Effects of Nanoclay on the Treatment of Core Material in Earth Dams

Abstract

The main objective of this paper is to investigate the effect of nanoclay on the hydraulic conductivity of compacted clayey sands as an earth dam core material. Furthermore, other mechanical characteristics, such as shear strength and dynamic parameters of the treated clayey sand soil, were investigated. The soil samples were prepared by mixing two types of soil including Kaolin clay (KC) and Firouzkooh sand (FS) in proportions of 1∶9 (1-9CS) (sand with 1% clay) and 1∶4 (sand with 25% clay) (1-4CS) by weight, respectively. In the experimental program, initially the compaction parameters (optimum moisture content) of each sample were obtained for preparation. Then, a series of hydraulic conductivity tests were conducted on prepared specimens for different weight percentages of nanoclay (1–4%). The results showed that adding nanoclay up to 3%, as its optimum limit, causes considerable reduction in the hydraulic conductivity to a desirable value for the core material of earth dams. In addition, it was observed that the strength of specimens in drained condition increased, while for undrained condition it decreased. The results also indicated that the treated soil dynamic parameters, such as shear modulus and damping ratio, were decreased and increased, respectively. A complementary series of swelling and self-healing tests were also performed and the results revealed that nanotreatment improved soil performance considering hydraulic conductivity.