Biogrouting for seepage control in rock fractures using on-site bioslurry formation method

Biogrout produced via microbially induced carbonate precipitation (MICP) has emerged as a promising solution for seepage control in fractured rock. However, achieving effective underground seepage reduction remains challenging due to the complex interactions among multiple influencing factors. In particular, balancing the rapid formation of calcium carbonate (CaCO 3 ) with the need to avoid clogging during biogrout injection is critical but not yet fully understood. This study investigates the key parameters affecting biogrouting performance, including the urease activity of the bacterial solution (BS), the concentration of the cementation solution (CS), and the flow rate of the grout. A novel on-site bioslurry formation method is proposed to enhance the efficiency of biogrouting within the fracture. To evaluate these factors, four small-scale and one large-scale model tests were conducted using transparent rock fracture models. The spatiotemporal evolution of CaCO 3 precipitates during biogrouting was monitored using three-dimensional (3D) scanning and image analysis. The results show that permeability in the large-scale model decreased by up to three orders of magnitude after 9 h of biogrouting. High urease activity (20 U) and elevated CS concentration (1.0 M) significantly shortened the biogrouting duration, while a higher flow rate (3 mL/min) led to faster and more uniform CaCO 3 distribution. Furthermore, the proposed on-site bioslurry formation method improved the calcium conversion efficiency and facilitated faster CaCO 3 formation. These findings provide important insights into the mechanisms of MICP-based biogrouting and offer practical guidance for its application in rock fracture seepage control.