Abstract: There is currently a limited amount of research on mathematical models for seepage in enzyme-induced calcium carbonate precipitation (EICP) solidified sand. Existing seepage models neglect the influence of calcium carbonate crystals formed during the EICP mineralization process, thereby rendering them insufficient in predicting the permeability behavior of EICP-solidified sand. To address this issue, this study establishes a mathematical model for seepage in EICP-solidified sand based on the Kozeny-Carman (K-C) equation, incorporating the effects of calcium carbonate crystals on pore filling, tortuosity, and specific surface area. By comparing the theoretical results of the model with experimental data, the feasibility and rationality of the model are validated. Furthermore, the impact of porosity, mean particle size, calcium carbonate content, and specific surface area on the permeability coefficient of the samples is analyzed. The research findings indicate that: 1) The proposed mathematical seepage model can effectively represent the permeability coefficient of EICP-solidified sand under various particle size distributions and cementation degrees, demonstrating broad applicability. 2) The permeability coefficient (k) increases with the rise in porosity (n) and mean particle size (D₅₀), with k being more sensitive to changes in porosity than mean particle size. 3) The permeability coefficient decreases significantly with increasing calcium carbonate content and specific surface area. As calcium carbonate content increases, the sample porosity gradually decreases, tortuosity increases, and the water film adhering to the calcium carbonate crystals thickens, leading to a substantial drop in permeability coefficient. The results of this study provide a theoretical foundation for the engineering application of EICP-solidified sand.

Key words: enzyme-induced calcium carbonate precipitation (EICP), Kozeny-Carman equation, calcium carbonate crystals, seepage modeling, sand solidification