Peeking inside rocks: why microstructures matter when they deform under stresses

Abstract

Rocks are often perceived as strong, immovable masses, yet their stability is shaped by both what we observe at large scales and what is concealed in the interior [1]. At the macro-scale, discontinuities such as fractures, joints, and bedding planes have a potent effect on the deformation and fractur¬ing of rocks [2]. Such characteristics form planes of weakness that can control the stability of rock masses. Even though rocks show no apparent cracks or joints at the macro-scale, their mechan¬ical behavior is strongly governed by their complex internal microstructure. The resistance or vulnera¬bility of a rock to stress depends on grain size, po¬rosity, mineral composition and cementation nature [3]. Although macro-discontinuities precondition the stability on the large scale, the microstructure defines the ultimate way in which a rock actually behaves as the stresses accumulate.