Geotechnical properties of materials used in landfill clay liner: A critical review

The earliest method of waste disposal is dumping waste in landfills. The important component of landfills which prevents the passage of leachate to the subsoil is defined as the bottom liner. A landfill liner must contain a specific range in terms of swelling behavior, strength, and permeability before placing down beneath the constructed landfills. The present paper summarizes the detail of the different materials and their feasibility which satisfy the criteria to be used as landfills liner. The detail of findings of microstructural analysis (SEM–EDX, XRD, FT-IR, etc.) along with the waste materials which compact the particles and enhance the strength and stability of soils is also discussed. A lot of landfill liner materials such as Bentonite, sand, fly ash, cement, biochar, marine clay, lateritic soil, and geosynthetics have been used to enhance the geotechnical properties of liners. Among all, geosynthetic clay liner (GCL) and compacted clay liner (CCL) show increased hydraulic conductivity for clay soil with high plasticity whereas this value reduces for clayey soil having low plasticity with the increase in the concentration of the salt solution. The hydraulic conductivity of the mix containing biochar, bentonite, and sand is found to be 1 × 10−9 m/s. The hydraulic conductivity and shear strength of the soil increases while the compressibility of the soil decreases with an increase in the biochar percentage having smaller particle size. Also, the alkaline activator is suggested to be best for soil stabilization as compared to standard Portland cement. The development of new materials must be environmentally sustainable and should contain sufficient shear strength so that it can sustain the overburdened load of dumped waste. It should also be free from cracking so that the contamination of subsoil and groundwater can be minimized.