Strain localization in soft rock—a typical rate‐dependent solid: experimental and numerical studies

Abstract

SUMMARYStrain localization developing inside soft rock specimens is examined through experimental observation and numerical simulation. In the experimental study, soft rock specimens are sheared at different strain rates under plane strain conditions and deformation and strain localization characteristics are analysed. Transition of localization mode from highly localized mode for higher strain rate to distributed and diffused mode of strain localization for lower strain rates was observed. In the numerical study, simulations of plane strain compression tests are carried out at different strain rates by using an overstressed-type elasto-viscoplastic model in finite element computations. The role of strain rates on setting gradients of strain fields across shear band is clarified. The probable mechanism for transition of localization mode is discussed.

Effects of model scale and particle size on micro-mechanical properties and failure processes of rocks—A particle mechanics approach

“…The continuum approach, such as finite-element methods (FEM), aims to capture the damage and failure processes by specially developed constitutive models such as elasto-plastic/elastoviscoplastic and damage mechanics models (e.g. [1][2][3][4]). As pointed out by Cundall [5], this approach may have two drawbacks: (1) the constitutive laws tend to become more and more complicated with many parameters that cannot be readily measured in laboratory tests and (2) simulation of fracture initiation/propagation processes and discontinuous large deformation (breakdown) are difficult challenges.…”

X‐ray Micro CT for Studying Strain Localization in Clay Rocks under Triaxial Compression

“…Such a method was applied to measure 2D displacement and deformation fields on the surface of a specimen already back in the 80s (Chu et al, 1985;Bruck et al, 1989). Since, DIC techniques have become widely used in geomechanics (e.g., Gudehus and Nübel, 2004;Bhandari and Inoue, 2005 -to mention just a few recent studies). Note that using two rather than just one digital camera, one can measure 3D displacements on the surface of a specimen (e.g., Helm et al, 1996).…”

Strain field investigation of limestone specimen under uniaxial compression loads using particle image velocimetry

“…WHITE et al [14] developed a deformation measurement system based on PIV and close-range photogrammetry to measure the movement of a fine mesh of soil patches. BHANDARI and INOUEN [15] examined the developing and transiting mechanism of strain localization deformation inside soft rock specimens using plane strain tests and finite element simulations. ZHANG et al [16] presented a microscopic measuring method for observing the movement of soil particles at sub-pixel accuracy from the image series during a soil-structure interface test.…”