The Study on Hydraulic Conductivity of Silty Sand and Bentonite Mixtures for Compacted Clay Liner Purposes

Abstract

The liner is an important component of landfill facility. The liner can also prevent the leachate leaking to contaminate in the soil layer and subsurface water reservoir. Construction of compacted clay liner, according to the standard requirement the layer should have hydraulic conductivity less than 1×10^-7 cm/s. Three mixtures were employed, ie. The silty sand obtained from Khon Kaen municipal landfill was mixed with bentonite at 3%, 5% and 7% by weight. Then, the mixtures were determined for values of hydraulic conductivity by Permeameter with Falling Head method. Bentonite is a clay mineral, which is mostly used in compacted clay liner construction because it performs high plasticity and high swelling. The experimental results showed that the required hydraulic conductivity of 1×10^-7 cm/s could be achieved when the silty sand mixed with bentonite 5% and 7% by weight. The hydraulic conductivity values are 3.75×10^-8 and 2.55×10^-8 cm/s, respectively. However, in order to reduce the construction cost, natural clays can be used as well.