عنوان مقاله [English]
The use of clayey soils as clay barrier in landfills is very common. This is due to the suitable adsorption, buffering capacity and water retention of clays (Yong et al., 1992). However, changes in geotechnical and microstructural properties of clayey soils in acidic and alkaline conditions have caused many challenges in the application of clayey soils in these projects (Cherian, 2018). In industrial regions, soils are subjected to the acidic rains; therefore they usually encounter acidic conditions. On the other hand, in humidity condition areas, due to the evaporation of soil pore fluid, soils usually run into the alkaline conditions. These environmental conditions have caused the soils to have different initial pH backgrounds (Chemeda, 2015). These changes in the pH of clayey soils may cause some changes in geotechnical and geo-environmental properties of soil. Such a change can affect the long durability of barrier properties. In spite of several researches which have been performed on the geo-environmental properties of clayey soil, the review of the previous researches shows that there is a lack of extensive research on the subject of pH effect of clay on its properties and behaviour (Ouhadi and Yong, 2003). In addition, in the recent years the use of kaolinite as a lowest barrier clay layer in landfills has increased. Therefore, the main objective of this paper is to investigate on the impact of pH variations of kaolinite upon some of its geotechnical and geo-environmental properties.
To achieve this objective in this research with addition of acid and alkaline to kaolinite, several soil samples with different initial pH were prepared. Then, with the application of a series of microstructural and macro-structural experiments such as Atterberg limits, grain size distribution, unconfined compression strength and XRD experiments on kaolinite samples having different initial pH (3, 5, 9, and 12), the variations of some of its geotechnical and geo-environmental properties are investigated.