Abstract
The existence of macroscopic flaws in geomaterial structures profoundly influences their load-carrying capacity and failure patterns. This paper is devoted to the numerical investigation of mixed–mode fracture propagation in a cracked Brazilian disk (CBD) specimen by means of the embedded strong discontinuity approach (SDA). A recently modified nonassociated, three-invariant cap plasticity model with mixed isotropic/kinematic hardening is used to predict the continuum response for the intact part of the specimen. In addition, this constitutive model adopts bifurcation analysis to track the inception of new localization and crack path propagation. For the post-localization regime, a cohesive-law fracture model, able to address mixed-model failure condition, is implemented to characterize the constitutive softening behavior on the surface of discontinuity. To capture propagating fracture, the Assumed Enhanced Strain (AES) method is employed. Furthermore, particular mathematical treatments are incorporated into the simulation concerning numerical efficiency and robustness issues. Finally, the results obtained from the enhanced FE simulations are analyzed and critically compared with experimental results available in the literature.
Highlights
Numerical simulation of geotechnical and geological structures, especially 11 in the platform of the finite element (FE) method, has attracted much re12 search interest with the advent of modern computational resources
In gravity dams most of the observed cracks are mixed mode (Kishen and Singh (2001); Roth et al (2015)), and hydraulic fractures propagate in mixed-mode condi31 tions from the walls of wellbores (Rahman et al (2002))
Post-localization model Regarding the nonlinear formulation proposed for the combined openingsliding fracture evolution Eq 3.13a, we use the standard N-R algorithm to solve for displacement jump ζ = on the band
Summary
Numerical simulation of geotechnical and geological structures, especially 11 in the platform of the finite element (FE) method, has attracted much re search interest with the advent of modern computational resources. Though several attempts have been made in a case of crack paths unknown a priori to generate robust and reliable tools for automatic remeshing procedure (see, for example, Ma69 ligno et al (2010); Boussetta et al (2006)), discrete-crack models still suffer 70 from some shortcomings, such as spurious stress transferring across crack sur faces and mesh bias To alleviate these numerical difficulties, fine meshes are needed, which lead to large-scale and in computationally expensive systems. Due to some of the appealing features of the EFEM, computational efficiency being a primary one, we have chosen to adopt this method for the simulation of mixed-mode fracture in CBDs. The remainder of this paper is organized as follows: Section 2 reviews a recently modified cap plasticity model for geomaterials.
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