Modélisation des massifs rocheux fissurés par la méthode des éléments distincts

The subject of this thesis forms part of a research program dealing with fractured rock masses being undertaken by the "Centre de Géologie de l'Ingénieur (CGI)" from the "Ecole Nationale Supérieure des Mines de Paris (ENSMP)" and the "Ecole Nationale des Ponts et Chaussées (ENPC)". In fractured rock masses, it is very difficult to undertake engineering works without analysing, beforehand, the fracture systems and their different mechanical and hydraulic behaviours. Fracture rock masses analysis should include the following : Systematic field measurement of rock mass discontinuities. Statistical analysis of the discontinuities to delimit fracturing sets in the rock mass. Study of the geomechanical properties of the discontinuities. General stability analysis. Hydraulic analysis. This research is concerned with general stability analysis. Classical methods of stability analysis, based on limit equilibrium conditions and not taking into account the deformability and the stress distribution present in the rock matrix, do not give very satisfactory results. The method developed here is called "distinct element" method, which allows modelling of fractured rock masses into distinctblocks delimited by the different fractures and the analysis of the interactions among them. Block interaction occurs at their points of contact (or joints) according to the joint mechanical behaviour. Joint stress can be expressed in terms of the joint stiffness and block displacement. By minimising the total potential energy of the studied system, a system of equations relating the forces present and the resulting block displacements by a stiffness matrix can be obtained. It is often necessary to take into account non-linear joint mechanical behaviour, resulting from a system of non-linear equation which should be solved incrementally. Using this method, we can analyse the deformations caused by excavation in a rock mass and take into account localised failures which might turn into progressive failure mechanisms. Furthermore, artificial support systems using active or passive anchor bolts were modelised. The mechanical behaviour of the bolts are considered as elasto-plastic with kinematic strain-hardening.