The characterization of the in-situ stress field is a key element of any large-scale underground engineering project (Hoek 2007). For projects requiring excavations, such as radioactive waste storage, underground infrastructure related to raw material extraction, energy projects (e.g., hydropower), or transport, the stress field governs the response of the rock mass to excavation and is an important factor in the design of support measures ensuring constructability and stability of the infrastructure. For projects involving wells and fluid injection or production, such as geothermal energy or CO₂ storage, the in-situ stress field governs not only well integrity but, more critically, the range of permissible operating pressures. By controlling the stability of the rock mass under pressure changes induced by injection or production, it ultimately constrains the achievable injection and production rates. Pressure perturbations can also be induced in radioactive waste storage projects by gas generation due to corrosion or thermally induced pore pressure. Underground laboratories, such as the Mont Terri laboratory, have made a major contribution to the development of in-situ stress measurement techniques, as well as to the current standards and guidelines governing these measurements (e.g., Zang & Stephansson 2010). They also provide the scientific community with unique datasets, both in terms of the variety of techniques deployed and the volume (spatial coverage) of measurements performed. The use of multiple techniques enables cross-validation, while the number of measurements and their spatial distribution highlight the complexity of the in-situ stress field. This complexity necessitates integrating stress measurements into a conceptual framework that accounts for both the primary and secondary controls on the in-situ stress field. In this paper, we briefly present stress measurement techniques in light of experiments conducted at Mont Terri. We also outline the key elements involved in conceptualizing the in-situ stress field, as well as the challenges associated with integrating these concepts. Finally, we discuss the implications for the development of geoenergy projects and the future prospects for advancing the understanding of in-situ stresses at Mont Terri.
Benoît Valley (Thu,) studied this question.