Abstract: Using FISH functions written in FLAC, the axial, lateral and volumetric strains as well as the Poisson’s ratio of rock specimen with a material imperfection in plane strain compression were calculated at different elastic moduli. The influence of elastic modulus on failure process and precursor of the specimen was modeled. In elastic stage, the adopted constitutive relation of rock was linear elastic; in strain-softening stage, a composite Mohr-Coulomb criterion with tension cut-off was used; and the post-peak constitutive relation was also linear. If elastic modulus is not very high, only an inclined shear band is formed all along. For very high elastic modulus, finally, the intense shear strain is concentrated into a shear band bisecting the specimen. The numerically predicted shear band’s inclination angles approach Arthur’s and Coulomb’s inclinations and decrease with an increase of elastic modulus, as cannot be explained by the classical theories. With an increase of elastic modulus, the peak stress increases and the pre-peak stress-axial strain curve becomes steep, while the post-peak slope of stress-axial strain curve does not change. The absolute values of axial strain and lateral strain, which correspond to the peak stress, decrease and the post-peak stress-lateral strain curve becomes steep with an increase of elastic modulus. The decrease of elastic modulus leads to greater deviations of lateral strain-axial strain curve, Poisson’s ratio-axial strain curve and volumetric strain-axial strain curve from linear states; higher non-elastic axial strain and higher maximum shear strain increment in the vicinity of material imperfection. Therefore, the precursor to failure is more apparent at lower elastic modulus.

Key words: elastic modulus, shear band, strain localization, precursor, stress, lateral strain, volumetric strain