Rock Splitting in the Surrounds of Underground Openings: An Experimental Approach Using Triaxial Extension Tests

Abstract

The phenomenon of rock splitting, i. e. the tensile crack formation under general pressure conditions, may be explained by different theoretical approaches such as critical stress conditions and critical strain based on the theory of elasticity, or critical angle of dilatation based on the theory of plasticity. Nevertheless, there are only rare attempts to simulate the rock splitting process in systematic rock mechanical experiments. In this paper we demonstrate results of experiments performed at different modes of extensional conditions in triaxial tests using three different boundary conditions and modifying pore pressure conditions as well as strain rates and stress rates. Our results partly confirm theoretical assumptions, nevertheless, they support the experience that tensile cracks in the triaxial extensional tests do not occur simply dependent from stress- or strain conditions. Additionally their occurrence depends on time, i.e. the velocities of changes of stress and strain as well as, presumably, on the scale of the observed space. Otherwise, the experimental results in decimetre dimensions do not sufficiently coincide with observations from several underground galleries with rock splitting and rock shell formation at their walls in meter to tens of meters dimension.