Hydraulic and mechanical characteristics of compacted sand–bentonite: tyre chips mix for its landfill application

Abstract

Compacted sand–bentonite mixtures are generally placed at waste dumping places as a means of avoiding contaminant movement to reduce or remove the potential for groundwater pollution. Owing to their almost impermeable nature and high pollutant adsorption tendency, bentonite generally treated as a liner material to avoid subsurface contamination. Cracks are formed in the landfill liner due to the desiccation, large interlayer shrinkage and differential settlement of bentonite. Fibres are commonly added to sand–bentonite mixture to act as a reinforcing material to eliminate the development of tensile cracks. Waste tyre chips are derived from the tyre retreated technique, and it can be included as short fibre in sand–bentonite mixture for the use as landfill barrier material. Hydraulic conductivity and shear strength are the two important parameters of the liner material, which are considered for hydraulic, and stability analysis in landfill application. In this context, consolidation and consolidated undrained tests were performed to study the hydraulic and mechanical behaviour of sand–bentonite mixture mixed in a proportion of 80:20 and mixed with 0, 5, 10 and 15% of waste tyre chips. From the consolidation test, swelling pressure and swelling potential reduced maximal at 15% of tyre chip content. Hydraulic conductivity and negative pore water pressure altered significantly with the application of tyre chips. Effective internal angle of friction enhanced from 24.9° to 30.5° and critical state parameter improved from 0.738 to 1.429 with the presence of 15% of tyre chips. Test result suggested that maximum of 10% of tyre chips can be used as a landfill liner and 15% tyre chips would be benefited for landfill cover.