Numerical simulation of damage evolution around the PF/PF-A experiment borehole in faulted Opalinus Clay

Le résumé fourni par la source

The Progressive Failure (PF/PF-A) experiment at the Mont Terri rock laboratory offers a unique opportunity to investigate damage evolution around underground openings in faulted Opalinus Clay under in-situ stress conditions. We present a 3D numerical modelling framework developed to simulate progressive failure in structurally complex clay shale and its long-term evolution subject to hydro-mechanical effects. The approach integrates a site-constrained discrete fracture network, explicit fault zone representation, and anisotropic material behaviour within a discontinuum formulation to capture structurally controlled damage processes around an experiment borehole. The simulations capture stress redistribution, fracture reactivation, and the emergence of a characteristic inner-outer damage zone structure governed by fault–fracture interactions and structural orientation. Sensitivity analyses demonstrate the importance of fault–borehole geometry in controlling damage localisation and extent. Ongoing model developments incorporate coupled hydro-mechanical processes, including suction-driven desaturation and effective stress evolution, to better represent the experimental conditions. Preliminary coupled simulation results indicate that hydraulic effects significantly influence near-borehole damage initiation and spatial distribution. Our modelling framework provides a physics-based tool for interpreting PF/PF-A experimental observations, with important implications for the safe design and performance assessment of nuclear waste disposal in Opalinus Clay.

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