Performances of microbe-based self-healing microcapsules on sealing fractures and reducing permeability of rocks

This study presents a novel self-healing system that uses epoxy resin microcapsules to encapsulate Sporosarcina pasteurii spores for autonomously sealing fractures in rock masses. The microcapsules, known for their strong mechanical properties and high encapsulation efficiency, are designed to rupture when cracking occurs, thereby initiating microbial-induced calcium carbonate precipitation (MICP). An extensive experimental program, including Brazilian splitting tests, industrial computed tomography (CT) scanning, and triaxial permeability tests, was conducted to assess the system's effectiveness. Results showed that crack width was the main factor influencing healing efficiency, with up to 89.3% healing observed in 0.3–0.4 mm cracks after 28 d. An optimal mix, consisting of 2% content and 150 μm particle size, decreased the permeability coefficient by over 70% on average, roughly one order of magnitude. The relationship between permeability and confining pressure followed a power law, and notably, the sensitivity of permeability to stress changes decreased significantly in well-healed specimens. Numerical simulations supported these results, revealing that MICP healing greatly improved the hydraulic barrier function of rock masses by lowering seepage velocity and raising the pressure gradient needed for fluid flow. Overall, this work quantitatively clarifies the relationship between healing extent, permeability reduction, and in situ stress, providing a scientific foundation for designing engineered microbial barriers for geotechnical applications such as groundwater isolation and seepage control.