Rock Anisotropy
Rock is frequently treated as a linearly elastic, homogeneous and isotropic medium. However, this particular behavior provides only limited insight into the true character of stresses and deformations within a rock mass.
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* All figures quoted in the text are at the end of the lecture. L. Müller (ed.), Rock Mechanics © Springer-Verlag Wien 1972
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G. Barla
Summary Rock is frequently treated as a linearly elastic, homogeneous and isotropic medium. However, this particular behavior provides only limited insight into the true character of stresses and deformations within a rock mass. A well-known behavior pattern which is of considerable interest in many engineering applications is the rock anisotropy. Significant errors can be introduced in stress and deformation analyses by assuming anisotropic rocks to be isotropic. Many Authors have given careful attention to this problem. It is the purpose of the two lectures to describe some of the efforts made in recent years as confined to anisotropic rocks. Introduction In engineering analyses, rock is frequently treated as a linearly elastic, homogeneous, and isotropic medium. However, rock material exhibits, in most cases, different anomalies in the physical behavior, which cannot be neglected if a complete solution of any given rock mechanics problem is to be attained. A well-known behavior pattern which is of considerable interest in many applications is the rock anisotropy. This behavior which involves deformation and strength characteristics, is not only confined to laminated or layered rocks. There is sufficient experimental evidence to support that even some granites can exhibit anisotropic behavior (Peres Rodrigues, 1966, Douglass and Voight, 1969). It has been shown that anisotropy can be of relevance in many rock engineering applications. For example, significant errors are introduced in stress determinations by assuming anisotropic rocks to be isotropic (Berry and Fairhurst, 1966; Becker and Hooker, 1967; Barla and Wane, 1970). Further, when determining the deformation moduli in stratified rock masses by in situ arrangements, the use of analytical formulations based upon elastic anisotropic theory is worth of attention (Oberti et AI., 1970). In recent years, many Authors have devoted a considerable effort to the problem of rock anisotropy, both from theoretical and experimental point of view. At first, this could appear a little out of the rock mechanics perspectives, as the continuum mechanics theory is generally called upon in order to produce the abstraction and formulate the solution to a given problem. However, it is generally recognized that with the use of numerical techniques (e.g. finite element method), some of the restrictions met in the solution
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Rock Anisotropy - Theory and Laboratory Testing
of rock engineering problems by continuum theory have now been overcome, so that the rock mass behavior can be described also including the influence of discontinuities. The necessity however remains to develop an appropriate model of behavior for the rock material. It is mainly with respect to such a model that the anisotropy is of relevance. Since with continuum theories we introduce a model of behavior, the experiment is needed in order that this behavior can be subs
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