Abstract: Dispersive clay is a type of water sensitive soils, which has the characteristics of dispersing and material losing when encountering water. The influence factors and modification mechanism of dispersive clay modified by calcium lignosulfonate were studied using dispersity tests, mechanical property tests, chemical property tests, microstructure tests and simulated rainfall scouring tests. The results indicated that with the increase of calcium lignosulfonate content, the dispersity, disintegration and erosion resistance of the modified soil were gradually improved, and it had a good modification effect when the content reached 3.0%; the unconfined compressive strength first increased and then decreased, and the compression coefficient first decreased and then increased, and both achieved extreme values at 0.5% content. With the increase of curing age, the dispersity and disintegration of the modified soil decreased gradually, the compression coefficient decreased significantly, and the compressive strength increased gradually. At the age of 28 days, the unconfined compressive strengths of the modified soil at 0.5% and 3.0% contents were increased by 50% and 20% respectively, compared with that of dispersive clay. The engineering properties of dispersive clay were improved by the addition of calcium lignosulfonate mainly through reduction of thickness for electric double layer, cation bridging, particle cementation and hydrophobic effect of hydrophobic group. However, when the content of calcium lignosulfonate was too large, the calcium lignosulfonate would preferentially combine with itself and weaken the attraction between soil particles, which would increase the porosity and decrease the mechanical properties of soil. The research concludes that calcium lignosulfonate has a good modifying effect on the dispersive clay, which can significantly improve the water sensitivity, water stability and erosion resistance of clay.

Key words: dispersive clay, lignosulfonate, mechanical properties, modification mechanism, simulated rainfall scouring