Effects of electrokinetic stabilization combined with addition of calcium ions on soil shear strength characteristics in the hilly granitic region of southern China

Enhancing soil shear strength is of great importance in preventing soil collapse and erosion in the hilly granitic region of southern China. However, limited studies have been conducted on improving soil shear strength in collapsing gullies. Electrokinetic stabilization (EKS) involves applying an electrical current through a soil mass to promote the migration of chemicals from injection points, thereby altering the chemical composition of the treated soil to improve its physical properties. In this study, we investigated the effects of adding calcium chloride (CaCl 2 ) and using EKS techniques on the soil shear characteristics (shear strength and its two components: cohesion and internal friction angle) of three different soil layers in collapsing gullies. The results showed that the EKS techniques significantly increased the migration of calcium ions from the anode to the cathode region of the power supply device used in the soils. Using the EKS process alone did not increase or even decrease the soil shear strength, but combining EKS with CaCl 2 injection (Ca-EKS) increased the soil shear strength, and this increase was mainly due to the increase in soil cohesion. The soil cohesion after Ca-EKS treatment increased on average by 49.84%, 83.11% and 100.36% compared with the soil without treatments (CK) for the red soil, sandy soil and detritus, respectively. However, soil amended only by CaCl 2 addition, Water-EKS or Ca-EKS does not show an increase in soil internal friction angles compared with the CK. These results demonstrate that Ca-EKS can be applied to improve the soil shear strength and stability of gully walls in hilly granitic regions.