In the modelling or design phase of many mining or civil projects conducted in rock masses, the designer is confronted with a set of questions that is not always easy to answer. This is mainly due to the anisotropy and heterogeneity of the fractured medium, and to the complexity of the fractures'¬" geometry and their mechanical parameters. In this work, a practical tool is provided for the purpose of numerical homogeneization and modelling of fractured mediums, using the finite elements method. Through this, this book intends to gives an answer to, amongst others: the estimation of elastoplastic properties of rock; the estimation of discontinuities by means of elementary tests; the most appropriate model to appraoch the rock'¬"s mechanical behaviour; the possibility of replacing fractured medium by a homogeneous equivalent one; size estimation of the mechanical representative elementary volume (REV); selecting the most suitable type of loading for numerical large-scale stress-strain tests; the calculation of homogenized elastoplastic properties of a rock mass or a fractured medium with the finite element method. Besides that it deals with a considerable number of questions from practice, in a more fundamental way, this guide presents a new numerical classification of some typical rock masses. With only a few mechanical and geometrical parameters of rock and discontinuities, the designer can refer to the performed classification tables to derive the elastic large-scale mechanical of a rock mass. This volume is intended for professionals, researchers and advances students in civil, geological and mining engineering and earth sciences working on rock mass and masonry structures.