Abstract:
Landslides are natural disasters that happen when rocks, debris, or soil along a slope, causing
harm to human life and the environment around them. Hilly regions of South Ethiopia pose a
significant danger to communities and infrastructure. In 2023, Fudale, Garasse, experienced a
landslide due to intense rainfall, leading to fatalities, property destruction, and disruption of
livelihoods. Therefore, this research was aimed at analyzing the geotechnical conditions and
stability factors associated with the landslides in the Fudale area. The study primarily aimed to
investigate the geotechnical conditions that contribute to landslide occurrences and identify the
key influencing factors. Slope stability analysis was conducted using FEM and LEM through
Plaxis 2D and GeoStudio (SLOPE/W) software, respectively. Additionally, the research sought
to propose remedial measures to mitigate future landslide risks in the affected area. To fulfill
these objectives, both fieldwork and experimental methods were used. Soil samples were
collected from the crest and toe of the slope at depths of 1.5-3 meters, following ASTM
procedures to test their index and engineering properties, with five test pits analyzed in the
laboratory. The findings from laboratory and field tests indicated that the predominant soil types
in the research area were fine-grained, comprising 37.60–55.96% clay and silt, 4.50–7.38% sand,
and 0.10–0.80% gravel, which are particularly susceptible to landslides when saturated. The
Fudale landslide, triggered by factors such as rainfall, slope aspect, curvature, and slope angle,
occurred. Triaxial test results demonstrated that cohesion and internal friction angles ranged
from 28.02 to 57.60 kPa and 9.0 to 16.94 degrees, respectively. The calculated factor of safety
(FOS) values are 0.972 (by Plaxis 2D) and 0.946 (by GeoStudio (SLOPE/W)) for slopes in
natural conditions, respectively. This shows the slopes are unstable. A modified slope angle
(gentle slope) using GeoStudio (SLOPE/W) is suggested, achieving a factor of safety (FOS) of
1.688. This FOS for the modified slope angle is greater than that of the natural slope, mainly as a
result of the impact of the steep gradient present in the natural slope. The proposed remedial
measures for the Fudale landslide include geometry modification, surface drainage, afforestation
rehabilitation, and engineering structures for damaged areas.
Description:
GEOTECHNICAL INVESTIGATION AND STABILITY ANALYSIS OF LANDSLIDE
USING NUMERICAL AND LIMIT EQUILIBRIUM METHODS: (A CASE STUDY OF
FUDALE, GARASSE WOREDA, GAMO ZONE, SOUTHERN ETHIOPIA
