This book was written to serve as a guide for students in the departments of Civil Engineering, Mineral Resources Engineering, Mining and Metallurgy Engineering, Geology, and Environmental Geology at the higher education institutions in our country.

Some of the courses that are directly related to this text are: “Rock Mechanics,” “Tunnels and Underground Works,” “Support of Underground Works,” “Engineering Geology,” “Rock Mechanics – Tunnels,” “Elements of Geotechnical Engineering,” “Advanced Geomechanics,” “Geology of Engineering Works and Rock Mechanics,” and “Experimental Rock Mechanics.”

The theoretical background of Rock Mechanics is extensively presented in the corresponding Greek-language books that cover this knowledge area. This text focuses on the analysis and explanation of solving simple and complex Rock Mechanics problems. To facilitate the reader, at the beginning of each chapter, a brief presentation of the relevant theory is provided, which is absolutely necessary for solving the corresponding exercises.

Special attention is given to the equations that define the various quantities as well as the relationships between them, while simultaneously presenting the methodology that is typically followed for solving these exercises. Furthermore, each step is explained in as much detail as possible, with continuous reference to the corresponding equations and relationships.

The content (after the Introduction – Chapter 1) is distributed among the following chapters: In the second (2nd) chapter, the mathematical background and the basic elements of vector and tensor theory, which are frequently used in the analysis of the theory and the theoretical applications of the subsequent chapters, are presented.

The third (3rd) chapter discusses the stress tensor that characterizes the stress state at any point in a body, while in the fourth (4th) chapter, the stress state in two dimensions is studied, with particular emphasis on understanding and how Mohr's circle is used.

In the fifth (5th) chapter, the magnitude of the twist or, alternatively, the reduced deformation that is directly connected with the stresses through a cause-effect relationship is presented. The sixth (6th) chapter describes the constitutive equation for elastic behavior in two and three dimensions. The elastic model represents the most common constitutive behavior of engineering materials, including many rocks, and serves as a useful basis for describing more complex behavior.

The elastic behavior of a body under specific stress loads is analyzed by applying Hooke's law for three dimensions. Failure criteria, which are mathematical expressions that have the ability to estimate when failure will occur in the rock, are studied in the seventh (7th) chapter. The application of two fundamental and widely applicable failure criteria is presented in the case of intact rock and rock mass.

The eighth (8th) chapter examines the stability of circular and elliptical underground openings (tunnels and shafts), their zone of influence, as well as the stability of underground openings in the form of chambers and pillars. After understanding the analysis and stereographic projection of the discontinuities that make the rock mass discontinuous in the ninth (9th) chapter, the tenth (10th) chapter presents the application of modern rock mass classification systems, which essentially assign values to those properties or characteristics that are considered likely to affect its behavior.

Finally, in the eleventh (11th) chapter, methods of applying support and reinforcement of the rock mass near the boundaries of underground openings are presented.