Conducting research on gas migration processes in buffer materials under multi-physics coupling conditions holds both theoretical and practical significance for ensuring the safety of deep geological repositories. Studies reveal that gas migration in buffer materials sequentially undergoes ultra-low permeability and gas breakthrough stages

characterized by gas dissolution-diffusion and significant gas seepage

respectively. The breakthrough mechanisms are categorized into capillary

mechanical

and interfacial breakthrough. To achieve continuous measurement of gas flux throughout the process and identification of breakthrough patterns

experimental setups have evolved through constant-volume

K0 confined

isotropic stress-controlled

and triaxial stress-controlled configurations. The newly developed triaxial testing system enables ultra-low flow rate measurement at 1/10 000 mL/min while incorporating eddy current sensing technology for real-time monitoring of localized volumetric changes in specimens

thereby facilitating breakthrough mode identification. Given the absence of characterization indices in empirical models and quasi-continuum theory-based theoretical models

researchers have established a conceptual model to identify gas breakthrough patterns based on the principle of preferential touching of breakthrough pressure curves. Future research should prioritize gas breakthrough testing methods with short testing cycle and high measurement accuracy

development of generalized breakthrough pattern identification models

and parameter scaling across different scales.