Abstract: Microbially induced calcite precipitation (MICP) has been widely applied for soil reinforcement, but its applications in rock mass permeability reduction have been rarely reported. To explore the plugging mechanism of rock joints using MICP, artificial rock joint specimens made of transparent resin were prepared, and laboratory MICP plugging experiments under six various conditions considering MICP reaction influence factors were performed. Through the plugging experiments, evolution laws of rock joint transmissivity and hydraulic aperture, accompanied with corresponding CaCO₃ distribution images, during plugging processes were obtained. The experimental results showed that the hydraulic aperture of rock joint approximately decreases linearly with grouting cycles during MICP plugging process, and the decreasing rate is closely related to the CaCO₃ distribution that is significantly affected by grouting rate, injection time of fixation, bacterial, and reaction solutions, and standing time. Among the six experimental conditions, both the plugging efficiency and effect are optimal under the fourth experimental condition, where the grouting rate is high and the grouting and standing time is the longest. After only two grouting cycles under the fourth experimental condition, the rock joint transmissivity decreases from 40.51×10^–6 m²/s to 0.52×10^–6 m²/s with a decrease rate of 98.72%, and the hydraulic aperture decreases from 0.367 mm to 0.086 mm with a decrease rate of 76.6%. Furthermore, the CaCO₃ distribution on the upper and lower surfaces of rock joint specimens were observed, and CaCO₃ in rock joints produced by MICP reaction was found to bring cementation strength in a short time, which helps improve mechanical properties of rock joints while reducing rock joint permeability.

Key words: rock mechanics, rock joint, microbially induced calcite precipitation, transmissivity, hydraulic aperture