Reinforcement of an avlamè lateritic gravel (benin) with jute fibers: mechanical characterization and hyperbolic modeling

The direct use of lateritic gravel in pavement base courses is limited by a well-identified technical constraint: insufficient bearing capacity. The incorporation of plant fibers, such as jute fibers, offers a mechanical and environmentally friendly reinforcement approach. This study examines the mechanical behavior of a composite material made of Avlamè lateritic gravel (Benin) reinforced with 0.75% jute fibers of 1 cm length. Direct shear and oedometer tests were carried out on the raw gravel and on the composite, compacted to 95% of the Modified Proctor Optimum. Their nonlinear hypoelastic behavior was modeled using the Hardin and Drnevich hyperbolic model, whose parameters were identified through an iterative nonlinear least-squares regression. Reinforcement significantly improves the cohesion, from 10.75 to 23.48 kPa, the shear modulus (+49%), and the CBR index, from 34% to 69.5%, meeting CEBTP requirements for low-traffic roads. The R² coefficients of the hyperbolic model range from 83.4% to 98.9% for the raw gravel and from 97.6% to 98.8% for the composite, confirming its adequacy. Young's modulus increases from 192.0 to 286.0 MPa, while Poisson's ratio remains constant at 0.50. The oedometer analysis reveals a preconsolidation stress 4.6 times higher for the composite (138 kPa versus 30 kPa). Reinforcement with 0.75% jute fibers constitutes an optimal, economical, and environmentally friendly solution for improving lateritic gravels intended for low-traffic (T1 and T2) road subbase layers.