Three-dimensional bonded-particle discrete element modeling of mechanical behavior of transversely isotropic rock

This paper presents the three-dimensional bonded-particle discrete element modeling of mechanical behavior of transversely isotropic rock as an extension to the previous work conducted in two dimensions (Park B, Min K-B. Bonded-particle discrete element modeling of mechanical behavior of transversely isotropic rock. Int J Rock Mech Min Sci 2015a;76:243-55). Systematic verifications of the elastic and strength anisotropy were performed by comparing the numerical results with the analytical solutions, which indicated that there was good agreement with appropriate consideration of overlapping ratio of smooth-joint contacts. Two validation cases are presented in this study. First, the three-dimensional bonded-particle DEM model successfully captured the monotonic and concave variations of elastic and strength anisotropy and Brazilian tensile strength anisotropy observed in the laboratory tests of Asan gneiss, Boryeong shale, and Yeoncheon schist. Improved match in Brazilian tensile strength was attributed to higher average coordination number in three-dimensional numerical model than that in two-dimensional model whereby leading to higher interlocking. The second validation case was conducted against CIU (isotropically consolidated undrained triaxial) and Brazilian tensile strength tests of a Tertiary shale from the Norwegian Continental Shelf (NCS). The three-dimensional bonded-particle DEM modeling of the triaxial tests with different initial effective confining pressures showed that the peak strength at failure provided by the numerical model reasonably simulated the strength variation as well as the various elastic moduli with respect to the inclination angles. Brazilian tensile strength of the numerical model was in range of the laboratory data. Furthermore, the numerical model produced similar post failure patterns as exhibited on the disk-shaped NCS shale, e.g., axial splitting and crushing failure. The results demonstrated that the three-dimensional bonded-particle DEM model with embedded smooth-joint contacts is a viable model for emulating the mechanical behavior of transversely isotropic rock with the potential of enhanced predictive capability of anisotropic numerical model.