3. Physical properties of rocks

The most commonly studied physical properties of a rock are its density, porosity, water content, degree of saturation, permeability and propagation velocity of elastic or ultrasonic waves, as well as its thermal properties. These properties are determined in the laboratory by means of identification tests. They influence the mechanical behavior of rocks.

The determination of these physical properties is based on a representation of the rock matrix by a porous medium consisting of a solid skeleton, made up of the various minerals in the rock, and voids, filled with air and/or water (figure 4 ).