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Rock anisotropy caused by inherent structures like bedding, foliation, and micro-fractures directly influences strength, deformability, and stress distribution variations. These directional changes can affect the stability of rock engineering practices, such as underground openings and slopes, and dealing with the anisotropic rock masses (ARMs) is one of the significant challenges. The commonly used conventional classifications are solely based on the isotropic behavior of rock masses and are unsuitable for anisotropic ones. Despite the limitations of these classifications, engineers tend to oversimplify the situation and characterize or design the ARMs, ignoring the impact of anisotropy. This study presents a summary of geological conditions, mechanical behavior, and classification systems of ARMs, as well as a review of numerical modeling techniques that may be applicable in the design phase within such medium. ARM Rating (ARMR), or any other type of alternative classification system that considers the directions in which rocks act instead of just their strength levels, can facilitate improved feasibility analysis for complex geological conditions and supporting systems design in ARMs. Moreover, the failure criteria considering the anisotropic behavior reflect the nonlinear development with long-term dependence on rock strength. Such criteria may be applied to numerical methods, such as the discrete element method (DEM), which offers more or less realistic simulations of ARMs' responses. Nevertheless, establishing standard procedures for the characterization, classification, and design of ARMs, especially in deep underground anisotropic conditions, is in high demand.
Ghorbani et al. (Fri,) studied this question.