Rock mass usually have cracks and joints, and can be considered anisotropic. Many numerical and experimental studies have been made on the mechanical properties. However the method of numerical analysis which can fully express the behaviour of such anisotropic rock mass with such discontinuities has not yet been developed. Recently the necessity of large scale excurvations and consequently establishment of an effective method of analysis is considered urgent to clarify the mechanical properties of jointed and cracked rock media.
This paper is based on the “rigid body spring models” proposed by Kawai, in which the elements themselves are assumed to be rigid and they are connected by two types of springs distributed over their interfase boundaries. Using the Mohr-Coulomb's failure criterion and considering the effect of contact as well as separation on the two points of interface boundaries of each elements, the perfect elasto-plastic analysis was carried out basing on the initial stress method.
In this paper the following results were obtained.
(1) Homogeneous and anisotropic mechanical characteristics of materials can be obtained by random or anisotropic discretization.
(2) In some cases of cracked rock masses, the crack propagates by slow stable fracture, while such as in splitting tensile test, it causes an instantaneous unstable fracture. This two modes of fracture are verified by numerical analysis.
(3) Fracture pattern results for jointed rock are good agreement with experimental and numerical results.
