INVESTIGATING THE SWELLING CHARACTERISTICS OF COMPACTED HIGH PLASTICITY CLAYS.

Impermeable layers consist of compacted clay mixtures, synthetic membranes or combinations of clay mixtures and synthetic membranes. When compacted clay liners are employed, they are required to have low hydraulic conductivity, high swelling characteristics, good radionuclide adsorption capacity and good self-sealing capacity. Investigation of the factors affecting the swelling behavior of zeolite-bentonite mixtures (ZBMs) is of great importance for controlling the stability and permeability of landfill sites. In this study, the effect of bentonite content in ZBMs on swelling behavior of compacted high plasticity clays were investigated. For this aim, two types of ZBMs containing 20% and 30% bentonite were prepared. 100% bentonite (pure bentonite) specimens were also tested. Compaction tests were performed on specimens of the ZBMs and pure bentonite, and compaction values were determined. Swelling tests were conducted at optimum water contents of the specimens of ZBMs and pure bentonite. The specimens of ZBMs were loaded under effective vertical stress levels of 1, 2.5, 5, 12.5, 25, and 50 kPa. Pure bentonite specimens were additionally subjected to 100 kPa effective vertical stress. Swelling was observed on ZBM specimens under all effective stress levels. Pure bentonite specimens exhibited limited swelling at 100 kPa effective vertical stress. Swelling of ZBMs increases with increasing bentonite content. The swelling behavior of compacted high plasticity clays was interpreted in terms of bentonite content and final void ratio. [ABSTRACT FROM AUTHOR]