ABSTRACT
Anisotropy (having different properties in different directions) is a well-known feature of rock and is of interest in the field of rock mechanics and engineering. In the context of elasticity theory, the numbers of mechanical properties required to characterise a rock are as follows: isotropic (2-Young’s modulus and Poisson’s ratio); transversely isotropic (5-two Young’s moduli, two Poisson’s ratios and a shear modulus); orthotropic (9-three Young’s moduli, three Poisson’s ratios and three shear moduli); and general anisotropy (twenty one constants). These cases are illustrated in Figure 7.1 and the associated properties are explained further in Hudson and Harrison (1997) via the elastic compliance matrix.
