Rock mechanics - Physical and mechanical characterization of rocks

Rock mechanics is a discipline at the interface of mechanics and geology. It belongs to both the geosciences and the engineering sciences. Its application to engineering problems forms part of geotechnics, in the same way as soil mechanics. While many of the concepts developed in soil mechanics are applicable to rock mechanics, the differences between these two geomaterials imply differences in mechanical behavior and therefore the definition of rock-specific concepts, which this article, together with [C 352] , aims to highlight. When it comes to rock mechanics, we need to distinguish between rock (also referred to as rock matrix in this article) and rock mass, the latter being made up of discontinuities in addition to the rock matrix.

In this article, the point of view adopted is that of the application of rock mechanics within the framework of engineering projects, which as a general rule concerns the scale of the rock mass. The writing is therefore oriented towards the application of rock mechanics concepts to the object of study that is the rock mass. Any project involving a rock mass requires the rock mass to be recognized and precisely characterized from a geotechnical point of view. A rock mass is a discontinuous medium made up of more or less intact blocks of rock, separated by discontinuities of various kinds. It is also a heterogeneous, anisotropic and multiphase medium, whose behavior is also affected by a strong scaling effect. The aim of this article is to present the essential concepts of rock mechanics, focusing on the properties of the rocks that make up rock masses. The characterization of discontinuities and rock mass is the subject of [C 352] .

The article is organized as follows. First, a general description of the rocks and the basic concepts needed to understand their behavior is provided. The following six sections present the main elements of rock characterization. The second section is dedicated to the petrographic description of rocks, while the third section focuses on the main physical properties of rocks useful for rock mechanics. The fourth section is devoted to the geomechanical characterization of the rocks making up the massif's rock matrix. This section presents the main mechanical...