Effect Analysis of Soil Saturation and Slope Angle on the Geotechnical Stability of an Engineered Soil Slope – Bir Al-Ghanam Road, Libya

Abstract

This study investigates the geotechnical stability of an industrial slope located parallel to the Bir al-Ghanam road in western Libya, with particular emphasis on the Effects of soil saturation and slope inclination on slope stability conditions. Field surveys were conducted to determine slope geometry, while laboratory testing was performed to evaluate variations in shear strength parameters (cohesion and internal friction angle) under different water quantities (10, 20, 30, and 50 mm). The findings indicate a progressive reduction in shear strength parameters with increasing saturation. However, the primary mechanism governing stability deterioration was the generation of pore water pressure, which significantly reduced the effective stress along the potential slip surface. Numerical simulations were carried out using RocPlane software to estimate the factor of safety under varying hydraulic scenarios. Results reveal that steep slopes (80–90°) remain relatively stable under low moisture conditions but approach critical stability states as saturation and pore pressure increase. Conversely, reducing the slope angle from 80° to 25° significantly enhanced stability due to reduced driving forces and increased resisting forces.