ABSTRACT:

The scope of this study is to simulate the behaviour of a homogeneous rock sample under standard laboratory triaxial compression test using an innovative combined finite-discrete element method (FEM/DEM) research code. The influences of confining pressure and displacement rate on samples mechanical behaviour are studied. The FEM/DEM code is capable of capturing the main phenomena observed in a triaxial test, e.g., the brittle-ductile transition. This paper demonstrates the suitability of FEM/DEM approach to explicitly model rock deformation and failure.

1 INTRODUCTION

It is well known that the strength of geomaterials depends on their triaxial stress state. Thus, a complete characterization of the rock behaviour requires conducting experiments where such a condition is reproduced. Over the past years many numerical techniques (e.g., FEM, DEM) have been used to simulate the compressive failure of confined rock specimens. In the current study an improved version of the combined finite-discrete element (FEM/DEM)Y-code originally developed by Munjiza (2004) is used to reproduce a series of standard laboratory triaxial tests. To the authors' knowledge at the present, the only existing studies using a hybrid continuum-discontinuum approach are those published by Klerck (2000), Klerck et al. (2004), and Stefanizzi (2007), using the code ELFEN (Rockfield 2002). In this paper the effect of confining pressure and displacement rate on the mechanical behaviour of the samples has been numerically investigated. The capability of the code to accurately model the mechanical behaviour of homogeneous rocks leading to realistic fracture patterns is validated against results published in the literature. The results show adequate accuracy to model laboratory tests, making the FEM/DEM code suitable for addressing more complex rock engineering problems related to the progressive development of cracks and fractures during excavation (e.g., spalling phenomena inTBMexcavated tunnels, caving phenomena in underground mines).

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