Behaviour of Sand Reinforced with Fibres

This study focuses on the effects of randomly oriented discrete crimped polypropylene fibres on the mechanical response of very fine sand. Compaction and direct shear tests were performed on sand specimens of different densities unreinforced and reinforced with fibres in different proportions. The presence of reinforcement provides an extra resistance to the compaction, causing a less dense packing as the quantity of fibres is increased. The results of the direct shear tests indicate that inclusion of fibres increases the peak shear strength and the strain required to reach the peak. The post-peak strength at large strains was also higher when fibres were included. The presence of fibres leads to more dilative behaviour. In this study, for the range of the effective normal stresses employed, a linear failure envelope has been recorded for all densities and fibre concentrations. The increase of the peak shear strength was almost linear for all densities at low effective normal stress and approached a limiting value for higher normal stresses. For the loosest specimens reinforced with the highest percentage of fibres that could be employed in the laboratory using a moist tamping fabrication method, the relative increase of the peak shear strength was more than 50%.