Mijo Nikolić

DISCRETE LATTICE ELEMENT APPROACH FOR ROCK FAILURE MODELING

This paper presents the ‘discrete lattice model’, or, simply, the ‘lattice model’, developed for rock failure modeling. The main difficulties in numerical modeling, namely, those related to complex crack initiations and multiple crack propagations, their coalescence under the influence of natural disorder, and heterogeneities, are overcome using the approach presented in this paper. The lattice model is constructed as an assembly of Timoshenko beams, representing the cohesive links between the grains of the material, which are described by Voronoi polygons. The kinematics of the Timoshenko beams are enhanced by the embedded strong discontinuities in their axial and transversal directions so as to provide failure modes I, II, and III. The model presented is suitable for meso-scale rock simulations. The representative numerical simulations, in both 2D and 3D settings, are provided in order to illustrate the model’s capabilities.

Modelling of Internal Fluid Flow in Cracks with Embedded Strong Discontinuities

This chapter presents a discrete approach for modelling failure of heterogeneous rock material with discrete crack propagation and internal fluid flow through the saturated porous medium, where the coupling conditions between the solid and fluid phase obey the Biot’s porous media theory. Discrete cracks and localized failure mechanisms are provided through the concept of embedded discontinuity FEM. Furthermore, the basis for presented discrete 2D plane strain model representation of heterogeneous material consisting of material grains, is an assembly of Voronoi cells that are kept together by cohesive links in terms of Timoshenko beams. Embedded discontinuities are built in cohesive links thus providing the discontinuity propagation between the rock grains in mode I and mode II. The model can also take into account the fracture process zone with pre-existing microcracks coalescence prior to the localized failure. Several numerical simulations are given to illustrate presented discrete approach.