Cleaning efficiency improvement of oil contaminated soil by plasma blasting

Plasma blasting which is generated by high voltage arc discharge of electricity is applied to soil mass to improve permeability of soil and cleaning efficiency of oil contamination. A new high voltage generator was manufactured which consisted of capacitor, power supply and switch, and three types of soil including silty sand, silty sand mixed with lime and silty sand mixed with cement were prepared. Soil columns were produced using these types of soil and plasma blasting was performed within soil columns to investigate the variation of soil volume penetrated by fluid and permeability. White paint mixed with water were injected under the pressure of 50 kPa during plasma blasting. Fluid penetration volumes by plasma blasting increased by 11-71%, compared with those only by pressure. Although plasma blasting with low electricity voltage induced horizontal fracture and fluid penetrated along this weak plane, plasma blasting with high voltage induced spherical penetration of fluid. Plasma blasting increased the permeability of soil. Permeability of soils mixed with lime and cement increased by 450-1,052% with plasma blasting. Permeability of soil increased as discharge voltage increased when plasma blasting was applied once. However, several blasting with the same discharge voltage increase or decrease permeability of soil. Oil contaminated soil was prepared by adding diesel into soil artificially and plasma blasting was performed to inject cleaning agent in these oil contaminated soil. TPH in soil decreased 50~85% compared with soil without plasma blasting. All these results indicated that plasma blasting might be used for in-situ cleaning of oil contaminated soil because plasma blasting increased permeability of soil and cleaning efficiency