Revisiting the self-sealing behavior of compacted bentonite in an annular technological void

The self-sealing capacity of compacted bentonite governs the effectiveness of engineering barriers constructed in deep geological repositories (DGRs) for high-level radioactive wastes. This research aims to elucidate bentonite’s self-sealing behavior when exposed to an annular technological void using visualization tests. Water infiltration initiated self-sealing behavior, induced cracking phenomena, and caused color changes on the bentonite surface. These cracks interfered with the self-sealing behaviors and resulted in a suboptimal sealing state. The color difference index was used to track the transition from a cracking state to microstructural reconstruction, revealing water migration pathways and hydration levels. The results confirm the temporal and spatial dependencies of color changes and pore structure evolution during self-sealing. Initially, bentonite exhibited a free swelling pattern, which gradually transitioned to a constant volume pattern as the sealing progressed. The gradual closure of the cracks is attributed to the compression from the swelled parts and the clogging effect of newly formed sealing materials within the water-filled cracks. This study provides a comprehensive understanding of the self-sealing behavior of compacted bentonite, which is essential for optimizing multi-barrier system designs and mitigating geological environmental risks in DGRs.