Mechanical Behaviour of a Tropical Soil Reinforced with Short Randomly Distributed Glass Fibres

Soil reinforcement using short discrete fibres as a mechanical stabilisation method has been recently gaining attention in its versatility in improving the engineering properties of soils. In this study, the effect of short randomly distributed glass fibres (RDF) on a tropical fine-grained soil was investigated. A series of California Bearing Ratio (CBR) tests and unconfined compressive strength tests were performed at the respective optimum water content and maximum dry density at fibre contents of 0.5, 1.0, 1.5 and 2.0%. The results showed that the fibre reinforcement caused an increase in unsoaked CBR with an optimum increase of 45% at 1.0% fibre. The fibres were still effective in the soaked state despite lowered CBR in the range of 6–13%. A decrease in swelling potential was observed and was pronounced at fibre contents of 1.5%. It was observed that the unconfined compressive strength increased up to 1.0% and then declined at higher fibre contents. The reinforced specimens failed at higher strains, exhibited reduced post-peak loss in strength and showed some ductility. The unconfined compressive tests indicated that the undrained shear strength of the reinforced soil showed improvements up to 88% over the unreinforced soil. An optimum fibre content on this basis was identified in the range of 1.0% to 1.5% fibre, and noticeable decrease in strength was apparent beyond 1.5%. This phenomenon was attributed to the decrease in fibre-soil interaction. Moreover, a ductile behaviour was observed with all reinforced specimens which maintained higher residual shear strength compared to unreinforced soil. This behaviour reduced the post-peak loss in strength and was physically accompanied by fewer crack formations. The performance of the soil has been improved by the addition of glass fibre, and it was identified that about 1.0% fibre would be optimal overall.