Investigation of MICP on Seepage Reduction in Fractures and Seepage Response Considering Size Dependency

Microbially Induced Calcite Precipitation (MICP) is a green and efficient technology for rock fracture sealing, demonstrating significant potential in engineering anti-seepage applications. However, while existing research has predominantly focused on grouting parameters, the influence of the size dependency on the MICP sealing mechanism within fractures remains inadequately understood. This study systematically conducted physical model tests on fractures across four scales (ranging from 25 cm×25 cm to 40 cm×40 cm), integrating 3D laser scanning and numerical simulation to quantitatively analyze the impact of fracture size on permeability, calcium carbonate distribution, and spatial morphological evolution. The results indicate that the 25 cm fracture exhibited the most effective seepage reduction and the highest filling rate. As the fracture size increased, the calcium carbonate content and coverage per unit area decreased, resulting in a sparser distribution of precipitation despite an increase in total precipitate volume. Notably, the 35 cm fracture showed a sharp decline in flow velocity, pressure, and filling efficiency within specific regions (S4–S5), revealing a critical size dependency. Numerical simulations further elucidated the coupling mechanism between flow field distribution and precipitation behavior. This study provides a theoretical foundation and empirical support for the scale-specific optimization of MICP technology in practical engineering scenarios.