Landfill Liner Design Employing Local Materials: Bentonite-Sand Mixtures Using Two Sand Types

The objective of this study is to create an impermeable layer for landfill liners to store solid household waste. The soil liner in the waste landfill should meet the saturated hydraulic conductivity, compressive strength and internal friction angle requirements. This paper presents a study on the valorization of local Saharan sands for use as cover soils in landfills. The results of preliminary tests on 10% bentonite - 70% silty sand - 30% crushed sand mixture show that it provides a minimum hydraulic conductivity of around 2 × 10−9m/s. Also, the mixtures showed that the swelling behavior is directly proportional to the water absorbed. This value has been verified using the Carrier and Beckman (1984) relationship. A mechanical study of the characteristics of these mixes using an unconfined compression test (UCS) and a triaxial test (CD) was carried out. The results of the unconfined compression strength test at an age of 90 days reached 1400 kPa for mixes containing 80% and 70% silty sand. In addition, this strength develops with the sedimentation of CaCO3. Triaxial tests were then carried out on these two mixtures. The results show that the angle of internal friction increases (φ’) with the quantity of crushed sand (between 30 ° and 35 °). Finally, the results show that a mixture composed of 10% bentonite, 70% silty sand and 20% crushed sand meets the hydromechanical requirements. This mixture represents an alternative ready-to-use material for designing the bottom layer of landfill sites, particularly in arid and semi-arid areas.