A review of rock macro-indentation: Theories, experiments, simulations, and applications

Rock macro-indentation plays a fundamental role in mechanical rock breaking for various rock engineering application, such as drilling, tunneling, cutting, and sawing. Over the past decades, extensive research has been conducted to understand the indentation mechanisms and responses through various approaches. This review aims to provide an overview of the current status and recent advancements in theories, experiments, numerical simulations, and applications of macro-indentation in rock engineering. It starts with elaborating on the mechanisms of macro-indentation, followed by a discussion of the merits and limitations of commonly used models. Influence factors and their effects on indentation test results are then summarized. Various numerical simulation methods for rock macro-indentation are highlighted, along with their advantages and disadvantages. Subsequently, the applications of indentation tests and indentation indices in characterizing rock properties are explored. It reveals that compression-tension, compression-shear, and composite models are widely employed in rock macro-indentation. While the compression-tension model is straightforward to use, it may overlook the anisotropic properties of rocks. On the other hand, the composite model provides a more comprehensive description of rock indentation but requires complex calculations. Additionally, factors, such as indentation rate, indenter geometry, rock type, specimen size, and confining pressure, can significantly influence the indentation results. Simulation methods for macro-indentation encompass continuous medium, discontinuous medium, and continuous-discontinuous medium methods, with selection based on their differences in principle. Furthermore, rock macro-indentation can be practically applied to mining engineering, tunneling engineering, and petroleum drilling engineering. Indentation indices serve as valuable tools for characterizing rock strength, brittleness, and drillability. This review sheds light on the development of rock macro-indentation and its extensive application in engineering practice. Specialists in the field can gain a comprehensive understanding of the indentation process and its potential in various rock engineering endeavors.