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Abstract An adequate understanding of the formation of new fractures around rock excavations is crucial for a good design. Discrete simulations of the initiation and growth of individual fractures help to create a better understanding, e.g. knowledge on fracture mode (shear and/or tensile) and quantification of the effect of heterogeneities in the studied material. In this paper, this is illustrated using three examples: (i) fracturing around a natural discontinuity, (ii) failure of transversely isotropic rock and (iii) fracturing around soft inclusions. In this way, the importance of the stiffness of a natural discontinuity is highlighted, the complex behavior of transversely isotropic material is better understood and discrete simulations have shown to create an added value in comparison to experiments. The latter is certainly the case for a large parametric study, as one can create a much larger number of models with a predefined percentage and distribution of soft inclusions. Of course, also for the latter set of simulations, a good calibration and comparison with experiments is needed.

1 Introduction In comparison to other engineering applications, fracturing of rock material is often an integral part of the design of an underground excavation. First, fractures have to be induced to be able to excavate the rock. Second, the level of the stress redistribution around deep excavations can be much larger than the strength of the rock resulting in a fractured zone or even in intentionally caving for certain mining methods [1]. Rock failure starts by the initiation of fractures, followed by the further B. Debecker and G. Van Lysebetten have formerly worked in the Department of Civil Engineering, KU Leuven A. Vervoort (&)
B. Debecker
G. Van Lysebetten Department of Civil Engineering, KU Leuven, Kasteelpark Arenberg 40, 3001 Leuven, Belgium e-mail: [email protected] © Springer Science+Business Media Singapore 2017 X. Li et al. (eds.), Proceedings of the 7th International Conference on Discrete Element Methods, Springer Proceedings in Physics 188, DOI 10.1007/978-981-10-1926-5_89

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growth of these fractures. At relatively low loads fracturing already initiates with micro-fractures. These micro-fractures grow further at larger load levels and form macro-fractures. The approximation by classical elasto-plastic continuum models is mostly fine to model the global deformation behavior, but not to clearly understand the fracturing process itself and the consequences of it. Several numerical approaches are available to model crack propagation. Here, the Distinct Element Method (DEM) is being used. The area under investigation is divided into a mesh composed of individual elements. The latter are connected by contacts. Several DEM codes have been developed, specifically for rock. In the research presented in this paper, the two-dimensional Universal Distinct Element Code (UDEC) is used. The original application of this code was the modeling of fractured rock masses [2]. The paper aims to