Gas transport and self-sealing in plastic materials within a multi-scale perspective

Abstract

This paper investigates, within a multi-scale perspective, the gas transport and self-sealing processes in plastic and low-permeability materials, which is crucial for managing deep geological disposal of radioactive waste. Laboratory gas injection tests revealed that, even at pressures lower than the minor principal stress, gas flowed through the material, inducing stress-dependant pathways that enhanced the gas permeability. However, self-sealing mechanisms, particularly clay mineral swelling during re-saturation, effectively restored the barrier function. Results suggest that despite gas invasion, water permeability post-re-saturation resembles initial levels. Microstructural techniques confirm the closure of fissures post-re-saturation, though some large pores remain. Multi-scale modelling integrating microstructural data with macroscopic properties provides insights into gas transport and self-sealing phenomena.

This project has received funding from the ‘European Joint Programme on Radioactive Waste Management (EURAD)’ (2019-2024) WP-Gas ‘Mechanistic understanding of gas transport in clay materials’ under grant agreement No. 847593, from ONDRAF/NIRAS under contract No. CCHO 2021-0377/00/00 (2021-2024) and from INTERMO2 project (PID2022-141429OB-I00) funded by the Spanish Ministry of Science/Research Agency MCIN/AEI/10.13039/501100011033/FEDER EU (2023-2027).

Postprint (published version)