Effect of randomly distributed polypropylene fibers on unconfined compressive strength, shear strength, and compressibility characteristics of Algerian high plasticity clay soil

Fibers are commonly used to improve the geotechnical properties of problematic soil (e.g., high-plasticity fine-grained soils). Such clays are characterized by low strength and high deformability, which creates many problems for structures that will be founded on these soils. This study examines the potential uses of polypropylene fibers (PP) to improve the geotechnical properties of a typical problematic soil from Algeria (Clay of Sidi-Hadjres) as many technical problems occur in the pavements and buildings of this region. To this end, raw clay and fiber-reinforced samples were compared with respect of stress-strain relationship, unconfined compressive strength (UCS), shear stress characteristics, and oedometric behavior were evaluated and compared according to the fiber content. The results showed a significant improvement in the mechanical and compressibility characteristics of this clay due to PP fiber addition. Therefore, UCS, residual strength, shear stress characteristics, and ductility of the clay were increased with increasing fiber content, while compression index, recompression index, coefficient of compressibility, and brittleness were decreased. The maximum increase in strength is obtained with a 1.2% of PP fiber addition.