Localization in plane strain compression of fluid-saturated rock

Localization in terms of a bifurcation from a homogeneous pattern of deformation is predicted to be different if the boundary conditions are drained or undrained. This phenomenon is evaluated in plane strain compression experiments with water-saturated Berea sandstone, where corresponding poroelastic and inelastic properties were measured. Non-uniformity of lateral deformation and clustering of acoustic emission events were used as the experimental evidence of localization, which occurred soon after the peak stress in both drained and undrained cases. These observations are in reasonable agreement with an analysis that predicted negative values of the critical hardening modulus (localization post-peak) for fluid-saturated sandstone under plane strain loading conditions.