Permecability
Coupling stress and transmissivity to define equivalent 1 directional hydraulic conductivity of fractured rocks
Context
The Permecability project addresses the challenge of understanding the hydraulic behavior of fractured rock masses, which is an essential component of groundwater resource management, the development of underground infrastructures and the design of deep geological repositories for nuclear waste. The project employs a Discrete Fracture Network (DFN) model to investigate the complex relationship between stress and fracture transmissivity in rocks, with a particular focus on the impact of in-situ stress fluctuations on groundwater flow. The Forsmark site in Sweden, which is characterized by its fractured crystalline rock, serves as the primary reference for testing this model due to its relevance to nuclear waste disposal projects.
Project Results
A robust methodology based on DFN was developed to couple in-situ stresses with fracture transmissivity, thereby enabling precise evaluation of hydraulic conductivity in fractured rock environments. The model demonstrated that stress-induced modifications to fracture apertures have a substantial influence on fluid flow characteristics when applied to the geological conditions observed at the Forsmark site. The results demonstrated a clear correlation between stress orientation, fracture connectivity, and flow directionality, with hydraulic anisotropy up to a factor of three. The model also demonstrated that transmissivity can vary by several orders of magnitude depending on fracture orientation and the degree of stress. Sensitivity analyses highlighted how variations in stress-transmissivity relationships affect the directional flow. This advanced understanding is essential for the design of secure geological repositories for nuclear waste and can be applied to other projects involving groundwater management and subsurface engineering in fractured rock environments.
Find out more
C. Darcel, R. Le Goc, E. Lavoine, P. Davy, D. Mas Ivars, E. Sykes, H.A. Kasani, Coupling stress and transmissivity to define equivalent directional hydraulic conductivity of fractured rocks, Engineering Geology, 2024, 107739, ISSN 0013-7952, https://doi.org/10.1016/j.enggeo.2024.107739.
Contact
r.legoc@itasca.fr
Collaborators
Svensk Kärnbränslehantering ab (SKB)
The Nuclear Waste Management Organization (NWMO)