7th January 2004 11:52 Elsevier/MFS mfs Chapter 1 Fundamentals of Poromechanics Yves Gu ´ eguen 1 Luc Dormieux 2 Maurice Bout ´ eca 3 1.1 Introduction The mechanical behavior of the Earth’s crust is often modeled as that of a porous, fluid-saturated medium. Crustal rocks, as are many other solids, are porous and fluid saturated down to at least 10 km depth. Because they are made of minerals and open pores, they show an internal structure. Classical continuum mechanics de- scribe such a medium as an idealized continuum model where all defined mechani- cal quantities are averaged over spatial and temporal scales that are large compared with those of the microscale process, but small compared with those of the investi- gated phenomenon. We follow this type of approach in this chapter’s presentation of the classical macroscopic theories of porous rock deformation. Such a separation of scales is a necessary condition for developing a macroscopic formulation. A complementary point of view is that of mixture theory. In that approach, solids with empty pore spaces can be treated relatively easily because all the com- ponents have the same motion when the solid is deformed. However, if the porous solid is filled with liquid, the solid and liquid constituents have different motion, and so the description of the mechanical behavior is more difficult. Interactions are taking place between the constituents. A convenient way to approximately solve that problem is to idealize the saturated rock as a mixture of two components that would fill the total space shaped by the porous solid. This is the model of mixture theory where each component occupies the total volume of space simultaneously 1 Ecole Normale Sup´ erieure, ENS, 24 rue Lhomond, 75231 Paris Cedex 05, France. [email protected] 2 CERMMO, ENPC, 6-8 Avenue Blaise Pascal, Champs sur Marne, 77455, Marne la Vall´ ee Cedex 2, France. [email protected] 3 Institut Fran¸ cais du P´ etrole, 1 et 4 avenue de Bois-Preau, 92852 Rueil-Malmaison Cedex, France. [email protected] 1
Fundamentals of Poromechanics
May 29, 2023
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