Experimental Study on Enzyme-Induced Calcium Carbonate Precpitation Solidification of Desert Sand

Although certain achievements have been made in desertification control in China, the fragile ecological attributes of sandy lands have not been fundamentally altered. This study systematically investigates the bio-reinforcement mechanism and engineering applicability of desert sand based on Enzyme-Induced Calcium Carbonate Precipitation (EICP) technology using soybean urease. Through regulating soybean powder solution concentration, standing time, temperature, and pH, we revealed the regulation mechanism of urease activity. Single-factor experiments with varying enzyme-to-gelatin ratios, cementing solution concentrations, and spraying volumes of reaction solution were conducted to examine their effects on surface strength, calcium carbonate content, and cured layer thickness of desert sand. Finally, water retention tests were performed to evaluate the application performance of EICP-treated aeolian sand. Results demonstrate that soybean powder concentration, temperature, and pH significantly influence urease activity, with maximum activity achieved at 100 g/L soybean powder concentration, 45°C, pH=7, and 12 hour standing time. The effects of enzyme-to-gelatin ratio and cementing solution concentration on reinforcement indicators (surface strength, CaCO₃ content, cured layer thickness) followed an initial increase followed by decrease pattern, peaking at enzyme-to-gelatin ratio 1∶1, cementing solution concentration 1.25 mol/L, and reaction solution spraying volume 5 L/m². Water retention tests revealed that cementing solution concentration and spraying volume are critical factors in controlling CaCO₃ crystal formation to fill sand particle pores, achieving maximum water retention enhancement of 42% and significantly inhibiting water evaporation.