Abstract: Bio-cementation technology based on crude soybean urease is a new environmentally friendly foundation treatment technology emerging in the field of geotechnical engineering. The uniformity of bio-cementation is a pressing issue that needs to be addressed to advance the application of this technology in practical engineering, and soil particle size stands as a significant influencing factor. In this study, 13 types of sand with varying particle sizes were selected, along with self-extracted crude soybean urease solution, to conduct urease percolation tests, sand column curing tests, and scanning electron microscope (SEM) examinations. These experiments aimed to analyze the influence of soil particle size on the effectiveness of bio-cementation using crude soybean urease and explore its underlying mechanisms. The findings reveal that soil particle size significantly affects the migration and adsorption of urease in the crude soybean urease solution. Smaller soil particle sizes facilitate the adsorption of urease. However, excessively small particle sizes (e.g., less than 0.425 mm) lead to the concentration of most adsorbed urease in the middle and upper regions of the soil column. Conversely, excessively large particle sizes (e.g., greater than 4.750 mm) hinder urease adsorption in these regions. Both scenarios tend to result in uneven bio-cementation. Besides the amount of urease adsorption, the influence of soil particle size effect on the biocementation efficacy based on soybean urease is also associated with factors such as pore size within the soil and the number of particle contacts per unit volume of soil. Larger soil particles result in larger interstitial pore sizes and fewer particle contacts, thus hindering the formation of effective calcium carbonate crystals.

Key words: biotechnology, grain size effect, crude soybean urease solution, biocementation effect, influencing mechanism