The significant deformations of collapsible loess have caused numerous geotechnical failures, severely compromising the safety and serviceability of infrastructure. In this paper, watermelon seed-urease induced calcium carbonate precipitation (WSICP) was used to treat collapsible loess. The study was conducted using different concentrations of Urea-CaCl2 mixture solution (0.2, 0.4, 0.6, 0.8 and 1 mol/L) on five soil samples with different moisture contents (14, 16, 18, 20 and 22%). The compression of the treated soil samples with 14, 16, 18, 20 and 22 % moisture content decreased by 8.3, 11.2, 20.2, 11.9 and 27.9 %, respectively. The void of the treated soil samples was the smallest after compression stability. This is attributed to the fact that the generated calcium carbonate optimizes the pore structure and limits the movement of particles. The optimum treatment concentration was 0.6 mol/L. At this concentration, the compressive deformation resistance of soil samples with different moisture contents was strong, and the collapsibility grade gradually changed from ‘strong’ to ‘moderate’ and ‘non-collapsible’. The Scanning Electron Microscope Test (SEM) of the treated soil samples showed that the generated calcium carbonate existed in two crystal forms of calcite and vaterite. They realised the solidification of soil by bridging, adhesion and coating.
Yating et al. (Tue,) studied this question.