Bearing Capacity and Strength of Fibre-Reinforced Sand: Experimental and Parametric Study

- In this paper, Polyolefin fibre which is produced from simple olefin (CnH2n) was mixed with dry sand to investigate the shear strength improvement of the admixture. Specimens with 0.5%, 1%, 1.5% and 2% fibre contents with yarns lengths of 15 mm and 30 mm are prepared in repeatable steps and tested in direct shear tests. Bearing capacity of hypothetical footing resting on ground surface of the tested fibre-reinforced-sand was estimated using Terzaghi’s bearing capacity equation. Moreover, a parametric study includes thickness of reinforced layer, depth of foundation, and fibres content percent is conducted. In the parametric study, the continuous footing was analysed using procedures estimating the bearing capacity of layered soils. Results of shear strength tests indicated that, the inclusion of randomly distributed discrete fibres significantly improved the shear strength of sand. The optimum fibre percentage for improving both friction angle was about 1%. Adding fibre more than this ratio resulted in a significant reduction in soil shear strength parameters. The effect of fibre on sand apparent tensile cohesion is more pronounced compared to its effect on the friction angle. The parametric study indicates that having a continuous footing resting on a soil layer reinforced with 30 mm artificial fibres at 0.5% content provides the highest ultimate bearing capacity. Finally, the thickness of the reinforced layer and the depth of the foundation are among the parameters that affect bearing capacity.