The failure process of heterogeneous rock specimen with initially random material
imperfections in uniaxial plane strain compression and the macroscopically mechanical response are
numerically modeled by using FLAC (Fast Lagrangian Analysis of Continua). A FISH function is
generated to prescribe the initial imperfections within the heterogeneous specimen by using Matlab.
The imperfection is weaker than the intact rock. Beyond the failure of the imperfection, it undergoes
ideal plastic behavior, while intact rock exhibits linear strain-softening behavior and then ideal plastic
behavior once failure occurs. The specimen with smooth ends is loaded at a constant strain rate and is
divided into 3200 elements. The maximum numbers of the initial imperfections in five schemes are
100, 300, 500, 700 and 900. The effects of the number of the imperfections on the fracture process, the
final fracture pattern and the complete stress-strain curve are investigated. Prior to the peak stress,
some imperfections extend in the axial direction and then a part of them coalesce to form inclined
shear bands. Beyond the peak stress, shear bands progressively intersect the specimen; in the process
the number of the yielded elements approximately remains a constant. With an increase of the number
of the initial imperfections, the spacing of shear fractures decreases, the peak stress and corresponding
axial strain decrease; the post-peak branch of stress-strain curve becomes steeper; much more
elements fail in tension; the number of the yielded elements in tension in the vicinity of the two lateral
edges of the specimen remarkably increases.
Strain and interface energy of ellipsoidal inclusions subjected to volumetric eigenstrains: shape factors
