Diffuse and localized deformation of a porous Vosges sandstone in true triaxial conditions

Abstract

This work presents an experimental study on the diffuse and localized deformation mechanisms of a high porosity (20%) Vosges sandstone (Eastern France) subjected to different stress paths in the deviatoric plane. The experimental campaign was performed using a high pressure true triaxial apparatus (TTA) in which the three principal stresses are independently controlled. A series of 10 quasi-static, monotonous loading tests was performed at 2 constant mean stresses, in the brittle-ductile transition regime, and at five prescribed Lode angles, from axisymmetric compression (ASC) to axisymmetric extension (ASE), as a measure of the deformation mode. The failure surface in each deviatoric plane and changes in macroscopic measurements, such as deformation band angles tracked by full field digital image correlation (DIC) technology, indicate a clear effect of the Lode angle on a transition between the brittle and ductile regime, independent from the mean stress level.