Development of self-healing model of rock fracture for PFC simulation

ABSTRACT Rock mass fractures often lead to structural instability, posing significant safety risks in underground engineering such as mines and tunnels, including water seepage, air leakage, and damage to concrete structures. This study aims to enhance grouting-based repair techniques by investigating the mechanisms of microbially induced calcium carbonate precipitation (MICP) and simulating fracture filling processes. Laboratory experiments were conducted to identify optimal culture conditions for maximizing calcium carbonate production. Additionally, Particle Flow Code (PFC) 5.0 was employed to simulate the filling of fractures with microbial calcium carbonate. The results indicate that urea, urease-producing bacteria, and ammonium ions exhibit continuous concentration distributions within fractures, regulated by chemical reaction kinetics. Bacillus pasteurii demonstrated the highest calcium carbonate yield under conditions of pH 9, urea concentration of 1–1.5 mol/L, and calcium ion concentration of 1 mol/L. Microbial calcium carbonate filling significantly improved the load-bearing capacity of fractured rock masses. However, the simulation has certain limitations, including the inability to model dynamic changes in reaction rates and product distribution, and the assumption of maximum calcium carbonate filling for analysis. Despite these constraints, the integrated experimental and numerical approach reliably captures the fracture-healing behavior driven by MICP. These findings provide critical theoretical support for optimizing microbial culture conditions, regulating reactant concentrations, and controlling pH to improve the efficiency of fractured rock repair and ensure the long-term safety of underground engineering structures. IMPORTANCE Cracks in rocks and concrete structures pose significant threats to the safety and longevity of underground engineering projects, such as mines and tunnels, leading to water leakage and instability. Traditional repair methods are often costly, disruptive, and environmentally taxing. This study harnesses the power of bacteria to create a self-healing material, effectively using microbes to produce a natural bio-cement that seals these dangerous fractures. By identifying the optimal conditions for the bacteria to work and developing a computer model to predict the healing process, our research provides a ground-breaking, eco-friendly strategy for autonomous infrastructure repair. This bio-based approach not only enhances engineering safety but also paves the way for sustainable construction practices, turning a biological process into a powerful engineering solution.