ABSTRACT:

This work presents numerical simulations of the excavation-induced fractures around galleries in Andra Underground Research Laboratory at Meuse/Haute-Marne department in France. An instrumented gallery with geological/geophysical surveys describing the surrounding fractures network was considered as case study. Fractures form a system of distinct, almost parallel discontinuities around the underground shaft. Finite Element simulations with joint elements (JFEM), constituting the potential fractures, were performed to reproduce their initiation and propagation in the rock. A damage cohesive fracture model representing the stress-displacements behavior and failure of discontinuities was adopted. Two configurations were analyzed. The first one consists in a JFEM model with a single potential crack to analyze in detail the modalities of the fracture evolution. The second one considers the occurrence of a sequence of fractures, along the excavation, characterized by a certain length and spacing.

1 INTRODUCTION

The current work proposes a simulation method for the excavation-induced fractures observed around a gallery in the Andra Underground Research Laboratory (URL), located in the Meuse-Haute-Marne department, France (URL-MHM). An anisotropic initial stress state characterizes the Callovo-Oxfordian claystone layer at the main level of the URL, at -490 m (Wiliveau et al. 2013, Armand et al. 2014).

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