By laboratory test

the potential use and effectiveness of soda residue as an additive for improving expansive soil are evaluated. The tests research the features of the basic physico-mechanical properties and expansibility of soda residues treated soil. The result shows that the increase of blending residue ratio has made the viscous composition decreased while the percentage of coarse granule increases so that the plasticity index

liquid limit

relative density

free swell index

load swell index are reduced significantly with the increase of soda residue. The test indicates that the soda residue has significant impact on the improvement of the expansibility of expansive soil. The range of compaction water content for soda residues treated soil is larger than expansive soil’s. It brings great convenience for the construction of soda residues treated soil roadbed. After 7 days conservation

there is a remarkable increase in unconfined compression strength and shear strength. Furthermore

a peak appears when the blending ratio of residue has come up to 30%. The remarkable increase in cohesion reflects the shear strength enhancement. However

the angle of internal friction changes little.