A Numerical Study on Road Embankment Stability Enhanced by Natural Reinforcement

This study numerically evaluates the effect of natural reinforcements on the stabilization of a road embankment built with poorly graded granular soil (SP - SM). The response of the structure under a continuous vehicular surcharge load of 24 kN/m² is analyzed using the GeoStudio suite, with the SLOPE/W and SIGMA/W programs utilized for limit equilibrium stability and finite element stress-deformation analyses, respectively. The unreinforced soil embankment yields a Factor of Safety (FOS) of 1.133, which falls below the Indian Roads Congress (IRC) accepted level of stability. Banana Fiber Geotextiles (BFG) are applied as planar reinforcement at varying vertical spacings from 0.25 m to 1.50 m. It is found that the optimum techno-economic spacing of 1.0 m results in a 36.6 % increase in FOS and a 46.4 % reduction in peak internal shear strain. In parallel, the bio-reinforced model, simulating a 2.0 m deep 6-month-old vetiver grass root matrix at the slope face, achieves an FOS of 1.406. Finite element contours reveal that the bio-reinforced zone, modeled as an equivalent-continuum block, provides significant structural confinement. The biological confinement completely arrests lateral face yielding, decreasing horizontal displacement by 70.8 %, reducing maximum vertical settlement by 60.0 %, and dropping peak internal shear strain by 80.0 %. Both natural reinforcement methods successfully satisfy the safety thresholds recommended by IRC: 75-2015, proving that bio-reinforcement provides superior deformation control and establishes itself as a highly effective, sustainable alternative to conventional stabilization techniques.