Mineral barrier protects the groundwater and soil from contamination by insulating the leakage of harmful substances from landfill. One of the most important parameters, which decides about usefulness of material to built-in sealing layers, is hydraulic conductivity.  Researchers have conducted investigations with the possibility of utilising fly ash as a mineral sealing layer material, which is justified by its low permeability and other properties. Using of combustion by-products, like fly ash, has many advantages to the environment. It is known that laboratory tests of hydraulic conductivity are often long-term and require expensive equipment. Therefore, to avoid this, researchers trying to assess permeability of tested material with empirical or semi empirical formulae. Depending on the equation, it can be based on particle size, specific surface, connections between pores or other factor.

The aim of the paper is to compare the results of hydraulic conductivity of fly ash obtained from the laboratory tests and from estimation using different empirical formulae. Fly ash was compacted by the Standard Proctor method at the optimum moisture content. The laboratory tests of fly ash permeability coefficient, k, was carried out on the previously consolidated samples, subjected to various effective stresses.

The results obtained from empirical equations was variable. It was observed that the results depends mostly on what component the formula has. The Kozeny-Carman formula and other, based on a few physical parameters of the ground, gave better results in prediction of hydraulic conductivity of fly ash than equations based on one parameter.

DOI: https://doi.org/10.3846/enviro.2017.062