DEM is now recognized as a powerful tool for simulating behaviors in rock mechanics. In particular, bonded particle model has been successfully applied in emulating the elastic modulus, Poisson's ratio and strength parameters of isotropic rock by controlling the microparameters in DEM model. In this study, the smooth joint contact model was introduced to represent the bedding planes in order to eventually model the transversely isotropic rock. Consideration of anisotropy is important for shale gas production because shale is shown to have a significant anisotropy in terms of elastic constants and compressive and tensile strengths. The chosen anisotropy model is transversely isotropic model which is believed to model the mechanical behavior of shale to a reasonable extent. The properties of Boryeong shale (Cho. et al., 2012) were used as a reference for transversely isotropic rock. Transversely isotropic rock model using DEM behaved in good agreement with the mechanical behaviors of Boryeong shale from the laboratory. The results can be evidence that development of anisotropic numerical model is promising through DEM. This anisotropic modelling is expected to pave the way for wide variety of engineering application ranging from traditional rock mechanics application to the emerging applications such as shale gas production.
We generalize our view of a bonded-particle model (BPM) to consist of a base material (of rigid grains joined by deformable and breakable cement at grain-grain contacts) to which larger-scale joints can be added and whose mechanical behavior is simulated by the distinct-element method using the two- and three-dimensional discontinuum programs PFC2D and PFC3D. The micromechanical processes that control brittle fracture and thus, should inform any micromechanical model, are summarized. The rich variety of microstructural models that can be produced by the bonded-particle modeling methodology are described and classified with respect to their microstructural and larger-scale features. These models provide a wide range of rock behaviors that encompass both compact and porous rock at both an intact and rock-mass scale, and examples are provided of how BPMs are being used to model rock at these scales. The examples include an intact anisotropic material that may swell and contract in response to changes in saturation, the behavior of two alternative BPMs that can match both the uniaxial and tensile strengths of compact rock and the embedding of an intact BPM within a larger continuum model to study fracturing around a gold-mine stope in quartzite.
Leelasukseree, Cheowchan (Chiang Mai University) | Pipatpongsa, Thirapong (Tokyo Institute of Technology) | Khosravi, Mohammad Hossein (Tokyo Institute of Technology) | Mavong, Narongsak (Tokyo Institute of Technology)