Unsaturated Strength Properties of Compost-Amended Soils for Landfill Biocovers

Landfill biocovers play a key role in lowering methane emissions and making waste management more sustainable. It is investigated in this study, how unsaturated strength varies in 75% compost with 25% laterite (75%C25%L) and 75% compost with 25% sand (75%C25%S) soils, when such soils are used as landfill biocovers. Tests such as geotechnical, compaction, shear strength, consolidation, mineralogical and SWCC tests were carried out. At the maximum dry density (MDD), the 75%C25%L blend measured 1955.1 kg/m³ (using the Standard Proctor) and 1992.3 kg/m³ (in West Africa) which was greater than 75%C25%S (using the same standards) and laterite. Laterite resulted in high cohesion (89.2 kPa), while its friction angle was rather low at 9.7°. Both SEM-EDX images revealed that silicon (56.31% atomic), calcium (9.31% atomic) and iron are present in equal amounts in 75%C25%L, suggesting support for microbial activity. Strong Water Conditions, as seen in SWCC analysis, prove that compost (θr= 0.4095, θs = 0.5737) holds more water than laterite (θr= 0.1906, θs =0 .4779). In 75%C25%L, XRD findings showed the addition of quartz, kaolinite and orthoclase improved the material’s hardness. Based on its density, strength and water- retaining properties, the 75%C25%L mix is best suited for sustainable landfill biocovers.