Silty sites are affected by natural and human factors, have a low soil strength and strong water sensitivity, and are prone to cracks, soil peeling, and other failures that urgently need to be repaired. Calcium lignosulfonate (CLS) from paper plant waste fluids is a natural bio-based polymer. In this paper, against the background of the reinforcement and protection project of the Qingtai Site in Xingyang, Henan Province, silty soil was modified by adding CLS, and the material ratio with the best restoration effect was determined by carrying out a series of mechanical and waterproof tests. The mechanism of action of the modified materials was analyzed through microscopic tests such as SEM and XRD. The test results showed that a 1.0% mass fraction of CLS in the silty soil was the optimal ratio of the modified material. The mechanical properties of the modified soil first increase and then decrease with the increase of CLS content, and the waterproof properties increase with the increase of CLS content. The lignosulfonate polymer generated by the displacement reaction between CLS and the soil particles was cemented with the soil particles, meaning that the mechanical and waterproof properties of the modified soil were improved. And the content of the main elements and the mineral composition in the modified soil did not change. The research results provide a reference for the restoration and protection of silty sites.

The special particle grading properties of silt lead to the strong water sensitivity and low soil strength of silt sites, many of which are severely damaged and urgently need to be repaired. This article takes the powder soil from a certain burial site area in Xizhu Village, Luoyang as the research object, which is improved by adding nanosilica and potassium methylsilicate. The modified soil is studied through mechanical and waterproof performance tests, and the mechanism of action of the modified material is analyzed through SEM and XRD. The experimental results show that the mechanical properties and waterproof properties of the composite modified soil were improved when the nanosilica content was 2% and the potassium methylsilicate content was 0.5%; the durability of the composite modified soil is improved, making this the optimum ratio. The mechanical properties and water resistance of the silty soil were significantly improved by adding the appropriate amount of nanosilica and potassium methylsilicate. Nanosilica can be evenly dispersed in the soil matrix, absorb a small amount of water to form a gel state, fill the pores in the silt aggregates, and improve soil compactness. In addition, nanosilica aggregates can attach to the surface of the soil particles and extend from the particle surface to the particle edge. By increasing the contact between soil particles and increasing the particle size, the mechanical properties of the modified soil are improved. When potassium methylsilicate solution is added to the soil, it reacts with water and carbon dioxide, decomposes into methylsilicate, and quickly generates a polymethylsiloxane film to cover the surface of soil particles, forming a waterproof film on the surface and thereby improving the waterproof performance of modified soil. Our research results can provide a reference for the restoration and protection of silty and silt-like sites. The next step is to apply the composite modified soil in engineering restoration through field tests in order to study the repairing ability of composite modified soil and its actual protective effects.