The analysis of structures in discontinuous rock masses has been receiving a particular interest in rock mechanics and rock engineering. A technique based on the finite element method together with the contact element to model rock masses consisting of blocks of arbitrary shapes is developed and its formulation is presented. This model considers blocks as sub-domains and represents them by solid elements. To model the block interactions such as sliding or separation, contact elements, which are far-superior to joint or interface elements, are used. Then this model is used to simulate the behaviour of typical rock engineering structures such as a single block or a pile of blocks on a incline and underground cavities and rock slopes in jointed rock masses.
The analysis of rock engineering structures excavated in discontinuous rock masses has been receiving a particular interest among rock mechanicians and rock engineers. Since rock mass consists of distinct blocks due to geological discontinuities, several techniques were developed to analyse masses consisting of distinct blocks. By reviewing the literature, it can be found that during the last three decades the limiting equilibrium analysis (Hoek and Bray 1977, Aydan et al. 1989) and some numerical analysis methods such as the finite element method (FEM) (Goodman et al. 1968, Ghaboussi et al. 1973, Aydan et al. 1990c), distinct element method (DEM) (Cundall 1971) and discontinuities deformation analysis (Shi 1988) have been developed for the analysis of problems involving discontinuities in rock mechanics. Inspite of all these technique, it is difficult to say that a unique technique, that guarantees satisfactory results, is developed. This research has also been carried out with the sole purpose to develop a suitable method for the analysis of rock engineering structures excavated in discontinues rock masses consisting of blocks of arbitrary shape. Among the several available techniques, the finite element method has been selected to assess the stability of block systems. The method proposed is essentially based on the finite element technique and is a hyperbolic type of formulation. It consists of a mechanical model to represent the deformable blocks and contact models that specify the interaction among them. Intact blocks and block contacts are modeled as a visco-elasto-plastic material. Small displacement theory is applied to the intact blocks while blocks can take finite displacement. Block interactions are simulated through contact elements. This model is used to analyse typical rock engineering structures to check its validity as well as its applicability.
Discontinuum is distinguished from continuum by the existence of contacts or interfaces between the discrete bodies that comprise the system. The actual geometry of interfaces or discontinuities are never smooth and has asperities of varying amplitude and wave length (Aydan et al. 1990, Aydan and Shimizu 1995). Relative sliding or separational movements in such localized zones present an extremely difficult problem in mechanical modeling and numerical analysis. However, these models are restricted to a very simple geometry and the elastic behaviour of adjacent materials.