Slope Stability Analysis along Selected Section of Arbarekete-Galamso Road, West Hararge Zone, Eastern Ethiopia

Abstract

Slope instabilities are among the most common natural geohazards in the world’s hilly and mountainous terrains causing loss of life and damage to infrastructures. The Arbarekete Galamso road is a critical area of road infrastructure construction that requires attention due to its traversing in hilly and mountainous terrains that can have issues with slope instability. So, the present study was conducted to identify and analyze the stability of the slope along selected Arbarekete-Galamso road sections and to suggest some remedial measures based on field investigation and analysis results. A detailed field investigation for this study includes a discontinuity survey, in situ rock testing, soil and rock sampling for laboratory analysis, slope geometry, and orientation measurements. Based on visual observation and some field manifestations, the study revealed seven critical rock slope sections along with two critical soil slope sections for stability analysis. A detailed stability analysis was carried out using kinematic, deterministic, limit equilibrium and finite element methods on these critical slope sections. Kinematic analyses performed with dips software showed wedge modes of rock slope failure occurring at slope sections RSS1 and RSS2, and planar modes of rock slope failure occurring at slope sections RSS1 and RSS5. Additionally, deterministic methods were conducted to determine the factor of safety by using Swedge and Rocplane for wedge and planar failures, respectively. Furthermore, the soil laboratory analysis result revealed that soils are classified as sand soils (medium to high plasticity) with moisture contents ranging from 11.5 to 20.7%, a liquid limit range of 44.42 to 67.24% and a plasticity index of 16.9 to 36.3%. The stability analysis was conducted for static dry, static saturated, dynamic dry, and dynamic saturated loading conditions using deterministic methods, limit equilibrium and finite element methods. The analysis revealed that changes in slope angle, height, and benching slope geometry can improve slope stability, and the installation of retaining walls, rock bolts, anchors, and drainage controls can prevent slope failure.