Abstract: Cohesive non-swelling soil (CNS) covering technology is a widely applied engineering method in expansive soil areas.To investigate the effects of solute transport in the CNS layer on the electrochemical properties and macro-deforma tion of expansive soil during rainfall infiltration,four laboratory model tests were conducted.The tests involved monitoring the swelling deformation of expansive soil,cation concentrations in pore solution,and self-potential of soil layers under the saturated process.The analysis focused on the relationships between water infiltration,solute transport,and swelling deformation and po tential difference of the expansive soil layer.Results showed that:① Cations such as Ca2+ and Mg2+ from the CNS layer migra ted downward and accumulated in the underlying expansive soil layer.The resulting ion exchange and the altered ionic environ ment in the pores improved the electrochemical properties of expansive soil,which is macroscopically manifested as an inhibi tion effect on its swelling deformation.② A thicker CNS layer leaded to a higher concentration of cations migrating and accu mulating in expansive soil,resulting in a more pronounced inhibition effect.③ Clear correlations were observed between varia tions in the soil seepage field,solute distribution,and potential difference of the expansive soil layer and CNS layer.Monitoring the self-potential difference allows for tracking ion migration during water infiltration,as well as assessing the degree of im provement in electrochemical properties and the inhibition of deformation development of expansive soil.These findings indicate that the self-potential method has potential application in safety monitoring in engineering projects located in expansive soil re gions.

Key words: expansive soil,cohesive non-swelling soil (CNS),self-potential,solute transport,laboratory model test