ABSTRACT
The contact consolidation is often used for the simulation of saturated jointed rock masses. An inertial extension of the contact consolidation is obtained using d' Alembert's inertia principle. Inertia extension needs to be completed with a closure relation. Depending on the closure relation the contact consolidation is transformed into a dynamic model.
INTRODUCTION
Water is an important actor in the stability of rock masses and their overlying structures. Recent disorders due to tunnelling in mountainous zones have brought to light a new role of water in hard rock masses (Pougatsch, 1990). It is its ability to produce delayed subsidence. This phenomenon is the consolidation process.
CONSOLIDATION MODELS
Two distinct models are at the basis of the different consolidation theories. These are the contact consolidation and the perfect consolidation. Contact consolidation supposes that a saturated media is one deforming entity in which water flows by contact using Darcy's law for water conduction. Perfect consolidation supposes that a saturated media is a superposition of two distinct deforming entities, a liquid and a solid, interacting and occupying simultaneously the same space. These two models are at the basis of the majority of the consolidation models and can be used for a practical classification of the consolidation theories (EI Tani, 2004).
Detournay et al. (1993) note that Biot reformulated the poroelasticity theory many times. There is a simple explanation to this. Bier's publication (1941) is based on the contact consolidation while Biot's publication (1956) is based on the perfect consolidation. These two publications have their roots in different consolidation concepts that lead to different developments.
The contact consolidation and the perfect consolidation are distinct concepts that reflect different philosophical interpretations of water presence in saturated media.
JOINTED ROCK MASSES
Joints exist in great variety and numbers in rock masses. Their edges form an integral part of the boundary of a rock mass. Their huge number imposes a statistical handling of their behaviour. Some of them will be considered a genuine part of the boundary of the rock mass. Others will be considered a part of the rock fabric. Many methods have been developed to deal with this transfer, allowing treating the rock mass as a continuum which contains fractures and border faults. The dimensions of an elementary volume of a jointed rock are related to the joints that are transferred to the rock fabric. If the remaining joints in the boundary set is still unaccommodating, a subsequent transfer of joints to the rock fabric will be operated, increasing, in so doing, the dimensions of an elementary volume. Every transfer of joints from the boundary set to the rock fabric reduces the number of constraints concerning mass impenetrability and the relative movement of joints edges. Every transfer reduces further more the complexity of the associated boundary conditions, although it needs to be compensated by an increasing complexity of the material relations and an increasing complexity of the continuum description of the jointed rock (Singh, 1973; Lombardi, 1992; Dawson et al., 1995; Muhlhaus, 1993).
