Experimental Studies on the Brittle Fracture Stress

Abstract

According to the simplest or “classical” view, the brittle fracture of a rock is a discrete event in which the failure of the rock occurs, without significant prior deformation and without warning, at a particular stress. In later chapters it will be shown that this view is over-simplified and is, in particular, inadequate for an understanding of the physical mechanisms of fracture. However, it is often sufficient from a phenomenologic point of view, and it is a view that underlies a great deal of research on the factors that affect the gross brittle behaviour of rocks. The present chapter and the two following deal with these studies, in which, apart from noting the gross nature of the fracture, the only quantity of interest is the peak stress (“brittle fracture stress”). Such studies, often essentially empirical in approach, provide much of the basis for applied rock mechanics in engineering and mining, as well as for the analysis of geologic faulting.