Abstract: Industrial wastewater contains various ions, which can affect the physical and mechanical properties of soils, but there is a lack of research on the relationship between the reticulated red clay and metal ions. To study the changing characteristics of the shear strength of the reticulated red clay under actions of metal ions, the saturated standard remodeled soil samples were prepared by adding metal ion solutions with different types and concentrations of ions, and then the changing curve of the shear strength by the consolidated undrained (CU) triaxial test was obtained. The microscopic tests such as XRD and XRF on soil samples after mechanical tests were performed to obtain changes in chemical elements and mineral composition. The test results showed that the change of cohesion of the reticulated red clay is related to the ion content in the undisturbed soil sample and the concentration of ions in solution of the immersed soil sample. The cohesion decreases with the increase of ion concentration, and the variation of internal friction angle is related to the valence state of metal ions. The curves of the cohesion and internal friction angle of the soil sample after the addition of Cu²⁺ have an inflection point when the ion concentration is 0.10 mol/L. The analysis of the triaxial test data shows that the inflection point is related to the change of the peak value of pore water pressure. Heavy metal ions enter the soil pores, change ion concentration of pore water and affect the changes in pore water pressure.

Key words: Reticulated Red Clay, Ion Concentration, Shear Strength, Microscopic Test