Effect of randomly distributed synthetic fibre in fine sand and fly ash

Fibre reinforced soil is one of the soil improvement techniques which has attracted increasing attention in geotechnical engineering. Fibers either natural or synthetic are mixed with the soil to improve tensile strength of soil due to restraining effect generated due to adhesion and friction between the fibre and soil. Though extensive studies on fibre reinforced soils are carried out by researchers, studies on effect of synthetic fibres addition in fine sand and fly ash are limited. Both fly ash and fine sand are not much preferred as construction material or backfill materials due to their lower shear strength and relatively lower permeability. So, in the present study, extensive experimental programme is undertaken to study the properties of fly ash and fine sand mixed with addition of randomly distributed polyester fibres of 6 mm and 12 mm length. The compaction, strength and permeability characteristics are determined for fibre reinforced fine sand and fly ash by varying fibre content (0.5, 1.0, 1.5 and 2.0 percent by weight) and fibre length. The study yielded optimum fibre content for stabilization as 1.5 percent. The fibre reinforced fine sand has yielded interesting results regarding its suitability as fill material in reinforced soil structures and as back fill material behind retaining structures. The fibre reinforced fly ash indicated improved shear strength and permeability characteristics with fibre addition and revealed its suitability as construction material for embankments.