Strain-hardening behaviour of fibre-reinforced sand in view of filament geometry

The results from a series of laboratory drained standard triaxial tests conducted on sand specimens reinforced with randomly oriented discrete fibres are presented. The purpose of the testing programme was to quantify the stress-strain-strength behaviour of polypropylene fibre reinforced sand specimens considering different fibre lengths (up to 50 mm) and diameters (from 0.023 mm to 0.1 mm fibre), resulting in a large spectrum of aspect ratios (up to approximately 2200). Fibre reinforced specimens exhibited either strain-softening or strain-hardening characteristics, depending on the specific ranges of aspect ratio. Generally, longer fibres (high aspect ratios) produce higher strengths and strain-hardening behaviour in sand, allowing the mixture to be used as a geomaterial for embankments over soft soil, in which the material must withstand large deformations without losing its strength. However, very thin fibres (such as 0.023 mm diameter), longer than 24 mm, tangle during mixture, significantly reducing the effects of the fibres on the soil behaviour.