Fibre reinforcement of a uniform sand: Stress-penetration and stress-strain responses

Fibres are one of many reinforcement types used to improve the mechanical response of soils, and can be natural, synthetic or waste. This paper studied the influence of polymeric fibres as randomly distributed reinforcement for sand. Fibres have proven useful for soil reinforcement, improving the strength and ductility of sands. Herein, the mechanical response of the sand-fibres composite material was characterised using CBR tests (stress-penetration response) and triaxial tests (stress-strain behaviour). The sand studied is a uniform material with an average particle size of 0.75 mm. Polypropylene fibres were used as reinforcement, with diameter and length of 0.031 mm and 12 mm, respectively. Two different fibre contents were studied (0.5% and 1.0%, in mass). The increase of fibre content led to an improvement of stress – penetration response for larger deformations. However, the CBR tests have some limitations, and the results may not be representative of the response under real conditions. The stress – strain behaviour, in general, was improved with the increase of fibre content, obtaining a better response with 1.0% of fibre content. The fibres need to be mobilised for the effect of reinforcement start to become effective. The soil-fibre interaction mechanism identified was the continuous thin filament fibre reinforcement.