Advances in permeability for bentonite-based hydraulic containment barriers

Permeability is one of the most important engineering properties of the barriers. The permeability of the barriers is overviewed based on literature studies. The performances of various laboratory test methods are compared, and the effects of properties of barrier materials as well as chemical solution conditions on hydraulic conductivity of the barriers are summarized. The results show that the accuracy of long-term performance evaluation of the barriers depends on proper selection of the test termination criteria. Well graded in-situ soil benefits the permeability resistance of the barriers. The hydraulic conductivity generally increases with the decrease in bentonite content in the barriers, in thickness of decreases electrical double layer of the bentonite, increases in cation valence and cation concentration, and/or decreases in dielectric constant of the chemical solution. The influence mechanism of prehydration of the bentonite and hydrated ionic radius on the permeability of the barriers is not fully clear. Finally, it is suggested that further researches on interaction between bentonite-based barrier and typical contaminant or multiple contaminant should be conducted, and applications of low-quality bentonite and/or its amended product should be promoted in China.