International Journal of Civil Engineering

en Effect of inorganic salt solutions on some geotechnical properties of soil-bentonite mixtures as barriers Soil Mechanics Classic Soil Mechanics Classic Research Paper Research Paper The main task in the design and construction of impermeable liners in landfills is to block the migration of pollutants to the groundwater systems or to reduce its rate to a reasonable amount. That is why environmental regulations force governments to construct engineered waste dumps for waste management purposes. These liners are exposed to various types of chemical, biological, and physical processes and are affected by the leachate which is produced from decomposition of waste materials accompanying methane gas. The leachate includes a lot of components such as water and different types of salts. For this reason, the geotechnical characteristics of clay liners which are evaluated in laboratories using distilled water or tap water might be far different from the representative sample of the in-situ conditions. There are some evidences regarding the effect of these salts on the physical and mechanical properties of clay barriers which could affect the long-term performance of these liners. Since the main criterion for impermeable bottom liners in landfills is their hydraulics conductivity, the increase of this parameter could have a considerable environmental impact. This paper embraces the results of a recent study on the effect of three inorganic salts, NaCl, CaCl2 and MgCl2 on some geotechnical properties of a common used clay soil in impermeable bottom barrier in Kahrizak landfill, the main waste disposal center of the Tehran Metropolitan. Also the effect of bentonite content by adding different percentage of this special clay mineral, 10 and 20 percent, on these properties was investigated. Laboratory tests like liquid limit, compaction, 1D consolidation and free swell tests were performed for this purpose. Results indicated that all of these salts could have a considerable effect on the geotechnical properties of the mixtures. The main reason of such effects is the changes which occur in diffuse double layer of clay particles. Landfill liners, Inorganic salts, Swelling and consolidation, Hydraulic conductivity, Liquid limit, Compaction characteristics 103 110 http://ijce.iust.ac.ir/browse.php?a_code=A-10-286-2&slc_lang=en&sid=1 Nader Shariatmadari shariatmadari@iust.ac.ir 1800319475328460010124 1800319475328460010124 Yes Iran University of Science and Technology Marzieh Salami 1800319475328460010125 1800319475328460010125 No Iran University of Science and Technology Mehran Karimpour Fard 1800319475328460010126 1800319475328460010126 No Iran University of Science and Technology