InterPore2026

Stress-Controlled Gas Transport in Boom Clay: From Oedometer to Isotropic Conditions

21 May 2026, 12:05

15m

Oral Presentation (MS12) Coupled Flow-Deformation Processes in Porous Media MS12

Speaker

Salar Lakimahalleh (Universitat Politècnica de Catalunya (UPC))

Description

Understanding gas transport mechanisms in low-permeability geomaterials is essential for a wide range of geo-energy and subsurface engineering applications, including underground gas storage, CO₂ sequestration, hydrogen storage, and the disposal of nuclear waste in deep geological repositories [1]. In clay-rich porous media such as bentonite barriers and argillaceous host rocks, gas migration may strongly influence both transport properties and mechanical response, affecting sealing efficiency, deformation and damage evolution. These coupled flow–deformation processes remain poorly understood and are highly sensitive to the applied stress state, highlighting the need for experimental approaches that can reproduce realistic mechanical boundary conditions.
In this study, gas transport is investigated in Boom Clay, a low-permeability argillaceous rock that is being extensively studied in Belgium as a potential host formation for deep geological disposal of radioactive waste [2]. Gas migration in this material has been previously examined under oedometer stress conditions, showing the development and propagation of preferential flow pathways [3-4]. However, the strong lateral confinement imposed by oedometer testing restricts lateral deformation, which plays a key role in the opening and evolution of these pathways, and therefore does not fully represent in-situ stress conditions. As a result, testing under isotropic stress conditions is required to more realistically capture the coupled volumetric and transport response of Boom Clay during gas migration.
To address this limitation and enable direct comparison with oedometer tests under more realistic mechanical boundary conditions, a high-pressure isotropic cell was developed and implemented at the Geotechnical Engineering Laboratory of UPC. The cell consists of a rigid pressure chamber capable of applying total confining stresses up to 10 MPa. The experimental setup is equipped with four radial LVDTs and one vertical LVDT, providing continuous monitoring of volumetric and directional deformation throughout the different testing stages. Gas is injected through an inflow line at the base of the specimen, while an outflow line is connected at the top. To minimise gas leakage and ensure reliable boundary conditions, a neoprene membrane with a lower gas diffusion coefficient than conventional latex membranes is used to enclose the sample.
The testing programme includes pre-conditioning, saturation, isotropic loading, gas injection and dissipation, unloading, and post-test microstructural analyses. Microstructural characterisation is performed using X-ray computed micro-tomography and mercury intrusion porosimetry. Tests are conducted on specimens with two bedding orientations (normal and parallel to the gas flow) to assess the influence of bedding anisotropy on gas migration.
Initial results already indicate systematic differences in volumetric response, gas breakthrough behaviour and pathway development between oedometer and isotropic stress conditions, reflecting the strong control exerted by the stress state on coupled flow–deformation processes. The ongoing comparison between the two testing approaches is expected to provide new insights into the mechanisms governing gas transport in Boom Clay under repository-relevant stress paths and, more generally, in low-permeability geomaterials.