Volume 22, Issue 1 (March 1999)
Shear Banding in a Sedimentary Soft Mudstone Subjected to Plane Strain Compression
A plane strain compression (PSC) testing system to observe shear banding in softrock was developed. The deformation characteristics of shear band in a sedimentary soft mudstone were evaluated by locally measuring axial and lateral deformations of specimens in drained PSC tests. Shear deformation and dilatancy of shear band that occurred between the peak stress state and the start of the residual stress state were on the order of 1 and 0.5 mm. Dilatancy of the shear band continued during the residual stress state, resulting in a high-residual friction angle mobilized along the shear band. Shear band deformation characteristics of two other sedimentary softrocks were obtained from axial strains measured locally in triaxial compression tests based on the stress-state dilatancy relationship obtained from the PSC tests.