Modeling of the hydromechanical response of underground structures relative to unloading during their excavation : initial EDZ analysis
Résumé
In 2005, Andra concluded that the feasibility of deep geological repository for high level (HAVL) and intermediate level (MAVL) long-lived waste is valid. Hence, Andra is now responsible for designing and implementing a repository disposal for HAVL and MAVL waste called: CIGEO (Geological Repository Project). A zone of interest for thorough exploration (ZIRA) was proposed in 2009. A simulation program is included in the project CIGEO. Various phenomenological themes have been addressed. One of the studied topics consists in the investigation of 'the mechanical evolution of structures", and especially the analysis of the mechanical (or hydromechanical) response of underground structures due to unloading during excavation. The main goal of this study is to analyze and compare the hydromechanical (HM) response due to unloading during excavation works and to have a relevant image of a coherent initial EDZ from a work to another (shafts, ramps, declines, galleries, HAVL and MAVL cells, intersection of works) on the basis of a same approach/model. This study will provide some answers with respect to the EDZ formation (location, onset of shear and/or extension fractures, diffuse damage of claystone between fractures ...), its features (3D spatial organization of fracturing, shape of initial EDZ, fracture density ...) and the HM response (stress and strain fields, pore pressure fields, particularly near fractures and in claystone between fractures ...).