Experimental Research on Sandy Soil Solidification Based on Soybean-Urease Induced Calcium Carbonate Precipitation

Soybean-urease induced calcium carbonate precipitation (SICP) is an effective and environmentally friendly method for soil solidification. However, multiple treatments are required to achieve the desired strength, resulting in low treatment efficiency and long time consuption. The sand column samples were treated once by adding additives such as non-fat powdered milk and magnesium chloride based on the SICP treatment technique. The unconfined compressive strength (UCS) in the saturated state, calcium carbonate content and conversion rate of the samples were tested. The results showed that: Adding non-fat powdered milk had the best effect. Under saturated state, the maximum strength after one treatment could reach about 0.6 MPa, which was about 70% higher than the SICP treatment without additives (0.35 MPa). Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis showed that: More spherical calcite crystals could be formed after adding non-fat powdered milk. Organic matter such as non-fat powdered milk would remain on the surface of the crystal particles, further improving the bonding and bridging between sand particles.