Mechanical Properties and Erosion Resistance of Loess Stabilized by Soybean Urease-Induced Calcium Carbonate Precipitation and Nano-SiO2

Loess is prone to structural softening and damage under rainfall conditions. To improve the scouring and erosion resistance of loess slopes, this study employed a combined soybean urease-induced calcium carbonate precipitation (SICP) and nano-SiO2 treatment for improving the erosion resistance of loess. The optimal urease concentration was determined through urease activity tests and triaxial shear tests, and the erosion resistance of specimens subjected to different treatments was further evaluated using laboratory simulated rainfall scouring tests. The experimental results indicated that, for loess treated by the combined SICP-nano-SiO2 method, the shear strength and resistance to shear failure increased markedly with increasing cementation solution concentration and nano-SiO2 content, and the improvement effect was superior to that of single treatment methods. When the combined treatment consisted of 1 mol/L SICP and 2% nano-SiO2, the enhancement in shear resistance was most pronounced, with the deviator stress at failure reaching 372 kPa. Under laboratory simulated rainfall conditions, the specimens treated with the combined SICP-nano-SiO2 method exhibited the lowest soil loss among the tested treatments. Compared with untreated loess, the reductions in soil loss at rainfall intensities of 60, 90, and 120 mm/h were 86.0%, 83.6%, and 96.3%, respectively. SEM observations further showed that the combined treatment was associated with a refined pore structure and improved distribution of cementation products. These results demonstrate improved laboratory-scale surface erosion resistance under the tested conditions. However, because the rainfall tests were conducted using 240 mm × 170 mm × 40 mm trays, the results should not be directly extrapolated to full-scale loess slopes, and further field-scale validation is required.