Computational modeling of deformation bands in a plug scale

Resumo

The strain localization phenomenon consists in the occurrence of narrow regions due to inelastic
deformations and irreversible phenomena. By porous materials such as soils and rocks, localized deformation can
affect the integrity and contribute to the initiation of structural failure. Typical examples of strain localization in
porous materials are the shear bands, which can be observed experimentally in laboratory tests. The formation of
shear bands can be represented through numerical models such as the finite element method (FEM). Thus, in this
study, we model the occurrence of shear bands at plug scale and perform a sensitivity analysis of the main
parameters involved. The Mohr-Coulomb model with strain softening was used to represent the elastoplastic
behavior of the materials. Strain softening was implemented through a progressive reduction of the friction angle
as a function of the plastic strain. In the results, structural features of the shear bands are analyzed, such as
orientation and band width. From the results, it was observed that the dilation angle is directly related to the
orientation of the shear band. Also, the Young's modulus exerts significant influence on the width of the band.
These analyses also allowed to identify convergence problems and dependence of the results on mesh
discretization level. In this work, we also discuss the source of these problems and mention some alternative
techniques that have been proposed to overcome such difficulties using FEM.