Abstract:
The evaluation of dam safety is paramount for ensuring the structural integrity and operational
reliability of embankment dams. Dam failure can have severe consequences, including
flooding, property damage, and environmental impacts. This study examines the effects of
rainwater infiltration on the stability of the Khalid Djido embankment dam, located in the
central Ethiopia region with high rainfall intensity and frequency. The dam’s stability was
assessed using numerical modeling techniques, with PLAXIS 2D employed for coupled stress
pore water pressure analyses under various rainfall scenarios. The Soil Conservation Service
(SCS) Curve Number (CN) method estimated infiltration rates at 3.12 mm/hr.
Complementarily, an Intensity-Duration-Frequency (IDF) analysis determined a 24-hour
rainfall intensity of 3.18 mm/hr using precipitation data from 1990-2021. These hydrological
inputs, combined with stability analyses, provided a comprehensive assessment of the dam’s
response to various rainfall scenarios. The analysis revealed significant variations in pore
pressure within the dam, with maximum and minimum values of 34.07 KN/m² and -381.8
KN/m², respectively. High negative pore pressures indicate potential zones of tension. The
downstream toe region was identified as a critical area susceptible to high pore pressures and
potential stability issues. Elevated pore pressures were found to significantly reduce soil shear
strength, leading to increased deformations and a heightened risk of slope failure, particularly
in the downstream slope and core regions. To assess dam stability, a factor of safety (FoS)
analysis was conducted using the strength reduction method. The calculated FoS values
ranged from 1.1 to 1.51, with lower values indicating increased risk of instability. While the
dam exhibited adequate stability under certain conditions, the analysis revealed critical
scenarios where the FoS approached unity, particularly during rainfall events. These findings
underscore the importance of effective drainage systems and monitoring to mitigate potential
risks posed by rainwater infiltration. This research contributes valuable insights to dam safety
knowledge and water resource management in regions susceptible to rainfall-induced
instability.
