The requisite functions of a bentonite buffer in a deep geological repository depend on the sealing/healing of bentonite interfaces, with particular emphasis on the self-healing (automatic healing upon wetting) of assembled bentonite-bentonite interfaces. This study determined the shear resistance (including the peak shear strength and secant modulus) of densely compacted Gaomiaozi (GMZ) bentonite and its assembled interface after confined water saturation. The effect of bentonite dry density and saturation time on the shear resistance of saturated healed interfaces was elucidated, and the interfacial self-healing capacity was assessed. The results indicate that the shear resistance of the saturated healed interfaces increased with the bentonite dry density but had a non-monotonic correlation with the saturation time. For a given dry density of the bentonite, the saturated healed interface exhibits a lower peak shear strength than the saturated intact bentonite but a higher peak shear strength than the saturated separated interface. The saturated healed and separated interfaces have comparable shear moduli (secant moduli), which are lower than that of the saturated intact bentonite. The saturated healed interfaces display smooth shear failure planes, while the saturated assembled interfaces and intact bentonite exhibit comparable frictional angles. This indicates that interfacial self-healing plays a pivotal role in enhancing interfacial peak shear strength by facilitating microstructural bonding at the assembled interface. Finally, it can be stated that densely compacted GMZ bentonite has a robust interfacial self-healing capacity in terms of shear resistance. These findings contribute to the design of the bentonite buffer and facilitate the evaluation of its safe operation at specified disposal ages.

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Keywords: Compacted bentonite, Interface, Self-healing, Peak shear strength, Shear modulus