Geotechnical properties and applicability of bentonite-modified local soil as landfill and environmental sustainability liners

Liners are provided under engineering landfill sites to block the downflow of leachates and their noxious components to minimize pollution in the underlying aquifers or neighboring water bodies. Compacted clays are widely employed as suitable materials for constructing landfill liners because of their low hydraulic conductivity, balanced swelling potentials, and appropriate compressive strength. However, the quality has to be improved if the locally available soil does not meet the minimum standards for constructing liner materials. Including bentonite dosage with local soil can show better stability and strengthened cohesion bonds between molecules. This paper aims at a recent study on specific geotechnical properties of bentonite amended local Khulna clay soil intended to be used as a liner material. Bentonite in varying proportions (e.g., 5%, 10%, 15%, and 20%) was mixed with local soil, and specific tests (e.g., compaction tests, consistency tests, hydraulic conductivity tests, free swell tests, unconfined compressive strength tests, and pH tests) were conducted on the mixtures. Results indicated that the optimum moisture content (14.03%–19.30%), liquid (35.39%–53.98%), plastic (22.20%–35.23%), plasticity index (13.19%–18.75%), pH (7.23–7.43), swell index (3.13%–24.2%) and unconfined compressive strength (156.21 kPa–244.46 kPa) increased while bentonite was in conjuncture with the soil. In contrast, maximum dry density (17.80 kN/m³ to 16.80 kN/m³) and hydraulic conductivity (2.39 × 10⁻⁷ cm/s to 0.09 × 10⁻⁷ cm/s) decreased. Also, at 10% bentonite content, the mixture matched the acceptable standards for liner construction (hydraulic conductivity 0.29 × 10⁻⁷ cm/s <10⁻⁷ cm/s, and unconfined compressive strength = 210 kPa > 200 kPa).The study identified that adding bentonite to local soil can improve its geotechnical properties, making it a suitable material for landfill liners with increased strength and decreased hydraulic conductivity.