Stability analysis of a compost-biochar mixed capping soil on Hydrophobised capillary barrier in an engineered landfill

Abstract

Engineered landfill is a final municipal waste disposal method. A capping system is the final component in the construction of an engineered landfill. In addition to permeability criteria that need to be satisfied, stability is also an important aspect in its design. In this study, the slope stability of the capping layer interfaces and waste interfaces was analyzed. A low permeable soil with or without mixing with biochar and compost can be used as a capping layer. In addition, a hydrophobized sand (using Oleic acid) can under lie the above layer for improved performance. The shear strength parameters between interfaces and of the waste were determined using the direct shear tests. Analyses were carried out for waste – capillary barrier interface and capillary barrier – top soil (with or without biochar and compost mixture) interface, for different side slopes of the capping. Numerical analyses were carried out using SLOPE/W software. A comparative analytical study was also carried out using infinite slope theory. It was found that circular type of slip surface developed within the capping is more critical than the slip surface develop along the interfaces and introducing compost and biochar into the topsoil infact has improved the stability of the slopes of the capping layer.