Shear Deformation, Failure and Instability of Rock Specimen in Uniaxial Compression Based on Gradient-Dependent Plasticity: Fid-Bau Portal

Shear Deformation, Failure and Instability of Rock Specimen in Uniaxial Compression Based on Gradient-Dependent Plasticity

Wang, X. B.

Abstract

For rock specimen in uniaxial compression subjected to shear failure in the form of a single shear band bisecting the specimen, the thickness of shear band, the distributed plastic and total shear strains in the band, the post-peak axial, lateral and volumetric strains as well as Poisson's ratio, the post-peak slopes of stress-axial strain curve and stress-lateral strain curve, the snap-back (Class II) condition in axial direction, the post-peak shear stiffness of shear band and that of elastic body outside the band, and the unstable criterion of shear band-elastic body system are analytically presented based on gradient-dependent plasticity where an internal or characteristic length reflects the interactions and interplay among microstructures due to the heterogeneous texture of geomaterial. Results show that the post-peak stiffness of shear band depends on the constitutive parameters of rock. The post-peak Poisson's ratio, the post-peak slopes of stress-axial strain curve and stress-lateral strain curves are concerned with the height and/or width of rock specimen. The height of the specimen also affects the axial snap-back condition and the axial unstable criterion. Once the axial snap-back occurs, the system composed of shear band and elastic body must lose its stability. A comparison of the present analytical solution of the post-peak stress-strain curve and the previously experimental data for normal concrete specimen for different heights (size effect of softening branches of stress-axial strain curve) in uniaxial compression is carried out and a good agreement is found.