Residual Strength and Fracture Energy from Plane-Strain Testing

Abstract

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 apparatus, developed to study localized failure under controlled conditions. Tests on a soft rock, a sandstone with a uniaxial compressive strength of 10 MPa and a modulus of 2 GPa, were conducted to estimate fracture energy