1) A new failure criterion, (τ/τR)α = 1 – σ/σt, is proposed based on the results of triaxial compression tests on rock and granular materials of various types. In this criterion, τ and σ are shearing stress and normal stress, respectively, τR and σt are τ- and σ- intercepts, respectively. ‘α’ is a failure envelope exponent. It is demonstrated that this criterion can express in the unified manner, the failure criterion of rock and granular materials of a wide range of types from hard rock to sand. 2)It is shown that the non-linear deformability of these materials can be expressed by D/Do = R 1/a, where D is a deformability, Do is its initial value and R is the relaxation factor. 3) One proposed technique is to apply the above-mentioned equations to numerical analysis of deformation behavior of rock masses during excavation.
In the excavation of large caverns or tunnels, rock masses undergo deformation, leading to a failure in some cases. The most important factors affecting the behavior of such rock masses are 1) failure criterion for rock mass and 2) non-linear deformability of rock mass. The authors studied the results of triaxial compression tests on a wide range of rock and granular materials, such as, hardrock, soft rock, concrete, sand, and others. A unique solution is obtained which can express in a comprehensive and unified manner, the failure criterion and non - linear deformation characteristics of these materials of different types.
The phenomenon in which a rock mass is subjected to an external force and the stress - strain relationship becomes non - linear, thereby causing a local failure can be considered in the following manner.
