An Investigation of the Effect of Variations in the pH of Leachate on the Physical and Mechanical Properties of Kaolinite clay soil in presence Bentonite

Today، sanitary landfills are one the basic needs of human societies. Clay liners are used frequently in landfills in order to prevent leachate''s leaking into the outside environment. Existence of different chemicals in leachate can affect the geotechnical properties of clay liners and arise their need for a more conservative design. Therefore، investigating into the possible changes in geotechnical properties of clay liners because of the chemicals of leachate will be important. The main purpose of this research is to probe different effects of the variations in the pH between 3 to 11 on hydraulic conductivity، shear strength and one dimensional swell or settlement potential of cohesive soils. The coefficient of hydraulic conductivity and one dimensional swell or settlement potential have been measured by conducting falling head and one-dimensional consolidation tests، and parameters of shear strength of soil have been evaluates by conducting triaxial compression tests. The experiments have been performed on Kaolinite and the blend of Kaolinite and Bentonite with different percentages of Bentonite. Acetic acid has been used to produce pHs below 7 and sodium hydroxide has been used to produce pHs above 7. The type of chemicals and the amount of them، the type soil minerals، and time are some important parameters for understanding the effect of changes in pH on properties of clayey soil. In these considerations، an increase in hydraulic conductivity and settlement potential of cohesive soil with changes in pH has been detected، Moreover، it is been concluded that shear strength of cohesive soils will be decreased in pHs above or below 7.