English：

The main building material of earthen sites is soil and has been exposed to the naturalenvironment for a long time, their damage is common and serious, and urgently needs to be restored.Especially in northwest China, there are many silty sites with poor engineering properties and difficultreinforcement. The modified soil samples were prepared by adding lime and polypropylene fibersseparately and in a mixed manner in loess. Direct shear, compression, wind sand erosion, freeze-thaw,and water stability tests were conducted to verify the feasibility of using polypropylene and lime asrestoration materials for silty sites. The test shows that the shear strength of the soil can be improved byadding lime or polypropylene fiber alone. When 9% lime or 0.25% polypropylene fiber is added, theinternal friction angle and cohesion of the modified soil can be as high as 48.9°and 107.11kPa, and thecompressibility of the soil is also significantly reduced. However, the addition of polypropylene fiberalone will lead to the deterioration of the water stability of the modified soil, which is due to the fact thatthe polypropylene fiber in the soil increases the infiltration channel of water. By using 0.25%polypropylene fiber and 9% lime to make mixed modified soil samples, the cohesion and internal friction angle are not only 66.7% and 28.9% higher than those of single-doped modified soil, but also the waterstability of the samples is significantly enhanced. The ability to resist wind-sand erosion and freeze-thawis also greatly improved, and the overall performance is better. Therefore, the mixed use of lime andpolypropylene fiber can more effectively improve the engineering performance of silt.