and built on a passive stiff-frame concept. The biaxial device, with U.S. Patent number 5,063,785, is unique, because it allows the failure plane to develop and propagate in an unrestricted manner, as opposed to conventional systems where the material is constrained by the testing apparatus. By placing the upper platen on a low friction linear bea...
A biaxial compression apparatus for investigating shear-band formation and growth in dry and water-saturated sand and clay specimens is described. This apparatus is a modification of the device designed by Vardoulakis and Goldscheider [1] for testing planar shear banding in sands. The modifications involve improved axial load guidance, low friction linear bearing, and enhanced load and displacement measurement instrumentation. The apparatus allows for accurate prelocalization material behavior a...
In heavily over-consolidated clays there is a marked peak in the observed relation between shear stress and shear strain. As the strain increases, the stress falls from a peak to a much smaller residual stress. Slopes made from such a clay often fail progressively many years after construction. Sliding occurs on a concentrated slip surface, and it is found that the mean resolved shear stress on that surface is markedly less than the peak shear strength. Concepts from fracture mechanics, and in p...
Abstract Closed-form solutions are obtained for the singular stress and displacement fields at the tip of a single crack in an infinite poroelastic transversely anisotropic saturated medium. Three different scenarios are considered: dry medium (no pore pressures), undrained loading (no dissipation of excess pore pressures), and drained loading (all excess pore pressures have dissipated). The results show that the stresses around the tip of a pressurized crack in a saturated medium with drained l...
