Numerical Benchmarking of GREAT Cell Experiments: Poly-Axial Stress Effects on Fluid Flow in Fractured Rock Using Smeared and Discrete Methods

The present work deals with the fracture mechanics of crystalline rocks and in particular with the barrier integrity for the isolation of hazardous waste. The experimental data base is derived from the GREAT cell, a rock mechanics facility at the University of Edinburgh. The GREAT cell is a unique experimental facility that allows the investigation of thermo-hydro-mechanical (THM) processes in fractured rocks in rotating stress fields. The main idea of this work is to define a systematic benchmark suite for the development and testing of hydro-mechanical (HM) fracture mechanics codes based on GREAT cell experiments. The benchmarks represent simplifications of the original experiments to facilitate code testing. Two numerical fracture mechanics methods were used to simulate the complete benchmark suite, namely the variational phase field (VPF) and the lower-order interface element (LIE) methods. The numerical methods as well as Jupyter notebooks for pre- and post-processing are available in the open-source platform OpenGeoSys, following the FAIR principles of open science. This work is part of the DECOVALEX 2027 project, an international project to validate models and codes against experimental data.